Quality of Groundwater in Delta State, Nigeria

The physical, chemical and microbial contents of groundwater across Delta State in the western Niger Delta were investigated for quality and usability by standard methods. Water samples from thirty-eight groundwater sources (boreholes) were analyzed. Hydrochemical analyses indicate groundwater of moderately low pH presumably reflecting the effect of gas flaring associated with petroleum exploration activities in the area, and low solute content. Cationic concentrations are in the order of Na>Ca>Mg>K while anions occur in the order of Cl>HCO3>SO4>NO3>PO4. Groundwater salinity generally increases steadily from the northern to the southern region apparently reflecting the increasing influence of seawater encroachment. Several water types were delineated. Most prominent among these are the chloride types, and others including mixed chloride-bicarbonate, mixed chloride-sulfate and bicarbonate types. Total coliform bacteria and enterococcus faecalis were encountered in the borehole water from the three regions while the faecal coliforms were absent from the northern boreholes. The faecal coliforms were greater in the borehole water from the south (0-2.8 log MPN/100ml) than from the central region (0-1.8log MPN/100ml) thereby suggesting a north to south increasing vulnerability of groundwater to contamination by pathogens. This is attributable to the shallow nature of the aquifers and the effect of high population density associated with the petroleum industry in the central and southern regions. Although the groundwater across the regions is suitable for irrigation, treatment, repair and proper maintenance of borehole materials are needed in order to ensure potable groundwater supplies.