1. Sustainable Development Conference – Brussels, 26 May 2009 Constructed treatment wetlands contributing to the paradigm shift in sustainable urban water management Diederik P.L. Rousseau Peter van der Steen, Hans van Bruggen and Piet N.L. Lens

2. - 1 - INTRODUCTION Sustainable Development Conference – Brussels, 26 May 2009

3. 3 Water Treatment Distribution network Sewer WWTP Effluent Shortcomings urban water management N2N2 Fertilizer

4. 4 Natural Treatment SystemsSWITCH

5. 5 Natural Treatment SystemsSWITCH Learning Alliances and Strategic Planning Demand-Led Research Demonstrations and Training Robust, flexible and adaptable technologies

6. 6 Paradigm shift 1 – wastewater as resource Water Nutrients Organics

7. 7 Paradigm shift 2 – fit for purpose water POTABLE WATER drinking, cooking RAINWATER laundry, toilet flushing GREY WATER treatment flushing, gardening BLACK WATER to anaerobic treatment

8. 8 Paradigm shift 3 – decentralization Keep water local Higher flexibility, Better participation

9. 9 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?

10. 10 Saxby, UK, domestic wastewater Bornem, Belgium, CSO Analândia, SP, Brazil, potable water Uses of constructed treatment wetlands?

11. 11 Natural Treatment SystemsAdvantages of CW u Low investment costs (~ land price) u Low operation and maintenance costs u Unskilled labour for maintenance u Little or no energy inputs u Effluents suitable for reuse (irrigation) u High buffering capacity u Biomass production for valorisation u Habitat provision and landscaping

12. 12 u Space requirement u Lack of good models for design and operation u Low prestige Limitations of CW

13. - 2 - INNOVATIONS Sustainable Development Conference – Brussels, 26 May 2009

14. 14 Natural Treatment SystemsSpace reduction by increased O 2 supply 1.Normal CW u Physical transfer u Plant root oxygen release HSSF-CW: 1 – 6 g O 2 /(m 2.day) 10 - 60% of daily cBOD 2.Intensified CW u Intermittent feeding u Passive aeration u Tidal flow u Active aeration up to 100 g O 2 /(m 2.day) SSF-CW: <0.1 kW.h/m 3 Intens-CW: 0.17 kW.h/m 3 Act. Sludge: 0.76 kW.h/m 3 O2O2 O2O2

15. 15 Natural Treatment SystemsSpace reduction by increased O 2 supply Forced Bed Aeration TM (picture Scott Wallace, NAWE) Tidal flow CW

16. 16 Natural Treatment SystemsSpace reduction by combining CW Anoxic denitrification Aerobic nitrification

17. 17 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

18. 18 Natural Treatment SystemsModel building and simulation u State-of-the-art in CW modelling: P-k-C* model u Simple first-order model u Lumping of processes (3 parameters describe all) u High uncertainty; low accuracy; only averages predicted u Recent developments u Dynamic, mechanistic models (cf. Activated Sludge) u Highly complex, high uncertainty u At present for research purposes only

19. 19 Natural Treatment SystemsModel building and simulation Modelling COD removal of batch-operated CW at 20 °C Modelling COD and NH 4 removal in pilot-scale CW

20. 20 Natural Treatment SystemsNeed for mentality change 1.NIMBY syndrome 2.Mosquitos 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

21. - 3 - CASE STUDIES Sustainable Development Conference – Brussels, 26 May 2009

22. 22 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)

23. 23 Natural Treatment SystemsCase 1 - Granollers, Spain

24. 24 Natural Treatment SystemsCase 1 - Granollers, Spain u Results u NH 4 on average from 31 to 4 mg N/L u 85% of samples has faecal coliform < 2400/100mL u Effectively removing pharmaceuticals and personal care products u Amphibians absent in inlet, abundant in outlet u 86 vascular plants u 35 avian species visiting or nesting u June 2006 – January 2007: 18,000 mostly local visitors u Travel cost method 60,000 Euro

25. 25 Natural Treatment SystemsCase 2 - Besòs Fluvial Park, Barcelona, Spain renaturalization of river 60 subsurface-flow CWs tertiary treatment park function

26. 26 Natural Treatment SystemsCase 2 - Besòs Fluvial Park, Spain

27. 27 Natural Treatment SystemsCase 2 - Besòs Fluvial Park, Spain u Results u Reduction of 40% SS, 62% COD, 20% NH 4, 58% P and 1.1 log faecal coliforms u River quality improved but not yet optimal u Popular for jogging, cycling, walking and picnic u Flood warning system in place u No data available on public use and acceptance

28. 28 Natural Treatment SystemsCase 3 - Polderdrift, Arnhem, The Netherlands 40 houses 270,000 Euro (1997) tenants involved in design tenants involved in maintenance

29. 29 Natural Treatment SystemsCase 3 - Polderdrift, Arnhem, The Netherlands

30. 30 Natural Treatment SystemsCase 3 - Polderdrift, Arnhem, The Netherlands u Results u 57% less potable water consumption u 85% less wastewater discharges u problems with leakage and clogging u in other similar cases: cross-connections

31. 31 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)

32. 32 Natural Treatment SystemsCase 4 - GeWooNboot, The Netherlands u Results u CW: 75% TSS, 97% NH 4, 28% TP, 55% COD and 2.2 log units reduction in total coliforms u Drinking water safe except nitrate concentrations u Build-up of salinity u Semi-closed system needed with additions of rainwater u Many hundreds of visitors

33. - 4 - CONCLUSIONS Sustainable Development Conference – Brussels, 26 May 2009

34. 34 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

35. 35 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

36. Sustainable Development Conference – Brussels, 26 May 2009 THANK YOU ! d.rousseau@unesco-ihe.org