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