Impact Assessment of Polluted Stream on Groundwater: Case Study of Polluted Gege Stream, Ibadan, Nigeria

Abstract

Contamination of groundwater may be as a result of human activities especially in urban cities where there is usually high population density. Release of domestic wastes and small scale agro-processing wastes into the environment has tendency to pollute the surface water which may ultimately leads to groundwater pollution. The study evaluated Physico-chemical and microbial characteristics of wells located along Gege stream from 4 tube wells (w1, w2, w3, and w4,) located at both sides of Gege stream at a radius of influence of 20 m (w1), 30 m (w2), 39 m (w3), and 20 m (w4), respectively. The samples were collected every forthnightly for 5 months early in the morning (7-8 am) when the waste water load on the receiving surface water is at its peak. Physico-chemical and microbial characteristics of the groundwater observed were; pH, 7.0-7.9, Temperature10-29 °C, Dissolved Oxygen 3.5-5.5 mg/L, Total solids 1375-2865 mg/L, Total dissolved solids 1.2-3.5 mg/L, BOD 5 4.3-9.6 mg/L, COD 7.0-18.3 mg/L, Electrical Conductivity 980-8075 mg/L, Pb ++ 0.0 - 0.1mg/L, Cu ++ 0.01- 0.4 mg/L, Mg ++ 0.5-2.7 mg/L, Al, 0.5-3.4 mg/L Fe ++ 0.2–0.6 mg/L, NO 3 1.2-3.5 mg/L, CL 15.0-18.3 mg/L and high microbial load was observed. All water samples collected from the well showed the presence of fecal contaminants which was higher than WHO water standard, the prevalent bacteria present in the sample include Enterobacter, Proteus sp;Pseudomonas, and Aeromonas. The values of Physciochemical parameters and Metal content values were higher in all the parameters except in TDS, Mg, P H and Temprature which were within recommended range. Nitrate in the samples collected from the wells are not to high compare to WHO water standard but its presence may be harmful especially to infants causing disease called cyanosis or blue baby syndrome in infant if consumed. The result showed that water samples from the Gege stream is highly polluted, contained toxic substances and high microbial load, which has great effect on the surrounding wells due to high strength of the waste water infiltrating into the wells. Improved monitoring of effluents from Abattoirs, and wastewater discharged into the stream is needed by the agencies saddled with the responsiblity of Public health, There is need to educate the residence of the environment where this study was carried out, that well water closer to Gege stream is not suitable for domestic use at home.