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.