Faecal contamination of groundwater self-supply in low- and middle income countries: Systematic review and meta-analysis.

Self-supply is a ubiquitous response by households to the public water supply inadequacies found worldwide. Self-supply is invested in and managed by an individual household, accessible on-premises and unregulated. Vulnerability to faecal contamination is a concern due to reliance on low-cost technologies and shallow groundwater. This review aims to evaluate the evidence base on the safety of groundwater self-supply in low- and middle income countries in relation to faecal contamination. Differences in microbial water quality between source types, settings, countries and ownership were investigated. A search of peer-reviewed studies in low- and middle income countries was conducted in online databases, including PubMed, Web of Science, ProQuest and Environmental Complete. Studies were included if they had sufficient detail about the water samples to be related to groundwater self-supply, contained extractable data on faecal indicator bacteria (FIB) including thermotolerant coliform or Escherichia coli and were published in English between 1990 and April 2020. A total of 30 studies were included, resulting in 100 datasets and 26,981 water samples across the studies. FIB were present in 36% self-supply samples. The odds of FIB being detected was significantly higher for unimproved sources (OR=8.19, 95% CI [4.04-16.59], p<0.001) and for sources in low income countries (OR=3.85, 95% CI [1.85-7.69], p<0.001). Self-supply was significantly more likely to be contaminated than piped supply (OR=3.45, 95% CI [1.52-7.82], p=0.003). However, water quality was highly heterogeneous (I2=90.9%). Egger's test found no evidence of small study publication bias for self-supply compared to public supply. No evidence of bias due to lack of randomization or season was found, but study design and quality could potentially bias the results. To achieve Sustainable Development Goal 6.1 on safe drinking water for all, more attention is needed from governments to engage with self-supply and formulate balanced policy responses.