INTRODUCING GREYWATER TO THE BUILT ENVIRONMENT 212 BUILT ENVIRONMENT VOL 42 NO 2 developing countries GW volumes often range from 20 to 30 litres per person per day, whereas in developed countries the production often exceeds 100 litres per person per day (table 1). GW, once appropriately treated, is considered suitable for non-potable purposes such as toilet flushing (March et al., 2004) and garden irrigation (Gross et al., 2007). To date, GW is mostly used for garden irrigation and toilet flushing in the domestic seting (Donner et al., 2010), but in public domains it can also be used for landscape, agricultural crop (Finley et al., 2009), golf course (Lazarova et al., 2013), or public park irrigation (Schaefer et al., 2004), along with enriching groundwater (Abu-Ashour and Lee, 2000; Abu-Ashour and Abu-Zreig, 2005). GW is lower in nitrogen, faecal material, and organic content compared to municipal WW (table 2) (Eriksson et al., 2002) and hence can be treated with relatively low-tech, Water scarcity and increasing worldwide demand has made water reclamation and reuse more popular. The practice of decentral- ized, on-site greywater (GW) treatment has become widespread with millions of reuse systems in use worldwide (Brix and Arias, 2005; Friedler et al., 2005; Lens, 2001). GW is the non-toilet portion of domestic wastewater (WW) stream which comes from bathing, laundry, and sometimes from the kitchen (Friedler, 2004). GW reuse can significantly reduce domestic and urban water demand and increase the exploitation efficiency of this scarce and restricted resource (Ghisi et al., 2006). According to several studies the proportion of GW produced by a typical household is between 40 per cent and 70 per cent of all the water disposed. Therefore, reuse can result in significant environmental and economic benefits on a local and regional level (Friedler, 2004; Oron et al., 2014). In Potential Health and Environmental Risks Associated with Onsite Greywater Reuse: A Review MAYA BENAMI, OSNAT GILLOR and AMIT GROSS The practice of decentralized, on-site greywater (GW) treatment, the non-toilet portion of domestic wastewater (WW) stream, has become widespread with millions of systems in use worldwide. GW reuse can bring a significant reduction in domestic and urban water demands and increase the exploitation efficiency of this scarce resource. However, environmental and human health concerns challenge onsite treatment, as its operation by non-professionals must be reliable, simple and economically feasible if such systems are to be used by many. While macro- and micro-pollutants found in GW are the main hazard to environmental health, pathogens are considered the principal risk to public health. Hence, a few major topics related to GW reuse are discussed in this review: (a) microbial and physico-chemical quality of GW before and after treatment; (b) plant health after GW-irrigation; (c) soil health risks as measured by changes of quality following GW irrigation; and (d) risks to public health via epidemiological data and quantitative microbial risk assessment (QMRA).