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.