Ascertaining the Bacteriological Quality of Water Drawn from Cast and Non-cast Wells in Zaria, Nigeria

Lack of access to safe drinking water is a threat to public health and wellbeing of the people as it exposes them to risk of waterborne diseases. This study assessed the bacteriological quality of well water samples obtained from Zaria communities and compared the level of contamination between wells with internal wall casting (cast wells) and wells without internal wall casting (non-cast wells). Water samples from 142 wells were collected for a period of six months encompassing both rainy and dry seasons (July to September for rainy season and November to January for dry season). The water samples were collected and analysed for faecal contamination using membrane filtration technique. The water samples contained high density of bacterial counts ranging from 1.73x103±2.73x102 – 2.02x102±1.85x102cfu/100ml during the raining season and 4.17x102±3.07x101 – 1.39x103±3.27x102cfu/100ml during the dry season. Coliforms and E. coli were present in all the samples with total coliform counts ranging from 1.06 x 103 – 2.12 x 104 cfu/100 ml and E. coli counts ranging from 5.10 X 102 – 5.0 X 104 cfu/100 ml Counts were higher during the raining season in all the locations compared to the dry season. Faecal coliform counts were higher in wells without casting (91.9%) compare to wells with casting (91.2%) while E. coli counts were higher in wells with casting (77.9%) compared to wells without casting (66.2%). There was no significant difference in the bacterial counts between cast and non-cast wells (p-values were all greater than 0.05).A total of 168 organisms were isolated from this study and they include; E. coli(48.3%), Klebsiella pnuemonaie(11.8%), Klebsiella ozanae(13.2%), Enterobacter agglomerans(11.8%), Enterobacter gergoviae(14.7%), Enterobacter aerogenes (8.8%), Citrobacter freundii(8.8%), Proteus mirabilis (5.9%), Serratia liquefaciens(10.3%) and Acinetobacter lwoffii (2.9%). E. coliwas isolated more frequently (48.3%) compared to other species and was more frequent in non-cast wells (50.0%) compared to cast wells (47.1%). Other species were more frequent in cast wells. The bacteria isolated from this study are mostly of enteric origin; these organisms acquire public health significance under certain conditions, therefore, their removal in drinking water should be given moderate priority. The wells in this study fail to meet the minimum standard for safe drinking water and are therefore not safe for domestic purposes especially for drinking purpose without adequate treatment.