Managing wastewater in the city of the future. Decentralized wastewater and rainwater reclamation and use in Urban Agriculture

Transcription

1 Managing wastewater in the city of the future Decentralized wastewater and rainwater reclamation and use in Urban Agriculture

2 Decentralized wastewater and rainwater reclamation and use in Urban Agriculture Session 4. Overview of sanitation systems for wastewater reuse in urban agriculture Dr. Claudia Pabon Pereira with contributions from: Dr. Adriaan Mels, Dr.Katarzyna Kujawa- Roeleveld, Dr. Grietje Zeeman

3 Sanitation System Components User interface for excreta collection Collection and storage(treatment) Conveyance Treatment Sludge handling Use and Disposal

4 Sanitation Systems for agricultural reuse Not all combinations are feasible/desirable Reuse possibilities vary according to input material as they substantially differ in quality a) Nutrients b) Organics (BOD, COD) c) Water content d) Solids e) Pathogens Collection (dilution) determines recovery

5 Sanitation flows Urine Faeces Dry cleansing material Anal cleansing water Excreta Brownwater Blackwater Flushwater Grey water Rainwater

6 Composition of household (waste)water COD 34% 6% 30% 30% Faeces N 11% 70% 10% 9% Grey water Urine P 46% 8% 23% 23% Kitchen waste

7 Separate collection of Black (Feces & urine) & grey water leads to: a) easy recovery of a large pool of relatively clean water (grey water) ; b) and controlled digestion of hazardous waste (Black water); i. Low dilution results in possibility for recovery of nutrients.

8 Faeces plus Urine plus kitchen waste A human being produces ca. 1.5 litres faeces plus urine plus kitchen waste; a) 91% of the nitrogen; b) 70% of the COD; c) 69% of the phosphate; d) main part of the pathogens; e) medicine rest and hormones

9 Sanitation Systems classification considering agricultural reuse Main criteria for classification a) Separation of Urine and Faeces i. Nutrient recovery ii. Pathogen confinement iii. Organic matter recovery b) Dilution i. Pollution potential ii. Resource use iii. Treatment costs

10 Sanitation Systems classification considering agricultural reuse Separation Dilution Separate concentrated flows F&U&GW Separate diluted flows DF&DU&GW Mixed(semi) concentrated flows Excreta & GW Mixed diluted flows F+U+W+GW

11 Sanitation Systems for separate concentrated flows i. Urine ii. Faeces/BrW Fertilizer Compost iii. iv. Greywater Rainwater Irrigation water Aquaculture Macrophyte pond

12 User interface Urine Diverting Dry Toilet (UDDT) Sanitation Systems for separate concentrated flows Collection and storage/treatment Urine container Conveyance Treatment Sludge handling Jerry can/tank Urinal Dehydration vaults Human powered Urine Diverting Flush Toilet (UDFT) * Composting chamber SP Transfer station Motorized emptying and transport Ponds VIP Simplified sewer Wetlands Double VIP Solids free sewer Trickling filter Biogas reactor UASB Activated sludge

13 Sanitation Systems for mixed (semi)concentrated flows i. Excreta/BW ii. Excreta/BW+KW Stabilized sludge/ Compost Biogas (from co-digestion) iii. iv. Greywater Rainwater Irrigation water Aquaculture Macrophyte pond

14 Sanitation Systems for mixed semiconcentrated flows User interface Collection and storage/treatment Conveyance Treatment Sludge handling Dry Toilet SP Human powered Sedimentation/thicke ning ponds Pour Flush Toilet VIP Transfer station Unplanted drying beds Double VIP Fossa Alterna Sewer discharge station Motorized emptying and transport Planted drying beds Co-composting Twin Pits Simplified sewer Ponds Anaerobic reactor Septic tank/uasb septic tank Solids free sewer Wetlands Composting chamber Anaerobic biogas reactor Trickling filter UASB Activated sludge

15 Black water (vacuum) versus yellow & brown water collection in a decentral concept yellow & brown water (+) Urine water free; collected concentrated; (-) 3 different tubes & treatment systems (when not directly reused); (-) only 60% of medicin rests in urine. Black water (-) urine diluted with 5 liters water (present vacuum toilets); (+) only 2 tubes & treatment systems; (+) all medicin rests & hormones in black water.

16 Urine separation saves energy at WTP Power use (W per cap) Source: Wilsenach, TU Delft 0% 50% 75% Degree of urine separation

17 DeSaR concept discharge agriculture Removal micropollutants/ pathogens biogas Removal micropollutants/ pathogens (ozone) Nirogen removal struvite precipitation reuse nutrient rich product UASBseptic sludge black water kitchen waste hygienisation grey water treatment

18 Sanitation Systems for diluted separated flows User interface Urine Diverting Flush Toilet Collection and storage/treatment Conveyance Treatment Sludge handling Twin Pits Jerry can Sedimentation/thick ening ponds Composting chamber Human powered Unplanted drying beds Septic tank Motorized emptying and transport Planted drying beds Anaerobic biogas reactor Transfer station Wetlands Co-composting Sewer discharge station Ponds Anaerobic reactor Anaerobic Aerobic

19 Sanitation Systems for mixed diluted flows User interface Pour Flush Toilet Collection and storage/treatment Twin Pits Conveyance Treatment Sludge handling Simplified sewer Cistern toilet Human powered Solids free sewer Septik tank Conventional sewer Wetlands Ponds Anaerobic Sedimentation /thickening ponds Unplanted drying beds Planted drying beds ABR Aerobic Cocomposting Anaerobic Filter Anaerobic reactor

20 Urine reuse Health aspects: Storage (up to 6 months) How? Mixed undiluted to soil before planting Poured into furrows and covered 2/year Diluted and used frequently around plants (3:1 for vegetables) Amounts Handling the reuse products 1 m 2 of cropland can receive the urine of one person per day (1.5/L)= in one year about 400 m 2

21 Handling the reuse products Urine use in agriculture Urine is stored for 6 months (to remove remaining pathogens) and is directly used in agriculture

22 Effects of storage on pathogens in urine

23 Handling the reuse products Dry faeces reuse Addition of ash, saw dust, rice husk to absorb moisture Volume reduced by 75% Storage for 12 to 18 months No urine or other liquid material Not as good as compost but useful for recovering poor soils

24 Handling the reuse products Stabilized sludge reuse (Biosolids) Good water retention, slow nutrient release Can be used in reforestation and mine reclamation Other uses depending on origin and composition Depending on water content can be separated in liquid and solid portion

25 Handling the reuse products Treated wastewater reuse Irrigation (Fertirrigation) Aquaculture Macrophytes

26 Handling the reuse products Treated wastewater reuse Irrigation (Fertirrigation) Only after secondary treatment Drip irrigation or surface water irrigation Long term use, danger of pollution by e.g. salt or heavy metal accumulation Preferable for crops with no direct raw consumption

27 Handling the reuse products Treated wastewater reuse Irrigation (Fertirrigation) Maize Alfalfa (other feed) Fruit trees Tobacco Fibers (cotton) Foods requiring processing (sugar cane) Energy crops (sorghum)

28 Precautions at application Fertilisation techniques Crop selection Human exposure control Annotated Bibliography on Urban Agriculture; ETC - Urban Agriculture Programme in cooperation with TUAN and other organisations ETC Urban Agriculture Programme (2001).

29 Handling the reuse products Treated wastewater reuse Aquaculture Ponds fed with sludge or effluent Maintain aerobic conditions: 1 gbod/m 2 d, 4 mgo 2 /l Up to 10,000 kg fish/ha : Tolerant non carnivorous fish- carp, milkfish, tilapia Land, freshwater, climate If for consumption move to fresh water for several weeks before harvesting

30 Handling the reuse products Treated wastewater reuse Macrophytes Ponds fed with sludge or effluent Roots uptake nutrients and filter BOD and SS removal, poor pathogen removal Duckweed: high protein, fed to poultry or fish Water hyacinth: fibre for rope, textiles, baskets or composted Maintain aerobic conditions, mosquito problems

31 Handling the reuse products Treated wastewater reuse

32 Handling the reuse products Rain water reuse Rain is a saturated solution of oxygen and contains other valuable elements too such as carbonic acid, nitric and other acids al in a beneficial form manufactured by natural forces. Rain picks up dust, microorganism, and many valuable minerals. In general it is not recommended as a source of drinking water for humans Useful for toilet flush, laundry, garden In urban and industrialized areas may contain various impurities absorbed from the atmosphere, including arsenic and mercury. Use of first-flush devices to filter and screen out contaminants before they enter the storage container. For consumption, filters and UV systems. Dirty containers may become a health hazard or a breeding ground for mosquitoes and other pests

33 Handling the reuse products Philippines case: Rain water reuse Roof area of 150m 2. Average rainfall mm Rainwater to be harvested: 150*0.626=94 m 3 If a family consumes 15 m 3 every month, they do not need not fetch water for six months. POMCAT-Jed Guinto

34 Handling the reuse products Groundwater recharge Advisable for aquifers at risk of salt intrusion or that have a long retention time Volume, point of discharge and water quality are to be considered Many parameters to consider: temperature, turbidity, SS, BOD, N and P Careful risk assessment