Assessment of Chlorine Residual and Microbial Quality of Piped Water at the Point of Use in Onitsha, Anambra State

Safe drinking water at the point of use is an essential determinant of public health outcomes. In Onitsha, a densely populated commercial city in Anambra State, South East Nigeria, piped water supply is irregular and distribution infrastructure is aging, potentially compromising water quality between treatment and household consumption. This study assessed chlorine residual levels and microbial quality of piped water at the point of use in forty households across three densely populated wards in Onitsha. Residual free chlorine was determined using the N,N-diethyl-p-phenylenediamine colorimetric method at the point of collection. Total coliform and E. coli counts were determined by membrane filtration and confirmed by MacConkey agar culture. Results were assessed against the WHO Guidelines for Drinking Water Quality limits of 0.5 mg/L minimum free residual chlorine and zero coliforms per 100 mL. Free residual chlorine was below the WHO minimum threshold in 72% of samples. Total coliforms were detected in 55% of samples, and E. coli was confirmed in 30% of samples, indicating faecal contamination. A statistically significant negative correlation was found between residual chlorine concentration and coliform count. Samples from households with leaking distribution pipes showed the highest contamination rates. These findings indicate that piped water reaching households in Onitsha is frequently microbiologically unsafe for consumption, necessitating household-level water treatment and infrastructure rehabilitation. Keywords: chlorine residual, microbial quality, drinking water, Onitsha, point of use.