Physico-Chemical Quality Of Groundwater In The Vicinity Of Municipal Solid Waste Dump Sites In Osogbo, Southwestern, Nigeria

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Date
2015
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Abstract
This study investigated the physico-chemical quality of groundwater sources (hand dug wells and a borehole) close to municipal solid waste dumpsites in Osogbo township, Osun State, southwest, Nigeria. It also assessed the seasonal variation pattern in groundwater quality in the study area and the effect of distance from the dumpsites on the investigated water quality parameters. The quality of groundwater sources was compared with the guideline of the World Health Organization and the Nigeria standards. This was with a view to determining the impact of leachate on the potability of the groundwater for human consumption in the study area. Sixty groundwater samples were collected from fifteen designated sampling stations over the dry and rainy seasons of one annual cycle and analyzed for some selectedphysico-chemical parameters of water quality. The investigated water quality parameters comprised; physical parameters (ambient air temperature, water temperature, apparent colour, true colour, turbidity, well water table and total depth), chemical parameters (pH, electrolytic conductivity, total acidity, total alkalinity, total hardness, bicarbonate and TDS), major ions (Ca2+, Mg2+, Na+, K+, Cl-, NO3-, SO42-), oxygen parameters (DO, BOD5, DO saturation) and some trace metals (Pb, Fe, Zn, Cd, Mn). All determinations were carried out using standard methods with adequate quality control measures. The data obtained were analyzed using the descriptive statistics (mean, range and percentage), ANOVA and cluster analyses. The results showed that most of the water quality parameters notably; ambient air temperature (30.48±0.20oC), water temperature (29.61±0.13oC), true colour (34.38±7.22Pt-Co), pH (6.15±0.06), total dissolved solids (188.65±37.49 mg/L), electrolytic conductivity (277.67±40.42 µScm-1), total acidity (27.93±3.62mgCaCO3mg/L), nitrate (1.38±0.24mg/L), sodium (20.08±2.34mg/L), potassium (10.20±1.14mg/L), magnesium (2.32±0.32mg/L), iron(0.11±0.0 mg/L), cadmium (0.02±0.002mg/L), manganese (1.78±0.54mg/L), dissolved oxygen (5.41±0.31mg/L), dissolved oxygen saturation (71.32±4.19 %) andbiochemical oxygen demand (2.11±0.16mg/L) were significantly higher (p ≤ 0.05) in the dry season than in the rainy season. On the other hand the values of apparent colour (110.09±12.07Pt-Co), turbidity (8.51±8.50 NTU), alkalinity (14.78±1.87 mgCaCO3mg/L), total hardness (27.18±3.32mgCaCO3mg/L), chloride (29.87±4.34 mg/L), bicarbonate (23.36±2.01 mg/L), calcium (4.84±0.63 mg/L) and lead (0.047±0.003 mg/L) were higher (p ≤ 0.05) in the rainy season than in the dry season. The impacts of leacheate on water quality generally decreased with distance away from dumpsites for most of the parameters. This generalization was particularly applicable to the concentrations or values of electrolytic conductivity, total dissolved solids, turbidity, chloride, sodium, potassium, total acidity, iron and manganese. In comparison with both international and Nigerian standards for drinking water guidelines, the water sources close to the dumpsites were poor and unwholesome for drinking with respect to colour, pH, lead, cadmium, manganese. In conclusion, this study established that the groundwater source within the vicinity of municipal dumpsites had been negatively impacted by leachate thus rendering them unsuitable for domestic uses.
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244p
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physico-chemica, groundwater, sources, southwest, variation, pattern
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