Assessment of Microbial Load in Water and Sediments of Rivers Otamiri and Nworie in Owerri, South Eastern Nigeria

Water pollution is a global problem. The study was carried out to assess the microbial constituents in water and sediment of Rivers Otamiri and Nworie during dry and rainy seasons (March and September, 2020) with comparison to WHO benchmark for drinking water .Samples were randomly collected at six (6) sampling points and analyzed using routine microbiological protocols.  The results revealed detectable amount of microbial activates in surface water of both rivers during the dry and rainy season. During the rainy season, a THB bioload average of 2.02x104 and 5.1x104CFU/mL for Nworie and Otamiri river respectively were measured. For the TCC, the average was 9.8x103 and 2.5x104 CFU/mL, while in the dry period there was corresponding reduction in the bioload value for both rivers. THB average value for Nworie river was 1.34x104 CFU/mL, with corresponding 3.5x104 values for Otamiri river, while in same inclination, TCC measured 6.1x103 and 1.8x104 CFU/mL. There were noteworthy variations in the values for the two rivers as well as in the two seasons. TBC value for Otamiri measured about 1.5 folds than the value for Nworie. In same trend, TCC value for Nworie measured about 39%. All values measured were above WHO permissible limit for drinking water. The biochemical and cultural features of the isolated microorganism in water showed the presence of E. coli identified in the entire stations (100%), Salmonella and faecal coliform occurred 83.3% each, while Vibrio and Shigella were detected in 4 of the 6 stations. The mean total bacterial count, total coliform count and total E. coli, were not in conformity with World Health Organization (WHO) Standard for drinking water and thus constitute a threat to the River; these were attributed to indiscriminate waste dumps around the rivers. The study underscores the need for adequate waste management system to forestall outbreak of pathogenic diseases in the area.