Determination of Water Quality Index (WQI) of Selected Rivers in Ezeagu Local Government Area of Enugu State, Nigeria

Abstract

Assessment of water quality of Ajali, Karawa and Nnam rivers in Enugu State, Nigeria, was determined over a 10 year-span, in order to ascertain the level of deterioration of the water over time. Water samples were collected in 2013 and 2023 from the aforementioned rivers. For these 2years, the samples were collected in April and July to represent early rainy season and peak rainy season respectively. The physicochemical parameters such as pH, electrical conductivity, total hardness, total suspended solids, total dissolved solids, alkalinity, dissolved oxygen, biochemical oxygen demand, calcium, magnesium, sulphate, nitrate and chloride were determined using standard methods. The water quality indicator ranges were found to be as follows: pH: 4.10–9.23, electrical conductivity (μs/cm): 6.88-53.30, total hardness (mg/L): 4.00-220.00, total suspended solids (mg/L): 0.002-91.00, total dissolved solids (mg/L): 0.08-9.52, alkalinity (mg/L): 10.00-31.50, dissolved oxygen (mg/L): 0.25-36.80, biochemical oxygen demand (mg/L): 0.05-73.60, calcium(mg/L): 0.31-9.40, magnesium (mg/L): 0.003-0.68, sulphate (mg/L): 119.35-425.65, nitrate (mg/L): 0.07-36.80, chloride (mg/L): 3.60-30.00. The WQI values of the three rivers were as follows: 72.93, 78.93 and 66.17 in April 2013; 47.34,85.79 and 75.81 in July 2013, while 425.3, 194.1 and 242.0 in April 2023; 70.68, 50.61 and 62.95 in July 2023  for Ajali, Karawa and Nnam rivers respectively. Ajali and Karawa river water were only suitable for drinking in July 2013 and July 2023 respectively. All the April samples show high level of deterioration and as such is very poor and unfit for human consumption. Generally, there was an increasing trend in the pollution level of the rivers over the period. The need for appropriate treatment cannot be over-emphasized,