Profiling chlorine residuals using DPD and amperometric field test kits in a chlorinated small drinking water system with ammonia present in source water

Effective chlorine residual monitoring of water treatment systems that have ammonia in the raw source water is crucial to ensure adequate disinfection. Understanding the limitations related to monitoring chlorine in these systems is important to help reduce risk from microbiological hazards. The presence of ammonia and the resulting chlorine demand can be very challenging to address in drinking water treatment, especially for small water systems. This study profiles a number of situations where erratic chlorine dosing, operational, and testing conditions create a false-positive free available chlorine result. This study identified that the field test kit using amperometric testing methodology is superior to the traditional DPD (N,N-diethyl-p-phenylene-diamine) tests in a water system that has the presence of ammonia with erratic chlorine dosage.