Real-time Control with Low DO Concentration in SBR Process

Abstract

In order to save operating costs of sewage treatment plant, the SBR process was investigated with low DO condition by means of real-time control. when the reaction temperature was 21±0.5, aeration rate was 30 L/h, the pH, DO and ORP probe were monitored online and the real-time control strategy has been set up. The results showed that the variation of DO increased slowly in the first 145 minutes and then began to increase sharply until the end of the reaction, this period lasted for approximately 25 minutes and DO was 1.98 mg/L at last. When the DO increased sharply, NH4+-N in the system was completely removed. When the reaction time was 93min, the pH was the maximum. At this time, PO43--P in the reactor was completely removed, and this feature was helpful to remove phosphorus of the system by the real-time control. But this time there is no obvious change for the ammonia nitrogen and COD. And NO3--N has some accumulation. The variation of ORP remained decreasing during the anoxic period, and it began to increase since aeration until reached the positive value. When ORP was at the value of 0, the COD in the system met with the wastewater effluent standards but this feature was not very steady. Through the above online monitoring methods, the real-time control strategy has been set up in the process of wastewater treatment with low DO condition, and this method could save the energy.