Assessment of the Groundwater Quality in Parts of Imo River Basin, Southeastern Nigeria: The Case of Imo Shale and Ameki Formations

Abstract

Hydro-geochemical survey is undertaken in parts of Imo River Basin, Southeastern Nigeria, particularly in the geologic formations of Imo Shale and Ameki, to assess the quality of groundwater. Eleven samples of groundwater are obtained from various boreholes in the study area and subjected to physico-chemical analysis using standard laboratory techniques. The study is aimed at the assessment of the groundwater quality indicators namely: pH, electrical conductivity (N), phosphate (PO 4 ), sulphate (SO 4 ), nitrate(NO 3 - ) and total dissolved solids (TDS). The result shows that the water from boreholes in Umuahia has low pH, and is therefore acidic. The pH values range between 4.40 and 5.60, which is below the acceptable range of 6.5-8.5. The acidity probably results from carbonic acid derived from the solution of CO 2 from both the atmosphere and the decomposition of plant materials in the soil zone. The acidity of the groundwater gives slight sour taste to drinking water, due to the mobilization of trace metals from the aquifer material into the groundwater system, because of the corrosive effect of acidic water. Since borehole supply is rarely treated, these trace metals end up in domestic supplies resulting in health implications and complaints. Acidic waters are typically low in buffering calcium minerals, but are high in dissolved carbon dioxide gas, which can cause the low pH or acidity. Calcite neutralizer tanks with natural crushed and screened pure calcium carbonate easily neutralize acidic water from 6.0 to 6.9. Below 6.0 a blend of calcite and Corosex is recommended. Common systems used to treat low pH: Calcite Neutralizer, calcite & Corosex Blend Neutralizer, pflow Neutralizer, Soda Ash Feed Pump Injection System.