4.7 Greywater treatment
Learning objectives: Get familiar with
various treatment options and with the
application of various processes
Greywater
(shower, washing,
cleaning, etc.)
constructed
wetland, gardening,
wastewater pond, biol.
treatment, membranetechnology
irrigation,
groundwater
recharge or
direct reuse
Application of processes
G
F
A
B
D
E
C
BOD,
suspended solids
Physical
Jan-Olof Drangert, Linköping university, Sweden
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, subsurface wetlands, irrigation
Biological II
(N & pathogen reduction)
Nitrification-denitrification in wetland or sandfilter,
maturation pond, crop production, mulch beds,
overland flow
Chemical
soil filters, reactive filters, precipitation pond,
(P, pathogen, metal removal) irrigation
Sludge management
Thickeners, centrifuge, sieve, fermentation, lime,
drainage bed, reed beds, composting, lime
stabilisation
Karin Tonderski, Linköping univeristy, Sweden
Screens and grease traps
screen
Overflow
Organics from kitchen pipe
sorted out in a plastic screen
Jan-Olof Drangert, Linköping university, Sweden
Sedimentation pond
Karin Tonderski, Linköping university, Sweden
Simple septic tank
Scum
layer
Bird’s eye
view
Sediment
Sediment
Jan-Olof Drangert, Linköping university, Sweden
Anaerobic pond
CH4, CO2
scum
layer
sludge
Karin Tonderski, Linköping university, Sweden
Off-plot system
Anaerobic Baffled
Reactor (ABR)
Anaerobic baffled reactor
Pedro Kraemer, BORDA, India
Anaerobic Filter (off-plot biogas system)
Courtesy of Pedro Kraemer, BORDA, India
UASB Reactor
biogas
Air pump
Jan-Olof Drangert, Linköping university
Horizontal subsurface flow wetlands
o2
o2
o2
o2
Internal water level
Influent
Outlet shaft
Cross distribution trench
Main filter filled with graded
gravel and sand
Cross collection trench
Collection and drainage pipe
Effluent
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
Vertical flow subsurface wetland
o2
o2
o2
o2
Influent
Main filter filled with graded gravel and sand
Collection and drainage pipe
Effluent
Courtesy of Roshan Shrestha, UN-Habitat, Nepal (revised)
Biofilter and wetland for greywater treatment
Biofilter
with nozzle distribution
Wetland
Total area 100 m2
Courtesy of Thor-Axel Stenström, SMI, Sweden
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,
1mineral particle shape)
2
3
4
Jan-Olof Drangert, Linkoping university, Sweden
Improved distribution using controlled clogging
Geotextile
unit
Pre- treatment in
sedimentation tank
10 m
0.6 m
in sand
3 m in silt
Courtesy of Peter Ridderstolpe, WRS. Sweden
Bird´s eye view of a mulch bed system
for a single house
Registro de
Distribution
división de flujos
boxes
Mulch
beds
Cajete
de acolchado
Bath
kitchen
Wash
room
Courtesy of Kim Andersson, Colombia
Mulch bed filter
Greywater
pipe from
household
Aguas grises de cocina,
lavamanos, regadera o
lavadero
Mulch
from
Acolchado
de
hojarasca, paja o
garden
viruta de madera
Isla de tierra
Cajete
Depth
max.
40 cm
Entrance
Punto
de efluente
with
cubiertostones
con piedras
3-10 litres of greywater per m2 per day
Courtesy of Kim Andersson, Colombia
Wetland irrigation and overland flow
Karin Tonderski, Linköping university, Sweden
Aerobic biofilters and energy
Extensive
Sorption and
irrigation systems
Intensive
Rapid infiltration
systems
- Drain mulch basin
Soil filters:
- Swales & resorption
trenches
- Infiltration (open,
covered submerged
- Wetland irrigation
(overland flow & subsurface flow, and
impounding wetlands)
- 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
Primary sedimentation:
Plain
Chemically assisted
Bacteria
Helminths
Viruses
Cysts
0-1
1-2
0-2
1-3
0-1
0-1
0-1
0-1
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:
Limits
Cd
Old
20-40
New
5
Cr
150
Treatment of sludge
Cu
Hg
Ni
1,100- 16-25 300-400
1,750
400
5
50
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
Pb
Zn
7501,200
250
2,5004,000
600
- 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
Source: EU, 2008
Start from the end !
(centralised example)
We decide what quality we
would like the final products
to have.
Sludge
drying bed
CO2 & methane
gases
Our thinking is now on global challenges as well as
on local wishes for system performance and status
percolating
effluent water
Jan-Olof Drangert, Linköping university, Sweden
Pathogen reductions achieved by selected
health-protection measures
Control
measure
Wastewater
treatment
Reduction Comments
(log units)
1-4
Drip irrigation:
- low-growing
- high-growing
2
4
Pathogen die-off
0.5-2
per day
Usually achieved reduction but depends on type and
functionality of the treatment system
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.
Die-off on crop surfaces between last irrigation and
consumption, depends on sunshine, crop type etc.
Crop-washing:
- with water
- disinfection
1
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
Numbers
A few hundreds: handfull
unknown added each year
Exposure
In food, by skin penetration,
insect bites, in aerosols.
Dose- One up to millions; a few to
response millions needed for infection
Chemical compounds
100,000 man-made; Hundreds
new man-made added each year
In food, by skin penetration, on
skin, in aerosols.
Water bodies, soil accumulation
Nano- to microgrammes; small
amounts that may accumulate.
Vulne- Humans but not environment. Both humans and environment.
rable Mainly children & elderly
All, but particularly babies
Barriers Wash hands & veggies, no
Only biodegradable, caution
finger in mouth, heat food, etc with medicines, effluents to soil
Jan-Olof Drangert, Linköping university, Sweden
Summary of strategies to improve
wastewater treatment and nutrient use in
agriculture and energy production
Principle:
•
•
•
•
•
Organic ≠ other solid waste
Stormwater ≠ sewage
Industrial ≠ household wastewater
Black toilet water ≠ greywater
Faeces ≠ urine
Jan-Olof Drangert, Linköping University, Sweden