Automatic control of wastewater treatment by DO controlling and detecting inflection points on ORP curves

Studies on the Automatic control system for rural sewage treatment II

Abstract

The automatic control system based on detected the inflection points on ORP curves was developed for extended aeration wastewater treatment system. In this system, the blowers were stopped at the end points of nitrification and restarted just after setting time for anaeration phase since nitrate knee was shown on ORP curves. Thus, aerobic, anoxic, and anaerobic phase were alternately made in an aeration tank for an aeration and non-aeration cycle. The removal rates of BOD, COD, TOC, T-N, and T-P in automatic control system were 97.9%-99.0%, 89.4%-95.4%, 91.1%-96.6%, 93.0%-95.9%, and 54.3%-85.1%, respectively. Overall, the results showed that this automatic control system was strongly reliable for the treatment of wastewater.