Groundwater Quality and Assessments of Heavy Metals and Bacteriological Parameters in Orumba North Local Government Area, Anambra State, South-East Nigeria

Abstract

Groundwater pollution is an environmental concern that affects life. There is little information on the nature or quality of groundwater in communities in Anambra State, South-East Nigeria. This study therefore assessed the nature and quality of groundwater for drinking and other related domestic uses in Orumba North Local Government Area, Nigeria. Eighty water samples were collected from ten selected groundwater sources (boreholes)-forty samples each during the dry and wet seasons-from Nanka, Oko, Amaokpala, Ufuma, and Ajali. Heavy metals and bacteriological parameters were determined using standard methods, and water quality indices (WQI) were evaluated. Data were analyzed using descriptive statistics. The groundwater samples were slightly acidic during the dry (4.82–6.57) and wet (5.12–6.87) seasons. Groundwater hardness (expressed as CaCO₃ in mg/L) ranged from 4.0 to 160.32 (dry season) and 3.07 to 149.30 (wet season). The water was moderately hard in one community (Nanka, BH1) in both seasons and soft in other locations (Oko, Amaokpala, Ufuma, and Ajali). Heavy-metal concentrations (mg/L) ranged from 0.030 to 0.126 (iron), 0.111 to 0.530 (manganese), and 0.001 to 0.060 (lead) during the dry season, and from 0.049 to 0.380 (iron), 0.109 to 0.471 (manganese), and 0.001 to 0.040 (lead) during the wet season. Total coliform counts recorded in the dry season (<2 MPN/100 mL at BH1–BH4) were below the WHO allowable limit, whereas values slightly above the limit (140 MPN/100 mL at BH10) were recorded in non-chlorinated borehole samples during the wet season. The WQI values of the borehole samples were classified as poor at BH1 (Nanka), good at BH2 (Oko), and very poor and unsuitable for drinking at other locations (Amaokpala, Ufuma, and Ajali). Confirmatory analyses of chlorinated (chlorine-treated) groundwater revealed that both physicochemical and bacteriological parameters were within regulatory standards for drinking water. Significant correlations (p < 0.05) were observed between total dissolved solids, calcium, magnesium, sodium, and total hardness, among other parameters. The findings reveal the presence of physical, chemical, and microbial contaminants associated with health risks and with the potential to degrade groundwater quality. The use of chlorine as a low-cost treatment method for groundwater was therefore recommended.