sustainable development conference – brussels, 26 may 2009 constructed treatment wetlands...

Sustainable Development Conference – Brussels, 26 May 2009

Constructed treatment wetlands contributing to the paradigm shift in

sustainable urban water management

Diederik P.L. RousseauPeter van der Steen, Hans van Bruggen and Piet N.L. Lens

- 1 -INTRODUCTION

Sustainable Development Conference – Brussels, 26 May 2009

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Water Treatment

Distribution network

Sewer

WWTP

Effluent

Shortcomings urban water management

N2

Fertilizer

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Natural Treatment SystemsSWITCH

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Natural Treatment SystemsSWITCH

Learning Alliances and Strategic Planning

Demand-LedResearch

Demonstrations and Training

Robust,flexible

andadaptable

technologies

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Paradigm shift 1 – wastewater as resource

Water

Nutrients

Organics

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Paradigm shift 2 – “fit for purpose” water

POTABLE WATERdrinking, cooking

RAINWATERlaundry, toilet flushing

GREY WATERtreatment flushing, gardening

BLACK WATERto anaerobic treatment

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Paradigm shift 3 – decentralization

“Keep water local”

Higher flexibility, Better participation

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“man-made copies of natural wetlands that optimally exploit their values and functions”

Most commonly used for:

- (waste)water treatment- water storage / flood

alleviation- mitigation / habitat creation

What are constructed wetlands?

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Saxby, UK, domestic wastewater

Bornem, Belgium, CSO

Analândia, SP, Brazil, potable water

Uses of constructed treatment wetlands?

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Natural Treatment SystemsAdvantages of CW

Low investment costs (~ land price)

Low operation and maintenance costs

Unskilled labour for maintenance

Little or no energy inputs

Effluents suitable for reuse (irrigation)

High buffering capacity

Biomass production for valorisation

Habitat provision and landscaping

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Space requirement

Lack of good models for design and operation

Low prestige

Limitations of CW

- 2 -INNOVATIONS

Sustainable Development Conference – Brussels, 26 May 2009

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Natural Treatment SystemsSpace reduction by increased O2 supply

1. Normal CW Physical transfer Plant root oxygen release

HSSF-CW: 1 – 6 g O2/(m2.day)

10 - 60% of daily cBOD

2. Intensified CW Intermittent feeding Passive aeration Tidal flow Active aeration

up to 100 g O2/(m2.day)

SSF-CW: <0.1 kW.h/m3

Intens-CW: 0.17 kW.h/m3

Act. Sludge: 0.76 kW.h/m3

O2

O2

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Natural Treatment SystemsSpace reduction by increased O2 supply

Forced Bed AerationTM

(picture Scott Wallace, NAWE)

Tidal flow CW

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Natural Treatment SystemsSpace reduction by combining CW

Anoxic denitrification

Aerobic nitrification

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Natural Treatment SystemsSpace reduction by hybridization

Rotating Biological Contactor+ HSSF CW

Aalbeke, Belgium, Aquafin NV

Trickling filter+ HSSF CW

Butlers Marston, UK, Severn Trent Water Ltd

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Natural Treatment SystemsModel building and simulation

State-of-the-art in CW modelling: P-k-C* model Simple first-order model Lumping of processes (3 parameters describe all) High uncertainty; low accuracy; only averages predicted

Recent developments Dynamic, mechanistic models (cf. Activated Sludge) Highly complex, high uncertainty At present for research purposes only

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Natural Treatment SystemsModel building and simulation

COD

Simulation time, days

0 10 20 30 40 50 90 100 110 120

COD,

mg/

L

0

200

400

6001st Period 2nd Period

Ammonium

Simulation time, days

0 10 20 30 40 50 90 100 110 120

Amm

oniu

m, m

g N/

L

0

20

40

60Influent Effluent measured Effluent simulated 1st Period

2nd Period

CONTROL

0

100

200

300

400

500

0 5 10 15 20

Time (days)

CO

D (

mg

/l)

.

Simu

Meas

TYPHA

0

100

200

300

400

500

0 5 10 15 20

Time (days)

CO

D (

mg

/l) .

Simu

Meas

Modelling COD removal of batch-operated CW at 20 °C

Modelling COD and NH4 removal in pilot-scale CW

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Natural Treatment SystemsNeed for mentality change

1. NIMBY syndrome

2. Mosquito’s and odour

3. Wastewater as a resource, not a waste

SOME SOLUTIONS

• SWITCH Learning Alliance

• Training

• Demo projects

• More studies/data needed on ancillary benefits

- 3 -CASE STUDIES

Sustainable Development Conference – Brussels, 26 May 2009

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Natural Treatment SystemsCase 1 - Granollers, Spain

• 1 ha surface-flow wetland• tertiary treatment• park and education function• 72,000 Euro investment• 12,000 Euro/year maintenance• reuse envisaged (future)

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Natural Treatment SystemsCase 1 - Granollers, Spain

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Natural Treatment SystemsCase 1 - Granollers, Spain

Results NH4 on average from 31 to 4 mg N/L 85% of samples has faecal coliform < 2400/100mL Effectively removing pharmaceuticals and personal care

products

Amphibians absent in inlet, abundant in outlet 86 vascular plants 35 avian species visiting or nesting

June 2006 – January 2007: 18,000 mostly local visitors Travel cost method 60,000 Euro

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Natural Treatment SystemsCase 2 - Besòs Fluvial Park, Barcelona, Spain

• renaturalization of river• 60 subsurface-flow CWs• tertiary treatment• park function

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Natural Treatment SystemsCase 2 - Besòs Fluvial Park, Spain

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Natural Treatment SystemsCase 2 - Besòs Fluvial Park, Spain

Results Reduction of 40% SS, 62% COD, 20% NH4, 58% P and

1.1 log faecal coliforms River quality improved but not yet optimal

Popular for jogging, cycling, walking and picnic Flood warning system in place

No data available on public use and acceptance

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Natural Treatment SystemsCase 3 - Polderdrift, Arnhem, The Netherlands

• 40 houses• 270,000 Euro (1997)• tenants involved in design• tenants involved in maintenance

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Natural Treatment SystemsCase 3 - Polderdrift, Arnhem, The Netherlands

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Natural Treatment SystemsCase 3 - Polderdrift, Arnhem, The Netherlands

Results 57% less potable water consumption 85% less wastewater discharges

problems with leakage and clogging

in other similar cases: cross-connections

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Natural Treatment SystemsCase 4 - GeWooNboot, The Netherlands

• autarctic houseboat• 2 vertical-flow CW floating alongside• closed water cycle by means of Reverse Osmosis and UV disinfection• 60,000 Euro (excl. VAT)

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Natural Treatment SystemsCase 4 - GeWooNboot, The Netherlands

Results CW: 75% TSS, 97% NH4, 28% TP, 55% COD and 2.2

log units reduction in total coliforms Drinking water safe except nitrate concentrations

Build-up of salinity Semi-closed system needed with additions of rainwater

Many hundreds of visitors

- 4 -CONCLUSIONS

Sustainable Development Conference – Brussels, 26 May 2009

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Natural Treatment SystemsConclusions

Constructed treatment wetlands can contribute to sustainable urban water management: Low energy consumption Recovery of water and nutrients Ancillary benefits

Continued attention is needed for: Space reduction Model-based design and operation Better understanding of socio-economic

impacts

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Natural Treatment SystemsAcknowledgements

• European Commission through the 6th FP Integrated Project SWITCH

(www.switchurbanwater.eu)

• dr. Joan García, Technical University of Catalunia, Barcelona, Spain

• Mr. Frank van Dien, ECOFYT, Oirschot, The Netherlands

• Ms. Roshani Shrestha, MSc student

• dr. Wenxin Shi, visiting Postdoc

Sustainable Development Conference – Brussels, 26 May 2009

THANK YOU !

d.rousseau@unesco-ihe.org