Health risks-greywater
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Transcript of Health risks-greywater
POTENTIAL HEALTH RISKS FROM GREY WATER
David Cunliffe
What is Grey Water ?
Shower and bath water 33 % of total wastewater generated
Hand basins5 %
Laundry23 %
Kitchen7 %
Total - about 70 % of wastewater is grey water
Purpose of Grey Water
Sanitation and cleaning
Washing hands, skin, clothes, food etc to remove pathogenic microorganisms, oil, grease and dirt
- higher loads from washing clothes/nappies from babies and young children
Aim is to separate people from harmful microorganisms by carrying them away in grey water.
Other uses
Washing animals, cleaning tools, transporting urine, disposal of hazardous waste (chemical)
What is in Grey WaterBathroomPathogenic microorganisms (Thermotol coliforms <10-106 per 100 mL), hair, skin, soaps, oil, grease (Sewage ~ 106-1010 thermotol coliforms per 100 mL)
LaundryPathogenic microorganisms (Thermotol coliforms <10-107 per 100 mL), bleach, soap powders (boron, sodium, phosphate, ammonia, surfactants), lint
KitchenPathogenic microorganisms (Thermotol coliforms <10-106 per 100 mL), detergents, food particles and residues, oils, fats, hazardous wastes
Unknowns
Washing of nappies and other faecally-soiled clothing
Washing of pets
Disposal of hazardous liquids
Washing of tools
Health Risk
Depends on hazards present in the source water and exposure (+ mosquitoes)
Exposure controlled by managing:
- method of application - public accessibility- use
Risk Source
Lower Laundry rinse
Laundry wash and rinse
Bathroom
Higher Kitchen
Other risk factors - young children and pets
Heath risk by source
Risk Method
Lower Sub surface
Drip
Spray
Higher Hose
Other risks - ponding/storage can support mosquitobreeding
Heath risk by application method
Risk Method
Lower Trees and shrubs
Lawn
Fruit trees
Vegetables
Higher In house (toilet flushing)
Other risks - non-approved cross-connections
Heath risk by use
Risk Accessibility
Lower No access
No access by young children
Higher Unlimited access
Heath risk by accessibility
Conclusions
Grey water usually contains fewer hazards than sewage but concentrations vary over a very wide range
For on-site systems the concentration and range of hazards will depend on household management
Restricting methods of application and types of use can reduce risk but for on-site systems this will rely on household management
Systems need to be robust and designed to involve a minimum of maintenance. Centralised management systems are best.