Treatment of Grey water and Recycling

1. Greywater treatment
constructed
wetland, gardening,
wastewater pond, biol.
treatment, membrane-
technology
Greywater
(shower, washing,
cleaning, etc.)
irrigation,
groundwater
recharge or
direct reuse

2. Application of processes
Physical
B
A
E
D
F
G
BOD,
suspended solids
C

3. 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, 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

4. Screens and grease traps
Organics from kitchen pipe
sorted out in a plastic screen
screen
Over-
flow

5. Sedimentation pond

6. Sediment
Bird’s eye
view
Sediment
Simple septic tank
Scum
layer

7. Anaerobic pond
CH4, CO2 scum
layer
sludge

8. Anaerobic baffled reactor
Off-plot system
Anaerobic Baffled Reactor (ABR)

11. Anaerobic Filter (off-plot biogas system)
Courtesy of Pedro Kraemer, BORDA, India

12. 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

13. Construction of horizontal flow wetlands

14. Soil filters –
leachfield or mound systems

15. Trickling filter

16. o2
o2 o2 o2
Vertical flow subsurface wetland
Influent
Main filter filled with graded gravel and sand
Effluent
Collection and drainage pipe

17. 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

18. Improved distribution using controlled clogging
Geotextile
unit Pre- treatment in
sedimentation tank
0.6 m
in sand
3 m in silt
10 m

19. Wetland irrigation and overland flow

20. 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

21. Removal rate of microorganisms in various
wastewater treatments (log units)
Process Bacteria Helminths Viruses Cysts
Primary sedimentation:
Plain
Chemically assisted
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