Fate and effect of benzalkonium chlorides in a continuous-flow biological nitrogen removal system treating poultry processing wastewater

► BAC initially inhibited nitrification in a BNR system at 5 mg BAC/L in the feed. ► Acclimation and degradation resulted in high nitrogen removal even at 120 mg BAC/L. ► Microbial resistance to BAC over time contributed to a stable BNR system operation. ► Use of QACs in poultry processing facilities requires QAC-acclimated BNR systems.