Assessment of water quality index and heavy metals in Sungai Bunus, Malaysia

Abstract

Water Quality Index (WQI) is an indicator of water quality. The index is shown in classes where Class I indicates a Natural Level of water quality, Classes IIA/IIB, Class III and IV indicate the presence of a certain amount of pollutant, and Class V highly polluted water. Hence, this study was conducted to evaluate the current WQI and the extent of heavy metals present in Sungai Bunus, a river in Selangor, Malaysia, by Harkins’s Standardized Distances Method (HSDM). Water samples were taken six times between 24th October 2016 and 11th November 2016 at the upstream, middle stream and downstream of the Sungai Bunus. Five in situ tests and eight laboratory tests were conducted. The findings showed that the upstream of the Sungai Bunus was the cleanest, measured 63.40 % while the downstream the dirtiest, 39.97 %. Secondly, it showed that this river contained the lowest heavy metals in the upstream compared to the other parts. The upstream Harkins index was 12.17, the middle stream between 11.33 and 30.47, and the downstream 15.67 - 28.70. Cadmium, chromium, iron, and manganese were found in the river water, which exceeded the Raw Water Quality and Drinking Water Quality Standards. It was also found that the cadmium and chromium exceeded the highest permissible effluent standards B, where cadmium was 0.02 mg/L while chromium 0.05 mg/L. To improve the water quality of this river to the Class IIB standard, it is recommended that the Bunus Sewerage Treatment Plant (STP) be upgraded and the source of pollutions identified.