Assessment of Water Quality Index and Heavy Metal Contents of Underground Water Sources in Doma Local Government Area, Nasarawa State, Nigeria

Abstract

Water quality index and heavy metal contents of underground water sources in Doma Local Government Area, Nasarawa State, Nigeria was assessed to ascertain the suitability of the water for domestic purpose. Physicochemical parameters; temperature, turbidity, TDS, TSS, pH, EC, total hardness, alkalinity, chloride, nitrate and sulphates in the water samples were determined using standard methods of analysis. The water quality index (WQI) was also evaluated using known standard method. The heavy metal contents were determined using atomic absorption spectrophotometric method. The results of the physicochemical analyses shows that in borehole and hand dug well water, the respective mean values were temperature (27.11±0.45 and 27.41±0.55 °C), turbidity (1.51±0.54 and 2.56±1.04 NTU), TDS (230.00±87.75 and 358.67±91.46 mg/dm3), TSS (3.64±1.25 and 4.17±4.17 mg/dm3), pH (5.63±0.69 and 6.60±0.95), EC 277.16 and 296.29±26.52 µS/cm), total hardness (90.00±15.55 and 125.13±16.33 mg/dm3), alkalinity (8.87±.083 and 9.24±1.08 mg/dm3), chloride (20.59±14.62 and 21.22±10.13 mg/dm3, nitrate (0.024±0.04 and 0.01±0.01 mg/dm3) and sulphates (1.05±0.74 and 2.09±0.45 mg/dm3). It was revealed that all the physicochemical parameters for both borehole and hand dug well water had values that were within the standard permissible values recommended by regulatory bodies, NSDWQ and WHO except for the pH of the borehole water which was not within the recommended range and which showed the water to be slightly acidic and which could attributable to the nature of the host rocks. WQI for borehole and hand dug well water were 29.65 and 27.38 respectively with the implication that both water sources presented good water quality for drinking based on the water quality index and water quality status. The results of the heavy metal analyses shows that in borehole and hand dug well water, the respective mean values were Cd (0.003±0.002 and 0.010±0.002 mg/dm3), Cr (0.187±0.075 and 0.19±0.070 mg/dm3), Cu (0.040±0.010 and 0.804±0.805 mg/dm3), Fe (0.500±0.330 and 0.916±0.543 mg/dm3), Pb (0.010±0.010 and 0.015±0.007 mg/dm3) and Zn (0.290±0.120 and 0.072±0.072 mg/dm3). The results shows that Cd, Cu, Pb and Zn for both borehole and hand dug well water had mean values that were within the standard permissible values recommended by NSDWQ and WHO while Cr and Fe had mean values that were higher and which can be attributed to anthropogenic activities close to the water sources. It is recommended the groundwater in these selected communities be monitored regularly and that there is the need for the water to be treated before use because of those parameters that are off the standards to avoid associated health risks.