RP-Department of Civil and Environmental Engineering

Permanent URI for this collection

https://repository.ku.ac.ke/handle/123456789/5395

Browse

Browsing RP-Department of Civil and Environmental Engineering by Author "Githuku, C."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Assessment of environmental and public health hazards in wastewater used for urban agriculture in Nairobi, Kenya
    (Universidad Autonoma de Yucatan, 2010) Githuku, C.; Karanja, N.; Njenga, M.; Prain, G.; Kang’ethe, E.; Kironchi, G.; Kinyari, P.; Mutua, G.K.
    Thirty percent of residents in Nairobi practise urban agriculture (UA) with a majority of the farmers using untreated sewage to irrigate crop and fodder. Due to the environmental and health risks associated with wastewater irrigation, a study was carried out in partnership with farmers in Kibera and Maili Saba which are informal settlements along the Ngong River, a tributary of the Nairobi River Basin. Soil, water, crops and human faecal samples from the farming and non-farming households were analysed to elucidate sources, types and level of heavy metal pollutants in the wastewater and the pathogen loads in humans and vegetable crops. Heavy metal accumulation in soils collected from Kibera and Maili Saba were Cd (14.3 mg kg-1), Cr (9.7 mg kg-1) and Pb (1.7 mg kg-1) and Cd (98.7 mg kg-1), Cr (4.0 mg kg-1) and Pb (74.3 mg kg-1), respectively. This led to high phytoaccumulation of Cd, Cr and Pb in the crops that exceeded the maximum permissible limits. No parasitic eggs were detected in the vegetables but coliform count in the wastewater was 4.8 x108±2.2 x1011/100ml. Soils irrigated with this water had parasitic eggs and non-parasitic larvae counts of 54.62 and 27.5/kg respectively. Faecal coliform and parasitic eggs of common intestinal parasites increased in leafy vegetable sampled from the informal markets along the value chain.
  • Thumbnail Image
    Item
    The heavy metal content of crops irrigated with untreated wastewater: a case study of Nairobi, Kenya
    (Jomo Kenyatta University of Agriculture and Technology, 2014) Kaluli, J. W.; Home, P. G.; Githuku, C.
    Use of untreated wastewater for irrigation could have devastating effects on crop quality. A study was conducted to determine the content of lead, cadmium and chromium in food crops irrigated with untreated wastewater at Kibera and Maili Saba, in Nairobi, Kenya. Crop samples were collected from farms irrigated with untreated wastewater during the dry and wet seasons. While the safe limits of lead and cadmium in food crops are 0.3 and 0.2 ppm, the concentration of lead and cadmium, at Maili Saba downstream ofthe industrial area, in the edible crops during the dry season was 48.4 and 26.5 ppm, respectively. Enrichment factor (EF)was used as a measure of the risk and hazard sustained when crops are irrigated with water that is contaminated heavy metals. Plots planted with black nightshade (BNS) and Kales at Maili Saba, downstream of Nairobi's industrial area, had the highest EF values. Lead in BNS at Maili Saba during the dry season had the highest EFvalue of about 2200, suggesting that irrigating BNS with contaminated sewage could be hazardous. This study has confirmed that irrigation of food crops increases the concentration of heavy metals such as lead and cadmium to unsafe levels.