economic feasibility analysis of the use of innovative

Economic feasibility analysis of the use of innovative alternative water sources in Cuba:

A case study

Carlos Alfredo Lanza Martinez

MSc Thesis UWS-SE 2017 Student Number 42355

July 2017

http://masaguaparatodos.un-ihe.org/home-english-version

Economic feasibility analysis of the use of innovative alternative

water sources in Cuba: A case study

Master of Science

by

Carlos Alfredo Lanza Martinez

Supervisors Carlos Arturo Madera Parra, Eng., MSc., PhD Associate Professor, Universidad del

Valle, Cali, Colombia

Mentors Carlos M. Lopez Vazquez, PhD, MSc, Associate Professor of Sanitary Engineering,

UNESCO-IHE Institute for Water Education, Delft, The Netherlands

Orestes A. Gonzalez Diaz, PhD, MSc, Professor of Sanitary Engineering, Centro de

Investigaciones Hidraulicas de la CUJAE, La Havana, Cuba

Jhonny Harold Rojas Padilla, Eco.,MSc, Assistant Profesor, Instituto Cinara,

Universidad del Valle, Cali, Colombia

Examination committee

Fernando J. Diaz Lopez, PhD, MSc, Senior Advisor & Programme Manager Innovation

for Sustainable Development, TNO Caribbean, Netherlands Organisation for Applied

Scientific Research TNO, the Hague, Netherlands & Associate Professor Extra-ordinary

in Sustainablity Systems, Stellenbosch University, Matieland, South Africa

This research is done for the partial fulfilment of requirements for the Master of Science degree at the

UNESCO-IHE Institute for Water Education, Delft, the Netherlands

Delft

July 2017

Although the author and UNESCO-IHE Institute for Water Education have made every effort

to ensure that the information in this thesis was correct at press time, the author and UNESCO-

IHE do not assume and hereby disclaim any liability to any party for any loss, damage, or

disruption caused by errors or omissions, whether such errors or omissions result from

negligence, accident, or any other cause.

© Carlos Alfredo Lanza Martinez, 2017.

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

http://creativecommons.org/licenses/by-nc/4.0/

http://creativecommons.org/licenses/by-nc/4.0/

i

Abstract

Water scarcity is a worldwide issue mainly caused by climate change and rapid growth with

increased urbanization. Nowadays, many countries, even traditional countries considered as

water ample are suffering of water scarcity. The direct use of seawater for toilet flushing and

the wastewater reuse are are not only economically competitive under specific conditions

(Cuban conditions). But, also has many environmental and social benefits such as: reducing the

problematic of water shortage by providing a source of water and improving the water quality

discharged into surface and groundwater.

The first case assessed was conducted towards the Cuban population with domestic water

consumptions from 145 LPPD up to 175 LPPD. Comparing the introduction of the use of

seawater for toilet flushing to when only freshwater is used to supply the population, several

scenarios were evaluated. When water scarcity occurs from 1 to 9 months, being this last one,

the most critical reported in Cuba. The Net Present Values (NPV) and the performance indicator

(Cost of water in US$/m3) of the different alternatives and scenarios showed interestingly

results that must be considered such as economic, social and environmental benefits.

When only freshwater is used to supply the population, the cost is US$ 0.37/m3 water supplied.

But, when water scarcity occur, this cost can rise up to US$ 0.80/m3 for 9 months of water

shortage. This happens because there is a need to purchase water to water trucks at an extremely

high cost of US$ 1.74/m3. The Dual water supply system shows cost of water supplied from

US$ 0.36/m3 for systems from 50 to 1000 persons and US$ 0.32/m3 for 15,000 persons.

Interestingly, this cost remains the same when evaluated from 1 to 3 months of water shortage.

This occurs, because there is enough freshwater saved by the use of seawater for toilet flushing

to cover this water shortage period and consequently there is no need to purchase water from

water trucks.

For the touristic market, the economy of scale has also affected in the results. A small hotel of

capacity for around 54 persons, with a water consumption around 950 LPPD, shows a cost for

the alternative of the use of seawater for toilet flushing of US$ 0.49/m3. For this condition, the

amount of saved freshwater allows a water shortage coverage period of 45 days remaining with

the same cost of water. When water scarcity extends, this cost can rise up to US$ 0.70/m3 for 9

months of water shortage. Regarding the reuse of wastewater, a conventional WWTP with a

capacity of 4500m3/day was evaluated by upgrading the plant with an MBR system. Membrane

replacement every 12 years was considered, as the water that is being treated is not industrial

wastewater. The cost of the treated water is of US$ 0.23/ m3.

The use of seawater for toilet flushing in a touristic hotel with capacity of 500 persons allows

to save enough freshwater to supply 103 people. The implementation of RO desalination water

plant produces the equivalent volume of water that can be used to supply 3,172 persons by not

consuming freshwater. In this same hotel, a WWTP with capacity of 380 m3/day was assessed

producing 138,700 m3/ year of treated wastewater ready for reuse. If this water is used for

irrigation, the amount of saved freshwater is sufficient to supply 2,620 persons. Assessing the

potential combination of the innovative alternatives water sources in a hotel with capacity of

500 persons, a total of 5,895 locals can be benefited with the saved freshwater.

iii

Acknowledgements

I want to start thanking God for being my protector in every single moment in my life and

especially during this 2 year of MSc period. Without your presence nothing of this could be

possible. Thank you God again.

I appreciate the Bill and Melinda Gates foundation who granted me a scholarship covering half

of my studies to pursue my career as a Sanitary and Environmental Engineer in one of the most

prestigious, Institute for water Education UNESCO-IHE Delft, The Netherlands and

Universidad Del Valle (UNIVALLE), one of Colombia’s renowned universities.

To my daughters: Cristina, Adriana, Sophia and Mia Lanza, who gave me the strength at all

times to achieve the goal.

I am very thankful to my grandmother, Olga Wong, who has been there in every single phase

of my education, without your support this could not be possible. To my parents, Carlos R.

Lanza and Olga C. Martinez, who were every single day taking care of me from far away.

To my siblings Suyen, Olga, Carlos J. Lanza and my cousin Fernando Cruz, who were there in

my lonely moments, behind the computer, giving me all the support through video-calls. In the

same way to all my big family.

Special thanks to my Research team: Dr. Carlos Lopez Vazquez, since the beginning, the ones

working under your mentoring, we were clear that we had the best mentor. Thanks for all the

advices and guidance along the research. To Dr. Carlos Madera who gave me support all time,

not only during the research but through all the period of study. Dr. Orestes Gonzales for all the

guidance during my field work in Cuba and Professor Johnny H. Rojas for the guidance during

my office work in Colombia.

I would like to end thanking my new friends in the water sector, Hydrodynamics, Water and

governance, Hydrology, Coastal, and Flood Risk Management. New people who I met enjoying

good moments and also the tough times UNESCO-IHE and UNIVALLE gives, but special

thanks to the Sanitary Engineering class of 2015-2017. This new water network among different

cultures was seeded and with new careers better opportunities should come for all of us.

Expecting to see each other at some other time I wish you all good luck.

v

Table of Contents

1. Introduction 1 1.1 Background 2 1.2 Problem Statement 4

2. Literature Review 5 2.1 Water availability 5

2.1.1. Freshwater 5 2.1.2. Saline water (brackish or seawater) 6

2.2 Water consumption 7 2.2.1 Agricultural use 9

2.2.2 Industrial use 9 2.2.3 Domestic use 9

2.2.4 Water consumption in Cuba 10 2.3 Water supply systems and technologies 11

2.3.1 Water supply 11 2.3.2 Conventional water treatments processes 12 2.3.3 Advanced water treatments 12

2.3.4 Alternative sources (Seawater for toilet flushing) 14 2.4 Wastewater treatment and technologies 17

2.4.1 Conventional wastewater treatment 17 2.4.2 Advanced wastewater treatment 17

2.4.2.1 Membrane Bioreactor 17 2.4.2.2 SANI Process 19

2.4.3 Wastewater reuse systems 20 2.5 Social and economic evaluation of projects 21

2.5.1 Principles 21

2.5.2 Project evaluation tools 23 2.5.2.1 The net present value methods 23

2.5.2.2 The internal rate of return 24 2.5.2.3 Return on investment 25 2.5.2.4 Benefit/Cost ratio 25

2.5.2.5 Payback period method 26

2.5.2.6 Other methods 27 2.5.3 Summary of project evaluation techniques 27 2.5.4 Case studies 28

2.5.4.1 Case 1. Comparison of engineering costs of raw freshwater, reclaimed

water and seawater for toilet flushing in Hong Kong. (Tang, Yue and

Li, 2007) 28 2.5.4.2 Case 2. Cost-benefit analysis in the Yarqon Recycling Project case

study in Israel. (Garcia and Pargament, 2015) 29

vi

3. Research Questions 32 3.1 General Question 32 3.2 Specific research questions 32

4. Research Approach 33

5. Research Objectives 35 6.1 General Objective 35 6.2 Specific Objectives 35

6. Methodology 36 7.1 Phase 1. Data Collection 36

6.1.1. Primary Data 36 6.1.2. Secondary Data 37 6.1.3. Determination of CAPEX and OPEX 37

7.2 Phase 2. Economic analysis 41

7.3 Phase 3. Scenario analysis 42

7.3.1 Case study of the replacement by seawater for toilet flushing in a

Cuban community 42 7.3.2 Case study of the touristic resort Villa Playa Hermosa in Guanabo 43

7.3.3 Case study of Punta de Hicacos, in La Peninsula de Varadero 45 7.4.4 Case study of Hotel Breezes Jibacoa: 47

7.5 Performance indicator 49

7. Results and Discussions 50 7.1 Cuban Economy 50

7.2 Economic and Scenario analysis 51 7.2.1 Case-study: domestic use of seawater for toilet flushing in Cuban

urban environments 51 7.2.2 Case-study of the touristic resort Villa Playa Hermosa: use of seawater

for toilet flushing in the tourism sector in Cuba 74 7.2.3 Case-study: wastewater reuse in Punta de Hicacos at La Peninsula de

Varadero 76 7.2.4 Case study at Hotel Breezes Jibacoa 79

8. Conclusions 84

9. Reference

10. Appendix 87 A. Case-study: domestic use of seawater for toilet flushing in Cuban urban

environments 91 B. Case-study of the touristic resort Villa Playa Hermosa: use of seawater for toilet

flushing in the tourism sector in Cuba 98 C. Case-study: wastewater reuse in Punta de Hicacos at La Peninsula de Varadero 99 D. Case study at the Hotel Breezes Jibacoa 100

vii

List of Figures Figure 1 Domestic water consumption by activity according to WHO (HIDROCAPITAL, 2003). ......................... 7 Figure 2 Percentages of water consumption in The United States (EPA, 2005). ............................................... 8 Figure 3 Water distribution by households in the U.S (EPA, 2005).................................................................... 8 Figure 4 A typical sea water supply system (Water-Supplies-Department, 2016) ........................................... 14 Figure 5 Conceptual diagram of the TWS system (Leung, Li, Yu, Chui, Lee, van Loosdrecht and Chen, 2012) . 16 Figure 6 MBR process configuration ............................................................................................................... 18 Figure 7 The SANI process concept (Tsang, Wang, Lu, Li, Chen and van Loosdrecht, 2009) ............................. 20 Figure 8 Research approach of the study ........................................................................................................ 34 Figure 9 Example of the data provided by PRESWIN 8.1. The table displays the costs of materials and hand

labour of the replacement of the sanitary equipment ............................................................................ 40 Figure 10 Description of the sanitary parts of a toilet that are replaced twice a year due to the use of

seawater for toilet flushing .................................................................................................................... 40 Figure 11 Monthly Salary of employees in the water sector (According to Water utility services) ................. 41 Figure 12 Estimated fresh water consumption in Cuba as a function of number or people served and local

standards. .............................................................................................................................................. 42 Figure 13 Location of Hotel Villa Playa Hermosa(Google-EarthPRO, 2016) ..................................................... 44 Figure 14 Location of Pensinsula Hicacos mostly known as pensinsula de Varadero (Google-EarthPRO, 2016)

............................................................................................................................................................... 45 Figure 15 Location of wastewater treatment plant Hicacos (Google-EarthPRO, 2016) ................................... 46 Figure 16 Location of Hotel Breezes Jibacoa (Google-EarthPRO, 2016) ........................................................... 47 Figure 17 Location of wastewater treatment plant of Hotel Breezes Jibacoa (Google-EarthPRO, 2016) ......... 48 Figure 18 Water consumption for 50 persons in m3/year assessed for the different scenarios ....................... 53 Figure 19 Percentage of water consumptions for the different scenarios ...................................................... 54 Figure 20 Percentage of fresh water saved by the use of seawater for toilet flushing ................................... 55 Figure 21 Percentage of persons that can be served with freshwater waved by the use of seawater for toilet

flushing .................................................................................................................................................. 55 Figure 22 Net Present Value (NPV) of Capital Expenditures (CAPEX) and Operation and Maintenance

Expenditures (OPEX) for a period of 20 years for the different scenarios and alternatives. .................... 57 Figure 23 Cost of water in US$/m3 of water for the different scenarios and alternatives .............................. 58 Figure 24 Number of persons that can be served with freshwater saved by the use of seawater for toilet

flushing .................................................................................................................................................. 60 Figure 25 Number of houses that can be served with freshwater saved by the use of seawater for toilet

flushing .................................................................................................................................................. 60 Figure 26 Water consumption for 5000 persons in m3/year assessed for the different scenarios .................. 62 Figure 27 Percentage of water consumptions for the different scenarios ...................................................... 63 Figure 28 Percentage of persons that can be served with freshwater waved by the use of seawater for toilet

flushing .................................................................................................................................................. 64 Figure 29 Number of houses that can be served with freshwater saved by the use of seawater for toilet

flushing .................................................................................................................................................. 64 Figure 30 Net Present Value (NPV) of Capital Expenditures (CAPEX) and Operation and Maintenance

Expenditures (OPEX) for a period of 20 years for the different scenarios and alternatives. .................... 66 Figure 31 Cost of water in US$/m3 of water for the different scenarios and alternatives ............................... 67 Figure 32 Fresh water saved by the use of seawater for toilet flushing for the scenarios of 50 up to 15,000

persons .................................................................................................................................................. 69 Figure 33 Cost of water in US$/m3 for the scenarios from 50 up to 15,000 persons ....................................... 70 Figure 34 Costs saved in US$/m3 when applying a dual water supply system................................................. 72 Figure 35 Percentage of the costs from saved freshwater due to the use of seawater for toilet flushing ...... 73 Figure 36 Water consumption of Hotel Guanabo for the different scenarios ................................................. 75

viii

Figure 37 NPV for a period of 20 years for the different scenarios and alternatives for the Hotel Villa Playa

Hermosa. ................................................................................................................................................ 75 Figure 38 Cost of water in US$/m3 of water for the different scenarios and alternatives for the Hotel Villa

Playa Hermosa. ...................................................................................................................................... 76 Figure 39 NPV for a period of 20 years for the different scenarios for the WWTP Hicacos in the Peninsula of

Varadero ................................................................................................................................................ 78 Figure 40 Cost of water in US$/m3 of treated water for the different scenarios for the different scenarios and

alternatives for the WWTP Hicacos in the Peninsula of Varadero .......................................................... 78 Figure 41 Water consumption of Hotel Breezes Jibacoa for the different scenarios (Scenario 1 to 3) ............. 80 Figure 42 NPV for a period of 20 years for the different scenarios and alternatives for the Hotel Breezes

Jibacoa ................................................................................................................................................... 81 Figure 43 Cost of water in US$/m3 of water for the different scenarios and alternatives for the Hotel Breezes

Jibacoa ................................................................................................................................................... 82 Figure 44 NPV for a period of 20 years for the different scenarios (Scenario 4 to 7) for the WWTP of Hotel

Breezes Jibacoa ...................................................................................................................................... 82 Figure 45 Cost of water in US$/m3 of treated water for the different scenarios for the different scenarios and

alternatives for the WWTP of Hotel Breezes Jibacoa .............................................................................. 83

ix

List of Tables Table 1 Annual freshwater use per regions (United Nations Environment, 2003) ............................................. 9 Table 2 Water consumption of freshwater in Cuba (NC-53:91, 1983). ............................................................ 10 Table 3 Water consumption for Hotels according to Torres-Rodriguez (2015). ............................................... 11 Table 4 WQO'S proposed by the WSD in Hong Kong (Water-Supplies-Department, 1992) ............................. 15 Table 5 Economic evaluation factors (Remer and Nieto, 1995) ....................................................................... 22 Table 6 Project evaluation techniques (Remer and Nieto, 1995) .................................................................... 23 Table 7 Acceptance criteria for the benefit/cost ratio method ....................................................................... 26 Table 8 Summary of project evaluation techniques characteristics (Remer and Nieto, 1995) ......................... 27 Table 9 Example of the CAPEX for the case study of the Cuban population where water is supplied to 50

persons .................................................................................................................................................. 38 Table 10 Example of the OPEX for the case-study of the Cuban population where water is supplied to 50

persons .................................................................................................................................................. 39 Table 11 Water prices according to the regulation of Cuba: (NORMA: Resolucion 287/2015) ........................ 51

xi

Abbreviations

AW: Annual worth

AYI: Average yearly interest

AYP: Average yearly profit

B/C: Benefit Cost ratio

CAPEX: Capital Expenditures

CAS: Conventional Activated Sludge

CBA: Cost Benefit Analysis

CUC: Cuban Convertible peso (one of the two official currencies in Cuba)

CWR: Clear Water Reservoir

D.C: Data Collection

EPA: Environmental Protection Agency

FAO: Food and Agriculture Organization

FW: Future worth

HKIA: Hong Kong International Airport

HKUST: Hong Kong University of Science and Technology

I: Interest

iMBR: Immersed Membrane Bioreactor

IRR: Internal Rate of Return

L: Litre

LPCPD: Litre per capita per day

MARR: Minimum attractive rate of return

MBR: Membrane Bioreactor

MED: Multiple effect distillation

MF: Microfiltration

MLSS: Mixed liquor suspended solids

MSF: Multi-stage flash

NPV: Net Present Value

xii

OPEX: Operational Expenditures

PAHO: Pan American Health Organization

PP: Payback period

PW: Present worth

RO: Reverse Osmosis

SANI: Sulphate reduction, Autotrophic denitrification and Nitrification Integrated process

sMBR: Side stream Membrane Bioreactor

SRB: Sulphate reducing bacteria

TVM: Time value money

TWS: Triple water supply

UF: Ultra filtration

UN: United Nations

USGS: The United States Geological Survey

UV disinfection: Ultraviolet disinfection

WFP: World Food Program

WSD: Water Supply Department in Hong Kong

WHO: World Health Organization

WQO’s: Water Quality Objectives

WTP: Water treatment plant

WWTP: Wastewater treatment plant

Introduction 1

CHAPTER 1

Introduction

Water scarcity is a worldwide issue mainly caused by climate change and rapid population

growth with increased-urbanisation. Temperature increase is a factor affecting the water cycle

raising the evaporation rate resulting in high water losses. Precipitation is the source of almost

all fresh water and uneven precipitations are resulting in flooding and drought which is

increasing the vulnerability of water resources. All this together results into different concepts

that are involved into water scarcity as water stress and water crisis.

Water scarcity is also being affected by human activities particularly in areas with high

population density, tourist inflow, intensive agriculture and water demanding industries. Today

many large urban areas, even in regions that were traditionally considered as water ample

(Japan, Europe), suffer from water scarcity. This implies the need for the development of

additional sources (Friedler and Hadari, 2006).

Seawater is an alternative source of water and is available in abundance as 96.5% of the total

available water in earth is in oceans (USGS, 2016). Seawater desalination is an advanced

technology that has been introduced successfully during the last decades to augment the water

supply in arid regions. Due to the high costs many countries are unable to afford the seawater

desalination technology. Nevertheless, the adoption of this technology by some countries has

demonstrated that seawater desalination offers a new water resource free from variations in

rainfall (Khawaji, et al., 2008). The direct use of seawater for toilet flushing can reduce the

highly treated seawater demand because does not require a strict treatment as for drinking water

and can be a potential solution to reduce the freshwater demand. One example of this alternative

is the dual water supply system that Hong Kong has been using since 1950’s (Lee and Yu,

1997).

Wastewater reuse is another alternative that has been recognized as an encouraging solution to

cope with the problem of water scarcity around the globe (Garcia and Pargament, 2015).

Reclaimed wastewater may also be used to restore the natural water bodies maintaining the

water quality to be environmentally friendly. Agricultural, fish farms, and park irrigations are

just some examples of the possible uses which can decrease the fresh water demand. Depending

on the type of reuse, different level of treatments can be chosen to comply with the standards.

One example of this alternative is the case of Singapore which imports water from Malaysia

since 1961 and due to failed water negotiations for extension from 2011 to 2061 Singapore was

forced to initiate with the NEWater study which consisted in the Singapore Water Reclamation

Study in 1998 to determine if reclaimed water treated comply with potable standards and if was

a viable source of water (Chew, et al., 2011).

Introduction 2

1.1 Background

Cuba is comprised by the Island of Cuba, Isla de la Juventud and several minor archipelagos.

Located in the northern Caribbean where the Caribbean Sea, the Gulf of Mexico, and the

Atlantic Ocean encounter each other. Due to its geographical location, topography and insular

character, Cuba is particularly vulnerable to climate change effects where water scarcity is one

of the consequences of major concern. Water scarcity is being affected also because water

sources with quality and quantity are insufficient, the water supply system is outdated and the

inappropriate wastewater treatments limits its reuse (López-Vázquez, et al., 2013).

According to CIH-UNESCO-IHE (2010) Cuba has a limited capacity of water storage and the

drought periods due to low precipitation has made the island susceptible to saline intrusion

which has been an increasing problem due to the excessive use of groundwater.

With a population of about 11.4 million (World-Bank, 2016)and a coverage of drinking water

sector in the urban areas reaching 98.2 % and in the rural zone an 87.3% around 79 % of the

population is receiving an intermittent service (average of 12 hours per day). It does not comply

with the normal standards of human use and consumption (López-Vázquez, Brjanovic,

Hooijmans and González Díaz, 2013).

Water scarcity in Cuba is being affected by the lack of water sources with the quantity and

quality to satisfy the water demand for human consumption. The old established water supply

network has a high percentage of water losses (55%) and the lack of an appropriate wastewater

treatment that can allow a possible reuse results in the intermittent water supply in Cuba (López-

Vázquez, Brjanovic, Hooijmans and González Díaz, 2013). This is a clear example of water

stress affecting a country, distributing around 1,220 m3/ person-year which is lower than the

United Nations (UN) minimum desired level of 1,700 m3/person-year. When water drops below

1000 m3/person-year the population faces water scarcity (U.N, 2014)

Water supply in Cuba estimates a demand of 604 LPCPD (Litre per capita per day) and around

55% are water losses due to leakage in the water supply network. The wastewater collection in

Cuba is up to 98%, but only 19% receives some treatment being discharged in the water bodies

affecting the freshwater sources (López-Vázquez, Brjanovic, Hooijmans and González Díaz,

2013).

Tourism in Cuba is one of the main sources of revenue for the island. Because of the beaches,

colonial architecture and cultural history, Cuba receives around 3 million of tourist per year

(World-Bank, 2016). Water consumption is around 1000 litres per tourist per day (Romero

López, et al., 2015, Torres-Rodriguez, 2015). The reduction of water consumption by the above

alternatives can contribute to the reduction of fresh water demand in the tourism sector. This

can enable more fresh water to the population, reducing one of the water problems and

potentially also contributing to solve the problematic of an intermittent water supply service.

Another important activity in Cuba is agriculture, and has been being affected by water

shortages because of drought and uneven precipitation that occur on the island. Agriculture in

Cuba is based on rice production, being this, basic in Cuban daily diet, grains, sugar cane, citrus,

banana, potato, and corn (F.A.O, 2016). However, a 70 to 80% of its domestic food is imported

Introduction 3

because of low agricultural productivity (W.F.P, 2016). To increase the agricultural production

the alternatives mentioned above like wastewater reuse for irrigation can be helpful and thus

contribute to the reduction of freshwater demand and thus reducing water scarcity in the

country.

Several cases can be used to illustrate the water scarcity issues affecting Cuba.

For example, in La Havana the touristic resort Villa Playa Hermosa in the city of Guanabo and

because of the proximity to the sea is one of the main options for National tourists with capacity

to hold around 54 guests. The actual situation in this city is critical. The overexploitation of the

freshwater wells has led to their exhaustion and intrusion of saline water to the wells themselves

and to the whole water supply system. This affects the whole population of the City of Guanabo,

including the economic sectors. For instance, the touristic resort previously mentioned pays

around $300.00 CUC1 (Banco-Central-Cuba, 2016) for saline water and a daily water truck of

8 m3 for $16.00 CUC per day which makes a total of $780 CUC per month. The yearly costs

rise up to around $ 9360.00 CUC. (Villasante-Castañeda, 2013)

In Matanzas, the city of Varadero, in the peninsula of Hicacos, is a touristic zone with several

hotels and, for instance, the hotels located in the end of the Peninsula (Punta Hicacos) discharge

the wastewater to the wastewater treatment plant (WWTP) of Hicacos located in the same area.

The total discharge from each room is around 378 L which 26.46 L are being reused for

irrigation representing a 7% of the total discharge (Torres-Rodriguez, 2015). With an increasing

and booming tourist sector it becomes essential to explore the potential increase in the reuse of

treated wastewater to alleviate the upcoming water consumption needs. This is a potential

strategy that an economic sustainability analysis should support.

In Mayabeque, the Hotel Breezes Jibacoa located in the Arroyo Bermejo Beach has 250 rooms

with one bathroom in between, pool area, bars, restaurants, nightclubs and sports area. This

hotel has a Reverse Osmosis (RO) treatment plant of two stages. Due to aggressive conditions

only one is in operation for a 24 hours period. Has a flowrate of 240 m3/day desalinating 233

m3/day. The water demand of the hotel ranges between 360-410 m3/day meaning that the plant

is insufficient and the water supply has to be covered by water trucks (Romero López, Lafargue

Verdecia, González Díaz and Medina Correa, 2015). The company responsible supplying water

has water trucks of 18, 20 and 30 m3 and different prices according to different circumstances

between $8.00, $9.75, or $ 21.00 CUC/ m3.

With a water consumption of 972 L and taking into account that 30 to 40 L/day is for toilet

flushing (López-Vázquez, Brjanovic, Hooijmans and González Díaz, 2013), a considerable

study can be done to implement the alternative of the seawater use for this particular activity.

Lopez-Vazquez (2013) analyses a case for the coastal zones of Cuba. Concluding that if the use

of this alternative source of water is applied to the 20% of the population living along the coastal

zone (4’631,377), a daily saving of 27’788,262 L/day or 27,798 m3/day of fresh water will be

achieved. This will be equivalent to a yearly saving of 10’142,716 m3 of fresh water.

According to the Standards, the tourist facilities pay $1.55 CUC per m3 of fresh water and $0.20

CUC per m3 of brackish water (Villasante-Castañeda, 2013). 1 tourist uses 30 L/day for toilet

1 $1.00 CUC = USD$0.87

Introduction 4

flushing that will be equivalent to $0.05/day. If brackish water is used the price will be reduce

to $0.003/day. If 3 million of tourists per year visit the island, using freshwater for toilet

flushing will cost around $150,000.00 while the use of brackish water will be $18,000.00 having

a total saving of $132,000.00 per year. This can be a promising strategy but inherently

associated operation and maintenance costs need to be considered to fully assess their potential

cost-effectiveness.

1.2 Problem Statement

The lack of an economic study in the area is leaving behind the implementation of the different

promising alternatives to reduce the fresh water demand. Replacing freshwater by the direct use

of sea water for flushing toilets and reuse of wastewater for irrigation can reduce the problem

of water scarcity.

As mentioned in a previous section the proposed alternatives have been implemented in other

places in the world. In the case of the use of saline water as a second quality water for toilet

flushing, Hong Kong has operated a dual water supply since 1950’s. The seawater supply has

contributed to preserve almost 16% of the freshwater supply which otherwise would be

provided for flushing toilet if seawater was unavailable (Lee and Yu, 1997). A study was made

evaluating flushing water sources in which the use of seawater for toilet flushing has the lowest

engineering cost compared with the use of raw freshwater and reclaimed water, even though

import and export pipelines are built for delivering seawater into and out of the seawater supply

zone (Tang, et al., 2007). The most recent innovative application in the Hong Kong

International Airport (HKIA) to conserve valuable freshwater resources was the

implementation of the triple water supply (TWS) system. This system saves up to 52% of

freshwater (Leung, et al., 2012).

For the wastewater reuse alternative there are several examples where it has been implemented.

In arid areas of Middle East and North Africa, wastewater reuse is commonly reused for

irrigation. In areas densely populated like Japan and without reliable water sources the

implementation of reuse systems have been implemented (Asanao, et al., 1996). Singapore

having one of the most crucial problems of water supply was forced to implement strategic

alternatives including local catchment, importing water, desalination and recycling water.

Adopting these options they develop NEWater (recycled water) by innovation. This enabled

the nation to successfully substitute 30% of freshwater demand (Chew, Watanabe and Tou,

2011). A study was made to analyse Singapore’s successive endeavours toward technology-

driven water. It shows how emerging economies can build up indigenous capabilities with long-

term planning and appropriate and timely government stimulations efforts. This is particularly

applicable since the intellectual property regime in most emerging economies is not well

enforced (Chew, Watanabe and Tou, 2011).

To assess the economic sustainability of these promising technologies applied in other parts of

the world but not validated in other latitudes like Latin America and the Caribbean, an economic

feasibility analysis can indicate whether they are or not promising alternatives to other regions

prone to and suffering of water scarcity like Cuba. A thorough analysis can help in the decision

making process concerning potential alternative water sources to reduce the freshwater demand

and contribute to minimize the water scarcity in Cuba, and regions with similar conditions.

Literature Review 5

CHAPTER 2

Literature Review

2.1 Water availability

2.1.1. Freshwater

Freshwater is all water forms on earth’s surface as ice sheets, icecaps, glaciers, icebergs, ponds,

lakes, rivers and streams and underground as groundwater in aquifers and underground streams.

Characterized by having low concentrations of dissolved salts and other total dissolved solids.

This term is used to differentiate to saline water (brackish or seawater). Fresh water is not

potable water due to the presence of chemical or biological contaminants.

Fresh water is mostly precipitation from the atmosphere in form of mist, rain and snow. In

industrialized areas rain is typical acidic because of dissolved oxides of sulphur and nitrogen

formed from burning of fossil fuels in cars, trains, aircrafts and factories. In coastal areas

freshwater may contain significant concentrations of salts derived from the sea if windy

conditions have lifted drops of seawater into the rain-bearing clouds. In desert areas rain-

bearing winds can pick up sand and dust and this can be deposited elsewhere in precipitation

and causing the freshwater flow to be measurably contaminated both by insoluble and soluble

components of the solids.

The climate in Cuba is tropical and characterised by a humid, warm and wet environment. The

maximum monthly temperatures in January around 16.7 °C and for August 31°C with a yearly

mean temperature of 24.5°C (Hernandez and Mon, 1996). The rainfall for the island is generally

high around 133 cm per year. The maximum yearly rainfall occurs on the western side of the

island (175 to 200 cm per year) and the minimum occurs in Guantanamo Bay area (71 cm per

year) (Solo-Gabriele and Perez, 2008).

Garcia Fernandez (2006) describes 8 watersheds along the country with several problems of

pollution. Almendares-Vento watershed and Ariguanabo which are close together presents

contamination of industrial and domestic wastewater with poorly treatment or untreated. The

Cauto Watershed is the largest in Cuba presents problems of soil erosion and poor drainage,

and the degradation of soil through salt accumulation. Similar problems of erosions occur in

The Cuyaguateje River which is located in Pinar del Rio. The Guantanamo-Guaso watershed is

known for its drought conditions, with some areas receiving less than 100 cm of rainfall per

year. The Habanilla watershed located in a mountainous terrain which has a large hydroelectric

plant and a man-made reservoir with very good water quality.

For example in the city of La Havana there are many small water supplies located along the

periphery of the city. Of the 55 water supplies along Almendares-Vento watershed, 42 are

Literature Review 6

freshwater and 13 are brackish. The water supply Vento Aquifer supplies 47% of Havana’s

drinking water and is located below one of the primary rivers (Almendares River) with a length

of 50 km and a contributing watershed of 402 km2 from the southeast to the northwest (Artiles

Egües and Gutiérrez Díaz, 1997).

2.1.2. Saline water (brackish or seawater)

Saline water is water that contains a significant concentration of dissolved salts (mainly NaCl).

The United States Geological Survey (USGS) classifies saline water in three salinity categories.

Salt concentrations in slightly (1000 to 3000 ppm), moderately (3000 to 10,000 ppm), and high

saline water (10,000 to 35,000 ppm) (USGS, 2016).

Seawater has a salinity of roughly 35,000 ppm equivalent to 35 grams of salt per one litre of

water (USGS, 2016). Brackish water has more salt concentrations than freshwater but not as

much as seawater. It may result from mixing of seawater with freshwater as in estuaries or in

brackish fossil aquifers. Certain human activities can produce brackish water, in particular civil

engineering projects such as dikes and the flooding of coastal marshland to produce brackish

water pools for freshwater prawn farming.

The over abstraction of freshwater wells has led to their exhaustion and intrusion of saline water

to the wells themselves and to the whole water supply system (Torres-Rodriguez, 2015). Also,

the large amount of yearly rainfall over most of the island water resources in Cuba are

susceptible to salt water intrusion. Salt water intrusion occurs probably due to pronounced

temporal variability of rainfall which results in exceedingly wet conditions followed by

exceedingly dry conditions or due to the topographic features of the island which promotes the

rapid loss of rainfall runoff to the sea (Scarpaci and Coyula, 2002).

Rainwater runoff reaches the sea within at most few hours. The mean length of all major Cuban

rivers is 93 Km. The country’s longest and most voluminous river (Cauto River) has a length

of 370 km. Other rivers as Sagua La Grande and Zaza has only 170 km and due to this short

distances the rainfall reaches the sea in a rapid way. Thus, a limited amount is recharged into

underground freshwater aquifers (Diaz-Briquets and Perez-Lopez, 1993). Thereby making the

aquifers vulnerable to saltwater intrusion from the coast.

For example in the city of La Havana as mentioned before in the previous section, 13 water

supplies from 55 are brackish. Another example is in the Hotel Breezes Jibacoa located between

La Havana and Varadero that has a desalination water treatment plant. Actually using

groundwater from two wells and due to the intrusion of saline water the desalination process of

Reverse Osmosis is included for the production of drinking water (Solo-Gabriele and Perez,

2008).

Literature Review 7

2.2 Water consumption

Water consumption in the world is based on different activities being agriculture with a 70% of

all water consumption. Followed by the industry with a 20% and a 10% for domestic use.

Industrialized countries have an 80% of water consumption in industries being the rest in

agricultural and domestic use (UN, 2006).

Regarding the domestic use, a high percentage of water consumption is for toilet flushing,

followed by the shower, washing cloth, dishes and others. In the following figure the

percentages for water consumption by activity according to WHO are shown:

Figure 1 Domestic water consumption by activity according to WHO

(HIDROCAPITAL, 2003).

Water consumption in the United States plays a big role starting from the thermoelectrical

power plant business and industries. Firefighting, municipal parks, and public swimming pools

all need high volumes of water. In the following figure is shown the percentages of water

consumption in the US.

40

48

24

4

20

Water consumption by activity according to WHO

Toilet flushing house cleaning dish washing Washing Cloth faucet shower

Literature Review 8

Figure 2 Percentages of water consumption in The United States (EPA, 2005).

In the United States the access to safe treated water is easily obtained. The average American

family uses more than 300 gallons of water per day at home. Roughly 70% of this use is indoors

and the rest use is outdoors. U.S Freshwater withdrawal (2005) apart from domestic use comes

from commercial, industrial, agricultural, and electric water use. The following figure shows

the U.S Freshwater withdrawals.

Figure 3 Water distribution by households in the U.S (EPA, 2005).

41.5

37

2.6 5

8.55.4

U.S Freshwater withdrawals (2005)

Thermoelectric Power Irrigation Aquaculture

Industrial Domestic Other public supplied users

26.7

13.7

5.321.7

15.7

16.8

Water distribution by households in the U.S

Toilet Leaks other Clothes washer Faucet Shower

Literature Review 9

2.2.1 Agricultural use

In Latin America and the Caribbean, more than 70% of freshwater use is in agriculture. Only

Brazil, Colombia, Cuba, Venezuela, and the countries in Lesser Antilles are below the regional

average (United Nations Environment, 2003). Regional values are shown in Table 1.

2.2.2 Industrial use

After agriculture, industry is the second largest user of water. However, in Latin America and

the Caribbean there are not industrialized countries and the amount of water use for the industry

sector is between 1 and 11%.

2.2.3 Domestic use

The most important uses for water are at our homes. Domestic water use is water used for indoor

and outdoor households purposes. Drinking, preparation of food, bathing, washing clothes and

dishes, brushing teeth, toilet flushing, watering the yard and gardens. Domestic use of water in

Latin America and the Caribbean fluctuates between 17 and 25% in the region as shown in

Table 1.

Table 1 Annual freshwater use per regions (United Nations Environment, 2003)

Area

Total water

consumption Agricultural

consumption per

sector in %

Industrial

consumption

per sector in %

Domestic

consumption per

sector in % Km3

Latin America and

the Caribbean 262.8 73.5 8.7 17.8

Caribbean 15.9 74 1 25

Mesoamerica 90 77.9 5.4 16.7

South America 156.9 70.9 11.4 17.7

Literature Review 10

2.2.4 Water consumption in Cuba

In Table 2 the water consumption of freshwater in Cuba is obtained from the Cuban Standards

of freshwater consumption. The following figures are used for water supply design and are

considered as the water consumption of freshwater in Cuba.

Table 2 Water consumption of freshwater in Cuba (NC-53:91, 1983).

Thousands

of people

Domestic

Use

Commercial

Use

Public

Use

Industrial

Use

Own

System

Total

Consumption

L/person-day

<2 145 87 44 15 9 300

2 to 10 160 96 48 16 10 330

10 to 25 175 105 51 18 11 360

25 to 50 190 112 57 19 12 390

50 to 100 200 116 59 20 15 410

100 to 250 215 125 62 22 16 440

250 to 500 220 132 66 23 19 460

>500 225 135 68 23 19 470

Tourism in Cuba is one of the main sources of revenue for the island. Because of the beaches,

colonial architecture and cultural history, Cuba receives around 3 million of tourist per year

(World-Bank, 2016). In this area water consumption has a different use than urban areas.

Potable water in the Touristic resorts is used in several activities depending on the water quality

received, for example in rooms, kitchens, restaurants, cafeterias, laundries, central air

conditioning systems, kids club, sport clubs, night clubs, service rooms for employees, the daily

replacement of water for pools for maintenance purposes, and irrigation for green areas in the

case that no wastewater reuse is available.

According to the Cuban Standards, the estimated water consumption as a function of the type

of touristic resort, accommodation or service are shown in Table 3.


Table 3 Water consumption for Hotels according to Torres-Rodriguez (2015).

Activity Unit m3/ unit

Hotels 4* and 5* Room 0.65

Hotels 3* Room 0.51

Hotels 1* Room 0.28

Motels 3* Room 0.60-0.70

Motels 1* and 2* Room 0.50-0.60

Restaurants User 0.04

Cafeterias User 0.03-0.006

Cafeterias ( fast food) User 0.15-0.012

Bars User 0.01

This values does not include:

A daily replacement of water for pools around 1.5% of the volume and a total

replacement of water every 3 months for maintenance purposes (60 L per day per

room).

Laundry service around 0.052 m3/ kg of clothes.

Central air conditioning system around 0.130 m3/room.

2.3 Water supply systems and technologies

2.3.1 Water supply

Water supply is the provision of water for domestic, urban, industrial, or agricultural use of any

type, for which the uptake of this resource in nature and the corresponding treatment is needed

before the distribution to the population.


Water is obtained from the available sources as surface or groundwater nearby the area. The

uptake for water consumption depends on the source. If it is surface water the uptake can be by

canals or pumping stations. If the source is groundwater the uptake must be through wells and

pumping stations in addition to this considering the groundwater table and the type of aquifer.

These sources of water do not have the characteristics for direct human consumption and is in

need of a drinking water treatments.

Drinking water in Cuba is available up to 72% through pipes. Via public taps or water trucks

around 21% of the population is served. Suggesting that 93% of the population is served by an

improved drinking water source (PAHO, 2000) from which 98% is access in urban areas and

82% access in rural areas (Vazquez, et al., 2002). The remaining 7% of the overall populations

without improved water sources. The time of service is also variable, PAHO (2000) reports that

79% of the population has access to an intermittent water supply (average of 12 hours per day).

The water supply system is unstable because pumps are in need of repair and because of

frequent interruptions in the electrical supply need to run the pumps. The network is in need of

additional water storage capacity and would benefit from increasing the interconnectedness of

various sections of the distribution network. Also, metering is needed to document water usage

by users, for purposes of charging for the water supplied (Hernandez and Mon, 1996).

2.3.2 Conventional water treatments processes

The conventional treatments process varies from the water quality of the source and consists

mainly of bars, sand trap, coagulation and flocculation, filtration, disinfection, sludge treatment,

desalination and softening.

Water treatment in Cuba is typically focused on Chlorination for disinfection. Some evidence

suggest that the water is not reliably chlorinated partly due to the lack of chlorine e.g. Canada’s

International Development Research Centre (2002) indicates that Santiago de Cuba chlorine

plant was no longer operating. In an attempt to improve the quality of drinking water within

this region, slow sand filters were installed within the area. This was an alternative mean for

treating water but not for disinfection. Urban systems with disinfection are estimated to be

around 84%.

Alonso Hernandez and Mon (1996) also reported that chlorination equipment at the water

treatment plant would benefit from improved maintenance. Given pressure losses of water

within the system due to intermittent power supply and lack of back-up generators, water within

the distribution system is at risk from contamination due to infiltration of untreated water during

times of low pressure. As a result, many residents are self-treating their water by adding

chlorine-tablets or boiling.

2.3.3 Advanced water treatments

Advanced desalination technologies are needed because saline water is unsuitable for human

consumption due to the high salt contents. Saline water can be considered to be unlimited source

of water and with the help of this advanced technologies can be converted into freshwater.


A seawater desalination process separates the saline water into fresh water with low

concentrations of dissolved salts and a concentrated brine. To obtain this separation a variety

of technologies has been developed over the years and can be distillation, membrane separation,

freezing, electrodialysis but the most important technologies are based on Multi-stage flash

(MSF), multiple-effect distillation (MED) , and Reverse Osmosis (RO) which has emerged as

the most cost-effective technology (Khawaji, Kutubkhanah and Wie, 2008).

Reverse Osmosis (RO) is a process that overcomes the osmotic pressure by applying external

pressure higher than the osmotic pressure on the seawater. Thus, water flows in the reverse

direction of the natural flow across the membrane, leaving the dissolved salts behind with an

increase in salt concentration. The major energy required for desalting is for pressurizing the

seawater feed. A typical large seawater RO plant consists of feed water pre-treatment, high

pressure pumping, and membrane separation and permeate post-treatment.

Pre-treatment is needed to eliminate the undesirable constituents present in seawater, which

could cause membrane fouling. The typical pre-treatments include chlorination, coagulation,

acid addition, multi-media filtration, and dechlorinating. The pre-treatment will depend on the

feed water characteristics, membrane type and configuration, recovery ratio and product water

quality (Sheikh, 1997).

After any of these treatments water is ready for storage, distribution and transport to the users.

Water storage is essential to comply with the water demand and water consumption of the

population. The capacity of Storages has to consider any emergency to supply the community.

Water reservoirs are essential in the water network. Water treatment plants (WTP) works well

if there are dealing with lower flows. Being the reservoirs the ones to receive the impact of the

water demand and not the WTP. The water network initially begins with the clean water

reservoir (CWR), pumping stations, main pipes, secondary and tertiary lines (Khawaji,

Kutubkhanah and Wie, 2008).

This technology has been introduced successfully during the last several decades to augment

the water supplies in arid regions of the world (Khawaji, Kutubkhanah and Wie, 2008). Due to

high costs, many countries are unable to afford these technologies as a freshwater source. RO

is a process using high amount of energy estimated around 3.5 to 5 kWh/m3 (López-Vázquez,

Brjanovic, Hooijmans and González Díaz, 2013) but recent research have been done to reduce

this energy consumption and operational costs showing values around 0.38 to 1.30 euro/m3

when is seawater and 0.21 to 0.43 euro/m3 when is brackish water (Karagiannis and Soldatos,

2008). Despite the reduction of costs, RO and other desalination processes remains expensive

and inefficient if comparable with the conventional treatments for drinkable water using surface

water as a source which have been estimated in 0.18 euro/m3(Costa and De Pinho, 2006).

In recent studies, the total cost of a project (CAPEX+OPEX), a seawater RO plant producing

100,000 m3/day is of 266 million USD. The average relative engineering procurement and

construction cost is of USD 1,207 per m3/day. This cost includes a 25.0% of equipment and

material, a 5.5% of membranes, a 1.5% in pressure vessels, 7.3% in pumps, a 2% in energy

recovery, 12.5% of piping and high grade alloy metals and a 69.5% of construction cost

(Linares, 2016).


2.3.4 Alternative sources (Seawater for toilet flushing)

Hong Kong is one of the most severe water-scarce areas in the world. Due to extremely high

population density the annual per capita renewable water supply is limited to only 125 m3. This

number is far below the scarcity level of 1000 m3 (World-Bank, 2007). To alleviate this problem

since the 1950’s Hong Kong has applied a dual water supply system which provides fresh water

for potable uses and seawater for toilet flushing.

The dual water supply system requires a separate network. One of them is for potable freshwater

supply and the other is for seawater for toilet flushing. The last one consists of pumping stations,

distribution mains and service reservoirs. Seawater is extracted and treated at the seafront

pumping stations and then supplied to the consumers via the water trunk and the distribution

mains (Lee and Yu, 1997).

Seawater for toilet flushing does not require treatment to the same standard as potable

freshwater, but its standard has to comply with the guidelines laid down by the authorities to

prevent objectionable characteristics. The current treatment is relatively simple and easy.

Seawater is screened by strainers to remove sizeable particles, and then disinfected by

chlorination before being pumped to service reservoirs and for distribution to consumers(Tang,

Yue and Li, 2007).

Figure 4 A typical sea water supply system (Water-Supplies-Department, 2016)


In Hong Kong, an electro chlorinator technique has been widely applied for the disinfection of

such flushing water instead of conventional chlorination process, because seawater contains

large amounts of sodium chloride. In some cases, after screening, aeration may be applied in

the intake culvert at the pumping station if the seawater is found to be low in dissolved oxygen.

The purpose of aeration is to refresh the water with sufficient oxygen to avoid anaerobic

conditions that may give rise to bad odours (Tang, Yue and Li, 2007).

Regarding water quality, as there is no other place in the world using seawater for flushing on

a larger scale and there are no international standards on using seawater for flushing. The Water

Supplies Department in Hong Kong proposed the Water Quality Objectives (WQOs) for sea

water at intake points of seafront pumping stations and the distribution systems for flushing

purposes in Hong Kong.

Table 4 WQO'S proposed by the WSD in Hong Kong (Water-Supplies-Department, 1992)

Hong Kong takes advantage of its close proximity to the sea and has been using sea water for

flushing toilets for more than 50 years. Their experience has shown that that the use of seawater

for flushing toilets is not a problematic since corrosion can be controlled by using materials that

can withstand the corrosive conditions (Lee and Yu, 1997).

The triple water supply (TWS) system in the Hong Kong International Airport (HKIA) is the

most recent example of conservation of water resources. The HKIA is situated on an artificial

island of 12 km2 and unlike other airports where the water conservation goal is mainly achieved

by reclaimed water and rainwater harvesting, the HKIA has a TWS system consisting of


freshwater supply system, seawater supply system for toilet flushing and air conditioning

system and a reclaimed greywater irrigation system (BAC, 2009, CA, 2009).

About 9000 m3/day of freshwater is used for catering services, water sinks, aircraft washing

and firefighting services in HKIA. To conserve the valuable freshwater resource, a grey and

black water separation system is provided for the terminal building, airport catering and

washing area while the rest is served by a combined system.

This system not only minimizes the risk of cross-connection between freshwater and seawater

supply as seawater can be easily detected through its taste, but also saves a significant amount

of energy and greenhouse gas emissions as compared to a water supply system supplying solely

potable freshwater. The application of this TWS system has been applied in the Hong Kong

International Airport with up to 52% of freshwater saved (Leung, Li, Yu, Chui, Lee, van

Loosdrecht and Chen, 2012).

Figure 5 Conceptual diagram of the TWS system

(Leung, Li, Yu, Chui, Lee, van Loosdrecht and Chen, 2012)


2.4 Wastewater treatment and technologies

Wastewater is any water that has been affected in quality by any human activity. Wastewater

can be originated by a combination of domestic, industrial, commercial or agricultural use,

storm water and from sewer infiltration. Municipal wastewater is usually conveyed in a sanitary

sewer and treated in a wastewater treatment plant (WWTP). Wastewaters generated in areas

without access sewer systems rely on on-site sanitation systems as septic tanks, pit latrines and

the worst case which is open defecation.

2.4.1 Conventional wastewater treatment

Conventional wastewater treatment consists of a combination of physical, chemical or

biological process and operations to remove solids, organic matter and sometimes nutrients

from wastewater. In general different degrees of treatment can be considered from a

preliminary, primary, secondary and tertiary or advanced wastewater treatments, and

sometimes some level of pathogen removal. Disinfection to kill pathogen organisms is needed

and is followed as a last treatment step. The sewage sludge that is produced in sewage treatment

plants undergoes sludge treatment.

In the preliminary treatment the removal of coarse solids and other large materials often found

in raw water occurs. A preliminary treatment typically is composed of coarse screens, grit

removal, flow measurements devices, often standing wave flumes are always included at this

preliminary treatment.

The primary treatment is basically the removal of settleable organic and inorganic solids by

sedimentation, and the removal of materials that will float by skimming. The secondary

treatment is the further treatment of the effluent from the primary treatment to remove the

residual organics and suspended solids. In most cases, secondary treatment follows the primary

treatment and involves the removal of biodegradable dissolved and colloidal organic matter

using aerobic biological treatment process.

One common example of the secondary treatment is the activated sludge. The dispersed-growth

reactor is an aeration tank or basin containing a suspension of the wastewater and

microorganisms known as the mixed liquor. The contents of the aeration tank are mixed by

aeration devices which also supply oxygen to the biological suspension. Following this aeration

step the microorganisms are separated from the liquid by sedimentation and the clarified liquid

is secondary effluent. A portion of the biological sludge is recycled to the aeration basin to

maintain a high mixed-liquor suspended solids (MLSS) level.

2.4.2 Advanced wastewater treatment

2.4.2.1 Membrane Bioreactor

Membrane bioreactor (MBR) specifically are a combination of bio treatment with membrane

separation by microfiltration (MF) or ultrafiltration (UF). Compared with conventional


activated sludge process (CAS), MBR ensures higher effluent quality for wastewater

reclamation and reuse. MBR’s have been widely used in wastewater treatment and reclamation.

The advantages offered by the process over conventional bio treatment process are widely

recognised (Henze, et al., 2008).

The configuration can refer to both the MBR process (and specifically how the membrane is

integrated with the bioreactor) or the membrane module. There are two main configurations:

submerged or immersed (iMBR), and side stream (sMBR). iMBR’s are generally less energy-

intensive than sMBR’s, since employing membrane modules in a pumped side stream crossflow

to scour the membrane incurs an energy penalty due to high pressures and volumetric flows

imposed.

Figure 6 MBR process configuration

This advanced technology has gained increasing popularity in municipality/domestic and

industrial wastewater treatment, in particular in the places where the footprint is limited and a

high product water quality is demanded (Judd, 2008). To date, there have been at least 50

individual MBR membrane suppliers and hundreds of large-scale MBR plants (with treatment

capacity larger than 10.000 m3/day) in operation worldwide (Wang, et al., 2008). In addition to

this, MBR systems are expected to continuously increase in capacity and broaden in application

areas due to more stringent regulations and water reuse initiatives.

The costs for complete MBR facilities have also been declining. For example, in 2001, the total

price of water for unrestricted urban irrigation produced by a 3800-m3/day MBR was $0.80/m3.

By 2004 the same facility declined to $0.48-$0.58/m3 (Daigger, et al., 2005). Despite of its

alleged benefits of better treatment performance and occupation of much less land, broader

application of MBR’s is still hindered by their relatively high construction cost and energy

consumption. Choosing between MBR and CAS for wastewater treatment remains unsettled,


even some researchers and engineers now reconsider whether MBR has been the best choice

for various engineering cases (Lesjean, et al., 2011).

Larger municipalities often include factories discharging industrial wastewater into the

municipal sewer system. If the final disposal requires higher quality than that given by the

secondary treatment, a polishing method must be used as a tertiary treatment. Nowadays

industrialised countries are applying most common technologies as microfiltration or synthetic

membranes. After membrane filtration, the treated has an excellent quality (Hammer, 2001).

2.4.2.2 SANI Process

Since the introduction of the Biological Nitrogen Removal (BNR) process in 1960’s (Ludzack

and Ettinger, 1962), the key biological process in municipal sewage treatment works has been

relying on the electron flow from organic carbon and nitrogen cycle, namely autotrophic

nitrification and heterotrophic denitrification. Depending on the sludge age, about 50-60% of

the organic carbon in the sewage will be converted to CO2 and the remaining to sewage sludge.

The innovative advanced technology developed by a research team from Honk Kong University

of Science and Technology (HKUST) called SANI Process which stands for Sulphate

reduction, Autotrophic denitrification and Nitrification Integrated process is an energy efficient

and low carbon sewage treatment technology that uses Sulphate in seawater as an oxidizer to

eliminate pollutants. It has shown remarkable results for saline wastewater treatment (Figure 7)

(Tsang, et al., 2009).

In the first stage of the SANI process, organic matter is removed anaerobically by sulphate

reducing bacteria (SRB) which grow on the sulphate concentrations (up to 600 mg/L)

outcompeting the methanogenic bacteria and producing sulphide (Lu, et al., 2009). In the

second stage autotrophic denitrifying organisms use the sulphide present in the water phase as

electron donor and the nitrate recirculated from the aerobic phase (third stage) as final electron

acceptor for denitrification purposes. Thus, sulphide is oxidized to sulphate during

denitrification ensuring full sulphur recovery and negligible hydrogen sulphide losses to the

environment (Lu, Wang, Li, Chen, van Loosdrecht and Ekama, 2009). Furthermore, CO2

production has been observed to be also negligible as most of the influent COD is converted to

alkalinity (Lu, Wang, Li, Chen, van Loosdrecht and Ekama, 2009). Finally in the third stage,

ammonia is aerobically oxidized to nitrate by nitrifying bacteria and recirculated to the anoxic

phase to drive the autotrophic denitrification and accomplish nitrogen removal (Tsang, Wang,

Lu, Li, Chen and van Loosdrecht, 2009).

Since all microorganisms involved in the SANI process are slow-growing bacteria, zero sludge

discharge has been observed (Lu, Wang, Li, Chen, van Loosdrecht and Ekama, 2009), which

makes it also very attractive in view of the major environmental concerns and high costs

associated to sludge handling and disposal (Øegaard, 2004).


Figure 7 The SANI process concept (Tsang, Wang, Lu, Li, Chen and van Loosdrecht, 2009)

2.4.3 Wastewater reuse systems

Wastewater can be reused after treatment or barely treated for a variety of beneficial purposes.

The direct wastewater reuse system consists of directly using the reclaimed effluents for urban

or agricultural purposes. (Bouwer, 2000) Untreated or barely treated wastewater may also be

reused for irrigation of crops following some technical guidelines to reduce health and

environmental risks. (WHO, 2006). The most relevant benefit of the direct wastewater reuse is

making a new water supply source available. This new source guarantees a high level of supply

reliability because its production is constants through the year and in between years (Friedler,

2001) which will bring benefits to users that suffer water shortages (Mesa-Jurado, 2012).

Reclaimed wastewater may be used to restore the previous characteristics of the natural water

bodies’ ecological status. This is the traditional wastewater disposal into a receiving media, but

fulfilling certain water quality and quantity standards, to restore wetlands, wildlife refuges,

urban lakes and rivers (Plumlee, 2012).

Several examples of this alternative source is being implemented in different parts of the world.

In the arid areas of Middle East and North Africa, wastewater is commonly reused for urban

irrigation. In japan, dense urban areas without reliable water sources have required the

development of innovative dual reticulation systems where wastewater is reused (from sink to

toilet flushing), within buildings, districts, and cities. In California, high per capita water

demand in densely populated cities has led to indirect potable reuse of wastewater. Wastewater

is treated to a high standard, pumped underground to replenish groundwater aquifers, and then

abstracted and transmitted as potable water.

Almeria province is an arid region of the southern Spain. The main activity of the region is

irrigated greenhouse horticulture (market gardening) which is spread over a surface of 22,000

ha. Due to over abstraction of the groundwater resources, saline intrusion appeared resulting in

abstraction from deeper aquifers. However, the pumped water salinity reached 3 g Cl/L and the

pumping costs increased to a point where it became too expensive for the farmers (Thomas and

Durham, 2003). The wastewater treatment system used is an activated sludge. The effluent is

then stored in a 10,000 m3 reservoir and treated through rapid sand filtration. Then is followed

by an ozonation system and is stored in a reservoir before gravity distribution to the farmers

occur.


Livermore is located southeast of San Francisco in the centre of California. The climate is semi-

arid. The main water sources are from the local aquifers and imported water. The treatment

plant is mainly a primary treatment followed by an activated sludge. Most of the effluent is

disinfected before being discharged into the San Francisco Bay, the remaining flow passes

through activated carbon filters and disinfection and then irrigates golf courses (up to 4,600

m3/day)(Thomas and Durham, 2003).

Singapore located just one degree north of the equator, south of the southernmost tip of

continental Asia and peninsular Malaysia, with Indonesia’s Riau Islands to the south is having

one of the most crucial problems related to water supply. It is dependent on a 33% on imported

water. As a consequence, strategic options including local catchment, importing water,

desalination and recycling water were adopted. Singapore has adopted these options uniquely

to develop NEWater (recycled water) by innovation which has enabled the nation to

successfully substitute 30% of freshwater demand (Chew, Watanabe and Tou, 2011).

The production process NEWater involves a comprehensive system of innovation conferred by

a sophisticated combination of innovation in membrane technologies and the optimal utilization

under extremely subtle operating parameters, enabling technology substitution for

conventionally treated water. The process has a conventional wastewater treatment in the water

reclamation plants in which the effluent is treated in the first stage of the NEWater production

process using membrane technology (microfiltration or ultrafiltration) to remove suspended

solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts. The filter

water after passing through the membranes contains only dissolved salts and organic molecules.

To remove the salts and organic molecules, this effluent is treated in reverse osmosis process

which will be the second stage of the NEWater production process. A semi permeable

membrane filters out contaminants such as bacteria, viruses, heavy metals, nitrates, chlorides,

sulphates, disinfection by-products, aromatic hydrocarbons, and pesticides. After these process

NEWater is thus free from viruses and bacteria and the water is of potable quality. But still for

safety precaution a third stage in the NEWater production process of UV disinfection is used to

ensure that all organisms are inactivated and the purity of the water can be guaranteed (Chew,

Watanabe and Tou, 2011).

The first year tender price for NEWater was S$0.30/m3 or USD$0.23/m3 which is significantly

less than the cost of desalinated water in Singapore. The selling price of NEWater is S$1.15/m3

or around USD$0.85/m3 which is covering production, transmission and distribution costs.

Because the production costs of NEWater is less than that of desalinated water, future water

demands plan to be covered with more NEWater rather than with the construction of

desalination plants (Chew, Watanabe and Tou, 2011).

2.5 Social and economic evaluation of projects

2.5.1 Principles

Profitable capital investment leads to the growth and prosperity of an economy. If profitability

is low, investment will be reduced. The investor needs tool to predict the profitability of


proposed investments (Remer and Nieto, 1995).There are many methods and techniques that

can be applied to help the investor make wise economic decisions. These evaluation methods

and techniques can be applied to independent projects to determine whether or not to invest in

each one, or they can be applied to several mutually exclusive projects for the purpose of

determining which, if any, should be pursued (Remer and Nieto, 1995).

To understand the use and application of most project evaluation methods, concepts as time

value of money (TVM), cash flow diagrams, minimum attractive rate of return (MARR) and

economic evaluation factors is required to be known. In the following table formulas, symbols

and purpose of each concept are shown.

Table 5 Economic evaluation factors (Remer and Nieto, 1995)

The steps of an economic evaluation are:

Define a set of investment projects for consideration

Establish the planning horizon (or analysis period) for economic study

Estimate the cash flow profile for each project

Specify the time value of money or minimum attractive rate of return (MARR)

Examine the objective and establish criteria to measure effectiveness

Apply the project evaluation technique (s)

Compare each project proposal for preliminary acceptance or rejection

Perform sensitivity analysis

Accept or reject a proposal on the basis of the established criteria


2.5.2 Project evaluation tools

There are many different evaluation tools; some are more widely used than others. According

to Remer and Nieto (1995) they categorized many various methods of project evaluation into

five basic types: net present value method, rate of return methods, ratio methods, payback

methods and accounting methods. Each method is shown in the following table.

The most popular techniques are the net present value criterion methods, the internal rate of

return method, external rate of return method, return on investment method, benefit/cost ratio

method and payback period method.

Table 6 Project evaluation techniques (Remer and Nieto, 1995)

2.5.2.1 The net present value methods

The net present value criterion method (NPV) is also known as the net present worth criterion

(Remer and Nieto, 1995). The net present value criterion method can be divided into four

subtopics or time analysis periods: present worth, future worth, annual worth, and capitalized

worth method.

One assumption that must be made whenever using any of the equivalence methods is that all

cash flows received from a project are reinvested at the same fixed rate used to calculate the

equivalent worth (Remer and Nieto, 1995). This rate is known as the minimum attractive rate

of return (MARR). Since all four methods are needed to judge the profitability of a project.

Thus, the use of the term net present value encompasses all the equivalence methods.


The present worth method examines the cash flows of a project over a given period of time and

resolves them to one equivalent present date cash flow through the use of an economic factors

listed in table 5. This method provides an easy way to evaluate projects by moving all cash

flows to the present. The steps to apply the present worth method are the following:

Determine the interest rate for which all future cash flows can be reinvested. This is

known as the required rate of return or minimum attractive rate of return (MARR)

Estimate the economic useful life of the project

Estimate the positive and negative cash flows for each period over the analysis period

Calculate the net cash flow of each period

Calculate the present worth of each of the net cash flows.

In general, a project is accepted if the net present value is positive and rejected if the net present

value is negative. If the net present is equal to zero, then the investor is indifferent to the project.

Also, if two or more projects are considered, the project which has the greater present value is

generally selected (Miranda, 2005). However, depending on the project situation, a project with

a lower present worth may be better.

Similarly, the future worth method resolves them to one equivalent cash flow at a future date.

This method can be thought of as a way to determine the future consequences of an investment.

The process for calculating the future worth of a project is similar to the one of the present

worth. Except that all cash flows are resolved to a future date, usually the end of the projects

life. The factors used when calculating this value are in table 5. Just as with the present worth

method, a project is accepted if the future worth is positive and rejected if the future worth is

negative. As before, if the future worth is equal to zero, then the investor is indifferent to the

project.

The annual worth method also examines the cash flow of a project, but does not resolve them

to any one cash flow at any one date. Instead, the annual worth method resolves all cash flows,

but, over an infinite time period from any given starting date. One disadvantage of this method

is that ignores the size of the project.

2.5.2.2 The internal rate of return

The internal rate of return method (IRR) is a measure of investment worth which calculates the

interest rate for which the present worth of a project equals to zero. The term “internal” implies

that the interest rate does not represent any “external” factors, such as the MARR, but only

“internal” confines of the cash flow (Remer and Nieto, 1995). Although this method does not

included the MARR in the calculation, the criteria to accept or reject a project depends on the

available MARR. If the interest rate is greater than MARR the project is accepted. If the interest

rate is less than the MARR the projects is rejected and if the interest is equal to the MARR,

then the investor remains indifferent to the project.

The calculations are based on the net present value criterion method, those same assumptions

of immediately reinvesting all future cash flows at the same interest rate must still hold. In

general, the value for interest of any project can be found either by using the exact formula


given in table 5 and solving directly for interest, or by using tables of interest factors for various

interest rates.

2.5.2.3 Return on investment

There are two variations of the return of investment (ROI) method. The first is the return on

original investment method. The second is the return on average investment method. The return

on original investment method measures a percentage relationship between the average yearly

profit and the initial investment the return on average investment method measures the

percentage relationship between the average yearly profit and the average yearly investment.

The amounts used to calculate the average are not discounted or not considering the time value

money (TVM) (Almond and Remer, 1979).

The return on original investment can be expressed as:

𝑅𝑂𝐼 = 𝐴𝑌𝑃

𝐼

Where: AYP is the average yearly profit

I is the initial investment

The return on average investment can be expressed as

𝑅𝐴𝐼 = 𝐴𝑌𝑃

𝐴𝑌𝐼

Where: AYP is the average yearly profit

AYI is the average yearly investment

This method does not have a set criteria for project acceptance. The greater rate is the one said

to be more favourable. One disadvantage is that this method does not consider the time value

of money and Remer and Nieto (1995) recommends the use of more than just one project

evaluation technique when used the rate of investment method.

2.5.2.4 Benefit/Cost ratio

The benefit/cost ratio method (B/C) was introduced primarily as a result of the US

Government’s need to evaluate project proposals submitted to Congress. In the 1930’s Congress

established the criterion for the acceptance of a project, which stated that the “benefits” of a

project must outweigh the “costs”. Thus the benefit/cost ratio method developed out of

Congressional legislation (Almond and Remer, 1979).

The criteria for the benefit/cost ratio method is described in the following table:


Table 7 Acceptance criteria for the benefit/cost ratio method

Benefit Cost Ratio (B/C) Decision

Positive Positive >1 Accept

Positive Positive equal 1 Indifferent

Positive Positive <1 Reject

Positive Negative any Accept

Negative Positive any Reject

Negative Negative >1 Reject

Negative Negative equal 1 Indifferent

2.5.2.5 Payback period method

The payback period method (PP) examines the number of years required for a project’s earnings

to equal the initial investment. In other words, it is the amount of time required for the project

to pay for itself. Thus, the name payback period method (Almond and Remer, 1979)

The procedure for applying the payback period method is analogous to the procedure for

applying the internal rate of return method. The only difference are that (1) the unknown

variable is n and (2) not all future cash flows need to be considered. Remer and Nieto (1995)

reported that most companies usually use either the net present value criterion method or the

internal rate of return method in conjunction with the payback period method.

There are two commonly used types of the payback period method. They are the conventional

payback period method and the discounted payback period method. The conventional payback

period method is sometimes easier to explain to people unfamiliar with project evaluation

techniques. However, the conventional payback period method assumes an interest of 0% while

the discounted payback period method usually uses the MARR. This is one criteria used to

recommend the discounted payback period method. In the case of two or more projects, the

project with the lowest payback period is usually preferred.

One of the disadvantages of this method is that it does not look at the cash flows after the

payback period. The cash flows after the payback period determine the project’s rate of return.

Remer and Nieto (1995) states that the payback period method should be used in conjunction

with other methods, such as the internal rate of return method or the net present value criterion

method.


An advantage of this method is that it sometimes provides a quick way of determining the risk

of a project based upon the length of the payback period. Also, as with the annual worth method,

this method is often easier understood by people without an economics background.

2.5.2.6 Other methods

Other less common methods include the life cycle costing method, maximum prospective value

criterion method, growth rate of return method, and profit to investment ration method, cost

effectiveness method, project balance method, and accounting methods. Remer and

Nieto(1995) states that no project evaluation using these methods was ever done without using

either the internal rate of return method or the net present value criterion methods.

2.5.3 Summary of project evaluation techniques

Table 8 Summary of project evaluation techniques characteristics (Remer and Nieto, 1995)


2.5.4 Case studies

2.5.4.1 Case 1. Comparison of engineering costs of raw freshwater, reclaimed water and seawater for toilet flushing in Hong Kong. (Tang, Yue and Li, 2007)

Hong Kong is a coastal city with a population of about 6.9 million and successfully utilizes

“dual water supply systems” operated by the Water Supplies Department (WSD) of Hong Kong

government from the 1950’s. The dual water supply systems include a freshwater distribution

system for potable use and a seawater distribution system for toilet flushing.

For this study seawater, raw freshwater from the Guaungdong of China and treated effluent

from the sewage treatment plant (STP) are assumed to be three water resources for the separate

flushing systems. Four areas of study were selected, in which they denominated Southern

District (SD), Sai Kung (SK), Northern New Territories (NNT), and Northwest New Territories

(NWNT). Six cases in the different areas of the country were selected to carry out an

engineering cost comparison. The cases were:

(1) The toilet flushing system using seawater in SD, SK, NNT, and NWNT.

(2) The toilet flushing system using raw water in SD, SK, NNT, and NWNT.

(3) The toilet flushing system using reclaimed water in SD, SK, NNT, and NWNT.

(4) The toilet flushing system using seawater in SD and SK, and raw water in NNT and

NWNT.

(5) The toilet flushing system using seawater in SD and SK and reclaimed water in NNT

and NWNT.

(6) The toilet flushing system using seawater in SD and SK, and raw water in NNT, and

reclaimed water in NWNT.

More possible cases can appear but only this six have been considered by the authors as sensible

and worthwhile for comparison.

In the analysis, the time duration (or time horizon) for comparison was the same for all six

cases. A time horizon of 60 years was assumed, which was the least common multiple of three

important renewal years of different categories of facilities: 15 years of E&M (electronic and

mechanical) equipment, 20 years for seawater mains, and 30 years for freshwater mains, plant

and machinery and meters. It was also assumed that water demand and supply was constant

throughout the running period of 60 years.

The NPV method was used for carrying out the comparisons. The NPV determined from the

calculation will be used to compare directly the engineering costs of the cases.

NPV= Fo +F1/ (1+i)1 + F2 +F2/ (1+i)2 +… + Fn +Fn/ (1+i)n

Where Fn is the net cash flow or (income – expenditure) in year n. Expenditure includes the

running cost for each year (n=1, 2,…, 60), the capital cost when n=0, the renewal cost when

n=30 for the freshwater, raw water and reclaimed water supply systems, and the renewal cost

when n=20 and 40 for the seawater supply system. E&M items are renewed when n=15, n=30,

n=45. The incomes for the six cases are not considered in this study and are assumed to be the


same in all cases, because they are practically so. If they are not considered, their values are set

to be zero when the above NPV formula is applied, and therefore the NPV calculated for each

of the six cases is in fact the present value of total cost. This will adequately serve the purpose

of the study to compare the present values of total costs of the six cases.

The results of this study showed that the dual water supply systems by adopting seawater for

toilet flushing in these areas have the best engineering economy then raw freshwater and then

reclaimed water. The use of seawater for toilet flushing is less expensive than the other options.

In addition using seawater provides a number of benefits, including reliability of supply,

cutting, cutting down the demand for potable water and reducing reliance on Dongjiang water.

The use of reclaimed water is more expensive than using raw water. But if the price of raw

water increases in the same way as it has been increasing the situation will reverse after some

time. From the results of cases 2 and 3, the NPV’s are HK$ -2492M and -2740M, respectively.

The current unit price of raw water purchased is HK$3.085/m3. When this unit increases and

reaches certain level, the raw water alternative would no longer be attractive. Repeated trial

calculations have been carried out by adjusting the unit price of raw water, and when the uit

price increases to HK$4.25 (based on year 2000 money value), the NPV of case 2 would

become HK$-2740M and is equal to the case 3.

Similar results were obtained when evaluating cases 5 and 6. This concludes that although the

use of reclaimed water is more expensive than that of raw freshwater at present, the situation

may reverse after some time if the price for raw water increases in the same way if=t has been

doing. The other conclusion was that the use of seawater for toilet flushing has the lowest

engineering cost compared with the use of the other water sources even though import and

export pipelines are built for delivering seawater into and out of the seawater supply zone.

2.5.4.2 Case 2. Cost-benefit analysis in the Yarqon Recycling Project case study in Israel. (Garcia and Pargament, 2015)

The Yarqon River flows through the Tel-Aviv Metropolitan Area and was once the second

biggest river in Israel in terms of volume of flow. Before the 1950’s, its annual discharge was

220 million m3 coming mainly from springs supplied by a large Karst aquifer. However, after

the creation of the State of Israel in 1948, the demand for water for agricultural, industrial and

drinking purposes increased, and so pumping rates from the aquifer almost ended the flow of

spring water into the Yarqon River (Garcia and Pargament, 2015).

As predetermined in the Yarqon River Rehabilitation project, in the upper reach of the river,

since the 1990’s the river received 200 m3 of the spring water pumped every hour from the

Yarqon Spring pumping station, allocated by the National Water Authority. In recognition of

the ecological needs of the river, this rate of flow was increasing, by June 2011 to 600 m3/h and

to 850 m3/h in July 2012.

In the middle and lower reaches of the river one of the main priorities was to stop the discharge

of poorly treated sewage water to this area. The Yarqon River Authority prompted upgrades to

the Kfar Sava-Hod Hasharon wastewater treatment plant (WWTP) established in 2009, and the


Ramat Hasharon WWTP, completed in 2011, by improving the water quality to a tertiary lever

treatment. Nowadays, the volume discharged into the river comply with the standards of the

Public Health Regulations.

By 2016, the National Water Company of Israel, Mekorot, will operate a water reuse facility

for the water flowing in the river at the end of the middle section. This facility will use a

submerged membrane bioreactor in order to enable reuse of the water for irrigating Tel-Aviv’s

parks as well as parks in the neighbouring municipalities. The main park that will reuse this

water for irrigation is the Yarqon Park. The reuse system will also supply water to the farmers

who currently are extracting water directly from the river and this will allow more flow in the

river. They state in this case that installing a water reuse facility downstream is the best solution

to solve the issues between competing uses of water for environmental and irrigation purposes.

The economic feasibility assessment of the Yarqon recycling project consists of a cost-benefit-

analysis. The procedure to achieve the objective consists of five steps.

Step 1. Selecting and evaluating the wastewater reuse plan: In this cases a “do nothing”

scenario is natural water body augmentation, and evaluated plan is an indirect

wastewater reuse plan, in this case the Yarqon Recycling Project. They applied a cost-

benefit analysis for a 20 year period to determine the economic efficiency of the project.

Step 2. Estimating the internal costs of the project: The total initial investment was

estimated to be $14,700,000 over the period 2014-2016. The capital costs of the pipes

represented a 5.84% of the investment costs ($857,000). The operation and

maintenance costs were estimated to be $0.16/m3. For this study three scenarios were

considered in the cost-benefit analysis, pessimistic, base case, optimistic. To take into

account the uncertainty in the capital and operating and maintenance cost estimates, a

range of -20% and +30% of the base-case was uses to estimate the optimistic and

pessimistic scenarios (Halaburka, et al., 2013).

Step 3. Estimating the external trade off: In this step the benefits and costs for

agricultural usage, urban use and environmental use were evaluated. For the agricultural

use elements as the water price of treated water, fertilization savings, and crop

composition were indicators. For the urban usage water price for park irrigation and

recreational costs were the indicators. For the case of the environmental usage the

pollution that could generate the discharge of nitrogen and phosphorus were indicators

to evaluate.

Step 4. The implementation of the cost-benefit analysis: for this study, a 3.5 and a 5.5%

discount rates are used to calculate both the present costs and benefits in the optimistic

and pessimistic scenarios. The net present value results for the base case scenario were

approximately $4.83 million. For the optimistic scenario resulted in $39.70 million.

However for the pessimistic scenario was negative with a result of -$26.92 million. This

results shows that the benefits obtained from the supply of water for irrigating the urban

parks are the factor that contributed the most benefits side, proportionally higher than

the benefits obtained from water supply for agricultural irrigation. The recreational costs

derived by the attitudinal impact on park visitors represented the largest costs in the

calculation of the net present value.

Step 5. A sensitivity analysis: the evaluation of the impact on the net present value

because of the uncertainty of the cost-benefit analysis parameters. A multi regression


analysis with standardized regression coefficients was used for that purpose.

Standardized regressions coefficients method requires performing Monte Carlo

simulation, 5000 in this case in order to get stable estimates of the coefficients.

Regarding the results it was found that obtaining a positive net present value was

64.28%. The simulated median net present value was %3.53 million, the percentile 25

was approximately -$2.57 million, and the percentile 75was $9.52 million. The

estimation of the standardized regression coefficients made possible to indicate which

of the input parameter has the greatest influence on Net Present Value. The 3 parameters

with a higher value of influence in the Net Present Value were: (1) the rate of change in

the recreational costs, (2) the water price for urban park irrigation, (3) the rate of change

in the capital costs.

The main objective of this CBA was to analyse the economic, social and environmental aspects

around the concept of wastewater reuse in order to assist policy makers, managers on the

implementation of the economic instruments for decision-making. The results of this cost

benefit analysis showed an economic viability obtaining a positive Net Present Value but when

a risk analysis was implemented the Net Present Value was not that high as expected.

The implementation of economically based decision-support tools has become essential in order

to advance towards water efficiency and assisting decision-makers in achieving Integrated

Water Resources Management socio-economic goals. As a relevant element in water

management particularly in water scarce regions, will require a helpful use of tools like cost-

benefit analysis. However, external costs and benefits also have to be considered to properly

assess the trade-offs involved in these kind of schemes (Garcia and Pargament, 2015).

Research questions 32

CHAPTER 3

Research questions

3.1 General Question

Is economically feasible the implementation of innovative alternative sources of water under

Cuban conditions to reduce the freshwater demand and alleviate water scarcity?

3.2 Specific research questions

1. What is the economic feasibility of the implementation of seawater for toilet flushing

in Cuba as an innovative alternative source of water to reduce freshwater demand?

2. What is the economic feasibility of practicing the treated wastewater reuse as

innovative alternative water source to reduce freshwater demand?

3. Is economically feasible to combine the use of seawater for toilet flushing and the reuse

of treated wastewater to reduce freshwater demand and contribute to alleviate water

scarcity?

Research approach 33

CHAPTER 4

Research approach

The following study will be done in three phases to carry out the Economic feasibility analysis

of the innovative water management approaches. In this research, four case-studies will be

selected to assess the feasibility of the innovative water practices: (1.) A case-study to assess

the use of seawater for toilet flushing by the Cuban population, (2.) A case-study at the touristic

resort Villa Playa Hermosa to study the potential replacement of freshwater by seawater for

toilet flushing and other potential non-potable uses, (3.) A case-study at Punta de Hicacos, in

La Peninsula de Varadero, where the potential reuse of treated wastewater is studied and (4.) A

case-study at Hotel Breezes Jibacoa, where the potential combination of seawater for toilet

flushing, wastewater reuse and seawater desalination are combined.

Figure 8 shows the research approach that was carried out in this study. The first phase consisted

of the Data Collection. The determination of capital expenditures (CAPEX) or all the

investment costs and operational expenditures (OPEX) mostly composed of the operation and

maintenance costs. The second phase involves the Economic analysis based on the Net Present

Value, economic and social benefits on the four cases. In the third phase, a scenario analysis

was undertaken incorporating a sensitivity analysis from each selected scenario on each of the

four case studies.

For the case study No.1, the sensitivity analysis was performed with the purpose of determining

the effects of water shortage periods from 1 to 9 months on the estimation of the cost, benefits,

and the indicators of interest. In the same way, for the case 2, the effects of experiencing water

shortage periods of 1.5, 3, 6, and 9 months. For the Case-study 3, the Hicacos WWTP, the

effects of the replacement of the membrane replacements every 5, 6, 8, 10 or 12 years were

studied on the overall costs. The upgrade of the RO desalination plant with the use of seawater

for toilet flushing and the membrane replacements for the WWTP of the hotel every 5, 6, 8 and

12 years were considered to execute the sensitivity analysis of the for the Case-study 4.

Research approach 34

Figure 8 Research approach of the study

Research Objectives 35

CHAPTER 5

Research Objectives

6.1 General Objective

To assess the economic feasibility of the implementation of innovative alternative water

sources under Cuban conditions to reduce freshwater demand and alleviate water scarcity.

6.2 Specific Objectives

To evaluate the economic feasibility of:

1. The implementation of seawater for toilet flushing as an innovative alternative source

of water to reduce freshwater demand in Cuba.

2. Of practicing the treated wastewater reuse as innovative alternative water source in

Cuba to reduce freshwater demand.

3. Of combining both, seawater use for toilet flushing and treated wastewater reuse, as

innovative alternative water sources to reduce freshwater demand and contribute to

alleviate water scarcity in Cuba.

Methodology 36

CHAPTER 6

Methodology

Based on the previous literature Review, this chapter presents the methodology that was applied

to execute an economic analysis based on the net present value criterion method (NPV) with

the objective of assessing the economic feasibility of the implementation of innovative

alternative water sources to reduce freshwater demand and alleviate water scarcity in Cuba.

This analysis was performed in three phases:

7.1 Phase 1. Data Collection

The first phase was the Data Collection. The determination of capital expenditures (CAPEX)

or of all the investment costs, and operational expenditures (OPEX) or operation and

maintenance costs. In order to gather accurate information, in this research two main ways to

collect data are identified: Primary data and secondary data.

6.1.1. Primary Data

The primary data was collected in two ways:

Interviews: A face-to-face interview was designed to gather information to collect more precise

information of CAPEX. Meetings with constructors, designers, directors in the ministry of

construction as a starting point to find out who is familiar with the facility and can provide

accurate information about real costs of capital investment. Capital investment can be divided

into initial capital costs and the renewal costs of the facilities. This included the costs of

purchasing equipment and the land costs. However, the land on which the facilities are going

to be built are owned by Cuba. This kind of information could be verified through interviews

directly with the corresponding authorities. As such, land costs were ignored. In the case of

Hotels, this information was gathered by questionnaires. The water work facilities for

freshwater supply system will include impounding reservoirs, water treatment plants, pumping

stations, service reservoirs, water mains. When upgrading RO water plants, the main costs were

represented mostly by the energy consumption and the investment costs for the upgrade. For

the case of the seawater supply system the facilities include only pumping stations, service

reservoirs, and seawater mains.

Questionnaires and surveys

This method was used to obtain data from the final users, directors and operators of hotels and

directors of water utilities. The results obtained from this method focused on the OPEX. These

Methodology 37

are expenditures spent every year in order to the hotels operate successfully. Other parameters

were water consumption, occupancy and awareness of flow rate in water supply appliances and

sanitary equipment to improve efficiency of water use. This information together will allow to

continue with the next phase of this research.

The interviews were hold with:

Owner of Hotel Playa Villa Hermosa

Director and Economist of Hotel Breezes Jibacoa

Director of Aguas de La Havana

Director of Aguas de Varadero

6.1.2. Secondary Data

Literature review

The data collected hereby consisted in the collection of all prices from suppliers, chambers of

commerce and construction, databases of ministries of construction. Previous theses were also

considered that contained technical designs, and costs of CAPEX and some OPEX that could

not be found or obtained from the primary data.

6.1.3. Determination of CAPEX and OPEX

Based in previous sections (Primary and Secondary Data), the data needed to calculate the

CAPEX and OPEX was gathered. In the execution of any project, one important point is the

budget preparation, which determines if it is possible the construction of the work and what the

cost is. To build-up the budget, it was necessary to identify the activities, material supplies,

pipes, labour and other activities that are carried out in the work during its execution and that

have a cost that influences the preparation of the budget.

Secondary data was used to obtain the CAPEX for the cases involving the use of seawater for

toilet flushing. Villasante-Castañeda (2013) used the PRESWIN software in version 8.1 taking

into account the provisions of PRECONS II of 2005.

Once all the data was identified, the CAPEX were calculated by quantifying the amount of

materials, labour, and the use of equipment with the support of PRESWIN 8.1. In a

representative way, to show how the CAPEX and OPEX are expressed in this document for the

different case studies and their respective scenarios, the case of the Cuban population where

water is supplied to a group of 50 people is described in Table 9.

The cost of the construction service were calculated for the first case study (Study of the Cuban

Population- for 50 persons) being of US$ 10,480.03. As shown in Table 9, this value has several

independent budgets as temporal facilities, bank costs, insurance of the construction works,

unforeseen costs that can occur during the construction work and other additional costs (this

independent budgets are regulated by the Cuban government for the different types of

construction works like the percentage rate applied to each independent budget), this presents

Methodology 38

a total cost of US$ 2012.19. To estimate the actual cost of construction, the independent budgets

can be neglected. Thus, for this case the actual cost of the construction is US$ 8467.84

(Villasante-Castañeda, 2013). As mentioned before, in the same way, the CAPEX for this first

case-study with all the scenarios from 100 up to 5000 persons was calculated (see appendix 1).

Similar calculations were done for case-study 2 (Hotel Villa Playa Hermosa) and the study of

the use of seawater for toilet flushing (case-study 4, Hotel Breezes Jibacoa) which can be seen

in the appendix 2 and 4, respectively for the scenarios proposed.

Table 9 Example of the CAPEX for the case study of the Cuban population

where water is supplied to 50 persons

The OPEX of the cases-studies (1, 2 and 4) are shown in Table 10, assessing the use of seawater

for toilet flushing. It was obtained based on the replacement of the sanitary equipment and parts

due to the potential corrosion caused by the seawater. This considers that the pieces described

in Figure 9 are replaced twice a year, the depreciation of the system by a 10% per year of the

cost of investment of the system, hand labour (qualified and non-qualified), and the staff needed

(technicians, engineers, sub-directors and directors if needed). In Figure 11, the monthly

salaries taken into account each of the staff members are shown. This data was collected from

the water utilities company in Havana.

Methodology 39

Table 10 Example of the OPEX for the case-study of the Cuban population

where water is supplied to 50 persons

Methodology 40

Figure 9 Example of the data provided by PRESWIN 8.1. The table displays the costs of

materials and hand labour of the replacement of the sanitary equipment

Figure 9 was obtained from the PRESWIN 8.1 software and it shows the materials that are

replaced twice a year. To better understand the sanitary equipment that is replaced twice a year

(as considered in the estimation of the OPEX). Figure 10 illustrates the pieces replaced.

Actually, they are:

Manguera Metalica P/inodoro (water line)

Sellador con rosca (Tank-to-bowl Gasket)

Latiguillo flexible ½ x ½ (water line)

Tornillo para piso (Tank bolt)

Valvula de entrada de inodoro (Fill valve)

Valvula de salida de inodoro (Flush valve and flapper)

Ayudante de construccion del grupo salarial II (Non-qualified labour)

Plomero del grupo salaria V (Qualified labour)

Figure 10 Description of the sanitary parts of a toilet that are replaced twice a year due to the

use of seawater for toilet flushing

Methodology 41

Figure 11 Monthly Salary of employees in the water sector

(According to Water utility services)

7.2 Phase 2. Economic analysis

After evaluating the advantages and disadvantages of the most used techniques in the evaluation

of projects shown in Table 8 of Chapter 2 (Literature Review) there are many different

evaluation tools; some are more widely used than others. According to Remer and Nieto (1995)

they categorized many various methods of project evaluation into five basic types: net present

value method, rate of return methods, ratio methods, payback methods and accounting methods.

The most popular techniques are the net present value criterion methods, the internal rate of

return method, external rate of return method, return on investment method, benefit/cost ratio

method and payback period method being the first one, the most commonly used. The technique

decided to be applied to develop the economic analysis is:

2.1 Net Present Value (NPV)

At this phase the external costs were identified and valuated to be included in the economic

analysis. Following the representative case-study (Study of the Cuban Population- for 50

persons) to show how the NPV was calculated using Excel software. Considering the total

CAPEX (See example Table 9) and OPEX (See example Table 10) of each case and each

scenario assessed for a lifetime period of 20 years. The NPV for the first case (Case study for

the Cuban population for 50 persons being supplied with inly freshwater) is US$ 19,417.37.

The NPV was calculated of the investment by assuming an interest rate of 14% according to

Miranda (2005) which states that common interest rates can be from 7% to 14%. Due to lack

of data from Cuban banks and according to data from the World-Bank, similar countries from

the area reported an interest of 13, 2% (Haiti) and 15, 1% (Dominican Republic) (World-Bank,

2016). Considering the average of both countries is 14, 1%.

The detailed description of the NPV of each case and respective scenario assessed in this study

are shown in the appendix section.

Methodology 42

7.3 Phase 3. Scenario analysis

In the third phase, a scenario analysis was performed by analysing possible scenarios that may

take place and considering alternative possible outcomes of every scenario for each case study

selected. In this phase an economic sensitivity analysis was studied for each selected scenario

from the four case studies. The sensitivity analysis was performed for the purpose of

determining the most critical parameter affecting the estimation of the cost in US$/m3 water

supplied for the case of the use of seawater for toilet flushing or US$/m3 treated water for the

case of reuse of treated wastewater. Several examples can be shown from the different

techniques. This was evaluated after phase two to determine which ones are the most critical.

The critical parameters of interest assessed in the sensitivity analysis were: (1.) water shortage

periods from 1 to 9 months, (2.) periods of expanded water coverage using freshwater saved by

the use of the different alternatives proposed, (3.) to identify for how long the scenarios will be

economically viable, (4) to study or estimate, when the WWTP are upgraded with a MBR

system, what are the periods of replacement of the membrane that still make the scenarios

feasible.

The following case-studies were evaluated in this phase:

7.3.1 Case study of the replacement by seawater for toilet flushing in a Cuban community

This study analyses several scenarios to assess the economic feasibility of the implementation

of innovative alternative water sources under Cuban conditions like the use of seawater for

toilet flushing to reduce freshwater demand and alleviate water scarcity. In Figure 12 are

presented the main key scenarios evaluated as a function of the Cuban population served and

the water consumption used for this analysis.

Figure 12 Estimated fresh water consumption in Cuba as a function of number or people

served and local standards.

Methodology 43

The water consumption volumes shown in Figure 12 are obtained from Table 2 presented in

Chapter 2 (Literature review). As such, it states that for less than 2000 persons the water supply

design consider a water consumption of 145 LPPD, for 2000 to 10,000 persons 160 LPPD and

from 10,000 to 25,000 a water consumption of 175 LPPD.

For each population served, several situations assessed considering: a) fresh yearly water use

per No. of persons, (b) potential length or duration of water shortages (ranging from 1 to 9

months of water shortage), and (c) the potential replacement of freshwater by seawater for toilet

flushing to alleviate the impact of water shortages. As such, several scenarios and potential

situations were developed and assessed, such as:

Scenario FW (Use of only fresh water)

Scenario FW+1 month of water shortage (Use of only fresh water and supplying water

with water trucks for the water shortage period)

Scenario FW+2 months of water shortage (Use of only fresh water and supplying water










Scenario FW+SW (Use of fresh water and the use of seawater for toilet flushing or the

Dual water supply system)

Scenario FW+SW+1 month of water shortage (Dual water supply system and 1 month

of water shortage)

Scenario FW+SW+2 months of water shortage (Dual water supply system and 2 months

of water shortage)


of water shortage)


of water shortage)


of water shortage)


of water shortage)

7.3.2 Case study of the touristic resort Villa Playa Hermosa in Guanabo

Because of its proximity to the sea, the touristic resort Villa Playa Hermosa in the 5th avenue

between 472 and 474 in the City of Guanabo (See Figure 13), is one of the main options for

National tourists with a capacity to hold around 54 guests.

Methodology 44

The actual situation in this city is critical. The overexploitation of the freshwater wells has led

to their exhaustion. Moreover, intrusion of saline water to the wells themselves and to the whole

water supply system has affected the water quality. This affects the whole population of the

City of Guanabo, including the economic sectors. For instance, the touristic resort previously

mentioned pays around $300.00 CUC for saline water and a daily water truck of 8 m3 for $16.00

CUC per day which makes a total of $780 CUC per month. The yearly costs rise up to around

$ 9360.00 CUC (Villasante-Castañeda, 2013). The proposed scenario to be analysed are the

following:

Figure 13 Location of Hotel Villa Playa Hermosa(Google-EarthPRO, 2016)

7.4.2.1 Scenario 1 (Real water consumption of potable water, the maintenance of the

swimming pool and floor washing)

7.4.2.2 Scenario 2 (Real water consumption of potable water and the use of seawater

for toilet flushing and other potential uses as the maintenance of the swimming

pool and floor washing)



pool and floor washing with a 1.5 months period of water shortage)



pool and floor washing with a 3 months period of water shortage)

Methodology 45







7.3.3 Case study of Punta de Hicacos, in La Peninsula de Varadero

In Matanzas, the City of Varadero, in the peninsula of Hicacos, is a touristic zone with many

hotels that discharge the wastewater to the wastewater treatment plant (WWTP) of Hicacos

located in the same area (See Figure 14).

According to Aguas de Varadero the rate for freshwater is $1.50 CUC/m3 and for wastewater

reuse is $0.50 CUC. The total discharge from each room is around 378 L which 26.46 L are

being reused for irrigation representing a 7% of the total discharge from each room (Torres-

Rodriguez, 2015). With an increasing and booming tourist sector it becomes essential to explore

the potential increase in the reuse of treated wastewater to alleviate the upcoming water

consumption needs. This is a potential strategy that an economic sustainability analysis should

support. For this reasons, the following scenarios are proposed to be assessed:

Figure 14 Location of Pensinsula Hicacos mostly known as pensinsula de Varadero (Google-

EarthPRO, 2016)

Methodology 46

7.3.3.1 Scenario 1 (WWTP for 4500 m3/day upgraded with an MBR for a better quality

effluent having the required O&M to replace membranes every 8 years)


effluent with a critical situation in O&M consequently forcing membrane

replacements every 5 years)


effluent with several situations in O&M forcing to replace membranes every 6

years)


effluent having the optimal personal and technicians operating the plant being

capable to well maintain and allowing membrane replacements every 10 years.


effluent. Taking into account that the wastewater treated in the plant is not industrial

water and the qualified personal to well operate and maintain the MBR system

allowing more lifetime period to the membranes, replacing them every 12 years)

Figure 15 Location of wastewater treatment plant Hicacos (Google-EarthPRO, 2016)

Methodology 47

7.4.4 Case study of Hotel Breezes Jibacoa:

In Mayabeque, the Hotel Breezes Jibacoa located in the Arroyo Bermejo Beach has 250 rooms

with one bathroom in between, pool area, bars, restaurants, night clubs and sports area.

Figure 16 Location of Hotel Breezes Jibacoa (Google-EarthPRO, 2016)

This hotel has a Reverse Osmosis (RO) treatment plant of two stages. Due to aggressive

conditions just one is in operation for a 24 hours period. It has a flowrate of 240 m3/day

desalinating 233 m3/day. The water demand of the hotel ranges between 360-410 m3/day

meaning that the plant is insufficient to cover the freshwater demand and that the water supply

has to be covered by water trucks (Romero López, Lafargue Verdecia, González Díaz and

Medina Correa, 2015).

The company responsible of supplying water has water trucks of 18, 20 and 30 m3 and different

prices according to different circumstances ( between $8.00, $9.75, or $ 21.00 CUC/ m3) for

this study an average around $11.00 CUC was used to estimate the costs needed to complete

the required water demand (Romero López, Lafargue Verdecia, González Díaz and Medina

Correa, 2015). If it is needed around 127 to 177 m3/day of water by water trucks, the total cost

will be approximately $1,397.00 CUC/ day to $1,947.00 CUC/day being annually costs around

$502,920.00 CUC to $700,920.00 CUC. Such costs can also be considered high, and the role

and importance of alternative practices to reduce the water consumption needs to become

Methodology 48

essential to secure the water supply if they are cost-effective. For this case study the following

scenarios are proposed:

7.4.4.1 Scenario 1 (Actual Reverse Osmosis water plant and supplying water from water trucks

to comply with the total water demand of the hotel)

7.4.4.2 Scenario 2 (Actual Reverse Osmosis water plant, the use of seawater for toilet flushing,

and to meet the water demand of the hotel purchasing water trucks)

7.4.4.3 Scenario 3 (Actual Reverse Osmosis water plant with an upgrade of 227 m3/day of the

plant and the use of sea water for toilet flushing)

7.4.4.4 Scenario 4 (WWTP for 380 m3/day upgraded with an MBR for a better quality effluent

having the required O&M to replace membranes every 8 years)


with a critical situation in O&M consequently forcing membrane replacements every 5

years)


with several situations in O&M forcing to replace membranes every 6 years)

7.4.4.7 Scenario 7 (WWTP for 380 m3/day upgraded with an MBR for a better quality effluent.

Taking into account that the wastewater treated in the plant is not industrial water and

the qualified personal to well operate and maintain the MBR system allowing more

lifetime period to the membranes, replacing them every 12 years)

Figure 17 Location of wastewater treatment plant of Hotel Breezes Jibacoa (Google-

EarthPRO, 2016)

Methodology 49

7.5 Performance indicator

The process of collecting, analysing and reporting the information of this research allowed to

select a performance indicator. This was carried out from the information related to the CAPEX

and OPEX, the economic analysis and the scenario analysis. The performance indicator or the

key parameter indicator is USD$/m3 of water of each innovative alternative water source. This

type of performance measurement allowed the assessment of the innovative alternatives applied

in each scenario for all the life time of the system (20 years) and is unified for an easy

comparison between them.

Other parameters or indicators that can be used for the assessment in this economic feasibility

analysis could be energy consumption in kWh/m3. This parameter will allow the comparison

based on energy consumption of each technology between the different scenarios evaluated.

Water consumption in m3/day or L/day will indicate not just how much consumption but how

much water is saved. This parameter will be linked to the water used by each tourist in m3/

tourist-day and consequently the water used per room in m3/room-day. This parameters will

facilitate each of the different stakeholders to choose their value of convenience. For example

the engineering cost manager or investor in USD$/m3, the engineer operator in kWh/m3, the

hotel managers or owners in m3/day or L/day, m3/ tourist-day or m3/room-day. As mentioned

before, this parameters will facilitate to achieve our key parameter in USD$/m3 of water from

each innovative alternative source of water in each scenario analysed.

Results and Discussions 50

CHAPTER 7

Results and Discussions

This chapter presents the results summarized of every step that was followed during the

methodology procedure and further discussed in detail. This chapter presents the CAPEX and

OPEX of the different alternatives proposed to alleviate water scarcity under Cuban conditions.

The different problems phased under the Cuban economy and the realistic situation to develop

the application of this technologies.

The objectives of this case study is to assess the economic feasibility of the different alternatives

as the use of seawater for toilet flushing and treated wastewater reuse, as innovative alternative

water sources to reduce freshwater demand and alleviate water scarcity.

7.1 Cuban Economy

As part of the process to understand the methodology applied during this case study, a primary

indicator was proposed which was the total cost in present value as US$/m3 of water either

water served in the case of the use of saline water for toilet flushing and water treated in the

case for the reuse of wastewater. All costs in this case study are expressed in US $ and this is

the importance to understand the different currencies that exist in Cuba. In this way trying to

obtain the best procedure to get acceptable results to analyse the economic feasibility of the

different alternatives.

It must be taken into account the characteristics of the Cuban economic system affecting

directly different situations. The conversion of the two currencies that exist in the country is

also being affected. The amplitude of the distortion of the prices, presence of the CUC

(Convertible Cuban Peso) in some markets and the difference between the accounting systems.

Due to a controlled system of prices and subsidies throughout the economy, the prices found in

the market are not fully representative to a real international price. The different variations in

prices is determined by the governmental institutions. Moreover, several products, construction

materials, and goods need to be imported which increases their price in Cuba.

For example, there is a drop in their monthly income because in most cases, the small quantity

of subsidized products received by the government makes the consumer to buy more products

in the market which uses the CUC currency and therefore makes the prices higher than usual.

Other utility services, like public transportation, electricity and water are also affected. Locals

pay for a ride in bus around US$ 0.008 (20 cents of Cuban Peso), for a ride in a Taxi between


specific points around the city about US$ 0.40. In contrast, a taxi for a foreigner is around US$

25.00- US$ 30.00 from the airport-to the centre of Havana. Electricity for Cubans is also

subsidized and they pay around US $ 2.00 for a family of 3 or 4 members. In the same way,

Cubans pay around US$ 0.20 for water per house (family around 4 members). This is because

they pay per inhabitant rather than volume of water consumed (e.g. per m3). Mostly caused by

the fact that the water consumption is not metered. But, metering is currently being deployed at

least in the most important cities of the country.

Water consumption in hotels and certain industries, is metered and regulated by the

corresponding institutions in each city under the regulation 287/2015 of the Republic of Cuba

(Norma: Resolucion 287/2015). This regulation states the prices of water as a function of the

two currencies, the CUC and the CUP. Therefore, the price of 1 m3 of freshwater for the non-

residential sector is CUP 1.55 (which is around US $ 0.062). For hotels, industries and any

commercial activity if their income is in CUP. In contrast, for the hotels and industries that

receive their income in CUC, the cost of 1 m3 of freshwater is CUC 1.55 (or approximately US

$ 1.35). This is a clear example of the condition of the Cuban economy which leads to a complex

analysis of any economic study in the country.

Table 11 Water prices according to the regulation of Cuba: (NORMA: Resolucion 287/2015)

Water price per cubic meter CUC US $

Potable water costs 1.55 1.35

Saline water costs 0.20 0.17

Wastewater reuse 0.55 0.48

7.2 Economic and Scenario analysis

7.2.1 Case-study: domestic use of seawater for toilet flushing in Cuban urban environments

The water consumption of 50 persons is 2,646.25 m3/year as shown in Figure 12. When water

shortage occurs, water should be supplied by other means and usually it is done through water

trucks to compensate the lack of water. If there is 1 month of water shortage in a year, 50

persons could use 2,425.73 m3/year of fresh water but they need 220.52 m3/year to be supplied

by water trucks to meet the yearly water demand. If there are 2 months of water shortage, they

could use 2205.21 m3/year of fresh water but 441.04 m3/year should be supplied by water

trucks. As the periods of water shortage extends the need of water trucks rises.

Under critical scenarios, the water scarcity periods can reach up to 9 months (Mekonnen, 2016).

As such, to evaluate the effect of a period of 9 months of water shortage in a year, 50 persons

in Cuba consume 661.56 m3/year of fresh water. To comply with their water demand they need

1984.69 m3/year extra which are supplied by water trucks.

The introduction of a dual water supply system as shown in Figure 18, can lead to a reduction

of fresh water demand. 50 persons consume 2098.75 m3/year of fresh water and 547.50 m3/year


of seawater can be used for toilet flushing. Evaluating a scenario of 1 month of water shortage,

if seawater for toilet flushing is implemented, they will use 1923.85 m3/year of fresh water,

547.50 m3/year of seawater for toilet flushing and there will be no need to supply water by

water trucks due to the fresh water saved by the use of seawater. This also happens for a 2 and

3 months period of water shortage.

Similarly to the scenarios where only fresh water is supplied, two more critical situations of 6

and 9 months with water scarcity were evaluated. For a 6 months water shortage period, 50

persons consumes 1399.17 m3/year of fresh water, 547.50 m3/year of seawater for toilet

flushing, part of this water shortage period is covered by the water saved from the use of

seawater for toilet flushing and to comply with the total water demand, 501.88 m3/year need to

be supplied by water trucks. For a 9 months water shortage period, they will utilize 524.69

m3/year of fresh water, 547.50 m3/year of seawater for toilet flushing, 547.50 m3/year with the

freshwater saved by the use of seawater and to meet the total water demand 1026.56 m3/year of

water will be needed to be purchased to water trucks.

As shown in Figure 19, if the number of months with water scarcity ranged from 1 to 9

(Scenarios FW+1 month of water shortage to FW+9 months of water shortage), the volumes of

water that need to be purchased from water trucks to cope with the lack of water increases from

8.3% to even 75% to satisfy the increasing demand. In this regard the evaluation of the

introduction of the dual system shows that fresh water consumption can be reduced by around

20.7% (Scenario FW+SW) with regard to the conventional or baseline scenario (Scenario FW).

This considerable reduction of about 20.7 % allows that, if the water shortage takes place as

previously discussed, the introduction of this alternative could allow a water coverage of at least

3 months and consequently avoid the supply of water by water trucks (from scenario

FW+SW+1 month of water shortage to FW+SW+3 months of water shortage).

If the length of the water scarcity scenarios expand to 4, 6, and 9 months the use of SW for

toilet flushing becomes insufficient to satisfy the water demand as higher volumes of freshwater

are required. As such, if a water shortage of 4 months takes place (Scenario FW+SW+ 4 months

of water shortage) there is a need to cope with the lack of water by continuing to purchase

around 5.7% of water from water trucks. If this critical scenario prevails and extends, after 6

and 9 months of water shortage there is a need to purchase about 19% and 38.8% of water,

respectively from water trucks. Still, when comparing scenarios FW+SW+4, FW+SW+6 and

FW+SW+9 months of water shortage these percentages (of 5.7%, 19.0%, and 38.8%) represent

less than half the water volumes that would need to be purchased from water trucks if there is

not SW for toilet flushing (Scenarios FW+4, FW+6 and FE+9 months of water shortage,

respectively, with purchase volumes of 33.3%, 50.0% and 79.3%).

Comparing the percentages of fresh water saved (Figure 20) shows how much fresh water is

saved by the use of sea water for toilet flushing as well as the percentage of water used during

water shortage periods. In particular, the volumes of water saved even during water shortage

periods (Scenarios FW+SW, FW+SW+1, FW+SW+2 and FW+SW+3 months of water

shortage) indicate that the replacement of freshwater by seawater for toilet flushing can allow

savings in freshwater. This data allows the presentation of how many cubic meters of freshwater

can be saved along the different scenarios. When the introduction of the seawater alternative is

applied 547.50 m3/year of freshwater are being saved (20.7%), when there is 1 month of water


shortage 372.60 m3/year of freshwater are being saved (14.1%), for 2 months of water shortage

197.71 m3/year (7.5%), and for 3 months of water shortage 22.81 m3/year of freshwater are

saved (0.9%).

Figure 18 Water consumption for 50 persons in m3/year assessed for the different scenarios


Figure 19 Percentage of water consumptions for the different scenarios


Figure 20 Percentage of fresh water saved by the use of seawater for toilet flushing

Obtaining the percentage of fresh water that could be saved by using seawater for toilet flushing,

the potential number of persons benefited, that can be served with the fresh water saved, was

calculated. This indicated that for an investment of 50 persons when there is no water shortage

in the year around 13 persons can be served or 26.1% more people can have sufficient water to

satisfy their needs. For 1 month of water shortage, around 9 persons can be served (17.8%);

with 2 months 9.4% more; and for 3 months around 1.1% more people. These savings and

expansion of the population that be benefitted by the water availability can be achieved

assuming that the savings in freshwater by its replacement with seawater would allow to reduce

the freshwater consumption per person and that the saved freshwater can be given to other

people.

Figure 21 Percentage of persons that can be served with freshwater waved by the use of

seawater for toilet flushing


The Net Present Value (NPV) of the Capital Expenditures or Capital Costs (CAPEX) and the

Operation and Maintenance Expenditures or Operation and Maintenance Costs (OPEX) was

calculated for a period of 20 years for the different scenarios and alternatives. This includes the

initial investment for the Dual water supply system, and the operation and the maintenance

(O&M) costs of this alternative. In the O-&-M, it is considered that, for the use of seawater for

toilet flushing, the replacement of the sanitary accessories twice a year and also the system

depreciation for a 10% per year of the cost of investment.

As shown in Figure 22, for the situation in which just fresh water is being used, when the months

of water shortage increase the NPV rises, making the situation more costly. The scenario where

only freshwater is supplied (Scenario FW) presents a NPV of US$ 19,417.37 and when water

shortage periods appear, for 1 month of water shortage (Scenario FW+1 month of water

shortage) the NPV increases to US$ 21,879.92, for 3 months of water shortage (Scenario FW+3

months of water shortage) the NPV is of US$ 26,805.03. As analysed before, the critical

situation of water scarcity can take up to 6 and 9 months of water shortage and the NPV for this

scenarios (FW+ 6, FW+ 9 months of water shortage) is of US$ 34,192.70 and US$ 41,580.37

respectively. This is because in these months there is a need to supply water by water trucks

with a cost of US$ 13.92 a truck of 8 m3 of water to compensate for the water shortage and the

price of the water provided by the water trucks is extremely high being US$ 1.74/m3.

Comparing the NPV of the Dual System (Scenario FW+SW), it can be seen that it is relatively

similar when there is no water shortage compare to the supply of only fresh water (Scenario

FW) with an NPV of US$ 19,247.01. But interestingly, when there is a water shortage from 1

up to 3 months, (from Scenario FW+ SW+1 to Scenario FW+SW+3 months of water shortage),

the NPV remains almost the same due to fresh water saving favoured by the use of sea water

for toilet flushing and by giving the saved water to more people since there is enough water and

there is no need of supplying water by water trucks.

Figure 22 shows the NPV for the scenarios previously studied and it is shown that for the

situations in which there is water shortage for 4,6 and 9 months (from Scenario FW+SW+4 to

Scenario FW+SW+9 months of water shortage), there is not enough water saved and water

trucks must be purchased. But, even under these conditions where there is a need to supply

water by trucks the NPV is lower when using seawater for toilet flushing (Scenarios

FW+SW+4, FW+SW+6, FW+SW+9 months of water shortage) than when only fresh water

and water trucks are needed (Scenarios FW+4, FW+6, FW+9 months of water shortage).


Figure 22 Net Present Value (NPV) of Capital Expenditures (CAPEX) and Operation and

Maintenance Expenditures (OPEX) for a period of 20 years for the different scenarios and

alternatives.


Figure 23 Cost of water in US$/m3 of water for the different scenarios and alternatives


For comparison purposes, a performance indicator consisting of the cost of cubic meter of water

supplied as US$/m3 was calculated from the NPV and the total amount of water supplied for 50

persons during the whole life span of the system. In Figure 23, the costs of water is shown in

US $/m3. As expected, the behaviour is similar to the NPV chart. The estimated cost of the

supply of fresh water when there is no water shortage is around US$ 0.37/m3. However, if water

shortage periods occur (Scenarios FW+1 to FW+9 months of water shortage), the cost can

increase up to US$ 0.79/m3 because the supply of freshwater is assumed to be insufficient and

water needs to be purchased from water trucks at a cost of US$ 1.74/m3. Interestingly, it can be

seen that US$ 0.36/m3 is the cost for the alternative of using seawater for toilet flushing

(Scenario FW+SW). And this cost remains for up to 3 months of water shortage (from Scenarios

FW+SW+1 to FW+SW+3 months of water shortage) and only increases marginally to US$

0.39/m3 for 4 months of water shortage (Scenario FW+SW+4 months of water shortage).

Compared to the scenarios where there is just fresh water supplied and water trucks the cost

can rise up to US$ 0.55/m3 (Scenario FW+4 months of water shortage).

As the water shortage periods increase (Scenarios FW+6, FW+9, FW+SW+6, FW+SW+9

months of water shortage) the cost continues rising, but even when with a 9 month water

shortage the dual system has a cost of water of US$ 0.58/m3 having US$ 0.21/m3 saved

compared to the costs of freshwater and water trucks for the same period of water shortage of

US$ 0.79/m3 (Scenario FW+9 months of water shortage).

In the same, several similar scenarios were evaluated, for 100, 200, 500, 1000 persons. Overall,

the results and trends (see Appendix A) were rather similar like for the scenarios assessed for

50 people, obtaining the same percent of water consumption, for fresh water saved and

percentage of persons that can be served with fresh water by using seawater for toilet flushing.

As an example (Figure 24), the scenarios performed for 1000 persons are presented in the

following paragraphs. It can be observed that when applying the use of seawater for toilet

flushing there is 10,950.00 m3 of fresh water saved being capable to supply freshwater to around

261 more persons when there is no water shortage. Around 177 persons when there is 1 month

of water shortage, 94 more persons when there is 2 months of water shortage and 11 persons

when there is 3 months of water shortage. Proportionally, this represents an increase in

freshwater availability and increase in population served of 26.1%, 17.7%, 9.4% and 1.1% by

the use of seawater for toilet flushing.


Figure 24 Number of persons that can be served with freshwater saved by the use of seawater

for toilet flushing

Furthermore, assuming that there is 6 persons per house living in a typical Cuban family, the

number of houses that can be benefitted by the water supply obtained from the fresh water saved

can be calculated. If there is no water shortage 43 more houses can be served (for Scenario

FW+SW), when there is 1 month of water shortage 30 houses can be served (for Scenario

FW+SW+1 month of water shortage), 2 months of water shortage 16 houses (for Scenario

FW+SW+2 months of water shortage) and 2 houses when there is a period of 3 months of water

shortage (for Scenario FW+SW+3 months of water shortage) as shown in Figure 25.

Figure 25 Number of houses that can be served with freshwater saved by the use of seawater

for toilet flushing


For a population of 5000 persons, the similar scenarios were analysed. Important to underline

that and as shown in Figure 12, the water consumption for a population of 5000 people is 160

LPPD. As such, a total water consumption of 292,000 m3/year is estimated as shown in Figure

26. Similar scenarios to those assessed previously for 50 persons were also evaluated.

It can be seen that the water supplied by water trucks increases for the scenarios where only

freshwater is supplied (from Scenario FW+1 to FW+9 months of water shortage) from

24,333.33 m3/year up to 219,000.00 m3/year. As seen in Figure 27, this increases from 8.3%

for 1 month of water shortage up to 75% for the most critical scenario (of 9 months of water

shortage). Introducing the dual water supply system around 18.8 % (Scenario FW+SW) of fresh

water consumption can be reduced compared to the baseline scenario (Scenario FW). If water

shortage occurs, this reduction will allow a water coverage of about 2 months avoiding the

purchase of water by water trucks (Scenario FW+SW+1 and FW+SW+2 months of water

shortage). It is important to underline that, with regard to the evaluations performed from 50 up

to 1000 persons, the amount of water saved is capable to cover up to 3 months of water shortage,

which is different from the previous analysis.

In the same way, as the periods of water scarcity extends from 3 to 9 months, the use of seawater

for toilet flushing becomes insufficient to comply with the water demand. Supplying water with

water trucks under these scenarios is rather needed and a 1.6% of water should be supplied by

water trucks for the Scenario FW+SW+3 months of water shortage. For Scenario FW+SW+4

months of water shortage an 8.3%, for 6 months a 21.9% (Scenario FW+SW+6 months of water

shortage) and for the most critical scenario of 9 months of water shortage a 42.2% (Scenario

FW+SW+9 months of water shortage) of water must be purchased to water trucks.

In Figure 28, it can be seen the percentages of fresh water saved by the use of a dual water

supply system. The number of persons benefited that can be served with this freshwater saved

was calculated resulting that for an investment of 5000 persons when there is no water shortage

in the year around 1154 persons can be served or 23.1% more people can have sufficient water

to satisfy their needs. For 1 month of water shortage around 737 persons can be served (14.7%)

and for a 2 month of water shortage 321 more persons can be served or 6.4% more people.

Moreover, as assumed that there is 6 persons per house living in a typical Cuban family, the

number of houses that can be benefitted by the supply of water obtained from the fresh water

saved can be calculated. If there is no water shortage 192 houses can be served (Scenario

FW+SW), when there is 1 month of water shortage 123 houses (Scenario FW+SW+1 month of

water shortage) and when there is 2 months of water shortage 53 houses can be served (Scenario

FW+SW+2 months of water shortage) as shown in Figure 29.


Figure 26 Water consumption for 5000 persons in m3/year assessed for the different scenarios


Figure 27 Percentage of water consumptions for the different scenarios


Figure 28 Percentage of persons that can be served with freshwater waved by the use of

seawater for toilet flushing

Figure 29 Number of houses that can be served with freshwater saved by the use of seawater

for toilet flushing


The NPV of the CAPEX and OPEX was calculated for a period of 20 years for the different

scenarios and alternatives in the same way like for the previous scenarios from 50 persons up

to 1000 persons. Figure 30 shows the scenario where freshwater is only supplied (Scenario FW)

with a NPV of US$ 2,027,713.66. As water shortage periods occur an increment in the NPV is

seen because there is a need of purchasing water to water trucks. For 1 month of water shortage

(Scenario FW+1month of water shortage) the NPV is US$ 2,299,443.88, for a 2 month water

shortage (Scenario FW+2 months of water shortage) the NPV is of US-$ 2,571,174.10, for a 3

months of water shortage (Scenario FW+3 months of water shortage) the NPV is US$

2,842,904.33. The increment in the NPV gets higher as the water shortage period extends and

at the most critical situation of 9 months (Scenario FW+9 months of water shortage) the NPV

reaches US$ 4,473,258.67. This value represent an increment of almost 120% more from the

baseline scenario where no water shortage occurs (Scenario FW).

The introduction of the Dual System (Scenario FW+SW) shows an NPV of US$ 2,010,677.94

being relatively similar when compared to the supply of only freshwater (Scenario FW).

Emphasizing that in the previous analysis for the scenarios from 50 up to 1000 persons there is

enough water saved from the use of seawater for toilet flushing to cover up to 3 months of water

shortage. Different from this scenario of 5000 persons which is able to cover periods up to 2

months of water shortage, the NPV remains almost the same from a period of 1 up to 3 months

of water shortage (from Scenarios FW+SW+1 up to Scenario FW+SW+3 months of water

shortage).

Interestingly for a water shortage period of 4 months, where there is a need to purchase water

for water trucks, the NPV is of US$ 2,262,848.63 (Scenario FW+SW+4 months of water

shortage) indicating a slightly small increment from the previous scenarios. And as shown in

Figure 12 is slightly lower than the scenario supplying just freshwater with 1 month of water

shortage (FW+1 month of water shortage). As the water shortage periods expands from 6 up to

9 months (from Scenario FW+SW+6 and FW+SW+9 months of water shortage) the NPV

increases. But the NPV is still lower when compared to the scenarios being supplied with just

freshwater (Scenarios FW+6, FW+9 months of water shortage).


Figure 30 Net Present Value (NPV) of Capital Expenditures (CAPEX) and Operation and

Maintenance Expenditures (OPEX) for a period of 20 years for the different scenarios and

alternatives.


Figure 31 Cost of water in US$/m3 of water for the different scenarios and alternatives


In figure 31, the costs of water are shown for the Scenario of 5000 persons. The behaviour of

the chart is similar to the NPV chart. The estimated cost of supply freshwater when there is no

water shortage is around US$ 0.35/m3 (Scenario FW). As the water shortage periods appear

(from Scenario FW+1 to Scenario FW+9 months of water shortage), the cost increases from

US$ 0.39 up to US$ 0.77/m3 because the supply of freshwater is assumed to be insufficient and

water is in need to be supplied by water trucks. Retaking previous analysis of the NPV chart,

in the same way, the cost of water for the alternative of the use of seawater for toilet flushing

(Scenario FW+SW) has a cost of US$ 0.34/m3. And this cost remains for up to 2 months of

water shortage (from Scenario FW+SW+1 and Scenario FW+SW+2 months of water shortage).

Interestingly, when 3 months of water shortage period occurs (Scenario FW+SW+3 months of

water shortage), the water cost is of US$ 0.35/m3. Taking into account that for this Scenario of

5000 persons served, for a period of 3 months of water shortage, there is already a need to

supply freshwater by water trucks and the cost of water shows a slightly increment of one cent

and being the same as that of the baseline scenario (Scenario FW).

The same trend occurs when there is a period of 4 months of water shortage (Scenario

FW+SW+4 months of water shortage) increasing marginally to US$ 0.39/m3. Compared to the

scenario where there is just freshwater supplied and water trucks needed to comply the water

demand for a period of 4 months of water shortage (Scenario FW+4 months of water shortage)

the cost can rise up to US$ 0.53/m3.

The costs continues rising as the water shortage periods extends. The critical scenarios for 6

and 9 months of water shortage presents for scenarios just supplying freshwater and purchasing

freshwater from water trucks (from Scenario FW+6 and FW+9 months of water shortage) costs

of US$ 0.63/m3 and US$ 0.77/m3 respectively. Compared to when a dual water supply system

is introduced and for the same period of water shortage (Scenarios FW+SW+6 and FW+SW+9

months of water shortage) the water cost is of US$ 0.46/m3 and US$ 0.58/m3 respectively. It is

clearly seen that applying this alternative of the use of seawater for toilet flushing can save

between US$ 0.16 and US$ 0.19/m3 of water.

Comparing the different scenarios from 50, 100, 200, 500, 1000, 5000 and 15,000 persons

(Figure 32) there is a potential effect of the economy of scale affecting the amount of water

saved. This assessment shows that increasing the number of people served leads to a lower

amount of freshwater saved, decreasing from 21% to 17% for 50 to 15,000 persons when there

is no water shortage. It is also shown that for 50 up to 1000 persons there is enough water saved

by the use of seawater for toilet flushing to cover up to 3 months of water shortage. But the

latter cannot be achieved when 5000 and 15,000 persons are served because the water

consumption for this population is higher.


Figure 32 Saved Fresh water by the use of seawater for toilet flushing for the scenarios from

50 up to 15,000 persons


Figure 33 Cost of water in US$/m3 for the scenarios from 50 up to 15,000 persons


The cost of water in US$/m3 for the different scenarios is also being affected by the economy

of scale showing that increasing the number of persons served results in a drop in the cost per

cubic meter of water as shown in Figure 33. When the Dual water supply system is applied it

is shown that the cost of water remains the same for up to 3 months of water shortage and with

a lower cost than when using just fresh water. As the water shortage periods extends for 4 ,6

and 9 months there is a slight increment when compared to when there is just water supplied

by fresh water and water trucks.

The cost of fresh water for populations of 50 and 100 persons served, the cost of fresh water is

about US$ 0.37/m3. As periods of water shortage occur this cost can rise up to US$ 0.79/m3,

this is because in this periods the population is being supplied by water trucks. For populations

of 200, 500, and 1000 persons the cost of water is about US$ 0.38/m3 and rises up to US$

0.80/m3 as water shortage periods extends up to 9 months. As mentioned before the economy

of scale affects when the number of people served increments. The cost of water for 5000

persons is of US$ 0.35/m3 and can rise up to US$ 0.77/m3 when water shortage occurs. For

15,000 persons the cost of water is being reduced by 3 cents to US$ 0.32/m3 rising up to US$

0.74/m3 for the most critical scenario of 9 months of water shortage.

The use of seawater for toilet flushing shows a reduction of 1 cent being of US$ 0.36/m3 for 50

and 100 persons. For 200 up to 1000 persons the cost of water for a dual water supply system

is of US$ 0.38/m3. Interestingly, the benefit of the dual water supply system is that this cost

remains for up to 3 months of water shortage. When compared for example 1000 persons served

for a period of 3 months being supplied by fresh water and water trucks the cost is of US$

0.52/m3 and for the dual water supply system is still of US$ 0.37/m3 having US$ 0.15/m3 saved

representing a 28.4% saved. (See Figures 34 and 35). This savings can be obtained because the

water needed to supply the population when water scarcity extends is enough due to the use of

seawater for toilet flushing and the freshwater saved by implementing this alternative.

As the water shortage period extends to 4 months there is a slight increment to US$ 0.41/m3.

This is because there is a need to supply water by water trucks. For the most critical scenarios

of 6 and 9 months of water shortage the cost of water is of US$ 0.48 and US$ 0.59/m3

respectively but even when compared to when just fresh water and water trucks are supplying

the population (US$ 0.80/m3) the saved cost can be up to US$ 0.21/m3 as shown in Figure 34.

For populations of 5000 and 15,000 persons the cost of water is of US$ 0.34 and US$ 0.32/ m3.

In this case the water consumption is of 160 and 175 LPPD as shown in Figure 12. As mentioned

before for this scenarios there is enough water to supply the population up to 2 months of water

shortage. For example the scenario for 15,000 persons the cost of water increments from US$

0.31/m3 to US$ 0.33/m3 (for 3 months of water shortage). For the most critical situation of 9

months of water shortage, the cost rises up to US$ 0.56/m3 (FW+SW+9 months of water

shortage) but compared to when just freshwater and water trucks are used (US$ 0.74/m3) the

savings can be up to 17 cents per cubic meter.


Figure 34 Costs saved in US$/m3 when applying a dual water supply system


Figure 35 Percentage of the costs from saved freshwater due to the use of seawater for toilet

flushing


7.2.2 Case-study of the touristic resort Villa Playa Hermosa: use of seawater for toilet flushing in the tourism sector in Cuba

The touristic resort Villa Playa Hermosa for 54 guests is located in the City of Guanabo. The

critical situation that the city is facing with the intrusion of saline water to the freshwater wells

have already forced them to use saline water. As mentioned before in Chapter 3, the touristic

resorts pays around CUC 780.00 per month which is around CUC $ 9,360.00 (US$

8,143.20/year).

The analysis for this case was based in different scenarios ranging from the only use of potable

water, the introduction of a dual water supply system and evaluating the critical situation when

water scarcity occurs and water shortage periods extends from 3 up to 9 months (See Appendix

2).

Scenario 1 (Actual water consumption of potable water, the maintenance of the

swimming pool and floor washing)

Scenario 2 (Actual water consumption of potable water and the use of seawater for toilet

flushing and other potential uses as the maintenance of the swimming pool and floor

washing)



washing with a 1.5 months period of water shortage)



washing with a 3 months period of water shortage)







As shown in Figure 36 and taking into account that the water consumption for each tourist is

around 950 LPPD (18,724.50 m3 per year) and other water uses as the maintenance of the

swimming pool and washing floors is of 1,683.91 m3 per year makes a total water consumption

per year of 20,408.41 m3. The introduction of the Dual water supply system allows savings of

2,275 m3 of water per year representing about an 11 %. Interestingly, saved freshwater by the

use of seawater for toilet flushing is enough to supply a 45 days period of water shortage. When

water shortage extends for a period of 3 months there is a need of purchasing 2,236.30 m3 of

water to water trucks. As water scarcity extends the amount of water needed to be purchased

can rise up to 11,178.60 m3 for a period of 9 months being around the 54.8% of the water

demand.


Figure 36 Water consumption of Hotel Guanabo for the different scenarios

When the system is served only by potable water (Scenario 1) the NPV is US$ 203,670.27 and

compared to the introduction of the Dual water supply system, the NPV is reduced marginally

to US$ 200,302.26 (Scenario 2) as shown in Figure 37. When a period of 45 days (Scenario 3)

of water shortage occurs there is enough fresh water to supply the guests and consequently there

is no need to purchase water to the water trucks making the NPV similar to Scenario 2. As water

shortage occurs the NPV increases from US$ 228,479.35 for 3 months up to US$ 284,833.54

for the most critical situation of 9 months of water shortage (from Scenarios 4 to 6). This

increment is because the high cost of the water purchased to the water trucks is US$ 1.74/ m3.

Figure 37 NPV for a period of 20 years for the different scenarios and alternatives for the

Hotel Villa Playa Hermosa.


Similarly, the performance indicator was calculated to compare the costs of water of the

different scenarios evaluated. It can be seen in Figure 38 that the trend is similar to the NPV

chart and the cost of water for scenario 1 (the use of only potable water) is of US$ 0.50/m3. The

introduction of the Dual water supply system shows a reduction of 1 cent per cubic meter being

US$ 0.49/m3. This cost remains stable for Scenario 3 in which there is no need to purchase

water from water trucks. When water scarcity occurs for 3 months the increase in the cost is of

7 cents being of US$ 0.56/m3. For a period of 4 months of water shortage (Scenario 4) the cost

is US$ 0.63/m3 and for a 9 months of water shortage is US$ 0.70/m3.

The major benefit of applying this technology in the touristic area is that the total water saved

by the use of seawater for toilet flushing allows a coverage of more or less 45 days of water

scarcity. The water demand for this period is of around 2,235.6 m3 and the fresh water saved

can reach up to 2275 m3. This makes the cost of this alternative lie around US$ 0.49/m3.

Figure 38 Cost of water in US$/m3 of water for the different scenarios and alternatives for the

Hotel Villa Playa Hermosa.

7.2.3 Case-study: wastewater reuse in Punta de Hicacos at La Peninsula de Varadero

In Matanzas, the city of Varadero, in the peninsula of Hicacos, for the wastewater treatment

plant (WWTP) of Hicacos located in the same area, it was proposed to improve the WWTP by

adding a MBR wastewater treatment system. Currently, the WWTP has a conventional

wastewater treatment process of 3 treatment lines with a total installed capacity of 4500 m3/day.

The CAPEX was estimated by focusing on the unit membrane cost since the energy costs was

stated to be included in the OPEX. This are generally the most costly capital equipment for

most large MBR installations (JUDD 2016). CAPEX must necessarily include installation, land

and legal/ administrative costs. As Judd (2016) states the estimation of the installation costs

vary widely between geographical regions and for this study it was focused on the unit of

membranes. However, labour costs for OPEX was gathered. The alternative of upgrading the

conventional wastewater treatment plant with an MBR are being evaluated for a lifetime period

of 20 years.


The CAPEX of this alternative was estimated to be the installations of the membrane units for

a cost of US$ 562,500.00. The OPEX was given mostly by the energy consumption. Knowing

that energy costs in the wastewater treatment plant is US$ 0.21/Kwh and having an energy

consumption of 3.06 Kwh/m3 (Alvarez, 2015) the total energy consumption is 5,026,050

Kwh/year for a total energy costs of 1,055,470.5 US$/year.

For this case, several scenarios were analysed taking into account mostly the membrane

replacement and the operation and maintenance of the plant. The former mostly because

membrane replacement costs are potentially very significant and later because the well

operation of the system can drop or increase the price. The different scenarios assessed are:

Scenario 1 (WWTP for 4500 m3/day upgraded with an MBR for a better quality effluent




years)




having the optimal personal and technicians operating the plant being capable to well

maintain and allowing membrane replacements every 10 years.

Scenario 5 (WWTP for 4500 m3/day upgraded with an MBR for a better quality effluent.




As shown in Figure 39 the NPV was calculated for the lifetime period of 20 years for each

scenario. As mentioned before, Scenario 1 considers the membrane replacement every 8 years.

This Means that at least 2 replacements occur in year 8 and year 16 after the start-up of the

MBR plant. The operation and Maintenance of the plant is assumed to have the required

personnel and technicians on charge to take care of mainly the aeration and the O&M activities

since this composes of the largest component of the process operating cost. Membrane cleaning

occur in this process but as data is not collected, this was assumed to be considered as part of

the scenarios of analysis within the membrane replacements at 5, 6, 10 or 12 years depending

on O&M.

The NPV in scenario 1 which is taken as the baseline, is estimated around US$ 7,838,114.85.

In Figure 39, the cost of water treated is shown, having the same trend as the NPV chart. The

cost for this scenario is US$ 0.24/ m3. When evaluating the most critical situation in which the

membrane replacement occurs every 5 years, the NPV increases to US$ 8,135,407.33 (3.8%

higher approximately) with a slight increase in the cost of the treated water of 1 cent (reaching

US$ 0.25/m3).

When the scenario 3 is evaluated (WWTP upgraded with an MBR for a better effluent quality

and membrane replacement every 6 years) the NPV is US$ 7,998,008.89 similar to the most

critical situation, even though there are less replacements than in scenario 2, the higher costs of

energy remains along all the scenarios making these alternatives or scenarios independent on


the replacement of the membrane units. But, assuming that the replacement occur every 10

years or twice for the lifetime period, the NPV drops around US$ 233,550.70 (2.97% less than

the baseline scenario) which is almost 41.5% of the cost of membrane replacements. However,

the cost of water treated remains of US$ 0.24/m3.

Figure 39 NPV for a period of 20 years for the different scenarios for the WWTP Hicacos in

the Peninsula of Varadero

Figure 40 Cost of water in US$/m3 of treated water for the different scenarios for the different

scenarios and alternatives for the WWTP Hicacos in the Peninsula of Varadero


Is important to consider that Scenario 5 (WWTP upgraded with MBR for a better quality

effluent replacing the membranes every 12 years) could have high chances to occur, if there is

adequate operation and maintenance of course but also taking into account that the water treated

comes from hotels. Thus, because it is wastewater from hotels and resembles or has the

characteristics of domestic wastewater (rather than that of industrial effluents) then it could

have a lower deleterious impact on the membranes. This will allow an extension period of up

to 12 years of membrane replacement showing a cost of water treated of US$ 0.23/m3. This

represents a decrease of 1 cent when compared to previous scenarios.

7.2.4 Case study at Hotel Breezes Jibacoa

This case study assesses the introduction of the combination of both alternatives, the use of

seawater for toilet flushing and the wastewater reuse by upgrading the conventional wastewater

treatment plant with an MBR, to obtain better quality effluent for reuse purposes. The Hotel

Breezes Jibacoa located in Mayabeque has 250 rooms with one bathroom in between. The full

capacity of the Hotel is assumed to be 500 guests for double rooms.

Actually the hotel has a reverse osmosis (RO) treatment plant desalinating 233 m3/day. This

amount of water is insufficient to comply with the water demand of the hotel and thus it is in

the need to get water by water trucks at a cost of US$ 9.57/m3 which is an extremely high price

for water. Monthly costs for a full capacity in the hotel can reach up to US$ 70, 443.16 for the

purchases of water to water trucks.

The CAPEX for the desalinating plant was obtained from Chapter 2 (Literature Review) which

states that the cost of 1m3/day is US$ 1207.00. This includes equipment and materials,

membranes, pressure vessels, pumps, energy recovery, piping and construction. The OPEX cost

considers that, for the use of seawater for toilet flushing, the replacement of the sanitary

accessories is performed twice a year and also the system depreciation by 10% per year with

regard to the cost of investment. The energy cost is significantly high being in the range of US$

0.21/ kWh. The energy consumption is set to be 0.91 Kwh/m3 for a total consumption of the

actual plant of 77,390.95 Kwh/ year.

For the case of the WWTP, the plant capacity is 380 m3/day. Upgrading the plant with an MBR

for a better quality effluent for reuse purposes is one of the objectives to reduce freshwater

demand and alleviate water scarcity. Like in the previous case study of Punta de Hicacos, the

present case-study evaluates the replacement of the membrane as one more of the several

circumstances that can occur regarding operation and maintenance. Membrane cleaning

requirements and operating conditions is set to be the factor determining the membrane

replacement. For this case, the energy cost is the highest cost of those that compose of the

OPEX in the same way like in the case-study in Punta de Hicacos.

Several Scenarios were evaluated to determine the economic feasibility of the innovative

alternatives comprising:

Scenario 1 (Actual Reverse Osmosis water plant and supplying water from water trucks

to satisfy the total water demand of the hotel)

Scenario 2 (Actual Reverse Osmosis water plant, the use of seawater for toilet flushing,

and to meet the water demand of the hotel purchasing water trucks)


Scenario 3 (Actual Reverse Osmosis water plant with an upgrade of 227 m3/day of the

plant and the use of sea water for toilet flushing)





years)



Scenario 7 (WWTP for 380 m3/day upgraded with an MBR for a better quality effluent.




Scenario 1 consists of the evaluation of the actual RO water plant that desalinates 85,045 m3

per year. To comply with the water demand, 88,330.00 m3 of water need to be purchased by

water trucks for a total water consumption of 173,375.00 m3. It is important to highlight that 1

tourists consumes around 950 LPPD. As shown in Figure 41, when evaluating the introduction

of a dual water supply system (Scenario 2), the amount of freshwater saved by the use of

seawater for toilet flushing is of 5,475.00 m3 representing a 3.15%. This value seems to be

insignificant, but when it is compared with the water consumption of a Cuban resident (160

LPPD), this amount of freshwater saved could be used to supply around 115 more persons in

the city. For scenario 3 (Actual RO with an upgrade of 277 m3/day plant to comply with the

water demand of the hotel and the use of seawater for toilet flushing) the water consumption is

being supplied mostly by RO water plant and the use of 5,475 m3/year of seawater for toilet

flushing.

Figure 41 Water consumption of Hotel Breezes Jibacoa

for the different scenarios (Scenario 1 to 3)


As shown in Figure 42, the NPV for the lifetime period of 20 years was calculated for the

different scenarios. Scenario 1 (which is the actual and critical situation) has the highest NPV

reaching US$ 6,153,880.09. As mentioned before, the need to supply water by water trucks is

of around 50.9 % making this alternative extremely costly. When the introduction of the Dual

water supply system is evaluated, the NPV is US$ 6,015,070.53, this is because there is still a

need to purchase 47.8% of the freshwater to water trucks. Interestingly, when upgrading the

RO water plant to reach a water desalination flowrate of up to 227 m3/day, the NPV is US$

1,130,143.60. This is because the cost of investment of the plant is not that high (US$

273,989.00) when compared with the cost of the water purchased by water trucks (US$

792,922.35 per year).

Figure 42 NPV for a period of 20 years for the different scenarios and alternatives for the

Hotel Breezes Jibacoa

For comparison purposes, the cost of water in US$ per cubic meter is calculated as a

performance indicator. In Figure 43 it can be seen that the trend of the performance indicator

has the same trend like the NPV chart. For scenario 1 the cost of water is extremely high, being

of US$ 1.77/m3. When the introduction of the Dual water supply system is evaluated, the

alternative of the use of seawater for toilet flushing drops the cost by 4 cents (US$ 1.73/m3). In

the same way, like in the NPV chart, the cost of water when upgrading the RO water plant to

reach a flowrate of up to 227 m3/day (Scenario 3) drops almost US$1.40/m3 being of US$

0.33/m3. This is because if this scenario is applied there will be no need to purchase the

extremely high cost water to water trucks and the use of seawater as an infinite source of water

will be used.


Figure 43 Cost of water in US$/m3 of water for the different scenarios and alternatives for the

Hotel Breezes Jibacoa

As shown in Figure 44, for the scenarios that evaluate the potential upgrade of the wastewater

treatment plant with an MBR the NPV of the baseline is US$ 669,649.67 (Scenario 4). The

Capex in this Scenario is affected mostly by the membrane replacement which in this scenario

occurs every 8 years. The OPEX, as stated previously, is mainly based on the energy

consumption which is almost constant for all scenarios evaluated in this case. For the most

critical scenario (Scenario 5), in which the membrane replacement is needed every 5 years, the

NPV is US$ 694,764.94. In the same way like for the case study of Punta de Hicacos, this

replacement period depends on the operating conditions and maintenance of the MBR. When

evaluated for a replacement period that occurs every 6 years the NPV is relatively similar, this

is because the energy cost is the parameter that has the strongest influence on the total cost of

this alternative.

Figure 44 NPV for a period of 20 years for the different scenarios (Scenario 4 to 7)

for the WWTP of Hotel Breezes Jibacoa


For comparison purposes, Figure 45 shows the cost of water treated for each scenario. This was

calculated based on the NPV and the total capacity of the WWTP. The behaviour is similar to

the NPV chart, showing that the baseline scenario (Scenario 4) has a cost of US$ 0.24/m3 of

treated water. This cost rises when the periods of replacement of the membranes is reduced to

5 and 6 years (Scenarios 5 and 6) with a cost of US$ 0.25/m3 of treated water for both scenarios.

For scenario 7, that evaluates the membrane replacement period every 12 years, the cost of the

treated wastewater is US$ 0.24/m3. Overall, this is the optimal scenario for the Hotel Breezes

Jibacoa with high operating conditions and qualified technicians to well maintain the MBR.

Figure 45 Cost of water in US$/m3 of treated water for the different scenarios for the different

scenarios and alternatives for the WWTP of Hotel Breezes Jibacoa

Conclusions 84

CHAPTER 8

Conclusions

The innovative alternative water sources as the use of seawater for toilet flushing and the reuse

of wastewater to reduce freshwater demand and alleviate water scarcity are not only

economically competitive under specific conditions (Cuban conditions). But, also has many

environmental and social benefits such as: reducing the problematic of water shortage by

providing a source of water and improving the water quality discharged into surface and

groundwater.

8.1 The use of seawater for toilet flushing in Cuban urban environments

The cost of water supplied with only freshwater under Cuban conditions is US$

0.37/m3 (from Cuban water supply systems from 50 to 1000 persons) and US$

0.32/m3 (for a Cuban system for 15,000 persons), but when water scarcity occurs,

this cost can rise up to US$ 0.79/m3 for a 9 months period of water shortage.

The introduction of the Dual water supply system (use of seawater for toilet

flushing) has a water cost of US$ 0.36/m3 (from Cuban water supply systems from

50 to 1000 persons) and US$ 0.32/m3 (for a Cuban system for 15,000 persons), but

when water scarcity occurs, this cost remains for the first 3 months and in the most

critical scenario can rise up to US$ 0.58/m3 for 9 months of water shortage.

The increase of cost when water scarcity occurs is because there is a need to

purchase water from water trucks at an extremely high cost of US$ 1.74/m3 making

the situation more costly.

Around 26.1 % more people can have sufficient water to satisfy their need with the

saved freshwater by the use of seawater for toilet flushing when no water scarcity

occurs.

When a period of 1 month of water shortage happens, 17.8 % more people can be

served, a 9.4 % more with a 2 months of water shortage and a 1.1 % more people

when there is 3 months of water shortage.

The economy of scale interfere in the cost of water. As more people is served, a

significant reduction can be observed. This is also affecting in the amount of

freshwater saved, because as more people is served, the water consumption is

higher.

8.2 The use of seawater for toilet flushing in the touristic sector

A small hotel of capacity for around 54 persons with a water consumption around

950 LPPD, shows a cost for this alternative of the use of seawater for toilet flushing

of US$ 0.49/m3.

The amount of saved freshwater by the use of seawater for toilet flushing allows a

coverage period of water shortage of 45 days (1 month and a half) remaining with

Conclusions 85

the same cost of water. As water shortage periods extends, the need of purchasing

water to water trucks makes more costly the situation rising this cost up to US$

0.70/m3 for a 9 month of water shortage.

The amount of freshwater saved of 54 tourists by the use of seawater for toilet

flushing and other potential uses as the maintenance of the pool and floor washing

is 2,275 m3/ year, equivalent water volume to supply around 43 locals per year.

8.3 Wastewater reuse by the upgrade of a conventional WWTP with a MBR treatment system

A conventional WWTP of Punta de Hicacos, with capacity of 4500 m3/day, was

evaluated with membrane replacement every 8 years and showed a cost of water

treated of US$ 0.24/ m3.

The water treated in the WWTP is not industrial, after assessments for a replacement

period of 12 years since the treated wastewater is from hotels with domestic

wastewater characteristics (not industrial wastewater) it showed a cost of treated

water of US$ 0.23/ m3 assuming that there is well O&M of the plant, since is the

largest component of the process operating cost.

A WWTP with MBR treatment system of 4500 m3/day produces annually 1,642,500

m3 of treated water ready for reuse. A population of 15,000 in Cuba has a water

consumption of 175 LPPD, the freshwater saved by practicing the reuse of treated

wastewater from this WWTP is enough to supply around 31,031 locals.

8.4 Potential combination of the use of seawater for toilet flushing, reverse osmosis desalination

and the reuse of treated wastewater

A touristic hotel with capacity of 500 persons using a RO water plant supplying

almost 233 m3/day which are insufficient to cover the total water demand forces the

hotel to purchase water at an extremely high price to water trucks of US$ 9.74/m3

showing the actual cost of water around US$ 1.77/m3.

The upgrade of the water plant by 227 m3/day more and the introduction of the Dual

water supply system drops the cost almost by US$ 1.40/m3 making the cost for the

alternative of US$ 0.33/ m3.

Similar to the WWTP of Punta de Hicacos, the WWTP of the Hotel with capacity

of 380 m3/day was evaluated showing a cost of US$ 0.24/m3 of treated water with

membrane replacements every 12 years.

In the hotel, by the use of seawater for toilet flushing, the amount of saved

freshwater is 5,475 m3/year which is enough water to supply around 103 locals.

After the upgrade of the RO desalination water plant in the hotel, the amount of

saved freshwater is equivalent to supply around 3,172 locals.

After the upgrade of the conventional WWTP of the hotel by MBR treatment

system, the quality effluent is ready for reuse. Producing approximately 138,700

m3/year which are equivalent to the amount of saved freshwater needed to supply

2620 locals.

In general, in a hotel of capacity of 500 persons (tourist), the potential combination

of the use of seawater for toilet flushing, the RO desalination and the reuse of treated

wastewater will allow to save enough freshwater (312,027 m3/year) to supply

around 5,895 locals.

Special acknowledgements 86

Special acknowledgements

This research study of the “Economic feasibility analysis of the use of innovative alternative

water sources in Cuba: A study case” was part of the project “Mas Agua Para Todos”. This

project whose English translation is “More Water for All”, and led by Dr. Carlos Lopez

Vazquez from UNESCO-IHE, contributes to the alleviation of water scarcity in Cuba through

the introduction of innovative practices, including decreasing the freshwater demand,

encouraging wastewater reuse, and the use of seawater as second quality water in the urban

environment. This project is funded by the European Union (project No. DCI-

ENV/2010/247-301).

http://masaguaparatodos.unesco-ihe.org/home-english-version

http://masaguaparatodos.unesco-ihe.org/home-english-version

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Appendix 91

Appendix

A. Case-study: domestic use of seawater for toilet flushing in Cuban urban environments

1. 50 Persons

Appendix 92

2. 100 Persons

Appendix 93

3. 200 Persons

Appendix 94

4. 500 Persons

Appendix 95

5. 1000 Persons

Appendix 96

6. 5000 Persons

Appendix 97

7. 15,000 Persons

Appendix 98

B. Case-study of the touristic resort Villa Playa Hermosa: use of seawater for toilet flushing in the tourism sector in Cuba

Appendix 99

C. Case-study: wastewater reuse in Punta de Hicacos at La Peninsula de Varadero

Appendix 100

D. Case study at the Hotel Breezes Jibacoa

economic feasibility analysis of the use of innovative

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