Estimating the recovery of ANAMMOX performance from inhibition by copper (II) and oxytetracycline (OTC)

The recovery performance of the anaerobic ammonium oxidation (ANAMMOX) upflow anaerobic sludge blanket reactors (R1, R2) that were previously subjected to copper (II) and oxytetracycline (OTC) inhibitors with respective levels of 0.5-5 and 6-50 mg L−1 and then operated in the absence of such inhibitors was investigated in this study. High nitrogen removal rates of 30.1 and 30.9 kg m−3 d−1, were accomplished respectively for R1 and R2 after reactivation. The performance recovery was well indicated by change in pH, stoichiometric ratio, specific ANAMMOX activity, and morphological and physical properties of ANAMMOX granules. The modified Stover-Kincannon model properly simulated the regain performance, and theoretical removal rates of 151.5 and 212.8 kg-N m−3 d−1 were predicted for R1 and R2, respectively. The ANAMMOX activity and performance initially stressed by copper (II) and OTC for a long time (nearly 200 days) were restorable and the recovery process lasted for a relatively short time (56 and 51 days for R1 and R2, respectively).