Physicochemical Quality of Borehole water of selected Settlements in the Coastal Area of Ondo-State, Nigeria

The quality of 264 borehole water samples of selected settlements covering 33 locations divided into four districts (identified as I, II, III & IV) between 2013 and 2015 were assessed. The physicochemical parameters of the water samples such as pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), turbidity, alkalinity, dissolved oxygen, biological oxygen demand (BOD), chloride, phosphate, sulphate and nitrate were determined using standard methods. Borehole water samples had temperature values within the acceptable limit as approved by WHO in districts I, II, III & IV for rainy (28.93±0.38, 29.44±0.56, 28.90±0.63 and 28.46±0.470C) and (29.63±0.78, 30.03±0.74, 28.84±0.83and 29.04±0.460C)for dry season. pH values of borehole water samples were slightly higher in rainy (6.467±0.29) than in dry (6.229 ± 0.46) seasons. EC for all samples in the dry season except for borehole water samples in districts II & III were within the permissible limit of 500 μS/cm set by WHO.Turbidity values were 4.45±1.33 NTU and 4.32±1.32NTU for rainy and dry seasons respectively.Higher concentrations of chloride were recorded in districts II, III & IV during rainy while phosphate concentrations in (districts I, II, III & IV) were 0.12±0.04 mg/L and 0.08±0.12 mg/L and were below <1 mg/L. High BOD values were observed in districts II & III; 7.37±1.54and 9.01±3.59 mg/L and 7.22±1.54 and8.98±3.59 mg/L for rainy and dry seasons.Total dissolved solid (TDS) values were 68.33±3.47, 346.05±78.87, 202.11±73 and 43.36±10.28 mg/L for rainy season and 69.333±3.28, 354.15±84.97, 199.40±74.46 and 40.68±9.39 mg/L for dry season respectively. The values of TSS in this study were 31.45± 11.69 mg/L and 46.043±24.30 mg/L for rainy and dry seasons respectively.The values of physicochemical parameters were within the WHO permissible limits with the exception of chloride, BOD and TSS. Keywords: Borehole, Physicochemical study, Pollution, Drinking water, Water-related disease.