ASSESSMENT OF THE EFFECTS OF EFFLUENT FROM MUMIAS SUGAR FACTORY ON WATER QUALITY AND PHYTOPLANKTON SPECIES DIVERSITY OF RIVER NZOIA, KENYA

Abstract

Phytoplankton species diversity were used to assess the effects of effluent from Mumias sugar factory on water quality in Kenya, on River Nzoia downstream of the discharge point in relation to variations in water quality in the course of 1st December 2009 to 31st March 2010. The study sort to deal with the gap, insignificant exploration of the linkage between physico-chemical water quality parameters and phytoplankton species diversity in the riverine environments of Lake Victoria basin and Kenya. A randomized experimental design and convenient upstream-downstream, independently repeated random sampling design was used to determine response of phytoplankton species diversity to spatial physico-chemical quality of the Nzoia River. EXCEL 2007 for windows 7 and STATISTICA program version 8 were used for univariate and multivariate statistical analysis considered (α < 0.05), used. The physico-chemical loads were measured using modified standard methods while phytoplankton species diversity and composition at species and community level was determined using Sedgewick Rafter(S-R) counting chamber. The process (S2) was significantly more polluting than milling (S1) and boiler (S3) while physico-chemical loads upstream (S4) and downstream (S6) sampling stations after treatment and before discharge were beyond the NEMA and WHO limits. Bacillariophyceae had the highest number of species (5). The bioindicators were Microcystis spp, Melosira spp, Closterium spp, Gomphenema spp and Synedra spp while the most pollution tolerant species were Euglena spp, Navicula spp and Nitzchia spp. Melosira spp (464) was the most abundant bioindicator species while Microcystis spp (14) were all found at RN3. Shannon-Weiner diversity (Hs), Margalef’s species richness (d) and Pielou species evenness (J) had similar spatial patterns except Simpson’s Diversity Index (1–Ds). All the realized Hs values were in the range of 0-1 while J < 0.4, being closer to zero (0) than one (1). A multiple criteria selected four (4) most significant principal components that yielded 99.90% of the total variance of the physico-chemical parameters corresponding to combined industrial (sugar) and domestic effluents; physico-chemical; soil leaching and agricultural run-off process variability. SMLR identified the contribution of each variable with a value of R 0.72, R² 0. 52(52%), F0 1.08 > Fα 0.003 and p>0.05 that confirmed a linear relationship between the variation of water quality explained on the phytoplankton diversity. The 48% may be due to partially decayed organic matters from domestic and sugar effluents discharge, soil leaching or agricultural run-off process variability, an imbalance of free metal availability for phytoplankton due to physico-chemical process and sand harvesting. Findings from the study can enable achievement of a more elaborate biomonitoring programs on the quality of Nzoia River. Management decisions by Mumias Sugar Company, National Environment Management Authority (NEMA) and the government made from the enhanced biomonitoring programs.