Melese Asfaw
People on the globe are under tremendous threat due to undesired changes in the physical, chemical and biological characteristics of air, water and soil. Due to increased human population, industrialization, excess use of fertilizers and other man made activities; water is highly polluted with different harmful contaminants. During the investigation of heavy metals and physicochemical parameters of borehole water in Woreilu town was analyzed to determine the water quality seasonally. Some physicochemical parameters such as temperature, pH, Conductivity, Turbidity, TDS, Alkalinity, Hardness, nitrate, sulphate, phosphate and heavy metal such as Zinc, Lead, cadmium, chromium, manganese, copper and Iron were evaluated using standard methods and ICP-OES respectively. Most of the parameters analysed were within the WHO and ES guideline limits for potable water. From the results, temperature varied between 11.17-15.67°C, total dissolved solids 2190-135 mg/L, turbidity 1.3-7 NTU, Electrical conductivity 0.28-0.37 μS/cm, pH 7.6-8.21, total hardness 142-264 mg/L, alkalinity 120-180 mg/L, nitrate 0.176-0.231 mg/L, phosphate 0.06-0.73 mg/L, Sulphate 2.7-22.87 mg/L and Heavy metals such as Fe varied between 0.123-0.642 mg/L, Cu 0.03-0.212 mg/L, Pb 0.009-0.098 mg/L, Mn 0.022-0.161 mg/L, Zn 0.144- 1.227 mg/L but Cd and Cr were below detection limit in all the sampling sites. All the parameters analysed were influenced by seasonal variations. There was a general increase in all the parameters during the wet season but temperature, TDS and zinc were higher during the dry season. However, all the sampled boreholes showed high concentration of Pb which were above WHO and ES drinking water standards during the dry and wet seasons and turbidity showed high concentration above the permissible limits at Jegola site in both seasons.
The results suggest that groundwater from Woreillu town boreholes need to be treated so that the water could meet WHO (2012) and ES (2011) drinking water standards. Plain sedimentation or use of cloth/membrane filters may remove turbidity while nanofiltration could be used to remove heavy metals such as lead.