Physico-Chemical Parameters, Bacterial Load And Heavy Metals, in Water and Vegetables Grown along Mitheu River, Machakos County, Kenya
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Date
2022
Authors
Kitulu, Linge
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Urban streams are increasingly utilized for irrigation farming to supplement the demand for food in cities, and towns. The susceptibility of these streams getting polluted by improperly treated industrial, and municipal effluent is high. The objective of this study was to investigate the bacteriological, and heavy metals contamination in Mitheu stream within Machakos municipality, and concentration of selected heavy metals in vegetables irrigated with water from the stream in order to contribute to measures towards safe disposal of effluent. This study investigated the water quality of Mitheu stream with respect to irrigation use, and the levels of selected heavy metals in Kales, and Spinach grown along the stream. Bacterial counts, physico-chemical parameters i.e., temperature, pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), nitrates, phosphates, and sulphates as well as selected heavy metals i.e., Cd, Cu, Zn, Pb, and Cr were analyzed in water. The concentration of these selected heavy metals in kales, and spinach were determined as well. water samples for physico-chemical, heavy metals, and bacteriological analyses were collected in four selected sampling points along Mitheu stream once every month from June to September 2019. Kales, and Spinach samples for heavy metals analysis were collected from farms along the stream adjacent to the selected sampling points. Physico-chemical, and bacteriological analyses were performed in Water Resources Authority Laboratory in Nairobi. Heavy metals analyses in both water, and vegetables were performed in Kenya Plant Health Inspectorate Services Analytical Laboratory in Nairobi. The results were subjected to One-Way Analysis of Variance to test significant differences. Comparison with WHO standards for the respective parameters was done to test suitability of the stream water for irrigation, and the vegetables for human consumption. The stream was found to contain higher-than-recommended levels of pH, TDS, EC, COD, BOD, and Bacterial contaminants. Concentrations of nitrates, and cadmium (Cd) in the stream were also higher than WHO safe limits for irrigation water. Concentrations of COD, BOD, and Total Coliforms bacteria had significant variation along the stream (p≤ 0.05). All other parameters investigated, were not significantly varied along the stream. The concentrations of Cd, Pb, and Cr in kales, and spinach exceeded WHO recommended limits. There was no significant correlation between the concentration of heavy metals in water, and in vegetables except for Cu. These findings implied inefficiency in the effluent management system within Machakos municipality. They further indicated that the stream was not fit for use in irrigation farming as it presented a health hazard from bacterial infections, organic chemicals as well as cadmium poisoning to the farmers, and consumers of their produce. Vegetables grown along this stream were also unsuitable for consumption as they threatened the health of consumers via Cd, Pb, and Cr poisoning. The County Government of Machakos working together with the National Environment Management Authority need to take appropriate measures to curb untreated effluent discharge into the stream. Public sensitization of residents of Machakos municipality with respect to the health implications of farming with heavily polluted water is also recommended.
Description
A Research Thesis Submitted in Partial Fulfillment of the Requirements for the award of the Degree of Master of Environmental Science in the School of Agriculture and Environmental Studies, Kenyatta University
Keywords
Physico-Chemical Parameters, Bacterial Load, Heavy Metals, Water and Vegetables, Mitheu River, Machakos County, Kenya