Abstract

The present study has undertaken to assess the water quality as well potential source of contamination of Rebu River by considering effluent discharged from soap and detergent factory. In the study, three sampling sites along the river course have chosen based on the objectives of the study and potential source of pollution. Composite sampling technique has used to collect the water samples and analyzed for some physic-chemical parameters and heavy metals using HACH’s Spectrophotometer and FAAS by following standard laboratory procedure. The instruments have calibrated using de-ionized water and standard solution by following standard procedures. The water quality was relatively acceptable at upstream (site A) of the river while both the physic chemical and heavy metals at sites B and C became impaired, an inference that might suggested a significant pollution from soap and detergent effluents and municipal discharges. Site B (effluent discharge site) recorded high values in E.C. (1592.6 µS/cm), TDS (2359.5mg/L), turbidity (800mg/L), salinity (2440mg/L), NO₃^- (324.5mg/L), PO₄^3- (163.3mg/L) NH₃ (15.8mg/L), Fe (2.02mg/L), Pb (0.16mg/L), Na (1557.6mg/L) and K (22.3mg/L). These results however implicated site B to be the most polluted site, probably being the point of discharge. Fluoride ion was the only parameter that did not detected. A comparison of the measured parameters with the national and international standards set by EDWQ (2010) and WHO (2008) shows that all the parameters measured (except NO₂^-, SO₄^2-and Cu) were above the standards. This indicates that the river water was significantly contaminated and therefore not suitable for domestic, agricultural and industrial uses. The concentrations of each parameter (except Fe) among the selected sites were significantly different (ANOVA, p≤0.05). The findings indicate that, there is a need to protect the quality of the river system. Therefore, it recommended that the government and other responsible authorities have to take appropriate corrective action and should support further study has to be conducted on other physical, chemical and untested biological parameters of significant health concern and identification of potential source of the contaminants of the river.

Keywords

Rebu River, water quality, heavy metals, FAAS, water pollution, assessment, ANOVA, analysis of variance; APHA, american public health association; CCME, Canadian council of ministers for environment; COD, chemical oxygen demand; DO, dissolved oxygen; EC, electrical conductivity; EDWQ, Ethiopian drinking water quality; EMA, Ethiopian mapping agency; ICMR, Indian council of medical research; ISO, international standard organization; SD, standard deviation; SPADNS, sodium 2-(para sulphonate)-1, 8-dihydoxy-3, 6-naphthalene disulphonate; SPSS, statistical package for the social science; TDS, total dissolved solid; US-EPA, united state environmental protection agency; WHO, world health organization