Adequately treated grey water is a suitable resource for urban water supply, where no drinking water quality is required. Grey water is collected from indoor sources other than toilets and kitchen sinks, such as showers and bathtubs, hand basins and washing machines. Grey water has typically lower BOD5, COD, N and P levels, is higher in temperature compared to domestic waste water, but higher concentrations of active surfactants are observed. In general similar treatment processes as for the treatment of municipal waste water can be used for treating grey water. Thus grey water treatment seems to be less complex as no nitrogen and phosphorus removal is necessary, and biochemical degradation rates are fast as a result of higher temperature especially at nearby treatment. Treated grey water can be used as service water, e.g. for toilet flushing and plant irrigation in intra-urban areas, which again fosters decentralized nearby treatment. The pilot plant, which is part of a BMBF funded project (Semi-centralized Supply and Disposal Systems for Urban Areas in China, Part II: 02WD0607), consists of five different treatment units. The size of this whole pilot plant is about 1,500 population equivalents. For the pilot plant synthetic grey water will be composed by adding wash powder, tooth paste, bubble bath, shower gel etc. to drinking water. The formula is based on consumption data given by IKW (Industrieverband Körperpflege und Waschmittel e.V. = German Cosmetic, Toiletry, Perfumery and Detergent Association). In addition some municipal waste water is added to simulate microbial pollution as well as particular matter and grease. The composition of this synthetic grey water is in good compliance with published data of real grey water, which anyhow shows a wide variance.

Bibliographic information

Chang, Y., Wagner, M., Cornel, P. (2007). Treatment of grey water for urban water reuse Technische Universität Darmstadt, Institut WAR, Darmstadt, Germany

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Greywater or wastewaterUrban (entire city)English

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