Greywater (GW) is household wastewater effluent originating from baths, showers, kitchen and hand wash basins and laundry and constitutes 50-80% of indoor household water use. It represents water that can potentially be intercepted at the household level for use. In Kenya, GW use is practiced on an informal basis to supplement irrigation water, either in urban gardens in middle to upper income suburbs or in food gardens in lower income informal, periurban and rural areas. However, the reuse of greywater for irrigation without any significant pre-treatment poses a potential risk to both human and environmental health due to microbial and chemical contamination. This study investigated the potential of a low cost greywater treatment (GWT) system for safe greywater reuse by households. The system comprises of discrete units of barrels that allows for filtration, flocculation, sedimentation and disinfection. GWT system produced water with both pH and electrical conductivity suitable for irrigation according to WHO guidelines. It was also efficient at eliminating Salmonella sp. and reducing total coli form in composite greywater from households in Homa Bay after the effluent was disinfected with commercial disinfectant, sodium hypochlorite (NaOCl). The cleaned greywater had a total coli form count (2.5x10 6 cfu/100 ml) comparable to 0->2.4 10 6 cfu/100 ml obtained when greywater was treated using an expensive biological aerated filter (BAF). Fecal coli form counts (2.1 10 2 cfu/100 ml) compare well with 10 3 cfu/100 ml provided in WHO guidelines for public parks and crops likely to be eaten uncooked. The treatment had no effect on dissolved oxygen, pH, salinity and electrical conductivity. The study concludes that the GWT system can be a sustainable and promising low cost low technology treatment system that can be run and maintained by unskilled operators.

Greywater, the untreated household wastewater that has not been contaminated by toilet waste, has been touted as a reliable all year-round source of water, especially in water scarce areas. Although it is commonly reused in water scarce urban and peri-urban settlements in Kenya, information on its bacteriological and physico-chemical properties is generally limited. The present study sought to compare the physico-chemical and bacteriological quality of kitchen and laundry greywater from an urban (Githurai) and peri-urban settlement (Homabay). Compared to the source water, kitchen and laundry greywater at the two sites had higher electrical conductivity (EC) and salinity, depressed dissolved oxygen (DO) levels and a wide pH range. Although significant differences in EC, DO and salinity of greywater from kitchen and laundry were noted (P < 0.05), the two sites differed significantly only in DO (P = 0.002). Total coliforms (TC) and fecal coliforms (FC) were also higher in greywater than in source water. The greywater types differed in TC (P = 0.003) while the two sites differed in both TC and FC (P 0.03). High loads of TC and FC suggest possible fecal contamination of greywater. This coupled with the occasional presence of Salmonella, Shigella and Vibrio cholerae means that reuse of untreated greywater is not safe in both sites, and should be treated before use. Owing to the differences in the quality of the different types of greywater as well as the sites investigated, the design of greywater treatment technologies should consider both type and source.