Practical evaluation of a stabilized single-reagent prototype for low-maintenance online free chlorine monitoring in treated water

Continuous free chlorine monitoring is important for drinking-water treatment and treated process-water control, but practical online deployment is often limited by reagent instability, multi-reagent fluidics, and maintenance burden. This study reports a practical evaluation of a stabilized single-reagent prototype for low-maintenance online free chlorine monitoring in treated water. The work focuses on implementation-level questions relevant to water practice, including prototype integration, treated-water matrix robustness, repeated-duty operation, and deployment-oriented reagent stability. The stabilized formulation was selected after comparative developmentstage testing showed that lower-concentration variants, although acceptable in simple standards, were less reliable in real treated-water matrices. The chemistry was then implemented in cabinet-based prototype analyzers with a single-reagent delivery path and short-window optical readout. Under development-stage operating conditions, the prototype was operated both at a 2.5-minute measurement cycle and at 24 tests per day for 90 days. Representative same-site point checks against routine handheld chlorine measurements across treatedwater-related matrices showed practically useful agreement at low residual chlorine levels, while also revealing matrix-dependent differences relevant to field use. Sealed storage studies further supported extended reagent holding time consistent with lower-maintenance deployment. Taken together, these results indicate that a stabilized single-reagent system can support a practical online monitoring configuration for treated-water applications where simplified reagent handling and reduced servicing burden are important.