Monitoring ORP, pH and EC for the Start-Up of an A/O SBR

With the synthetic municipal wastewater as influent, the aim of this paper is to investigate the information provided by monitoring oxidation reduction potential (ORP) , pH, electric conductivity (EC) and analyzing wastewater samples in an anaerobic/aerobic sequencing batch reactor (A/O SBR) during the start-up period. The reactor was seeded by activated sludge from a municipal wastewater treatment plant. The results show that anaerobic P-release finished and EC reached maximum point after 45 minutes´ operation, while ORP reached the minimum point at that moment. Then, the ORP curve was flat. During the aerobic phase, PO₄ ^3- concentration decreased to 0.7 mg/L and there appeared a bending-point in the EC curve after 105 minutes´ aeration, then pH began to slightly decrease. According to these results, the reactive cycle was optimized: the anaerobic and aerobic phases were shortened to 45 minutes and 105 minutes respectively. The nitrite and nitrate disappeared from the reactor after 8 cycles. The anaerobic P-release and aerobic P-uptake rate greatly increased. Therefore, it is realistic to quickly start up the A/O SBR using ORP, pH, EC as control parameters.