4.7 Greywater treatment

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


screen

Over-flow

Sedimentation pond

Karin Tonderski, Linköping university, Sweden

Sediment

Bird’s eye view

Sediment

Simple septic tank

Scum layer


Anaerobic pond

CH4, CO2 scum layer

sludge


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


Soil filters – leachfield or mound systems


Trickling filter


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


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.


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


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

4.7 Greywater treatment

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