Grey water is a waste water derived from kitchens, bathrooms (i.e., discharges from
shower, hand basin, bath), and laundry water. Grey water does not include the waste
water produced from toilet use, which is considered black water. The generated quantity
of grey water can greatly vary between different households within one community and
depends on different factors, such as availability of water and lifestyle of households. In
general, the volume of grey water accounts between 50 per cent and 80 per cent of the
domestic household water uses. The quality of grey water is highly variable due to the
variability in household water use. Grey water contains the same contaminants (organic
compounds, nutrients and pathogens) as raw sewage water. However, grey water
contains low concentrations of contaminants compared to those in raw sewage water and
black water. The potential risks, as there is some concern that the high levels of organic
load produced in kitchens might pose an unacceptable risk of pathogenic contamination
in gray water. Reuse of grey water systems as an opportunity to conserve potable quality
water, generate locally sustainable water sources, and match.
the water supply quality with that required for the intended use. Grey water or sullage is
defined as all wastewater streams generated from households or office buildings except
for the wastewater from toilets.
Sources of grey water include for example sinks, showers, baths, clothes washing
machines or dish washers. As grey water contains many fewer pathogens than domestic
wastewater, it is easier to treat and to recycle onsite for uses such as toilet flushing,
landscape irrigation or even irrigation of crops. Application of grey water reuse in urban
water system provides a substantial benefit for both water supply and wastewater
subsystems by reducing the need for clean water in water distribution system as well as
generated wastewater in sewer system
There is a high amount of variability in the chemical and physical quality of grey water
produced by any household, due to factors such as source of water the water use
efficiency of appliances and fixtures, individual habits, product used (eg. Detergents,
shampoos, soaps etc) and other site-specific characteristics. The amount of salt (sodium,
magnesium, potassium and other salts), oils, greases, fats, nutrients and chemicals in grey
water can largely be managed by the types of product used within a household. Most
cleaning agents contain sodium salts, which can cause excessive soil alkalinity, inhibit
seed germination, and destroy the structure of soils by dispersing clay. Cleaning products
containing ammonia are safe to use, as plants can use it to obtain nitrogen.