Impact Of Seasonal Variation And High Industrial Effluent Discharge On Water Quality In Nankhaka River, Lilongwe, Malawi

Abstract

Water quality is influenced by physico-chemical and biological factors, and in Malawi, surface water faces significant pressure from diverse forms of pollution, including domestic, agrochemical, and industrial effluent. This study aimed to assess the impact of seasonal variation and industrial effluent on water quality of Nankhaka River. Standard laboratory methods and on-site measurements were employed at six sampling sites along the river to generate data on various parameters. The study assessed Turbidity, pH, Alkalinity, Dissolved Oxygen, Biological Oxygen Demand, Chemical Oxygen Demand, Suspended Solids, Temperature, Electrical Conductivity, Escherichia coli, Lead, Cadmium, Iron, Copper, and Zinc. Statistical analyses, including one-way Analysis of Variance (ANOVA) and paired sample t-tests, were conducted to examine differences between upstream and downstream and seasonal variations in water quality at a 95% confidence interval. Results revealed significant seasonal and spatial differences between upstream and downstream in certain parameters. EC, TDS, BOD, and E. coli were notably higher downstream during dry season. Conversely, Temperature and TSS were higher in rainy season. pH, turbidity, DO, and COD showed no significant seasonal variation. The findings suggest fluctuation in selected water quality parameters in Nankhaka River, with higher concentrations downstream attributed to increased industrial activities and effluent disposal. Cadmium, Lead, EC, Turbidity and Alkalinity showed significant risk to downstream water users of Nankhaka river in both seasons. The study emphasizes the importance of industrial effluent treatment before discharge into waterbodies. Additionally, it recommends strict enforcement of existing by-laws by local environmental authorities to prevent high effluent discharge into waterbodies.