Determination Of Levels Of Selected Physico-Chemical Parameters And Heavy Metals, And Assessing Associated Human Health Risks In Protected Dug-Well Drinking Water Of Elfeta District, Oromia, Ethiopia

Abstract

Ground water is one of the most important sources of drinking water in rural areas of Elfeta district, Oromia, Ethiopia; hence, it is important to assess and evaluate the quality of these water sources. The objective of this study was to investigate the levels of some selected physicochemical parameters and heavy metals, and assess associated health risks in protected dug well water sources of Elfeta district of Oromia, Ethiopia. For this purpose, from seven different protected dug well in seven rural villages, water samples were collected using composite sampling technique during the wet season to serve as the subject of the study. Level of nine heavy metals and twelve physicochemical in water were determined using Flame Atomic Absorption Spectroscopy and standard analytical methods respectively. The observed mean values of the physicochemical analysis were in the range of 6.4 ± 0.2- 6.9 ± 0.03, 14.5 ± 0.2 - 16.9 ± 0.3 °C, 59 ± 4 - 715 ± 4.1 μS/cm, 0.013 ± 0.001 - 0.03 ± 0.02 mg/l, 7.3 ± 0.5 - 33 ± 3 mg/l, 7.1 ± 0.01 -12.9 ± 0.02 mg/l, 38. ± 2.4 - 435 ± 10.8 mg/l, 38 ± 3 - 62 ± 4 mg/l, 31 ± 0.9 - 77 ± 1.9 mg/l, 2.15 ± 0.3 - 8.8 ± 0.8 mg/l, 0.01±0.002- 0.06 ± 0.002 mg/l and 0.7 ± 0.1 - 4.3 ± 0.3 NTU for pH, temperature, conductivity, nitrite, nitrate, sulphate, total dissolved solid, total hardness, total alkalinity, chloride, phosphate and turbidity, respectively. The concentrations of heavy metals (mg/l) in the water samples were found within the range of 0.07± 0.003 - 0.22 ± 0.008, 0.0078± 0.0004 - 0.0091 ± 0.0001 and 0.04 ± 0.001 - 0.13 ± 0.004 for Fe, Cd, and Zn, respectively. The heavy metals including Pb, Co, Cu, Ni, Cr and Mn were not detected. The concentration levels of all the studied heavy metals, except Cd, were below the permitted limits for drinking water established by the WHO and Ethiopian Standard Agency (ESA). The results of the non-carcinogenic human health risk assessment for individual and mixture of the studied heavy metals indicated that the examined heavy metals were can pose negligible human health risk (i.e., total hazard quotients (i.e., HQ < 1 and HI < 1). However, the incremental lifetime cancer (ILCR) risk assessment result showed that the observed concentration level of Cd can cause severe cancer risk (ILCR > 1x10-4) to the consumers