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4.7 Greywater treatment
Learning objectives: Get familiar with various treatment options and with the application of various processes
Can we remove all the
pathogens and heavy
metals?
What is in the sludge?
constructedwetland, gardening,
wastewater pond, biol.treatment, membrane-
technology
Greywater (shower, washing,
cleaning, etc.)
irrigation,groundwater recharge ordirect reuse
Application of processes
Jan-Olof Drangert, Linköping university, Sweden
Physical
Chemical Biological
BA
ED
F
G
BOD, suspended solids
BOD,
nitrogen, pathogens
p
hosphoru
s,
pathogens, m
etals
C
Overview of possible technical options
Treatment: Possible technical solutions for greywater:
Physical
(SS and BOD-levels)
Screen, grease trap, septic tank, sedimentation pond
Biological I
(BOD-level reduction)
ABR, anaerobic filter, UASB, soil filters, reactive filters, trickling/bio-filter, stabilisation pond, sub-surface wetlands, irrigation
Biological II
(N & pathogen reduction)
Nitrification-denitrification in wetland or sandfilter, maturation pond, crop production, mulch beds, overland flow
Chemical
(P, pathogen, metal removal)
soil filters, reactive filters, precipitation pond, irrigation
Sludge management Thickeners, centrifuge, sieve, fermentation, lime, drainage bed, reed beds, composting, lime stabilisation Karin Tonderski, Linköping univeristy, Sweden
Screens and grease traps
Organics from kitchen pipe sorted out in a plastic screen
Jan-Olof Drangert, Linköping university, Sweden
screen
Over-flow
Sedimentation pond
Karin Tonderski, Linköping university, Sweden
Sediment
Bird’s eye view
Sediment
Simple septic tank
Scum layer
Jan-Olof Drangert, Linköping university, Sweden
Anaerobic pond
CH4, CO2 scum layer
sludge
Karin Tonderski, Linköping university, Sweden
Anaerobic baffled reactor Off-plot system Anaerobic Baffled Reactor (ABR)
Pedro Kraemer, BORDA, India
Anaerobic Filter (off-plot biogas system)
Courtesy of Pedro Kraemer, BORDA, India
UASB Reactor
Jan-Olof Drangert, Linköping university
biogas
Air pump
o2
o2 o2 o2
Horizontal subsurface flow wetlands
Influent
Main filter filled with graded gravel and sand
Cross distribution trench Cross collection trench
Outlet shaft
Internal water level
Effluent
Collection and drainage pipe
Courtesy of Roshan Shrestha, UN-Habitat, Nepal
Construction of horizontal flow wetlands
Karin Tonderski, Linköping university, Sweden
Soil filters – leachfield or mound systems
Jan-Olof Drangert, Linköping university, Sweden
Trickling filter
Jan-Olof Drangert, Linköping university, Sweden
o2
o2 o2 o2
Vertical flow subsurface wetland
Influent
Main filter filled with graded gravel and sand
Effluent
Collection and drainage pipe
Courtesy of Roshan Shrestha, UN-Habitat, Nepal (revised)
Biofilter with nozzle distribution
Wetland
Total area 100 m2
Courtesy of Thor-Axel Stenström, SMI, Sweden
Biofilter and wetland for greywater treatment
Common problems in soil filters
1. Overloading (suspended solids, high BOD, water)
2. Uneven distribution (over surface, over clay)
3. Failure in drainage (waterlogging, roots)
4. Wrong choice of sand and gravel (texture, mineral particle shape)
1
2
4 3
Jan-Olof Drangert, Linkoping university, Sweden
Improved distribution using controlled clogging
Geotextile unit Pre- treatment in
sedimentation tank
0.6 m in sand
3 m in silt
10 m
Courtesy of Peter Ridderstolpe, WRS. Sweden
kitchen
Cajete de acolchado
Wash room
BathRegistro de división de flujos
Bird´s eye view of a mulch bed system for a single house
Distribution boxes
Mulch beds
Courtesy of Kim Andersson, Colombia
Mulch bed filter
Islade tierraAcolchadode hojarasca, pajao virutade madera
Aguasgrisesde cocina, lavamanos, regaderao lavadero
Puntode efluentecubiertocon piedras
Cajete
Islade tierraAcolchadode hojarasca, pajao virutade madera
Aguasgrisesde cocina, lavamanos, regaderao lavadero
Puntode efluentecubiertocon piedras
Cajete
3-10 litres of greywater per m2 per day
Depth max. 40 cm
Mulch from garden
Entrance with stones
Greywater pipe from household
Courtesy of Kim Andersson, Colombia
Wetland irrigation and overland flow
Karin Tonderski, Linköping university, Sweden
Extensive Intensive
Sorption and irrigation systems
- Drain mulch basin
- Swales & resorption
trenches
- Wetland irrigation
(overland flow & sub-
surface flow, and
impounding wetlands)
Aerobic biofilters and energy
Rapid infiltration systems
Soil filters:
- Infiltration (open,
covered submerged
- Sandfilters
Artificial filter media:
- Indrän, infiltra etc.
Biofilter reactors
- Trickling filter- Bio-rotors
Revised from P. Ridderstolpe, WRS, Uppsala
Removal rate of microorganisms in various wastewater treatments (log units)
Process Bacteria Helminths Viruses Cysts
Primary sedimentation: Plain Chemically assisted
0-11-2
0-21-3
0-10-1
0-10-1
UASB 1-2
Activated sludge 0-2 0-2 0-1 0-1
Sub-surface flow wetland 1-2 2-6 2-3 0-2
Aerated lagoon 1-2 1-3 1-2 0-1
Slow sand filtration/infiltration 2-3 3-6 2-3 3-6
Disinfection 2-6 0-1 0-4 0-3
Waste stabilization pond 3-6 1-3 2-4 1-4
Large variations in practice due to quality of management Sources: WHO, 2006 and Jimenez et al., 2010
E: Treatment of sludge
- All treatment processes produce sludge, be it much or little
-Choice of treatment according to kind of reuse
- We need to de-toxify our chemical society
New limits on organics proposed under Option 3 from EU (2008)
PAH 6 mg/kg dry matter
PCB 0.8 mg/kg dry matter
PCDD/F 100 ng ITEQ/kg dry matter
LAS 5 g/kg dry matter
NPE 450 mg/kg dry matter
Limits Cd Cr Cu Hg Ni Pb Zn
Old 20-40 - 1,100-
1,750
16-25 300-400 750-
1,200
2,500-
4,000
New 5 150 400 5 50 250 600
Source: EU, 2008
Start from the end ! (centralised example)
Our thinking is now on global challenges as well as on local wishes for system performance and status
percolating effluent water
Dried sludge itself
We decide what quality we would like the final products to have.
Jan-Olof Drangert, Linköping university, Sweden
Sludge drying bed
CO
2 &
met
ha
ne
ga
ses
Pathogen reductions achieved by selected health-protection measures
Control measure
Reduction(log units)
Comments
Wastewater treatment
1-4 Usually achieved reduction but depends on type and functionality of the treatment system
Drip irrigation: - low-growing
- high-growing2
4
Root crops and crops such as lettuce that grow just above but partially in contact with soil.
Crops such as tomatoes and fruit trees not in contact.
Pathogen die-off 0.5-2 per day
Die-off on crop surfaces between last irrigation and consumption, depends on sunshine, crop type etc.
Crop-washing: - with water
- disinfection1
2-3
Washing salad crops, vegetables and fruit with:
clean water.
Weak disinfectant and rinsing in clean water.
Produce peeling
Produce cooking
1-2
6-7
Fruits, cabbage, root crops.
Immersion in boiling or close-to-boiling water. Source: Bos, R., Carr, R. and Keraita, B. 2010.
Environmental and Human health hazards
Pathogenic microorganisms Chemical compounds
Num-bers
A few hundreds: handfull unknown added each year
100,000 man-made; Hundreds new man-made added each year
Expo-sure
In food, by skin penetration, insect bites, in aerosols.
-
In food, by skin penetration, on skin, in aerosols.
Water bodies, soil accumulation
Dose-response
One up to millions; a few to millions needed for infection
Nano- to microgrammes; small amounts that may accumulate.
Vulne-rable
Humans but not environment. Mainly children & elderly
Both humans and environment. All, but particularly babies
Barriers Wash hands & veggies, no finger in mouth, heat food, etc
Only biodegradable, caution with medicines, effluents to soil
Jan-Olof Drangert, Linköping university, Sweden
Principle:
• Organic ≠ other solid waste
• Stormwater ≠ sewage
• Industrial ≠ household wastewater
• Black toilet water ≠ greywater
• Faeces ≠ urine
Summary of strategies to improve wastewater treatment and nutrient use in
agriculture and energy production
Jan-Olof Drangert, Linköping University, Sweden