determination of domestic wastewater

8/16/2019 Determination of Domestic Wastewater

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DETERMINATION OF DOMESTIC WASTEWATER

CHARACTERISTICS AND ITS RELATION TO THE TYPE AND SIZE OF

DEVELOPMENTS.

SOHAIMI KLING

A project report submitted in partial fulfillment of the

requirements for the award of the degree of

Master of Engineering

Faculty of Civil Engineering

Universiti Teknologi Malaysia

MAY 2007


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I declare that this thesis entitled “ Determination of Domestic Wastewater

Characteristics and Its Relation to the Type and Size of Developments ’ is the result

of my own research except as cited in the references. The thesis has not been

accepted for any degree and is not concurrently submitted in candidature of any

other degree.

Signature : ………………………………………….

Name : ………………………………………….

Date : ………………………………………….


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To my beloved wife, sons and daughters


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ACKNOWLEDGEMENT

In preparing this thesis, I was in contact with many people including

academicians and practitioners. They have contributed towards my understanding

and thoughts. In particular, I wish to express my sincere appreciation to my main

thesis supervisor, Professor Dr. Ir. Mohd.Azraai Kassim and all lecturers especially

Professor Dr. Razman Salim, Professor Madya Dr. Fadil Othman and Dr. Azmi Aris

for their guidance, advices and motivation. Without their continued support and

interest, this thesis would not have been the same as presented here.

I am also indebted to my employer Indah Water Konsortium Sdn Bhd for

funding my study. Librarians and other staff at UTM and IWK also deserve special

thanks for their assistance in supplying the relevant literature.

My sincere appreciation also extends to all my colleagues and others who

have provided assistance at various occasions. Their views and opinions are useful

and unfortunately, it is not possible to list all of them in this limited space. I am

grateful to my family particularly to:

Rihanah Ahmad

‘Umayr Hasan Sohaimi

Muhammad Suhail Sohaimi

Ahmad Naufal Sohaimi

Syakir Husein Sohaimi

‘Ali Jabri Sohaimi

Faris Muhsin Sohaimi

Zaid Harith Sohaimi

Nur Safiah Sohaimi

Yusuf Fadhli Sohaimi Nur Khodijah Sohaimi


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ABSTRACT

Ciri-ciri air-sisa domestic mentah di negara ini kini ditetapkan berdasarkan

kepada dua (2) parameter utama iaitu; 250 mg/l BOD and 300 mg/l SS bagi

merekabentuk kemudahan Logi Rawatan Kumbahan (STP) , sepertimana yang

digariskan di dalam MS 1228. Suatu semakan telah dilakukan terhadap standard

efluen ini, yang membahagikan STP kepada tiga (3) kategori iaitu:-

Kategori 1 yang ditetapkan kepada semua STP yang diluluskan setelah tarikh

had baru efluen digazetkan;

Kategori 2 ditetapkan kepada semua STP yang diluluskan selepas

penguatkuasaan 'Guidelines for Developers, Sewage Treatment Vol. 4

(GDV 4), 2nd Edition' yang dikeluarkan olih Jabartan Perkhidmatan

Pembetungan mulai Januari 1999;

Kategori 3 ditetapkan kepada semua STP yang diluluskan sebelum GDV 4

dikuatkuasakan.

Yang demikian, logi baru dibawah Kategori 1 (satu) hendaklah di rekabentuk bagi

mecapai samaada Standard A atau B dibawah semakan standard rekabentuk yang

baru. Bagaimanapun, tidak banyak kajian yang telah dilakukan untuk mengesahkan

ciri-ciri air-sisa domestic mentah berdasarkan kondisi setempat. Suatu tahap

rekabentuk optima akan dapat dihasilkan jika komposisi dan ciri-ciri air-sisa

domestic ditentukan dengan lebih jelas. Dengan menjalankan kajian ini, suatu

pemahaman yang lebih baik akan dapat diperolehi mengenai ciri-ciri air-sisa

domestic yang tipikal, dengan mengenalpasti air-sisa yang berpunca daripada

pelbagai jenis pembangunan (kediaman, perdagangan, perindustrian dan


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pembangunan bercampur). Selain itu, kajian ini, akan seterusnya menentukan

perbezaan ciri-ciri air-sisa bedasarkan pembangunan dengan saiz yang berbeza. Ini

akan menjadi asas kepada penetapan garispanduan akan datang, yang boleh

mendorong kepada penambahbaikan serta menghasilkan rekabentuk optima bagi

proses rawatan air sisa domentik.


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ABSTRACT

Currently, the characteristics of raw domestic wastewater in the country

adopted two (2) main parameters i.e. 250 mg/l BOD and 300 mg/l SS in the design

of Sewage Treatment facilities, as spelt out in MS 1228.

A new revised effluent discharge standard will categorise all STPs into three

categories:

Category 1 applies to all STP approved after the gazette date of the new

effluent discharge limits;

Category 2 applies to all STP which were approved after the 'Guidelines for

Developers, Sewage Treatment Vol. 4 (GDV 4), 2nd Edition' was enforced

by Department of Sewerage Services beginning January 1999;

Category 3 applies to all STP, which were approved before GDV 4 was

enforced.

Hence, new plants under Category 1(one) shall be designed to meet either Standard

A or B under the new revised design standards. However, not many studies have

been carried out to validate the characteristics of raw sewage based on local

conditions. An optimal design of sewage treatment can be established if the

composition and the characteristics of domestic wastewater are clearly determined.

By initiating this study, a better understanding on the typical characteristics of raw

domestic wastewater can be obtained that will also identify the domestic wastewater

generated from various types of developments (residential, commercial, industrial

and mixed development. Likewise, this study will further verify the difference of

raw sewage constituents that originated based on different sizes of the

developments. This will serve as a guide for future adoption that will help to

improve and optimize design of domestic wastewater treatment processes


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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

TABLE OF CONTENTS viii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF ABBREVIATIONS xii

LIST OF SYMBOLS xiii

I INTRODUCTION

1.1 Background 1

1.2 Objectives of the Study 3

1.3 Scope of Study 3

II LITERATURE REVIEW

2.1 Domestic wastewater generation 5

2.2 In-pipe treatment 11

2.3 Water consumption, norms, ethnic and religious

practices 132.4 Effect of trade wastewater into sewer 15


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2.5 Environmental and hydraulic influences 16

2.6 Sediments in sewer pipe 19

III METHODOLOGY

3.1 Analysis of all influent sampling data 21

3.2 Analysis of influent sampling data from

different type of developments 21

3.3 Analysis of influent sampling data from

different size of developments 22

3.4 Sampling 22

3.5 Elimination of outliers 23

IV RESULTS AND DISCUSSION

4.1 Mean and percentile value of overall samples 24

4.1.1 Mean and percentile value of BOD 24

4.1.2 Mean and percentile value of COD 26

4.1.3 Mean and percentile value of AMN 27

4.1.4 Mean and percentile value of SS 29

4.1.5 Mean and percentile value of pH 30

4.2 Mean wastewater characteristic based on

type of developments 32

4.3 Mean wastewater characteristic based on

size of developments 36

V CONCLUSIONS

5.1 Wastewater characteristics based on the

overall analysis 44

5.2 Recommendations 46

REFERENCES 47

Appendices 51


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LIST OF TABLES

TABLE NO TITLE PAGE

Table .1.1 Proposed revised effluent discharged standard

for Category 1 STP 2

Table 2.1 Typical Characteristics of Untreated Domestic

Wastewater 7

Table 2.2 Mean Results of Domestic Wastewater

Characteristics 10

Table 4.1 Characteristics of Domestic wastewater from

all Samples 32

Table 4.2 Mean Domestic wastewater characteristics

based on type of Developments 34

Table 4.3 Size of Development- Mean Domestic

wastewater characteristics 37

Table 5.1 Characteristics of Domestic wastewater from

all Samples 45


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LIST OF FIGURES

TABLE NO TITLE PAGE

Figure 4.1 BOD Concentration range 25

Figure 4.2 BOD Percentile 25

Figure 4.3 COD Concentration range 26

Figure 4.4 COD Percentile 27

Figure 4.5 AMN Concentration range 28

Figure 4.6 AMN Percentile 28

Figure 4.7 SS Concentration range 29

Figure 4.8 SS Percentile 30

Figure 4.9 pH Concentration range 31

Figure 4.10 pH Percentile 31

Figure 4.11 Mean Domestic wastewater characteristics

based on type of Developments 35

Figure 4.12 Mean Domestic wastewater characteristics

by size of Developments 38

Figure 4.13 BOD variation with increase of development size 39

Figure 4.14 COD variation with increase of development size 40

Figure 4.15 AMN variation with increase of development size 41

Figure 4.16 SS variation with increase of development size 42

Figure 4.17 pH variation with increase of development size 42


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LIST OF ABBREVIATIONS

A/ITI - Alkalinity

AMN - Ammonical Nitrogen

BOD - Biochemical Oxygen Demand

COD - Chemical Oxygen Demand

DOE - Department of Environment

GDV - Guidelines for Developers

IWK - Indah Water Konsortium

MS - Malaysian Standard

PE - Population Equivalent

pH - Hydrogen-ion concentration

SS - Suspended Solid

SSD - Department of Sewerage Services

STP - Sewage Treatment Plant

UTM - Universiti Teknologi Malaysia


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LIST OF SYMBOLS

mg/l Milligram per litre

l/p/d Litre per person per day


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CHAPTER I

INTRODUCTION

1.1 Background

The Environmental Quality Act 1974 specifies two standards of effluent

discharges i.e. Standard A for discharges upstream of raw water intakes and

Standard B for discharges downstream of raw water intakes. A new revised effluent

discharge standard will categorize all STPs into three (3) categories in accordance to

the type of plants and the date when the design is approved:

Category 1 applies to all STPs approved after the gazette date of the new effluent

discharges limits;

Category 2 applies to all STPs which were approved after the 'Guidelines for

Developers, Sewage Treatment Vol. 4 (GDV 4), 2nd Edition' was enforced by

Department of Sewerage Services beginning January 1999;

Category 3 applies to all STPs, which were approved before GDV 4 was

enforced.


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Therefore, new plants under Category 1 shall be designed to meet either Standard A

or B based on compliance to the proposed revised effluent standard in Table 1.1

shown below.

Table 1.1: Proposed revised effluent discharge standard for Category 1 STP.

Parameter(mg/l )

Effluent Discharge toRiver/Stream

Effluent Discharge toStagnant Water Bodies**

Standard A Standard B Standard A Standard B

BOD 5 20 50 20 50

SS 50 100 50 100

COD 120 200 120 200AMN 10 20 5 5

Nitrate Nitrogen

20 50 10 10

Phosphorus na na 5 10

O&G 5 10 5 10

Notes: na = Not Applicable

**Stagnant Water Bodies refer to enclosed water bodies such as lakes, ponds

and slow moving watercourses where dead zones occur.

Currently, data with regards to the characteristics of raw sewage in the country is

based on MS 1228, which emphasizes on 2 main parameters i.e. 250 mg/l BOD, and

300 mg/l SS as design parameters. However, no local in-depth studies have been

carried out to verify the characteristics of raw sewage in the country.

Differences in the constituents that are generated from various types of development

have not been determined to observe its significance. Similarly, no record has ever

been initiated to determine the variables that influence the domestic wastewater

generated from difference sizes of developments. Estimation of wastewater

characteristics is necessary to determine the design capacity of the treatment plant.In

case of new development projects where the actual wastewater data is not available,

the wastewater loading and flowrates are derived from population estimates and the


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wastewater load and composition are solely based on the locally accepted typical

values.

By initiating this study, a better understanding on the typical characteristics of raw

sewage can be obtained that will help to improve design of sewage treatment

processes.

1.2 Objectives

The objectives of this study are as follows:-

To determine the ranges of typical composition of raw sewage in terms of BOD,

SS, COD, AMN, and pH values.

To study the typical characteristics of raw sewage generated from various types

of developments in the country i.e. from residential, commercial and from mixed

developments.

To identify the typical raw sewage measured in relation to the size of the

developments.

1.3 Scope of study

The study is based on data of periodical influent sampling results generated

from year 2003 to 2005 at all sewage treatment plants in the country. The study does

not include a 24 hours sampling to gauge the diurnal fluctuation pattern in the

concentration load.


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Although the data are gathered based on grab sampling carried out during half-

periods of the weekday, yet it involved an extensive representation in samplings

with a total number of approximately 30,000 samples, and cover a broad span in

terms of locations, numbers, type and size of developments.

This study however, does not include Phosphorous and Oil &Grease constituents in

the domestic wastewater.

Likewise, this study does not include treatment processes applied to meet the

prescribed effluent standards.


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CHAPTER II

LITERATURE REVIEW

2.1. Domestic wastewater generation

Domestic wastewater by definition is the discharge from domestic residences,

commercial or industrial premises into the public sewer, originated from all aspects

of human sanitary water usage. It typically constitutes a combination of flows from

bathroom, toilets, floor traps, kitchen sinks, dishwashers and washing machines.

However, apart from domestic wastewater originated from residence, other premises

such as commercial, institutional and industrial also contribute a domestic

wastewater component to the sewer system. In Malaysia, a separate sewerage

conveyance system is adopted from the domestic use only and do not combine with

either storm water or industrial process wastewater.

Adoption of design parameters for biological process design is difficult because

domestic wastewater concentration vary greatly from one country and one

community to another for various reasons, such as differences in food consumed,

water use and personal hygiene practices. Hence, the average daily rates of flow

generation are also dependent significantly on the socio-economic status of the

community particularly with respect to its affluence and standard of living.


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The most accurate way to determine the character and quantity of domestic

wastewater is to measure the existing wastewater flow over a sufficient length of

time to determine its variability in terms of composition, concentration and load.

However, in the case of new development, a prescribed wastewater flow and typical

characteristics of the domestic wastewater need to be adopted for the design stage of

a new treatment system in meeting with the stipulated discharge standard.

There were literature that outlined the typical influent characteristics of domestic

wastewater studied elsewhere and one which is widely refered to is tabulated in

Table 2.1.

The treatment of sewage will require the processing of both organic and inorganic

solid matter as explained by Rendell (1999). This matter will be in the form of

dissolved solids and suspended solids. The inorganic load is comprised of grits and

salt. Sewage with high industrial waste element will consist of compounds and

possibly include highly toxic chemicals. To enable the nature of the liquid to be

described there is a need to define two things: firstly a characteristic that reflects the

nature of the compound and secondly, its concentration in the solution. The

concentration will be expressed in terms of mass per unit volume The more usual

units is mg/l. Another form in which the quantity of a compound will be expressed is

a load. This type of unit is used to define loadings on the system and is calculated

from concentration and the flowrate e.g gm per day.

The characterization of domestic wastewater involves an examination of all essential

elements of wastewater characterization; namely its typical composition in terms of

BOD, SS, COD, AMN and pH. BOD 5 is used to measure the biodegradable organic

fraction in raw sewage.


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Table 2.1: Typical Characteristic of Untreated Domestic Wastewater

ConcentrationContaminants Unit

Weak Medium Strong

Solids, total (TS) mg/L 390 720 1230Dissolved, total (TDS) mg/L 270 500 860

Fixed mg/L 160 300 520

Volatile mg/L 110 200 340

Suspended solids (SS) mg/L 120 210 400

Fixed mg/L 25 50 85

Volatile mg/L 95 160 315

Settable solids mg/L 5 10 20BOD 5, 20°C mg/L 110 190 350

Total organic carbon mg/L 80 140 260

COD mg/L 250 430 800

Nitrogen (total as N) mg/L 20 40 70

Organic mg/L 8 15 25

Free ammonia mg/L 12 25 45

Nitrites mg/L 0 0 0 Nitrates mg/L 0 0 0

Phosphorus (total as P) mg/L 4 7 12

Organic mg/L 1 2 4

Inorganic mg/L 3 5 10

Chlorides mg/L 30 50 90

Sulfate mg/L 20 30 50

Oil and Grease mg/L 50 90 100Volatile organic

compound

mg/L 400

Total Coliform #/100mL 10 6~10 8 107~10 9 107~10 10

Fecal Coliform #/100mL 10 3~10 5 104~10 6 105~10 8

Source: Metcalf and Eddy .Wastewater Engineering, Treatment and Reuse.

4th Edition. 2004. Table 3-15.


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In the standard measurement of BOD 5, the oxygen demand measured is influenced

by three conditions: (a) Oxygen demand by the breakdown of soluble carbonaceous

matter (b) Oxygen demand by the breakdown of suspended particulate carbonaceous

matter (c) Oxygen demand by the oxidation of ammonia to nitrate by nitrifying bacteria present in the effluent sample. As the amount of residual soluble

carbonaceous BOD 5 matter in the effluent, after undergoing treatment in the

secondary reactor, reduces in concentration to below 15 mg/l, nitrifying bacteria

populations tend to grow rapidly feeding on ammonia present in the partially treated

sewage. Nitrification may not be complete at levels of 5 mg/l of residual soluble

carbonaceous biodegradable matter; it depends on whether sufficient oxygen is

available for oxidation of ammonia to nitrate.

BOD is used not only to indicate the strength of a wastewater but also that of a

treated effluent and the efficieny of the various stages of treatment. The BOD of

domestic sewage may be expected to lie in the range of 150 to 600 mg/l whereas for

industrial wastes values from 0 to 100,000 mg/l may be found, depending upon the

nature of the industry. (Pescod, 1999)

Sewage also contains solid material that can settle on the bottom or in suspension

solids form that can increases turbidity and impact the light availability for aquatic

life. The desired solids removal in sewage treatment should reflect the absolute SS

discharge limit of 50mg/l and 100mg/l for Standard A and Standard B catchment.

COD content reflects the chemically oxidized organic matter; hence it includes

refractory fractions of organic matter as well as reduced inorganic constituents

present in the wastewater. The measure of COD offers a quick estimate of

carbonaceous material compared to conventional BOD measurements. Additionally,

high COD reflects the potential industrial contamination in the form of inert reduced

inorganic elements and unbiodegradable organics. Based on the bisubstrate

hypothesis, COD fractions of readily biodegradable, slowly biodegradable and

unbiodegradable estimates are also adopted in advanced modeling for STP design

whereby the different fractions vary in susceptibility to microbial respiration and

degradation.


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Wastewater may contain high levels of nutrients. Excessive release to the

environment can lead to a build-up of nutrients, i.e. eutrophication, which can in turn

encourage the overgrowth of algae. Not just an aesthetic issue, some algal species

produce toxins which contaminate drinking water supplies, while in serious cases, so

much algal/plant matter can be present that the consumption of dead plant matter by

bacteria decay depletes the oxygen in the water and suffocates fish and other aquatic

life. Removal of nitrogenous compounds needs to be considered in STP design. It is

found in varying forms that are detrimental to natural water bodies and potable

consumption. To ensure compliance with the prescribed effluent discharge standard,

the characteristic of the nitrogenous constituent shall be determined in order that

adequate nitrifications and denitrification in the secondary biological reactors design

is provided. (Sewerage Services Department, 1998).

The hydrogen-ion concentration, which is expressed as pH, is an important

parameter for wastewater as a suitable concentration range allows for the survival,

growth and existence of most biological life. For carbonaceous removal, pH in the

range of 6 to 9 is tolerable, while optimal performance occurs near a neutral pH.

Nitrification is affected by a number of environment factors and the rates declined

significantly at pH values below 6.8. Optimal nitrification rates occur at a pH range

of 7.5 to 8.0. Alkalinity is produced in denitrification reactions and the pH is

generally increased instead of being depressed as in nitrification reactions. In

contrast to nitrification, there has been less concern about pH influence on

denitrification rates. Wastewater with an extreme concentration of hydrogen ion is

difficult to treat by biological means, and if the concentration is not altered before

discharge, the wastewater effluent may alter the concentration in the natural

waterbody.

Collaborative research between IWK and UTM (Othman,2003) was conducted to

determine the per capita loading and water consumption in sewage treatment design.

Six (6) different sites were identified with PE ranging from 1,000 to 20,000. For

each site, a full 14-day study was done. Composite as well as 24 hours sampling

were carried out for the first 3 days and 4 times per day for the next 11 days and the

result is tabulated in Table 2.2 below.


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recommended that for sewerage system design purposes it can be assumed that a

single person resident generates an average daily sewage flow of 225 litres per day.

The inherent wastewater load will also change due to changed diet habits e.g.

consumption of more processed food and use of kitchen grinder/macerator for

disposal of scrap food into sewerage system. Also, a tendency for using household

chemicals which include detergent and cleaning agents increased the amount of less

degradable materials into the sewer. Determination of wastewater characteristic and

concentration is necessary to ensure that the design capacity as well as the process

requirements of the treatment plant is fulfilled. The availability of the actual flow

and loading pattern will lead to a better design and ways of operating the STP

facility.

2.2. In-pipe treatment

Tanaka et al.(2000) reported that microbial transformation of organic matter in

wastewater takes place during transport in sewers. These processes occur in the bulk

water phase, in biofilms, and in temporarily settled sediments under aerobic and

anaerobic conditions .Under aerobic conditions in a gravity sewer, readily biodegrad-

able substrate, either directly discharged to the sewer or originating from

hydrolysable substrate, is removed, and biomass is produced .

On the same note Vollertsen et al (2005),clarified that wastewater quality undergoes

changes when conveyed in sewers. How and to what extent such changes occur

depends on the physical, chemical, and microbial conditions in the sewer as well as

the composition of the wastewater. Under aerobic conditions, the sewer biomass

consumes easily biodegradable organic matter, resulting in a wastewater improved

for mechanical and chemical treatment. On the other hand, when conditions become

anaerobic, the biomass consumption of readily biodegradable substrate is


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considerably reduced and fermentation of organic matter will result in a more easily

biodegradable wastewater.

Boon (1995) further testified that septicity in sewerage systems results from the

activity of bacteria, growing in sewage and on submerged surfaces which, under

anaerobic conditions, reduce sulphur-containing organic compounds and sulphates

to form sulphides and other malodorous sulphur compounds.Lack of adequate

ventilation, low velocity of sewage in large diameter sewers or small diameter rising

mains and high temperature, BOD or COD of sewage, will inevitably result in

septicity.

Balmer and Tagizadeh-Nasser (1995) in their paper states that wastewater engineers

often are heard to blame their failures on the fact that wastewaters are so different.

As long as wastewaters are predominantly of domestic origin it is however suprising

that they are different. The only rational explanation is that wastewaters are

transformed during transport from households to the wastewater treatment plant. The

per capita lengh of sanitary sewers is 3m to 10m and if the biofilm of the wetted

sewer perimeter is assumed to have the same activity as a biofilm in a trickling filter

or in a rotating biological contactor, it is obvious that a substantial part of the

organic matter in the wastewater can be metabolised before the wastewater enters

the wastewater treatment plant.The study also confirmed that energy dissipation is a

key factor for oxygen transfer in sewers.

Abdul-Talib et al (2003) hence advocated that sewer networks can and should be

designed not only for conveyance of water and pollutants, but also for obtaining a

wastewater quality that is suitable for the treatment processes at the receiving

wastewater treatment plant. It is well known that more than half of the cost to

provide a sewerage system is taken up by the sewer network. Therefore, it will be a

waste if the lengths and volumes of the sewers, which have potential treatment

capability are not fully utilised.

Conventional sewer systems in urban areas are designed and constructed in order to

transport wastewater from its source to treatment plants. During the transport of wastewater in sewer systems, many physical, chemical and biological


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transformations may result in significant changes in the wastewater composition.The

microbial transformation can be determined based on three types of conditions:

aerobic,anaerobic or anoxic, depending on the type of electron acceptors that are

present in the wastewater. Each of them produces different processes that will

change the quality of the wastewater transported upon arrival to the wastewater

treatment plants. Therefore, it is possible to design sewer systems to achieve dual

purposes: transport and biotransformation of wastewater as presented by Ujang et al

(2004). Results from a laboratory-scale sewer system as a bioreactor under tropical

anoxic condition revealed that the overall removal efficiency between 0 to 3 km

samples in the sewer system are as follows:suspended solids 58%,turbidity 24%,

COD 30% and BOD 25%.

Today, the importance of the sewerage system as a biological reactor ,in which

aerobic or anaerobic biochemical processes will occur, has been recognised. The

benefits of wastewater pretreatment under aerobic conditions can be maximised by

ensuring that sewerage systems are designed to achieve reaeration of wastewater at a

rate greater than the rate at which microorganisms (present in the wastewater and

attached to submerged surfaces in the pipework) consume dissolved oxygen.

Sewerage systems should include long gravity sewers which operate at self-

cleansing velocities, ensure adequate reaeration and include vertical-lift pumping to

avoid excessive periods of wastewater storage in the absence of adequate reaeration

(Pescod, 1999 ).

2.3. Water consumption, norms, ethnic and religious practices

There is growing realisation among water suppliers and academics that water

demand stems from routine behavior and norms which develop within a particular

social background and this has been studied by Smith and Ali (2006).This is is in

contrast to other types of consumer demand in which customers exercise consciouschoice. Despite such acnowledgement, the idea that ethnic background and religion


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may both form a fundamental basis for water consumption norms and practices is

largely overlooked.The study conducted in UK revealed that water use patterns are

highly characterised by ethnicity and religious practice.

Design Guidelines for Water Supply Systems published by the Malaysian Water

Association (1994) specified that, per capita water demand should be classified

under three categories. The guideline below gives a range of per capita consumption

for each of the three categories:

Urban-230 to 320 liters/ head/day,

Semi-Urban-180 to 230 liters/ head/day,

Rural- 135 to 180 liters/ head/day.

The design guidelines also reported that the daily demand varies slightly due to the

weather and festive seasons. In most states, daily water demand increases slightly in

the month of January and February. During festive seasons, experience has shown

that in some urban centres, there is a change in demand due to shutting down of

factories while there is an increase in demand in rural areas and smaller urban

centers due to people leaving big urban centres for their hometowns and villages.

The MS 1228 specify that sewerage systems be designed based on an average daily

per capita flow of 225 litres and the process design of a domestic waste treatment

shall be on the basis of 55 grams of BOD per capita per day and 68 grams of

suspended solids per capita per day, which equate to concentration of 245 mg/l and

302 mg/l for BOD and SS respectively

Galil and Shpiner (2001) explained the effect of kitchen sink macerator; that the

domestic garbage disposer is an electro-mechanical device which is installed

underneath the kitchen sink and is used to grind solid wastes resulting from food

preparation. The mixture of grinded solids and water is flushed to the sewerage

system and to the sewage treatment works. As a result of grinded garbage

discharged to the collection system, a change in the quality and quantity of crude

sewage is usually reported due to the addition of suspended solids, as well as theincreased water consumption for the flushing action. The disadvantages associated


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with garbage grinders are based on the fact that the solid waste is grinded and mixed

with fresh water, transforming it into wastewater, and adding to the load on the

sewerage system. This may cause deposition and clogging problems in sewers, and

can result in an additional organic loading and an increased amount of sludge.

Greywater as defined by Howarth (2002) is wastewater from sinks, baths, showers

and domestic appliances. Kitchen sink or dishwasher wastewater generally has high

levels of contamination from detergents, fats and food wastes.

The separation at source could be an option for public health protection: blackwater

from toilets is treated in individual septic tanks or small sewage plants, and the

greywater or sometimes called sullage, is discharged to the hydraulically well

designed stormwater drain, or into a sullage soakaway (Abdul-Hamid and Ujang,

2006). However, separation at source can also contribute to water pollution. In this

situation, stormwater drains contain high concentrations of washing chemicals, oil

and grease and residuals of food. Most of the stormwater drains in urban areas in

tropical countries are connected to tributaries of major rivers. As a result it is a

phenomenon that tropical rivers are mainly polluted due to untreated greywater.

2.4. Effect of Trade wastewater into sewers

Lesikar et al (2006) published literature which indicates that designers' use of

industry-accepted methodologies and design values for sizing treatment systems for

restaurants has, in the past, resulted in systems that are inadequately designed with

regard to hydraulic and organic loading A study evaluating the failure rate of two

restaurants against the mean age to failure rate for lower strength residential

wastewater treatment systems of 18 years indicates concern in allowing existing

residential-based design guidelines to be used for commercial or industrial facilities.

This is particularly true of treatment-system designs used in food-service


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establishments. Comparison of the above-mentioned studies shows that higher

wastewater strengths can induce a faster decline of treatment-system performance.

A Guide published by the Pollution Prevention Committee, Water Environment

Federation, highlighted that facilities that service vehicles, whether automobiles,

trucks, airplane, or boat have been shown to discharge heavy metals, solvents, and

oil and grease to both sanitary sewer and storm drain system. These facilities not

only include retail repair shops but also fleet maintenance operations within

organizations that exist primarily for purposes other than servicing vehicles (e.g.

delivery services and corporate fleets).Although many of these facilities, particularly

retail repair shops, may not be large, they often are numerous within a community

and have a combined effect on both sanitary sewers and storm drain

systems.(Brosseau et al, 1995)

Studies by Jenkins (1988), have demonstrated that numerous sources contribute to

the levels of heavy metals found in municipal wastewater, including the water

supply, industry and residential activities. An earlier study identified the heavy

metals contribution of household washing products compared to other sources.

2.5. Environment and Hydraulic influences

Muirhead (2005) states that microorganisms in wastewater collection systems

can affect the alkalinity and pH of wastewater. Depending on the organism, the

environmental conditions, and the biological mechanism, alkalinity can increase or

decrease and have beneficial or detrimental effects. Means by which

microorganisms can affect alkalinity and pH in wastewater collection and treatment

systems are: biological respiration, fermentation, nitrification, denitrification,

photosynthesis, sulphate reduction and sulphate oxidation. Hence, environmental

conditions in wastewater collection and treatment system can promote the growth of a wide range of microorganisms that can affect alkalinity and pH. Understanding of


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these effects can help operators optimize facilities and minimize the negative effect

on capital and operations and maintenance cost, as well as permit compliance.

Infiltration into sewer systems are contributed by factors such as (i) age of sewer, (ii)

condition of connection either direct to pipe or to manhole, (iii) illegal connection of

roof gutter and drain to sewer system, (iv) permeability of soil around sewer, (v)

groundwater elevation and (vi) quality of construction. Besides infilling during

raining season due to high water table, on the contrary will cause leakages and

diffusion of wastewater to the ground adjoining the pipeline during dry weather.

A study conducted by UTM-IWK (Norhan, 2003) at four housing estates in Johor

Bahru identified that, infiltration in many areas is as low as 88l/d per km per mm

and as high as 4700l/day per km per mm. Leakage is more than 20% of flow in most

sewers tested and in some places even reaches 8000l/d per km per mm. Leakage is

more severe during drier periods than wetter periods. In comparison, the allowance

of infiltration given in MS 1228:1991 states that infiltration sewerage system may be

designed to cater for a maximum infiltration rate of 50 litres per mm diameter per

km of sewer per day. Hence, the above study shows that the measured value of

infiltration has exceeded the permissible rate. Among the reasons for this is ageing

sewer systems and porous soil with infiltrative capacity.

Madsen et al (2006) identified that ventilation of sewer systems is important to

maintain aerobic conditions in the wastewater and to control odor and corrosion. The

following five factors have been identified as the major contributors to natural sewer

ventilation: (i) wind speed may create suction or pressure across manholes, (ii) flow

of wastewater drags the sewer gas, (iii) variations in wastewater level forces the air

into and out of the sewer, (iv) temperature differences between the sewer gas and the

urban atmosphere result in differences in gas densities and (v) differences in

atmospheric pressure lead to gas volume expansion and compression.

When planning, designing and operating a wastewater treatment plant in a warm

region, the climatic specifics must be taken into account to make best use of the

many favourable characteristics enabled by the higher temperatures. In similar way,


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for a treatment plant in a developing region, the aspects relevant to its sustainability

must be judiciously incorporated (Von Sperling and Chernicharo, 2006).

In the design of treatment process or a transfer system, the ideal condition for the

design is that the loadings should be constant. Because the limited buffering of flows

within the sewerage system (unlike buffering effect of a water service reservoir), the

design and operation of a sewerage system become more difficult due to the high

flow variation. (Rendell, 1999) The term population and water consumption are

closely linked to social changes and the way in which a community uses water. The

industrial loads have to be estimated with knowledge of the type of industry that

exists in the catchment. The daily and seasonal variation in industrial flows will be

dictated by the type of the industry and the mode of operation.

The causes of flow variation within a system are: (a) a long term variation due to

change in water use (b) the annual flow variations due to such factors as holiday

populations and seasonal industrial processes (c) weekly variation will be

predominantly caused by commercial and industrial work patterns and (d) diurnal

variation due to the normal life patterns of the domestic consumer. For a large or

widely spread sewerage system with flow within the system that have average

velocities of 0.8 m/s, thus the time between flows entering the system and arriving at

a collection point will vary greatly. The effect of this is that the system, due to its

volume, will act as a buffer and attenuate the peak flow. The contribution of

industrial wastes can be biological in nature dictated by the industrial process such

as poultry packing and dairies although the concentration is much higher.

Both turbulence in the water phase and the pH were found to play a crucial role in

the transfer of hydrogen sulfide. The air-water transfer process of hydrogen sulfide,

which also incorporates the association process, can be related to the reaeration

process in terms of their transfer rates. A relationship between the two processes is

primarily established for the pH range typical for domestic wastewater (Yongsiri et

al, 2004).

Depending on the length of sewer networks, the flow generated from source mayrequire several hours to flow through the sewer network system because of flow


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dampening effect and prolonged by the available storage capacity in the sewer

system. Intermittent inflow can also occur due to the collection and delayed

discharged via network pumping stations that is being controlled and triggered the

flow by water levels or timer which is then transferred to the downstream trunk line.

Delay inflow hence is due to the collection and discharged via network pumping

stations that transferred flow to the downstream trunk line toward the headworks of

the treatment plant.

2.6. Sediments in sewer pipes

For the provision of a new sewerlines system, it is a common practice to

provide a conservative design gravity sections which usually convey peak flows to

justify a worst case scenario for the new system. The peak flows occurrence may

happen only over a shorter period or even on instantaneous mode of the peak flow.

At minimum flow situation, the least flowrate and minimum velocity will lead to

built-up of solids in the sewer.

Rushforth et al (2003) states that the presence of sediments in sewers can cause a

number of problems for operators. Deposits of sediments in pipes can reduce

hydraulic capacity, either by reducing the flow area or increasing the hydraulic

resistence.In-sewer deposits are also believed to store pollutants which are released

when deposits are mobilized during intense storm events. Accordingly, erosion of

such deposits is thought to be responsible for sudden large increases in suspended

solids which are observed at the leading edge of storms in a number of catchments.

Sewage treatment plants are designed to flow as much as possible under gravity, in

order to minimise the number of pumps in the catchment area depending on

topography. The hydraulic processes in the pumping stations may include pumping

system hydraulics, closed conduit hydraulics and in some cases transient hydraulics.In the event of pump failures, which may be due to electrical failures, mechanical


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failures or breakdown of the pumping systems, the hydraulic processes in the

approaching sewers will change drastically. In the sewage pumping stations, the

operations are intermittent as the incoming flow varies over time according to

diurnal distribution. The intermittent operations of pumps may lead to occurrences

of transient flow and no flow conditions. This in a way will have effect to the

mobilization and deposition of sediments in the sewer pipes.


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CHAPTER III

METHODOLOGY

3.1 Analysis of all influent sampling data.

The study was conducted through analysis of an approximately 30,000 raw

influent sampling data gathered for year 2003 to 2005 representing an approximately

4,200 sewage treatment systems nationwide (with the exception of Johor Bahru city

area; states of Kelantan, Sabah and Sarawak.) The influent sampling exercises are

part of the operational monitoring requirement carried out by IWK .The sampling

frequency and visitation are principally determined by the size of the STP. All

sampling results including influent and effluent information are recorded that linked

to specific STP asset references.

3.2 Analysis of influent sampling data from different type of developments.

Another set of data was made available defining the type of customer (residential, commercial and industrial premises) that are connected to a particular


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3.5 Elimination of outliers.

Outliers were removed by eliminating data that fall within one percent of the

lowest band and also those data that fall within one percent of the uppermost bands

These data are considered extreme values that may be influenced by sudden surges

of loading due to the possibility of illegal pollution discharge from unidentified

sources or may be due to the effect of high rate infiltration that severely diluted the

raw sewage influent into the sewerage system.


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CHAPTER IV

RESULTS AND DISCUSSION.

4.1 Mean and Percentile value of overall samples

The mean and at 90 th and 95 th percentile value of typical composition are

being analysed in this study based on 3 years influent sampling data of raw sewage

taken at headworks of all the Sewage Treatment Plants. The parameters that are

being studied covers the five main sewage characteristics i.e. BOD, SS, COD, AMN

and pH. Other parameters including phosphorous and oil & grease are not included

in this study.

4.1.1 Mean and Percentile for BOD.

From a total number of 29,660 samples sorted and analysed as shown in

Figure 4.1 below, the highest number of samples recorded for BOD concentrations

are within the 151 to 200 mg/l range. By averaging the total number of data, it was

found that the mean value of BOD is 135 mg/l.


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OD

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0

5 1 - 1 0 0

1 5 1 -

2 0 0

2 5 1 -

3 0 0

3 5 1 -

4 0 0

4 5 1 -

5 0 0

5 5 1 -

6 0 0

6 5 1 -

7 0 0

7 5 1 -

8 0 0

BOD Concentration mg/l

N o o f S a m p l e s

Figure 4.1: BOD Concentration range

OD

0

0.2

0.4

0.6

0.8

1

1.2

0 0 - 5

0

5 1 - 1 0 0

1 0 1 -

1 5 0

1 5 1 -

2 0 0

2 0 1 -

2 5 0

2 5 1 -

3 0 0

3 0 1 -

3 5 0

3 5 1 -

4 0 0

4 0 1 -

4 5 0

4 5 1 -

5 0 0

5 0 1 -

5 5 0

5 5 1 -

6 0 0

6 0 1 -

6 5 0

6 5 1 -

7 0 0

7 0 1 -

7 5 0

7 5 1 -

8 0 0 8 0 1 -

BOD Concentration mg/l

% C u m m u l a t i v e F r e q u

e n c

Figure 4.2: BOD Percentile

Further analysis based on the percentage of cumulative frequency versus BOD

concentration range graph in Figure 4.2 above shows that the value of approximately


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220 mg/l and 280 mg/l of BOD at 90% and 95% percentile respectively, which is

within the typical value of 250 mg/l adopted in the local guideline.

4.1.2 Mean and Percentile for COD.

The amount of oxygen needed to oxidize reactive chemicals in water system

as defined by the Chemical Oxygen Demand (COD) is another parameter used to

determine sewage characteristics. The COD chart shown in Figure 4.3 below

indicated that the highest numbers of samples for COD concentration are under the

range of 251 to 300 mg/l. The mean value of COD from a total number of 29,676

samples is 294 mg/l.

It is also observed that the mean characteristic of COD: BOD ratio is approximately

2.3 which roughly shows the organic matter content of the raw domestic wastewater

characteristic.

COD

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0

1 0 1 -

1 5 0

2 5 1 -

3 0 0

4 0 1 -

4 5 0

5 5 1 - 6 0

0

7 0 1 - 7 5

0

8 5 1 - 9 0

0

1 0 0 1

- 1 0 5

0

1 1 5 1

- 1 2 0

0

1 3 0 1

- 1 4 0

0

1 6 0 1

- 1 7 0

0

1 9 0 1

- 2 0 0

0

2 2 0 1

- 2 3 0

0

COD Concentration mg/l

N u m b e r o f S a m p l e s

Figure 4.3: COD Concentration range


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COD

0

0.2

0.4

0.6

0.8

1

1.2

0

1 0 1

- 1 5 0

2 5 1

- 3 0 0

4 0 1

- 4 5 0

5 5 1

- 6 0 0

7 0 1

- 7 5 0

8 5 1

- 9 0 0

1 0 0 1

- 1 0 5

0

1 1 5 1

- 1 2 0

0

1 3 0 1

- 1 4 0

0

1 6 0 1

- 1 7 0

0

1 9 0 1

- 2 0 0

0

2 2 0 1

- 2 3 0

0

COD Concentration mg/l

% C u m m u l a t

i v e

F r e q u e n c y

Figure 4.4: COD Percentile

Based on the graph in Figure 4.4 above, the number of samples analysed depicted

that the value of COD at 90% and 95% percentile are approximately 470 mg/l and

625 mg/l respectively. The 90% percentile value of COD above falls within themedium strength value of 430 mg/l as shown in Table.2.1.

4.1.3 Mean and Percentile for AMN.

The AMN chart in Figure 4.5 below, shows that the highest number of samples for AMN concentration falls under the 16 to 25 mg/l. range. The mean

value of AMN averaging from a total number of 29,674 samples is 23 mg/l.


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AMN

0

1000

2000

3000

4000

5000

6000

0 1-5 6-

10

11-

15

16-

20

21-

25

26-

30

31-

35

36-

40

41-

45

45-

50

51-

55

56-

60

60-

65

65-

70

AMN Concentration mg/l

N u m b e r o f S a m p l e

Figure 4.5: AMN Concentration range

MN

0

0.2

0.4

0.6

0.8

1

1.2

0 1-5 6-10

11-15

16-20

21 -25

26-30

31-35

36-40

41-45

45-50

51 -55

56 -60

60-65

65-70

AMN concentration mg/l

% C u m m u l a t i v e P e r c e n t i l

Figure 4.6: AMN Percentile

In addition, the number of samples analysed in the percentage cumulative format

also shows that the value of AMN at 90% and 95% percentile are approximately 36


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mg/l and 45 mg/l respectively, which fall within the medium and the high strength

category presented in Table 2.1.

4.1.4 Mean and Percentile for SS.

From the SS chart in Figure 4.6 below, it is found that the highest number of

samples for SS concentration fall under the range of 100 to 200 mg/l. The mean

value of SS from a total number of 29,655 samples is 124 mg/l.

SS

0

2000

4000

6000

8000

10000

12000

14000

0

5 1 - 1

0 0

1 5 1 -

2 0 0

2 5 1 -

3 0 0

3 5 1 -

4 0 0

5 0 1 -

6 0 0

7 0 1 -

8 0 0

9 0 1 -

1 0 0 0

1 1 0 1

- 1 2 0

0

1 3 0 1

- 1 4 0

0

> 1 5 0

0

SS concentration mg/l

N u m b e r o f S a m p l e s

Figure 4.7: SS Concentration range

Results from the percentile distribution shown in Figure 4.8 below demonstrate that

the value of SS at 90% and 95% percentile are approximately 200 mg/l and 330 mg/l

respectively. The 95% percentile is within the typical value of 300 mg/l SS adopted

in the local guideline.


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SS

0

0.2

0.4

0.6

0.8

1

1.2

0

5 1 - 1

0 0

1 5 1 -

2 0 0

2 5 1 -

3 0 0

3 5 1 -

4 0 0

5 0 1 -

6 0 0

7 0 1 -

8 0 0

9 0 1

- 1 0 0

0

1 1 0 1

- 1 2 0

0

1 3 0 1

- 1 4 0

0

> 1 5 0

0

SS concentration mg/l

% C u m m u l a t i v e F r e q u e n c

Figure 4.8: SS Percentile

4.1.5 Mean and Percentile for pH

From the pH graph as shown in Figure 4.9 below, the highest number of

samples for pH value falls under the range of 6.7 to 7.4. The mean value of pH from

a total number of 29,374 samples is 6.96.


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Figure 4.9 pH concentration range

H

0

0.2

0.4

0.6

0.8

1

1.2

0 5.9-6.2 6.3-6.6 6.7-7.0 7.1-7.4 7.5-7.8 7.9-8.2 8.3

pH value

% c u m m u l a t i v e p e r c e n t i l e

Figure 4.10: pH Percentile

Likewise, from Figure 4.10 above, the number of samples analysed also shows that

the value of pH at 90% and 95% percentile are approximately 7.2 and 7.4

respectively. All the values for pH either the mean or the 90% and 95% percentile,

H

0

2000

4000

6000

8000

10000

12000

0 5.9 -6.2 6.3-6.6 6.7-7.0 7.1-7.4 7.5-7.8 7.9 -8.2 8.3

pH value

% c u m m u l a t i v e p e r c e n t i l e


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are considered within the optimum value that is conducive for bacterial growth

which lies between 6.5 and 7.5 levels as suggested in Metcalf and Eddy (2004).

Table 4.1: Characteristics of domestic wastewater from all samples.

Concentration

Contamin

antsUnit

Number

of

Sample

s

Mean

90th

Percen

tile

95th

Percen

tile

UTM-

IWK

Study

(mean)

Metcalf

& Eddy

(medium

strength)

BOD mg/L 29,660 135 220 280 239 190

COD mg/L 29,676 294 470 625 420 430AMN mg/L 29,674 23 36 45 28 25

SS mg/L 29,655 124 200 330 103 210

pH - 29,374 6.96 7.2 7.7 - 6.5-7.5

Table 4.1 shown above summarised the value of all the five parameter analysed

from the entire data made available in the study. The result illustrates that the 90th

percentile values in the analysis are the values comparable with the results from both

the UTM-IWK collaborative study (2003) and the value outlined in Metcalf & Eddy

(2004).

4.2 Mean sewage characteristics based on type of Developments.

In domestic wastewater, the composition of sewage varies from location to

location. It also varies with the time of day or season (weekday, weekend, holidays,

and climatic condition) and fluctuates even at the same location due to changes of

activities. Domestic wastes are mostly originated from showers, toilets, washing of

dishes and clothes, and from the kitchen. It is also important to note that not all of


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the residential units are fully discharging domestic wastewater loads to the sewer

system. There are many instances in which the outflow from kitchen sinks and

washing machines are directly discharged to the perimeter drainage system mostly

located at the back of residential units.

In addition, the domestic wastewater load is also affected by the type of the

development it originated. Townships are today encouraging industrial parks and

commercial complexes to spur economic growth for the area. Commercial premises

include assembly halls, camps, clubs, hotels, institutions, offices, restaurants,

schools, stores, laundry, swimming pool, theater, rest and service areas, bus station,

wholesale, retail, finance, auto repair, amusement centres, clinic, museum and

airport etc. Whilst, industrial establishment include factories that manufacture food,

textile, paper, printing, chemical, plastic and electronic product etc. Although the

sewer system provided for these areas are designed to cater for domestic wastewater

(the trade wastewater are to be treated separately), it is an almost impossible task to

control the wastewater from entering the sewage especially via spillage, inflow from

washing activities or illegally discharged into the sewer connection. All these has

bearing to the sewage characteristics transported into the treatment system .

A typical example is wastewater generated from verhicle services centre that include

spills in the form of lubrication oil, engine coolant, traces of petrol and diesel,

solvent from paintworks, cleaning agent and eletrolyte from batteries. Since source

control at service centres are not enforced, the result is considered ineffective due to

lack of enviromental awareness amongst the workshop operators. Hence, what is

needed is effective enforcement efforts that help to contain illegal trade waste

discharge.

This scope of the study is an attempt to identify the typical difference in the

characteristics of raw sewage generated from various types of developments in the

country i.e. from residential, commercial, industrial and also mixed developments.

The raw sewage data are divided into seven different types of development

categories that have been identified as: (i) residential only (ii) commercial only (iii)

industrial and commercial institutions (iv) developments with industrial plots (v)developments with commercial plot (vi) Industrial and industrial plus commercial


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and (vii) residential and commercial developments. Samples were sorted and

analysed based on the above category of developments. A summary of the mean

value of sewage characteristics is as in Table.4.2 below.

Table 4.2: Mean domestic wastewater characteristics based on type of

Developments.

Types of Development BOD COD AMN pH SS No of

Samples

Commercial only 227 482 19 6.9 212 401

Commercial and

Industrial 210 43523 6.8 170

106

Industrial and

Commercial plus

Industrial

174 365 21 6.8 147 134

Mixed development with

commercial plots* 134 295 20 6.9 144 5866

Residential only 130 290 20 7.0 140 9575

Residential and

Commercial 127 281 20 6.9 139 5453

Mixed development with

Industrial plots** 121 262 17 6.7 130 352

Note: The influent from fully Industrial plots are not being analysed as

the sampling data are very minimal from only 3 areas with full

industrial premises.

* Development with commercial only and commercial plus residential.

**Development with industrial only, industrial plus commercial, industrial

plus residential and industrial plus commercial plus residential.


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Based on the results as show in Table 4.2 above and Figure 4.11 below, all the three

BOD, COD and SS parameters were found higher from source that originated from

development with commercial plots, medium from residential premises and thelowest from mixed development with industrial plots.

All the three parameters i.e. for BOD are descending from 227 mg/l to 121 mg/l ,

COD from 482 mg/l to 262 mg/l and SS from 212 mg/l to 130 mg/l.

As for parameter for AMN, the level was found lower from mixed development with

industrial plot areas and higher from commercial plus industrial premises. The AMNvalues ranged from 17mg/l to 23 mg/l.

Dev.type

0

100

200

300

400

500

600

Commercialonly

Commercialand Industrial

Industrial andCommercial

plusIndustrial

Developmentwith

commercial plots*

Residentialonly

Residentialand

Commercial

Developmentwith

Industrial plots**

Type of Developments.

C h a r a c t e r i s t i c m g / l ( e x p H )

BOD

COD

AMN

PH

SS

Figure 4.11: Mean domestic wastewater characteristic from different

type of Developments.


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Mean levels of pH concentrations are within the range of 6.7 to 7.0 indicating that

the results are within the tolerable value.

All the values identified in Section 4.2 differ slightly from the results gathered and

anlysed in Section 4.1. The finding in Section 4.1 dealt with influent data collected

from more than 4,200 STP for overall analysis. In comparison, the analysis in

Section 4.2 are based on a lower number of samplings linked to customers database,

from roughly 1,400 sewage treatment systems of which the types of connected

premises of the development have been duly verified.

4.3 Domestic wastewater characteristics based on size of Developments.

The study in this section will identify the typical raw sewage characteristics

measured in relation to the size of developments which are normally linked to the

length of sewer reticulation, area of coverage, in-pipe storage, duration of flow and

infiltration. The determination in the size of development in this analysis is based on

the connected PE to the Sewage Treatment Plant.

Wastewater collection system conveys wastewater from its sources to locations

where it may be treated and ultimately discharged to a receiving water body.

Wastewater collection systems are laid in such a pattern with smaller sewers flowing

into larger sewers. Although it is designed to collect and transport wastewater from

human sanitary activities, nevertheless unintended or illegal connection frequently

resulted in the entry of additional flow into the system. Infiltration is water that

enters the system from the ground through defective pipes, pipes joints, lateral

connection or from manhole walls.


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Table 4.3 Size of Developments – Mean domestic wastewater characteristic

PE Range BOD COD AMN pH SSNo of

Samples

< 1000 164 393 25 7.1 202 11,266

1,001 - 2,000 152 342 23 7.1 165 4,645

2,001 - 3,000 153 338 23 7.1 156 4,052

3,001 - 5,000 147 316 22 7.1 141 3,624

5,001 - 10,000 141 313 22 7.0 137 3,267

10,001 -20,000 140 308 22 7.0 140 2,057

20,001 - 50,000 122 279 20 6.9 139 898

50,001 - 100,000 126 285 22 7.1 138 233

>100,001 119 261 18 6.9 147 268

Table 4.3 above and Figure 4.12 below illustrated the relationship between sizes of

development and human populations with concentration of the wastewater

constituents. Based on the analysis as tabulated above, the sewage characteristics

from the various development shows a peculiar and distinctive pattern thatcorrespond to the changes in size of the development. Seemingly, the sewage

concentration is indicating a significantly lower value from the large developments

and the parameters incrementally higher from those that originated from smaller

development.


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Depending on the length of sewer networks, the flow generated from the source may

require several hours to flow through the sewer network system because of flow

dampening effect and prolonged by the available storage capacity in the sewer

system.

The findings generated from the above scenario prompted this study to further look

at the impact of the decreasing pattern associated with the changes in size of the

development. Pursuant to this, all the parameters analysed earlier are now plotted

individually to observe its significance. It is necessary to be aware that the current

sewerage guideline which stipulates that development with more than 30 units

(150PE) shall be served by a connected sewerage system and a treatment plant.

Likewise, a sewerage asset record shows that only two percent of the developments

in the country are served by STPs with more than 100,000 PE. In the following

analysis, all development less than 150PE and 150,000PE and above are omitted and

consideration is made to observe only developments between the 150PE to 150,000

PE range.

BOD

y = -0.0003x + 135.93

0

100

200

300

400

500

600

700

800

0 20000 40000 60000 80000 100000 120000 140000

Size of Development

B O D C o n c e n t r a t i o n m g /

Figure 4.13: BOD variation with increase in development size .


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The BOD analysis involved a total number of 29,070 sampling data. Comparison

done to BOD concentration levels in the graph in Figure 4.13 shows that for

development with 150 PE indicates BOD mean value of 135 mg/l and the value

decreases to 106mg/l. for development with more than100,000 PE. This is

equivalent to a reduction of approximately 20% in the value of BOD concentration

between this two development ranges.

COD

y = -0.0007x + 300.45

0

500

1000

1500

2000

2500

0 20000 40000 60000 80000 100000 120000 140000

Size of Development

C O D C o n c e n t r a t i o n m g /

Figure 4.14: COD variation with increase in development size .

The COD analysis involved a total number of 29,173 sampling data. Again

comparison is made to the COD concentration levels as shown in Figure 4.14 which

illustrated that for development with 150 PE indicates the a COD value of 300 mg/l

and the value decreases to 230mg/l for development with more than 100,000 PE.

This is equivalent to a reduction of approximately 23% in the value of COD

concentration between this two development ranges.


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AMN

y = -6E-05x + 23.35

0

10

20

30

40

50

6070

80

0 20000 40000 60000 80000 100000 120000 140000

Size of Development

A M N c o n c e n t r a t i o n m g /

Figure 4.15: AMN variation with increase in development size .

The AMN analysis involved a total number of 29,191sampling data. As for

Ammonia Nitrogen concentrations, the analysis in Figure 4.15 shows that for

development with 150 PE indicates the AMN mean value of 23 mg/l and the value

decreases to 17mg/l for development with more than 100, 000 PE. This is equivalent

to a reduction of approximately 25% in the value of AMN concentration between

this two development ranges.


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SS

y = -0.0002x + 125.65

0

200

400

600

800

1000

12001400

1600

1800

0 20000 40000 60000 80000 100000 120000 140000

Size of Developments

S S c o n c e n t r a t i o n m

g /

Figure 4.16: SS variation with increase in development size .

The SS analysis involved a total number of 29,176 sampling data. The SS

concentration level in the graph in Figure 4.16 shows that for development with 150

PE indicates the SS mean value of 126 mg/l and the value decreases to 106mg/l for

development with more than 100,000 PE. This is equivalent to a reduction of

approximately 16% in the value of SS concentration between this two development

ranges.

pH

y = -1E-06x + 7.0525

0

1

2

3

4

56

7

8

9

0 20000 40000 60000 80000 100000 120000 140000

Size of Development

p h v a l u e

4.17: pH variation with increase in development size


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Meanwhile, analysis of pH in relation to different development size involved a total

number of 29,165 sampling data. Figure 4.17 shows the pH level for development

with 150 PE indicates the mean value of 7.0 and the value decreases to 6.9 for

development with more than 100,000 PE. This is equivalent to a reduction of

approximately 1.4% in the value of pH concentration between this two development

ranges.

Results from analyses for all the 5 parameters as depicted in the above

charts, revealed that the domestic wastewater characteristics generated from

100,000PE developments are lower in strength (by 20% for BOD, 23% for COD,

25% for AMN, 16% for suspended solids and 1.4% for pH) compared with

characteristics of wastewater originated from 150 PE developments.


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CHAPTER V

CONCLUSIONS

5.1 Wastewater characteristics based on the overall analysis

The characteristics of influent wastewater are different depending on

numerous factors, including variations in the size and type of developments, the

extent and nature of industrial and commercial premises in the catchment area,

community composition and the seasonal variability of sewage entering the

treatment facility. The magnitude of its material composition is a function of

environmental variables in the wastewater generated from source including the

length of sewer network, volume of storage, pipe gradient, oxygen content in the

sewer system, ethnic and religious norms in water usage, type and composition of

the establishments in the service areas. The characteristics of influent wastewater

identified in this study are as follows:

i) The mean and at 90 th and 95 th percentile values for all samples of raw

domestic wastewater based on five main sewage characteristics i.e. BOD, SS,

COD, AMN and pH are as shown in Table 5.1.


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Table 5.1: Characteristics of domestic wastewater from all samples.

Concentration

Contaminants UnitMean

90th

Percentile

95th

PercentileBOD mg/L 135 220 280

COD mg/L 294 470 625

AMN mg/L 23 36 45

SS mg/L 124 200 330

pH - 6.96 7.2 7.7

ii) For analysis based on different type of developments, three parameters for

BOD, COD and SS were found to be higher from sources originated from

commercial plots, medium in strength from residential premises and lower in

strength from industrial developments. The value of BOD descended from

227 mg/l to 121 mg/l, COD from 482 mg/l to 262 mg/l and SS from 212

mg/l to 130 mg/l. The characteristic for AMN was found to be lower from

mixed developments with industrial plots areas and higher from industrialwith commercial premises with values ranging from 17 mg/l to 23 mg/l.

Mean levels of pH concentrations are within the tolerable value of 6.7 to 7.0.

iii) Domestic wastewater also shows patterns that correspond to the changes in

size of the developments. The domestic wastewater concentration indicated a

lower value from large developments and the characteristics are

incrementally higher from those that originated from smaller developments.Large developments with high PE normally have wider area of coverage and

longer sewer piping system. This clearly consolidated the findings by other

research studies regarding the influence of in-pipe treatment in the sewerage

conveyance system.


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5.2 Recommendations

Due to a wide variation of sewerage characteristic recorded, it is proposed that the

parameter to be adopted for the design of a new plant built by the industry shall be

based on the value within the range of 90% and 95% percentile, which are

equivalent to the current typical value for BOD and SS. However, for treatment

works financed by the Government of which the capital investment is drawn from

public funds, the characteristics of sewage adopted in the design shall be based on

lower values (mean or median) to optimize the design and in ensuring for priority

and the economic viability of Government projects.

In order to identify the factors associated with the changes of wastewater

characteristics affected by the difference in size of developments, it is recommended

that a further study be carried out to identify the coefficient or factor to be adopted

as multiplier to wastewater characteristic in proportion to the increase in the size of

development. Similarly, a further study is also needed to be initiated to identify the

basis for the variation of wastewater characteristic significantly affected by a

particular type of trade activities involved and also due to the differences in

composition/ percentage of industrial and commercial premises in the study area.


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Abdul-Talib, S., Thorkild, J.V. and Jacobsen, T.H. (2003). Benefiting From

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Brosseau, G., Healy, S. and Watson, J. (1995).Controlling vehicle service facility

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Galil, N. and Shpiner, R. (2001). Additional Pollutants and Deposition Potential

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Lesikar, J., Garza, O.A., Persyn, R.A., Kenimer, A.L. and Anderson, M.T. (2006).

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Metcalf and Eddy. (2004). Wastewater Engineering, Treatment and Reuse, 4th

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APPENDIX A

Table A1: Cumulative frequency of BOD range

BOD range

Number of

samples Percentage

Cumulative

percentage.

0-50 4489 15.13% 15.13%

51-100 6765 22.81% 37.94%

101-150 7842 26.44% 64.38%

151-200 5809 19.59% 83.96%

201-250 2369 7.99% 91.95%

251-300 986 3.32% 95.27%

301-350 551 1.86% 97.13%

351-400 236 0.80% 97.93%

401-450 155 0.52% 98.45%

451-500 115 0.39% 98.84%

501-550 85 0.29% 99.13%

551-600 66 0.22% 99.35%

601-650 65 0.22% 99.57%

651-700 49 0.17% 99.73%

701-750 32 0.11% 99.84%

751-800 31 0.10% 99.94%

>801 15 0.05% 100.00%

29660 100.00%


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APPENDIX B

Table B1: Cumulative frequency of COD range

COD range

Number of

samples Percentage

Cumulative

percentage.

0-50 1357 4.57% 4.57%

51-100 2316 7.80% 12.37%

101-150 2763 9.31% 21.68%

151-200 3619 12.20% 33.88%

201-250 3936 13.26% 47.14%

251-300 4237 14.28% 61.42%

301-350 3583 12.07% 73.49%

351-400 2671 9.00% 82.49%

401-450 1586 5.34% 87.84%

451-500 852 2.87% 90.71%

501-550 484 1.63% 92.34%

551-600 414 1.40% 93.74%

601-650 281 0.95% 94.68%

651-700 265 0.89% 95.58%

701-750 196 0.66% 96.24%

751-800 176 0.59% 96.83%

801-850 123 0.41% 97.24%

851-900 93 0.31% 97.56%

901-950 72 0.24% 97.80%

951-1000 53 0.18% 97.98%

1001-1050 62 0.21% 98.19%

1051-1100 39 0.13% 98.32%

1101-1150 46 0.16% 98.47%

1151-1200 42 0.14% 98.62%

1201-1250 31 0.10% 98.72%

1251-1300 26 0.09% 98.81%

1301-1400 54 0.18% 98.99%

1401-1500 40 0.13% 99.12%


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1501-1600 57 0.19% 99.32%

1601-1700 42 0.14% 99.46%

1701-1800 29 0.10% 99.56%

1801-1900 34 0.11% 99.67%1901-2000 37 0.12% 99.80%

2001-2100 22 0.07% 99.87%

2101-2200 20 0.07% 99.94%

>2201 18 0.06% 100.00%

29676 100.00%


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APPENDIX C

Table C1: Cumulative frequency of AMN range

AMN range

Number of

samples Percentage

Cumulative

percentage.

0 0 0 0

1-5 1419 4.78% 4.78%

6-10 2393 8.06% 12.85%

11-15 4108 13.84% 26.69%

16-20 5517 18.59% 45.28%

21-25 5184 17.47% 62.75%

26-30 4229

determination of domestic wastewater

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