Continuous monitoring of residual chlorine concentrations in response to controlled microbial intrusions in a laboratory-scale distribution system

Chlorine Residual Management for Water Distribution System Security

“…The results of this panel of experimental contamination scenarios showed that commercially available colorimetric sensors respond rapidly to induced changes in residual concentration and that these changes are directly proportional to the initial background free chlorine concentration, the injected contaminant concentration, and the amount of contact time available between the injection location and sensor, which is a function of flow rate and distance. Further, it was shown that reaction kinetics can be applied within a general advection-reaction transport model to predict the sensor response over a large range of experimental conditions (Helbling and VanBriesen, 2008). These results support the use of chlorine sensors as nonspecific sentinels for contamination events within the distribution system.…”

“…PVC pipe and equipped with contaminant injection ports (Helbling and VanBriesen, 2008). To ensure that all of the induced changes in chlorine concentration that were observed were attributable to the contaminant of interest, all contaminants were suspended in a chlorine demand free buffer (pH=7.4).…”

“…Using the colorimetric sensor integral to the LDS, a panel of experimental contamination scenarios was developed by considering various contaminants, hydraulic conditions, background free chlorine concentrations, and injection locations (Helbling and VanBriesen, 2008). The goals of these experiments were to evaluate the ability of a free chlorine sensor to rapidly respond to contaminantinduced changes to in situ free chlorine concentrations and to determine whether the induced changes were predictable using hydraulic data and batch-determined reaction kinetics.…”

Detection

“…Microbial suspensions are likely to exert a chlorine demand, making chlorine residual an effective water quality parameter for detecting microbial suspensions (Helbling and VanBriesen, 2008). Helbling and VanBriesen (2008) found that chlorine residual is a suitable indicator for bacterial intrusions in a DSS, although they found that fairly high bacterial concentrations of 10 5 CFU/ml, 10 4 CFU/ml, and 10 3 CFU/ml are required for Escherichia coli, Staphylococcus epidermidis, and Mycobacterium aurum, respectively, to incur a chlorine demand in the suspensions of these organisms.…”

Combating Accidental Microbial Episodes by Back-Ground Chlorine Residuals in a Scaled-up Distribution Network (Rig) Using a Central Composite Design (CCD)

“…pathogens transmission and may even contribute significantly to gastrointestinal diseases in the community [3]. Nowadays, preserving the water quality throughout the water distribution system is therefore the most challenging technological issue.…”