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Mong Hoo Lim

Deputy Director, PUB, Singapore

Singapore’s experience in Stormwater Harvesting: The Lower Seletar / Bedok Water Scheme

Singapore’s experience in Stormwater Harvesting: The Lower Seletar / Bedok Water Scheme

12 May 2011 2

2. 2. SungeiSungei SeletarSeletar / / BedokBedok Water SchemeWater Scheme

1. 1. Overview of Singapore Water SupplyOverview of Singapore Water Supply

4. 4. Water Quality of Storage ReservoirsWater Quality of Storage Reservoirs

3. 3. StormwaterStormwater QualityQuality

Outline

5. 5. Important FactorsImportant Factors

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Singapore

Land Area 710 km 2

Population 5 mil

Average Annual Rainfall 2,400 mm

Average Water Demand 1.6 mil m 3/day

Country Information

Singapore

Overview

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“To deliver and sustain a clean and healthy environment and water resources for all in Singapore.”

“To ensure an efficient, adequate & sustainable supply of water”� Clean Water

“To ensure a sustainable quality environment in Singapore”

� Clean Land

� Clean Air

� Public Health

A Statutory Board constituted under

the Public Utilities Act 2001 to provide

integrated water supply, sewerage and

drainage services

PUB’s Vision and MissionOverview

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Rain Sea

Direct Non-

Potable Use

PUB Manages the Complete Water CycleFrom drainage of storm water to sourcing, collection, purification and supply of drinking water,

treatment of used water and turning it into NEWater

NEWater

Overview

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Water Resource Management

Ensuring a diversified and sustainable supply of water for Singapore with the Four National Taps Strategy

Overview

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Location map of Lower Seletar and Bedok stormwater harvesting systems

40 Km 2

22 Km 2

Sungei Seletar / Bedok Water Scheme

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Drop inlet diversion structure

Sungei Seletar / Bedok Water Scheme

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Main pump

motor

Pumping station

Reservoir

Wet well

Start pumping!

grating

Downstream canal going to sea

Drainage pump

Start Pumping!Stop pumping!

Rain comes

Water in canal rises

Water overflow thru’ grating into inlet chamber

Water flow into the pond

Drainage pump starts to remove 1 st

flush

Water continue to flow in and water level rises

Main pump starts to pump water to reservoir

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Barrage gate lateral diversion structure

Sungei Seletar / Bedok Water Scheme

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Stormwater Quality

• Sources of pollutants– Surface itself (eg, roads and litters)– Motor vehicles (leakage of fuel, oil, and coolants, worn-off portions

of tires, clutches, and brake linings, and particulate exhausts)– Atmospheric ‘fallout’– Spills and industrial wastes

• Parameters of concern– literature review of SW studies: nutrients, metals, organic matter,

suspended solids, PAHs– Other important parameters include:

– Microbiological parameters, eg, Faecal coliforms, E coli, Enterococci– Contaminants of emerging concern, eg, PPCPs, EDCs etc.

���� Grouped under 6 categories:(1) Nutrients, (2) TSS and bulk organic, (3) Metals, (4) organic contaminants, (5) microbiological parameters, (6) contaminants of emerging concern

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Approach to Water Quality Evaluation

• Fate of pollutants in SW harvesting– A direct catchment stream

(L Seletar catchment)before, during and afterstorm

– A SW collection pond (Bedok catchment)before, during storm,‘first flush’ and waterpumped to reservoir

• 20 years’ WQ data– Lower Seletar & Bedok

Reservoirs Vs MacRitchie Reservoir

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Lower Seletar direct catchment stream

(1) Nutrients

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Lower Seletar direct catchment stream

(2) TSS andbulk organic

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Lower Seletar direct catchment stream

(3) Metals

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Lower Seletar direct catchment stream

(3) Metals(cont’d)

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Lower Seletar direct catchment stream

(3) Metals(cont’d)

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Lower Seletar direct catchment stream

(4) Organiccontaminants(63 comp’ds)

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Lower Seletar direct catchment stream

(5)Microbiologicalparameters

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Lower Seletar direct catchment stream

(6) Emerging contaminants

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Lower Seletar direct catchment stream

(6) Emerging contaminants (cont’d)

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Bedok Collection Pond(1) Nutrients

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Bedok Collection Pond(2) TSS and bulk organic

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Bedok Collection Pond(3) Metals

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Bedok Collection Pond(3) Metals (cont’d)

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Bedok Collection Pond(3) Metals (cont’d)

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(4) Organiccontaminants(63 comp’ds)

Bedok Collection Pond

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Bedok Collection Pond(5) Microbiological parameters

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Bedok Collection Pond

(6) Emerging contaminants

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Bedok Collection Pond(6) Emerging contaminants (cont’d)

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Bedok Collection Pond(6) Emerging contaminants (cont’d)

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Bedok Collection Pond

(6) Emerging contaminants (cont’d)

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20 years’ WQ data(1) Nutrients

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20 years’ WQ data(2) TSS and bulk organic

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20 years’ WQ data(3) Metals

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20 years’ WQ data(3) Metals (cont’d)

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20 years’ WQ data(4) Organic contaminants

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20 years’ WQ data(5) Microbiological parameters

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20 years’ WQ data(6) Emerging contaminants

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20 years’ WQ data(6) Emerging contaminants (cont’d)

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• Well coordinated land use planning and integrated catchment management– close consultation among all relevant government agencies

(HDB, URA, JTC, NEA, MND etc)

• Effective pollution control measures– Termination of pig-farming and other agricultural activities– domestic wastes, waste-collection centres

• Separation of stormwater from sewage• Integrated water and wastewater management

– $400m spent to reline sewers to prevent leaks

• High dilution factor– (2400mm of rainfall pre year)

Important Factors

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• The pollutants loadings in the Lower Seletar / Bedokstormwater runoff are low

• The water quality of Lower Seletar and Bedok stormwaterstorage reservoirs is good and is comparable to that of a reservoir in the protected catchment (i.e., MacRitcheReservoir)

• Effective pollutant source management is key to the success of stormwater harvesting

Conclusion

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