On‐line Water Quality Monitoring in Drinking Water Distribution Systems: A Summary Report of USEPA Research and Best Practices

Abstract

This article discusses the 2009 U.S. Environmental Protection Agency (USEPA) report “Distribution System Water Quality Monitoring: Sensor Technology Evaluation Methodology and Results”, which summarizes the testing of on‐line (i.e., real‐time) water quality sensors. The report includes operation and maintenance data that drinking water utilities need in order to make informed decisions about sensor selection. Best practices and lessons from practical, hands‐on experience that comes from working with water quality sensors every day are also presented. Finally, the report discusses sensor testing protocols that are being used at USEPA's test and evaluation facility that benefit equipment vendors and manufacturers interested in designing sensors for community water systems.

Protecting Water Supply Critical Infrastructure: An Overview

“…However, Hall et al (2007) and Hall and Szabo (2010) point out that no single water quality sensor responded to all of the contaminants used in the study, yet some sensors responded to a greater number of contaminants than did others. Hall and Szabo (2010) describes water quality sensor test results from a single pass pipe in addition to a recirculating loop. Hall and Szabo (2010) indicate that detecting contamination in a single pass pipe is more challenging.…”

“…However, it is important to recognize that some potential contaminants do not react significantly with chlorine. Hall et al (2007) and Hall and Szabo (2010) indicate that TOC responded to all the organic (carbon-containing) compounds. The TOC monitor, however, has a much higher capital cost when compared with other sensors (Hall et al 2007, Hall andSzabo (2010).…”

“…Hall et al (2007) and Hall and Szabo (2010) conducted an in-depth evaluation of how changes in water quality parameters associated with real-time sensors can be used to potentially indicate the presence of contamination. The sensors investigated were off-the-shelf commercial products designed to monitor standard drinking water parameters such as pH, free chlorine, ORP, dissolved oxygen, specific conductance, turbidity, TOC, chloride, ammonia, and nitrate.…”

“…The sensors investigated were off-the-shelf commercial products designed to monitor standard drinking water parameters such as pH, free chlorine, ORP, dissolved oxygen, specific conductance, turbidity, TOC, chloride, ammonia, and nitrate. Sensors were mounted within a re-circulating pipe loop and challenged with contaminants including secondary effluent from a wastewater treatment plant, potassium ferricyanide, a malathion insecticidal formulation, a glyphosate herbicidal formulation, nicotine, arsenic trioxide, aldicarb, and Escherichia coli K-12 strain with growth media (Hall et al 2007 andSzabo (2010). Overall, the sensors that responded to the most contaminants were free chlorine, TOC, ORP, specific conductance, and chloride.…”

“…Hall and Szabo (2010) describes water quality sensor test results from a single pass pipe in addition to a recirculating loop. Hall and Szabo (2010) indicate that detecting contamination in a single pass pipe is more challenging. When used in contamination event detection, it is not only the absolute magnitude of the change that is important, but also the magnitude relative to the size and fluctuations in the baseline along with the slope of the change (i.e., to determine whether the changes occur over several hours or several minutes).…”