Evaluation of TSS, BOD5, and TP in Sewage Effluent Receiving Sambul River

Abstract

Proper treatment of sewage to remove suspended solids, organic matter and nutrients is necessary before the effluent is discharged into aquatic bodies. The major environmental concern at Sambul river is the potential pollution by effluent received from sewage treatment plant in Moi University. In this study, evaluation of the Sambul river was analysed using key water quality parameters, and comparisons made with those of the National Environmental Management Authority (NEMA). Purposive sampling design was used to select three sampling points; outlet where sewage effluent from STP is discharged into Sambul river, downstream of Sambul river where bio-treated sewage has mixed with river Sambul waters, and upstream (control) of Sambul river where the river water does not mix with STP effluent. A total of 72 water samples were collected for this study. At each sampling point, triplicate water samples for analysis were collected bi-weekly in sterilized plastic bottles from May to August 2015. Total suspended solids (TSS), BOD 5 and total phosphorus (TP) were determined using standard laboratory methods. Results showed that levels of TSS, BOD 5 and TP were within the acceptable standards of NEMA. Upstream parameters showed no significant differences with those of downstream (BOD F 4,115 =38965.46; p=0.9734; TSS F 4,115 =708.50; p=0.9999; total phosphorus F 4,115 =2107.17; p=0.9972), indicating that there is no change in water quality at river Sambul as a result of effluent received from STP.