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

Transcription

1 Singapore s experience in Stormwater Harvesting: The Lower Seletar / Bedok Water Scheme Mong Hoo Lim Deputy Director, PUB, Singapore 1 5 July 2012

2 Outline 1. Catchment Characteristics 2. Collection Systems 3. Water Quality Evaluation 4. Important Factors 5. Conclusion 2

3 Catchment characteristics Location map of Lower Seletar and Bedok stormwater harvesting systems 40 Km 2 87% (residential & green) direct drainage Remaining residential, indirect catchment Water in L Seletar Reservoir pumped to Bedok Reservoir 22 Km 2 Residential Indirect catchment Water in Bedok Reservoir supplied to an adjacent waterworks for treatment 3

4 Drop inlet diversion structure Collection system 4

5 Rain comes Pumping station Drainage pump starts to remove 1 st flush Downstream canal going to sea Water in canal rises Start Stop Pumping! pumping! Drainage pump motor Water overflow thru grating into inlet chamber Water flow into the pond grating Wet well Main pump Reservoir Water continue to flow in and water level rises Start pumping! Main pump starts to pump water to reservoir 5

6 Collection system Barrage gate lateral diversion structure 6

7 Water Quality Evaluation 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 7

8 Water Quality Evaluation Fate of pollutants in SW harvesting A direct catchment stream (L Seletar catchment) before, during and after storm A SW collection pond (Bedok catchment) before, during storm, first flush and water pumped to reservoir 20 years WQ data Lower Seletar & Bedok Reservoirs Vs MacRitchie Reservoir 8

9 Lower Seletar direct catchment stream (1) Nutrients 9

10 Lower Seletar direct catchment stream (2) TSS and bulk organic 10

11 Lower Seletar direct catchment stream (3) Metals 11

12 Lower Seletar direct catchment stream (3) Metals (cont d) 12

13 Lower Seletar direct catchment stream (3) Metals (cont d) 13

14 Lower Seletar direct catchment stream (4) Organic contaminants (63 comp ds) 14

15 Lower Seletar direct catchment stream (5) Microbiological parameters 15

16 Lower Seletar direct catchment stream (6) Emerging contaminants 16

17 Lower Seletar direct catchment stream (6) Emerging contaminants (cont d) 17

18 Bedok Collection Pond (1) Nutrients 18

19 Bedok Collection Pond (2) TSS and bulk organic 19

20 Bedok Collection Pond (3) Metals 20

21 Bedok Collection Pond (3) Metals (cont d) 21

22 Bedok Collection Pond (3) Metals (cont d) 22

23 Bedok Collection Pond (4) Organic contaminants (63 comp ds) 23

24 Bedok Collection Pond (5) Microbiological parameters 24

25 Bedok Collection Pond (6) Emerging contaminants 25

26 Bedok Collection Pond (6) Emerging contaminants (cont d) 26

27 Bedok Collection Pond (6) Emerging contaminants (cont d) 27

28 Bedok Collection Pond (6) Emerging contaminants (cont d) 28

29 20 years WQ data (1) Nutrients 29

30 20 years WQ data (2) TSS and bulk organic 30

31 20 years WQ data (3) Metals 31

32 20 years WQ data (3) Metals (cont d) 32

33 20 years WQ data (4) Organic contaminants 33

34 20 years WQ data (5) Microbiological parameters 34

35 20 years WQ data (6) Emerging contaminants 35

36 20 years WQ data (6) Emerging contaminants (cont d) 36

37 Important Factors 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) 37

38 Conclusion The pollutants loadings in the Lower Seletar / Bedok stormwater runoff are low The water quality of Lower Seletar and Bedok stormwater storage reservoirs is good and is comparable to that of a reservoir in the protected catchment (i.e., MacRitche Reservoir) Effective pollutant source management is key to the success of stormwater harvesting 38

39 THANK YOU 39