Characteristics of grey wastewater Eva Eriksson * , Karina Auffarth, Mogens Henze, Anna Ledin Environment & Resources DTU, Technical University of Denmark, Bygningstorvet, Building 115, DK-2800 Kgs. Lyngby, Denmark Received 1 February 2001; received in revised form 7 September 2001; accepted 25 October 2001 Abstract The composition of grey wastewater depends on sources and installations from where the water is drawn, e.g. kitchen, bathroom or laundry. The chemical compounds present originate from household chemicals, cooking, washing and the piping. In general grey wastewater contains lower levels of organic matter and nutrients compared to ordinary wastewater, since urine, faeces and toilet paper are not included. The levels of heavy metals are however in the same concentration range. The information regarding the content of xenobiotic organic compounds (XOCs) is limited. From this study, 900 different XOCs were identified as potentially present in grey wastewater by the use of tables of contents of household chemical products. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Characteristics; Grey wastewater; Greywater; Literature review; Reuse; Water quality; Xenobiotic organic compounds 1. Introduction There is an increasing interest in the reuse of waste- water in many parts of the world, including both in- dustrial and developing countries. One reason is water shortage, caused by too low amounts of rainfall in combination with high evaporation (e.g., Australia) or too large demands of freshwater from the population (e.g., Japan). On the other side in some countries, the driving force for reuse of wastewater is environmental and economical considerations. The reuse will lower the total costs for wastewater handling, since there will be a reduced load of water to the treatment plants. Greywastewaterisdefinedaswastewaterwithoutany input from toilets, which means that it corresponds to wastewater produced in bathtubs, showers, hand basins, laundry machines and kitchen sinks, in households, of- fice buildings, schools, etc. The total grey wastewater fraction has been estimated to account for about 75 vol% of the combined residential sewage (Hansen & Kjellerup, 1994 and references therein). Possibilities of reuse for grey wastewater have come into special focus. The explanation is that this fraction of wastewater is less polluted than municipal wastewater in the absence of faeces, urine and toilet paper. The characteristicswillbeofimportancewhenevaluatingthe possibilities for reuse, including the need for pre-treat- ment. Health aspects, mainly micro-organisms, and environmental perspectives like accumulation of xeno- biotic organic compounds (XOCs) and metals in soil and groundwater, have to be taken into account. Use of grey wastewater for urinal and toilet flushing is one of the possibilities since the water that is used for toilet flushing in many countries today is of drinking waterquality.Ithasbeenestimatedthat30%ofthetotal household water consumption could be saved by reusing grey wastewater for flushing toilets (Karpiscak, Foster, & Schmidt, 1990). Reuse of grey wastewater from bathroomshasbeensuccessfullyusedinGermanywhere it has been shown that it is technically feasible and health requirements can be met. Substantial volumes of water ð15–55 l pd 1 Þ can be reused and a dual system is possible (Nolde, 1999). A review of the current water demands in large buildings revealed that not only grey wastewater from bathrooms but also washing machine wastewater or stormwater is needed to provide sufficient recycled water for non-potable uses (Surendran & Wheatley, 1998). Outdoor applications for grey waste- water could be irrigation of lawns on college campuses, athletic fields, cemeteries, parks and golf courses as well as in the domestic garden (Okun, 1997). Washing of vehicles and windows, fire protection, boiler feedwater and concrete production are examples of other suggested usages (Okun, 1997; Santala et al., 1998). In Urban Water 4 (2002) 85–104 www.elsevier.com/locate/urbwat * Corresponding author. Tel.: +45-4525-1600; fax: +45-4592-2850. E-mail address: eve@er.dtu.dk (E. Eriksson). 1462-0758/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S1462-0758(01)00064-4