Seasonal assessment of groundwater quality in Ruiru Kiambu County, Kenya
Otieno, Rachel Olonga
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Water is essential for life and the bloodstream of the green economy. Lack of access to wholesome drinking water adversely affects the public health of many developing countries and Kenya is not an exception. Ruiru, a small but fast growing town in the outskirts of Nairobi, is one area where limited resources and services are facing relentless pressure due to rapid population growth. The residents experience unreliable water supply and are therefore highly dependent on groundwater sources such as boreholes and shallow wells as the main source of water for domestic use. The present study is an attempt to assess the groundwater quality and the seasonal variation with a view of ascertaining its suitability for domestic use. A total of 109 drinking water samples from groundwater source from Ruiru were randomly sampled and assessed to determine their physico-chemical and bacteriological characteristics together with their seasonal variations. Water samples were collected during the dry (January- February, 2015) and Wet season (March- April, 2015) and analyzed for temperature, pH, colour, turbidity, conductivity, total dissolved solids, total alkalinity, total hardness, iron, manganese, fluoride and major cations (calcium, magnesium, sodium and potassium) and major anions (chloride, sulfate, Nitrate) using Standard Methods for the Examination of Water and waste water. The results obtained were compared to guideline values of the World Health Organization (WHO) and Kenya Bureau of Standards (KEBS) to establish the suitability of groundwater for domestic purposes. Generally, seasonal variations showed that there was a decrease in most of the parameters in boreholes with a shift of the season from dry to wet and vice versa for shallow wells. The concentration of fluoride, nitrates, turbidity and Iron in some of the samples exceeded the prescribed KEBS and WHO standards of ISm/I, 10 mg/l, NTU and 0.3 mg/l respectively. The student's Hest performed showed a significant difference (p :s 0.01) between the means of the sampled boreholes and shallow wells water for the following parameters; pH, Electrical conductivity, total Dissolved solids, calcium, total alkalinity, chlorides, fluorides, nitrates, Iron, manganese, total coliforms and E.coli. The difference was also significant (p :s 0.05) for colour,turbidity, total hardness and magnesium. The sampled boreho!es and shallow wells had faecal coliform contamination and did not conform to the WHO and KEBS guideline value of 0 MPNIl 00 ml. The study revealed poor bacteriological quality of drinking water sources. Therefore the need for the provision of reliable potable water to the local dwellers by government is highly recommended to avert waterborne related diseases.