Exploring the relationships between small non-community drinking water system characteristics and water system performance in Ontario, Canada

The objectives of this work were to investigate the relationships between characteristics of small non-community drinking water systems (SDWSs) and the performance of these systems with respect to Escherichia coli testing and risk ratings. Ontario-wide SDWS data were analysed using regression models with outcomes of (1) having an adverse E. coli test result in the 12 months prior to the last inspection and (2) the SDWS risk rating (high/medium vs. low risk) that is assigned by public health inspectors. Almost 34% (2,364/7,003) of SDWSs did not utilize treatment, more commonly for ground water than surface supplies (P < 0.001). The odds of having a positive E. coli test result were greater in systems using ground water with treatment (OR = 2.00; 95% CI 1.23-3.24) and surface water with treatment (OR = 1.97; 95% CI 1.05-3.71) compared to ground water with no treatment. The odds of having a water system rated high or medium compared to low risk was greater if the water system operated seasonally (OR = 1.36; 95% CI 1.17-1.59), had an adverse E. coli test result (OR = 1.66; 95% CI 1.09-2.53), and in specific facility types. This research helps to inform existing training opportunities available to SDWS operators in Ontario, and to better standardize the SDWS risk assessment process.