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

Abstract

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 E. 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.