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UNESCO-IHE Institute for Water Education, Delft (2006)

Phosphorus budget of a household system in a low income peri-urban area : case study Kibera, Kenya

Koech, D.K.

Titre : Phosphorus budget of a household system in a low income peri-urban area : case study Kibera, Kenya

Auteur : Koech, D.K.

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2006

Résumé
Phosphorus is an essential element to both plants and animals. The phosphorus mainlyoccurs as rock phosphates in the earth’s crust and is mined for making fertilisers. Thesereserves are finite and other potential sources needs to be explored. Household wastescontain phosphorus which can be recycled into agricultural use while at the same timereduce environmental pollution from these wastes.The aim of this thesis is to quantify the amount of phosphorus from household wastes.This is based on a study in the low -income area of Kibera in Nairobi, Kenya. Weeklymapping of the food consumed together with soaps and detergents used by five selectedfamilies was done for a period of two months. The total amount of phosphorus in thematerial flow and the wastes was estimated on the basis of the composition of eachgroup. In order to assess the phosphorus losses to the environment, water and soilsamples were taken and analysed. A social survey was done using structured and semistructuredinterviews to get as many respondents as possible.The inflow of phosphorus through foods and soaps amounted to 42.2 g P/p. month and2.2 g P/p.month respectively. Cereals in the food groups contributed the highestphosphorus (20.3 g P/p.month) whereas in the soaps and detergents group, detergentscontributed the most (1.3 g P/p.month).The P-outflow through urine, faeces, grey water, and solid waste was 25, 8.3, 2.2 and2.5 g P/p.month respectively. Urine was the largest contributor to the P loadingswhereas grey water was the lowest. It was estimated that in total, a person consumes44.4 g of Phosphorus per month and generates 38 g Phosphorus per month as waste.The P- concentration of the streams and Motoine river ranged from 1 to 9 mg P/l againstthe Kenyan guidelines of a maximum of 0.1mg P/l. The P concentration was found todecrease downstream towards the Nairobi Dam, which could be attributed tosedimentation and dilution effect in the surface water. The Nairobi dam is a reservoir ofall the wastes transported via the streams and Motoine river. This research establishedthat the P-concentration of the dam was 5.8 mg P/l with the total P-loading of 166gP/m2.yr. The dam was found to be highly eutrophic which explains the invasion ofwater hyacinth plants in the dam. The residence time of water in the lake was estimatedat 6 days less than the original design time of 10-20 days.The P-loading should be reduced by 98 % if the dam is to be restored to a desiredoligotrophic state.

Sujets  : eutrophication phosphorus household wastewater solid wastes dams Kenya

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Page publiée le 3 mars 2020