Groundwater Quality Determination from Hand-Dug Wells in Ososo Town, Akoko-Edo North Local Government Area Edo State

Abstract

Groundwater is water beneath the surface of the earth. The primary source is precipitation from rain, snow, and hail. Groundwater commonly occurs as water that fills pore spaces between mineral or rock grains in sediments and sedimentary rocks. This study is to evaluate the physiochemical characteristics and selected heavy metal levels of Water from Hand Dug Wells in Ososo in Akoko Edo Local Government Area of Edo State, Nigeria. A total of twenty (20) water samples were collected in very clean containers from twenty (20) hand dug wells in Ososo town, and taken to the laboratory immediately for physical, chemical and heavy metal analysis using standard laboratory techniques. The physical analysis results from the study show that depth to ground water is very shallow. Ph was below 7.5. Conductivity varies from 167.8-2120.00 /cm. The temperatures were uniform. The ground water is odorless and tasteless. The amounts of total suspended soil (TSS) in all the samples vary from 10--20 ppm. The total dissolved solid content (TDS) concentration for all the samples varies from 132--1320.00 ppm. Total hardness is soft to moderately hard. Total alkalinity values vary between 3.0 to 18.0 ppm. The phenolphthalein value for the sample tested was zero. Chemical analysis results for the cations shows that Calcium (Ca) is one of the most abundant cations in the entire well water samples with concentration varying from 6.4 -- 40.0 mg/L. Magnesium (Mg) concentration vary from 2.0 -9.5 ppm. Dissolved Sodium (Na) content values vary from 17.9- 92.5 mg/L. Chemical analysis results for the anions shows that the concentration of sulphate (SO_4) ions varies from 93--125 mg/L. The bicarbonate (CO_3) concentration in all samples varies from 25.7--90 mg/L. The dissolved nitrites and nitrates concentrations varies from 5.7 -- 9.1. Heavy metals analysis shows the concentrations of copper (CU) in the samples range from 0.1 -- 0.5 mg/l. The result of the analysis indicates high values of lead (Pb) in nine samples, but lead was not detected in wells 6 and 7. The values for other wells ranged between 0.1-0.2 mg/l. The values for the concentration of chromium (Cr)range from 0.4 -0.89 mg/l. The values of barium (Ba) range from 0.05- 0.3 mg/l. Result from the heavy mineral analysis for Cadmium (Cd) gave an approximate value of 0.2 and below detectable limit in the other wells. The values of Zinc (Zn) range from 0.8 – 11.4 mg/l. The values of Nickel (Ni) range from 0.1--0.5 mg/l.The hand-dug wells in the study area contain free Carbon IV Oxide and the alkalinity of the well water is entirely due to Bicarbonate ions. Sodium, chloride, bicarbonates, calcium, iron, potassium and magnesium are the most abundant. All the dissolved anions in the well water sample are generally below the recommended maximum limits by WHO.Samples also showed high bacteria load which primarily originated from effluent discharge from pit toilets and waste dumps and can constitute health risk on ingestion. Highly populated areas have groundwater with high concentration of dissolved ions and the converse for areas of low population. From the results of the analysis, conclusion is drawn to the fact that, the groundwater chemistry in the study area has been influenced greatly by human activities than the bedrock geology of the area. It is therefore recommended that well location should be at least, 30 m away from any source of contamination such as soak-ways, adequate treatment must be given to well water such as chlorination, boiling to destroy any bacteria and filtration to remove all unwanted/undesirable constituents that may be present, and a policy on land use planning and urban development to guard against indiscriminate setting of wells within the centre of the village should be established. This study has been able to enhance sustainable water development, since the health of inhabitants in a community depends to a large extent on the quality of groundwater supply.

http://dx.doi.org/10.4314/njt.v40i3.20