Microbial Contamination of Groundwater Self-Supply in Urban Indonesia: Assessment of Sanitary and Socio-Economic Risk Factors

In urban Indonesia, more than 40 million people rely on groundwater self-supply, but the extent to which self-supply delivers safe water and the associated risk factors for fecal contamination remain unclear. This study quantified Escherichia coli (E. coli) for 511 self-supply sources and at point-of-use for 173 households in the Indonesian cities of Bekasi and Metro. A structured questionnaire collected information about the household, water sources, and potential contamination sources. Univariate and multivariate logistic regression analysis examined risk factors for fecal contamination. E. coli was detected in 66% of sources, including 55% of boreholes, 64% of protected dug wells, and 82% of unprotected dug wells. Widespread boiling of water meant microbial quality improved significantly between source and point-of-use, with E. coli detected in 30% of self-supply samples at point-of-use. Unprotected dug wells were significantly more likely to be contaminated than boreholes. In Bekasi, the analysis found a significant association between presence of E. coli and sanitation systems located within 10 m of the groundwater source. In Metro, poorer households had significantly higher odds of contamination than wealthier households. Other significant factors included shallower borehole depths in Bekasi, use of a rope and bucket, and absence of a concrete platform in Metro. In Bekasi, E. coli concentration at source was significantly associated with water quality at point-of-use. Risk of fecal contamination could be reduced by supporting households to invest in improved protection, and by facilitating promotion for safe household water treatment. Support for self-supply improvements should be weighed against the expansion and improvement of piped water services.