Waste water

Updated: Apr 13

Wastewater is any water that has been affected by Human activities. Wastewater is used water from combination of any of the following activities domestic, commercial, industrial or agricultural, surface runoff or storm water and any sewer or sewer infiltration. Wastewater can be categorized based on their use are :

· Municipal Wastewater (Wastewater generated from domestic, commercial and Institutional activities)

· Industrial Wastewater (Wastewater generated from industrial activities)

· Agricultural Wastewater (Wastewater generated from agricultural activities)


Domestic wastewater or sewage, generated from residential as well as commercial areas, is the liquid component of waste. Domestic wastewater can be categorized as black and grey water.

Black water, which originates as toilet waste from water closets (WCs) – faeces, urine, toilet paper and flush water- has a concentration of proteins, carbohydrates, and fats, nutrients like nitrogen and phosphorus and pathogens. The presence of disease-carrying pathogens makes black water hazardous.

Grey Water: The total volume of water generated from washing food, clothes and dishware, as well as from bathing but not from toilets. It may contain traces of excreta and therefore, also pathogens. Grey water accounts for approximately 65 percent of the wastewater produced in households with flush toilets. Compared to black water, grey water is less contaminated.

Composition of Grey Water

1. Grey Water from Bathroom

Water used in hand washing and bathing generates around 50-60% of total greywater and it is considered to be the least contaminated type of grey water. Common contaminants in grey water includes soap, shampoo, hair dye, toothpaste and cleaning products.

It has also some fecal contamination and the associated bacteria and viruses through body washing.

2. Grey Water from Cloth Washing

Cloth washing generates around 25-35% of total grey water. Wastewater generating from the cloth washing varies in quality from wash water to rinse water to second rinse water. Grey water generated due to cloth washing can have fecal contamination with the associated pathogens and parasites such as bacteria.

3. Grey water from Kitchen

Kitchen grey water contributes about 10% of the total grey water volume. It is contaminated with food particles, oils, fats and other wastes. It readily promotes and supports the growth of micro-organisms. Kitchen grey water also contains chemical pollutants such as detergents and cleaning agents which are alkaline in nature and contain various chemicals.

Therefore, kitchen wastewater may not be well suited for reuse in all type of grey water systems.

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