Assessment of seasonal variations in water quality of river Tordzie, Ghana

Abstract

River Tordzie is one of the poorly studied rivers in Ghana in terms of its water quality. There is little data on the quality of water from this river. The purpose of the study was to assess the water quality of River Tordzie which runs through some communities in the Volta Region. Samples were taken in March (dry season) and July (wet season) in seven communities along the river in the study area. Sixteen physicochemical parameters and three heavy metals were analysed. Lead and cadmium were determined using Flame Atomic Absorption Spectrophotometer using an air-acetylene oxidizing flame. Total hardness, pH, turbidity, chloride and phosphate were determined by EDTA titration, a PC 700 Eutech multi-parameter bench top meter, a potable metalyser HM 1000 Trace2O, argentometric titration and ascorbic acid spectrophotometric method respectively. From the analysis, it was found that the pH, Total hardness, sulphate, phosphate, electrical conductivity, total dissolved solids, chloride, and nitrate were within the permissible limit of Bureau of Indian surface water quality standard as per IS: 2296. Heavy metals such as cadmium, lead, and iron were also within the standard during the dry season but the concentrations of cadmium and lead were above the standard limits during the wet season. Water quality index (WQI) analysis was conducted and the result for the dry season was found to be 92.19 and for the wet season to be 1227.84. The results showed that, the water from this river cannot be used for domestic purposes without treatment. When Nemerow’s Pollution Index (NPI) was conducted, it was found that colour, biochemical oxygen demand (BOD), dissolved oxygen (DO), cadmium, and lead were the main parameters causing the quality of the river to decline. The result from the t-test analysis showed that there was no statistically significant difference between the observed values during the dry season and wet season (p = 0.815 > 0.05). The quality of water from river Tordzie was therefore affected by changes in the seasons.