An evaluation of the bacteriological and some Physico-chemical qualities of water in the UpperAthi River Basin, Kenya

Abstract

.Water, in its many forms, is used and abused in a variety of sectors of human society. By virtue of its unique capacity as a solvent, water can carry massive flows of solutes. The role water plays as the bloodstream of the biosphere explains the biological damage and reduced biodiversity inflicted by water pollution. The importance of the rational development of water resources and provisions of adequate quality water supplies have been recognized worldwide. High prevalences of water-borne diseases in communities particularly those living in areas with poor hygiene and sanitation are quite common. These are caused by the presence of certain pathogens in water such as Salmonella .Spp, Shigella Spp, Escherichia coli, Yersinia enterocolitica, faecal Streptococci, Campylobacter jejuni, viruses, helminths and protozoa. The rural and urban waters are constantly being polluted with waste discharges, for example, from sewerage treatment plants and overflowing of sewerages. Thus, the importance of physicocbemico- microbiological procedures for surveillance of river water pollution has been recognized worldwide. This study was designed to determine the bacteriological quality and some physicochemical aspects of pollution of water in the Upper Athi River Basin. The study area was divided into zones and forty random water samples were collected from both the tributaries and the main Athi River. Each sample was subjected to physical, chemical and bacteriological analyses. The variation of these parameters among the various zones were statistically evaluated. The results of the physico-chemico analyses showed that there were significant (p=O.002) variations in water temperatures between zone 1 and zone 5. The overall mean was 20.9°C. The temperatures ranged from 16.0°C to 25.0°C with a standard deviation of 1.9267. A marginally significant (p=O.0542) zonal variation of pH was obtained. The overall pH values ranged from 6.1 to 7.7 with a mean of7.21 and a standard deviation of 0.3793. The conductivity values ranged from 0.1 to 3.2 with a mean of 0.74 and a standard deviation of 0.7 and showed significant (p=0.0015) zonal variation with zone 1 being significantly different from zones 3, 4, 5, and 6. The fluoride levels were fairly low and ranged between 0.08 and 0.8 ppm. No significant (p=0.5039) zonal variations were observed. However, a critical examination showed that fluoride levels were slightly higher in the relatively dry zones. The Most Probable Number (MPN) of coliforms was determined using the multiple tube fermentation technique and computed from statistical tables. The total viable bacterial counts ranged from 598 x 103 to 3600 X 103 colonies per ml of water, with a mean of 1183.3 x 103 colonies per ml of water. No significant (p=0.1566) variations among the zone-specific means were observed. The faecal coliforms were enumerated on the basis of positive or negative production of acid and gas at 44°C. All samples were positive for faecal coliforms. The faecal contamination was further confmned by the enumeration of faecal streptococci using sodium azide medium. The counts ranged from 11 x 103 to 542 X 103 . colonies per ml with no significant (p=0.383) zonal variations. All water samples were positive for E. coli. None of the forty isolates could be specifically serotyped using the antisera available at KEMRI. However, colony hybridization of DNA of these isolates was performed using synthetic alkaline-phosphatase-labelled oligonucleotide probes specific for Heat Stable (ST) and Heat Labile (LT) toxins. Twenty two point five per cent of the forty strains were positive for ST, 7.5 % were positive for LT and 5 % for both. Susceptibility to four commonly used antibiotics namely, Chloramphenicol, Tetracycline, Ampicillin, and Kanamycin was done on the forty E. coli isolates. Twenty per cent of the samples showed multiple resistance while 80 % showed no resistance to any of the four antibiotics used. None of the isolates was resistant to Kanamycin, while 25 % were resistant to Tetracycline, 25 % were resistant to Ampicillin and 10.5 % to Chloramphenicol. From visual observation, four different sources of pollution to the upper Athi River Basin were observed. The overt ones included Sewage, industrial effluents, and storm, urban and agricultural runoff. In conclusion, the water in the Upper Athi River Basin is heavily polluted and should not be used for domestic and other related purposes before treatment