Evaluation of the suitability of real-time continuous water quality monitoring in a chloraminated drinking water distribution system

Significant contamination events that have occurred in drinking water distribution systems over the last decade have raised public concern and the attention of regulators seeking to protect the safety of municipal drinking water systems. In response, municipalities are interested in using online, real-time continuous sensors to monitor water quality in locations throughout their distribution systems. Despite the significant effort being devoted to developing low-cost and energy-efficient water quality sensors, the reliability and utility of commercial water quality sensors for monitoring municipal drinking water systems have not been validated. In this study, the performance of a real-time, commercial sensor system was compared to conventional laboratory analysis of grab samples collected from fire hydrants in a chloraminated drinking water distribution system. Relationships between sensor output and direct/indirect laboratory analysis were established in both laboratory experiments and field applications. Finally, the stability of the water quality sensor was examined by analyzing the temporal and spatial changes in output over a three-week fire hydrant trial. The results of the study found that the ORP sensors are insensitive to changes in chloramine changes between 1.5 and 2.5 mg/L Cl₂ in an oxic system. Overall, the optical sensors in the commercial systems performed poorly for monitoring water quality in the DWDS when the samples were drawn from fire hydrants. Transient pressure changes in the barrel of the fire hydrant released particles that fouled the optical sensor units. Recommendations for real-time water quality sensors installation, performance validation, and data interpretation for municipalities interested in using fire hydrants as DWDS sampling points are provided based on a case study conducted in a chloraminated drinking water distribution system.Civil, Architectural, and Environmental Engineerin