Use of DSS-MBR-PACT Process to Improve Nitrification and AOX Removal in the Treatment of Herbicides Production Wastewater

This study assessed whether the addition of powdered activated carbon (PAC) to a continuous dual-sludge membrane bioreactor system (DSS-MBR-PACT) can improve the removal of various contaminants from complex herbicide production wastewater. The main focus was on the removal of nitrogen compounds, TOC, and AOX. The dual-sludge pilot setup comprised a CAS system feeding MBR system. The dilution ratio was gradually decreased (with well water) from 0.8 to 0 (no dilution), and PAC was added in the last phase to maintain an equilibrium concentration of 2,000 mg/L. PAC addition effected a high and steady removal (98%) of the ammoniacal nitrogen conforming to the sea discharge limit of 5 mg/L. However, the effluent concentrations of total nitrogen, TOC, and AOX were still above the stringent discharge limits of 20, 100, and 0.5 mg/L, respectively. It is recommended that complementary physico-chemical treatment steps be added in the treatment of this kind of wastewater.