Potential Impact of Wash Bay Effluent on the Water Quality of a Subtropical River

Abstract

Washbay effluents have received scant attention as a potential source of water pollution globally. This study is the first to investigate the potential impact of the total wash bay effluent content released into river water in Africa. We investigated the potential ramifications of wash bay effluxent released off Charter Estates, Chimanimani in the Eastern Highlands of Zimbabwe on the water quality of the receiving subtropical Nyahode River by measuring selected water limnochemical aspects which included biological oxygen demand (BOD), chemical oxygen demand (COD), oil and grease, pH, sulphates, phosphates, iron, total suspended solids (TSS), dissolved oxygen (DO) and electrical conductivity (EC) once every 3 months from October 2011 to July 2012. The obtained mean levels of the limnochemical parameters from the Nyahode River were compared to the local Environmental Management Agency (EMA) and international World Health Organisation (WHO) effluent standards. Our results show that the control point and the off effluent discharge source downstream points in the Nyahode River had water quality parameters that were below the local EMA and WHO water quality threshold values. Cluster analysis showed a strong linkage in the values of water quality parameters measured at sampling sites 3 and 4 which were below the discharge point. Wash bay effluent released from the Charter Estate has an impact on some aspects of the water in the Nyahode River but the river has a functional self-purification capacity. Onsite industrial purification of wash bay effluent before discharge reduces its potential deleterious impact on water quality, river habitat integrity and aquatic biodiversity.