Feed-forward dose control of wastewater chlorination using on-line pH and ORP titration

In this study, a simple automatic pH–ORP titration device was developed for identifying the various ammonia concentrations and chlorine dose requirements for wastewater chlorination by identifying the peaks in the ORP-slope profiles and knees/valleys in the pH profiles. In addition, breakpoint chlorination experiments have shown that the ORP values at the monochloramine humps and breakpoints are linearly correlated with the ammonia concentrations. Therefore, a feed-forward control strategy, based on the chlorine/ammonia weight ratio (Cl/N), is proposed in this paper, to control the chlorine doses for a continuous wastewater chlorination experiment in a laboratory-scale reactor. The result of this continuous wastewater chlorination experiment has shown that the pH–ORP titration was able to precisely determine the variations of ammonia concentrations in the chlorination influent. Under this control strategy, effective and stable disinfection efficiencies in terms of total coliform count were obtained.