The Effectiveness of Sanitary Inspections as a Risk Assessment Tool for Thermotolerant Coliform Bacteria Contamination of Rural Drinking Water: A Review of Data from West Bengal, India

Abstract

The use of sanitary inspections combined with periodic water quality testing has been recommended in some cases as screening tools for fecal contamination. We conducted sanitary inspections and tested for thermotolerant coliforms (TTCs), a fecal indicator bacteria, among 7,317 unique water sources in West Bengal, India. Our results indicate that the sanitary inspection score has poor ability to identify TTC-contaminated sources. Among deep and shallow hand pumps, the area under curve (AUC) for prediction of TTC > 0 was 0.58 (95% confidence interval [CI] = 0.53-0.61) and 0.58 (95% CI = 0.54-0.62), respectively, indicating that the sanitary inspection score was only marginally better than chance in discriminating between contaminated and uncontaminated sources of this type. A slightly higher AUC value of 0.64 (95% CI=0.57-0.71) was observed when the sanitary inspection score was used for prediction of TTC > 0 among the gravity-fed piped sources. Among unprotected springs (AUC = 0.48, 95% CI = 0.38-0.55) and unprotected dug wells (AUC = 0.41, 95% CI = 0.20-0.66), the sanitary inspection score performed more poorly than chance in discriminating between sites with TTC < 1 and TTC > 0. Aggregating over all source types, the sensitivity (true positive rate) of a high/very high sanitary inspection score for TTC contamination (TTC > 1 CFU/100 mL) was 29.4% and the specificity (true negative rate) was 77.9%, resulting in substantial misclassification of the sites when using the established risk categories. These findings suggest that sanitary surveys are inappropriate screening tools for identifying TTC contamination at water points.

An Assessment of Inter-Observer Agreement in Water Source Classification and Sanitary Risk Observations

“…To our knowledge, there have been no previous studies of ambiguity in water source classification and only one previous study of inter-observer agreement in sanitary risk observation, despite widespread use of sanitary risk protocols (Mushi et al 2012;Parker et al 2010;Snoad et al 2017) Table 3 Cross-tabulation of water source type classification made by the most experienced observer (JOO-rows) versus five less experienced observers (columns) for 80 water sources during the first visit Our inter-observer agreement study indicates that where households adopt strategies to cope with water insecurity, their sources proved difficult to classify unambiguously using the standard typology used for international monitoring (WHO/UNICEF 2006). Such strategies included construction of 'hybrid' sources to cope with water insecurity, such as water tanks that stored both rainwater and piped water to cope with the sporadic nature of rainwater and frequent interruptions to piped water.…”

An assessment of the replicability of a standard and modified sanitary risk protocol for groundwater sources in Greater Accra

“…Whilst many studies have sought to compare the presence of individual hazards and/or overall sanitary risk scores to faecal indicator bacteria counts, results have often been mixed. Perhaps because of the transient nature of contamination in some water supply systems, some studies have found little or no relationship between observed sanitary risk and faecal indicator bacteria (Luby et al 2008 ; Ercumen et al 2017 ; Parker et al 2010 ; Snoad et al 2017 ), particularly when looking at individual source types (Misati et al 2017 ), whilst others have found stronger relationships (Wright et al 2013 ; Howard et al 2003 ; Dey et al 2017 ). Low reliability in sanitary scores is a possible explanation for the weak relationship that has sometimes been observed between sanitary risk scores and faecal contamination of source water, but as noted above, there are no studies to date examining the reliability of sanitary risk protocols.…”

Thermotolerant coliform counts and nutrient levels as indicators of water quality in sub-Mediterranean karst river

“…Communal wastewaters contribute to increased phosphorus levels in surface waters [8]. Phosphorus is rarely found Cyclic variations in TTC numbers in water are attributed to water influx due to rainfalls [9][10][11]. However, according to the results obtained during fall and winter, it is clear that lower temperatures do not significantly impact decrease in TTC numbers.…”