Investigating the effects of sewage on the groundwater quality in Minna, Niger State, Nigeria

Abstract

This study considers the effects of sewage on groundwater quality using Bosso area of Minna as a case study. Water samples were collected from three wells (boreholes) in three different locations within the study area in two different seasons (dry and wet) and were analyzed for physicochemical and bacteriological qualities. A multipurpose parameter was used for physicochemical analysis while for bacteriological the standard plate count method and the spread plate method were used. For physico-chemical analysis, the results show that well 3 has the highest values of the parameters observed: Total dissolved solids have the highest value of 540.02 mg/L during the dry season, nitrates and nitrites, 38.03 mg/L and 0.96 mg/L respectively during the wet season with standard deviations of 2.47 and 0.05 respectively. The highest values of chloride in well 3 during the wet season was 143.93 mg/L with standard deviation of 6.88 and the lowest value observed in well 1 as 12.42 mg/L with standard deviation of 1.33 during the wet season. Dissolved oxygen had the highest in well 3 as 10.22 mg/L in wet season. For bacteriological analysis, well 2 recorded the highest value of total coliform as 8.92 cfu/100 ml during the wet season as against dry season of 1.46 cfu/100 ml. Highest value of total bacteria was also observed in well 1 during the wet season as 25.44 cfu/100 ml with standard deviation of 1.64 and lowest in well 2 as 6.03 cfu/100 ml with standard deviation of 0.38. High concentration of the tested parameters during the wet season in well 3 was attributed to the nearnesss of sewage to the well and surface-groundwater interaction due to shallow nature of the well. Not all the samples meet the WHO and NSDWQ standard on drinking water quality most especially the bacteriological properties. It was recommended that wells most especially for community use should be deep enough and should be sited some distance away from any source of sewage and that water from wells should be treated before consumption.

Keywords: Sewage, Wells, Groundwater, Microbiological analysis