Abstract
In Onitsha, borehole water serves as the primary source of drinking water for most residents, However, many boreholes are located close to open solid waste dumpsites, raising concerns about bacterial contamination, particularly during seasonal rainfall which can exacerbate the risk increasing the risk. This study examined the effects of seasons on prevalence of bacteria in borehole waters in Onitsha. Water samples were collected aseptically after flushing taps for 2 minutes. Isolation and identification of bacterial organisms were carried out using nutrient agar and selective media including MacConkey, EMB, TCBS, SSA, and Cetrimide. Isolates were identified based on colonial and biochemical characteristics. A total of 126 isolates were recovered and identified as Escherichia coli, Vibrio cholerae, Vibrio parahaemolyticus, Pseudomonas, Salmonella, and Shigella species. Out of the total isolates, 55.6% were recorded in the rainy season, while 44.4% were recovered in dry reason. E. coli occurred highest in both rainy and dry season at 27.14% and 25% respectively, whereas other isolates except Shigella spp, were more prevalent during the rainy season. These findings indicate that borehole water in Onitsha is bacteriologically contaminated and unsafe for direct consumption without treatment.