Bacteriological analysis of faecal pollution and solar radiation disinfection of domestic water sources within Lake Naivasha basin, Kenya

Abstract

There is an increase in exposure of water sources to faecal contamination as a result of expanding anthrogenic activities in Lake Naivasha basin in Kenya. This contamination exposes water users in the region to a variety of health risks. This study investigated faecal pollution of community water sources (lake, rivers and boreholes) within Lake Naivasha basin through determination of the concentrations of total coliforms, Escherichia coli, intestinal enterococci, Clostridium perfringens and heterotrophic bacteria in various water sources using Membrane Filtration Technique (MFT) and Heterotrophic Plate Count (HPC) procedures. The potential of solar pasteurization in disinfecting domestic water was also explored by heating known volumes of water samples in a black solar box cooker at given time intervals. In addition, determination of E. coli to intestinal enterococci ratio was used in faecal pollution source tracking. Physico-chemical parameters were measured in situ for all water sources. Data was analysed for mean variation using Statistical Package for Social Sciences (SPSS) version 17 software. Surface water sources gave higher values for all microbiological parameters than borehole sources. Borehole direct sources showed no significant variation for all microbial parameters (E. coli, total coliform, intestinal enterococci, C. perfringens and HPC) with respect to sampling sites, the same was also observed in borehole at the Points of Access (POA). Surface water sources on the other hand, showed significant spatial variation for all microbial parameters (P<0.05). Samples from borehole POA, households in Karagita, Mirera and Kamere villages and vendors showed no significant variation for all the microbial parameters. The use of solar radiation in water disinfection showed that temperature of 75 0C attained after 30 minutes from pasteurization point completely eliminated E. coli and total coliforms from all the water sources. E. coli to intestinal enterococci density ratios from all the water sources were closer to 0.7; showing that non-human warm blooded animals were the most possible sources of faecal pollution into these water sources. In conclusion, there was faecal contamination of domestic water sources in Lake Naivasha basin and poor human handling practices contributed to further deterioration of the water quality. The use of solar radiation can be recommended as a cost-effective method of disinfecting water for domestic consumption to reduce likely incidences of waterborne diseases. Use of other methods such as ribotyping is also recommended in tracking the possible sources of faecal pollution into water sources in Lake Naivasha Basin.