Browsing by Author "Kariuki, F.W."

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    A Comparison of the physico-chemical and bacteriological quality of greywater from water deficient households in Homabay Town and Githurai Estates in Kenya.
    (Academic Journals, 2012) Ngángá, V.G.; Kariuki, F.W.; Kotut, Kiplagat
    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.
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    Hydrochemical Characteristics, Plant Nutrients and Metals in Household Greywater and Soils in Homa Bay Town
    (2012) Kariuki, F.W.; Ng`ang`a, V.G.; Kotut, Kiplagat
    Greywater recycling has been identified as an efficient method to conserve water. The purpose of this study was to investigate some selected hydrochemical characteristics, plant nutrients and metal content of greywater and soils in residential areas of Homa Bay town. Laundry greywater had the highest pH (9.1 ± 0.01), Electrical conductivity (2900 ± 215 􀀁S cm-1) and salinity (0.4 ± 0.02 - 0.8 ± 0.01 mg L-1). The lowest electrical conductivity (400 ± 50 􀀁S cm-1) was recorded in bathing greywater. The highest SAR (4.63 ± 0.23) was recorded in laundry gerywater from non-sewered households and the lowest SAR (0.72 ± 0.12) in kitchen greywater from sewered households. The SAR values of greywater in Homa Bay were lower than the acceptable limit of 6 for moderate restriction on the use of such water for irrigation. The SAR values for soils in Homa Bay were 2.12 ± 0.13 and 4.21 ± 0.11 in soils that had received kitchen and bathing greywater respectively and 27 ± 0.5 for rainfed soil. Nitrogen, Phosphorus, Sodium, Iron, Copper, Cadmium and Chromium concentration were highest in laundry greywater. The highest values of Zinc and Manganese were in kitchen greywater from non-sewered households. Levels of metals in soils that had been exposed to greywater were lower than the recommended limits. A significant (p<0.05) positive correlation was recorded between concentration of Cd in bathing greywater and in the soil. A significant (p<0.05) negative correlation between the concentration of Cu in kitchen greywater and in soils was also recorded.
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    Physico-Chemical and Microbial Quality of Greywater from Various Households in Homa Bay Town
    (2011) Kotut, Kiplagat; Nganga, V.G.; Kariuki, F.W.
    In recent years concerns over dwindling reserves of ground water and overloaded or costly sewage treatment plants has generated much interest in the reuse or recycling of greywater. Re-use of greywater offers several advantages including a reduction in the demand on potable water supplies. Despite the prevalent direct reuse of greywater, especially in water scarce areas, its quality is not well documented. This study determined the physico-chemical and microbial quality of greywater produced by households in Homa Bay town. Most of greywater generated had a higher electrical conductivity and salinity and lower concentration of dissolved oxygen. Greywater pH values varied widely but were mostly higher than that of clean water. Biological oxygen demand varied widely (410-6250 mg L-1). Total coliform (TC) counts in greywater samples ranged from 1.3 to 7.6 colony forming units (CFU)/ 100 mL while fecal coliform (FC) counts varied between 3000 and 7.4 million CFU/ 100 mL. Field observations showed that the variation in TC and FC counts resulted from differences in the level of households’ personal hygiene, difference in the intensity of greywater reuse and duration of storage. Among the potentially pathogenic bacteria investigated, Salmonella was the most frequent, occurring in 31% of all the greywater samples collected. Vibrio occurred in the least number of samples (9%). The study concludes that greywater produced is most likely to be contaminated by pathogenic bacteria and should therefore be disinfected prior to reuse.
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    The Potential of a Low Cost Technology for The Greywater Treatment
    (2011) Kariuki, F.W.; Kotut, Kiplagat; Ngángá, V.G.
    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 (2.5x106 cfu/100 ml) comparable to 0–>2.4 􀀁 106 cfu/100 ml obtained when greywater was treated using an expensive biological aerated filter (BAF). Fecal coli form counts (2.1􀀁 102 cfu/100 ml) compare well with 103 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.