Enhancement of anammox performance by Cu(II), Ni(II) and Fe(III) supplementation.

Abstract This study explored the influence of metal ion addition on specific anaerobic ammonium oxidation activity (SAA). Batch assays were used to demonstrate the enhancement of the SAA upon the addition of Cu 2+ , Ni 2+ and Fe 3+ . The SAA was enhanced by 41.0% when the Cu 2+ concentration was below 1 mg L −1 , while it was improved by 63.5% at Ni 2+ concentrations below 1.74 mg L −1 . An enhancement of 533.2% was obtained when 3.68 mg L −1 Fe 3+ was supplied. The effects of Fe 3+ , Cu 2+ and Ni 2+ on the SAA were analyzed and optimized by a response surface methodology, which demonstrated that the interaction between Fe 3+ and Cu 2+ was significant and that 6.61 mg Fe 3+ L −1 , 1.18 mg Cu 2+  L −1 and 1.11 mg Ni 2+  L −1 were the optimal values for metal dosing. Subsequently, an Fe 3+ –Cu 2+ –Ni 2+ continuous test was carried out under optimal conditions and revealed that the addition of Fe 3+ , Cu 2+ and Ni 2+ could stimulate the reactor potential at ambient temperature. The maximum nitrogen removal rate (NRR) of the test reactor was 52.8% higher than that of the control reactor (8.1 versus 5.3 kg N m −3  d −1 ). Moreover, a continuous test conducted by adding Fe 3+ achieved an average nitrogen removal efficiency and maximum NRR of 67.4% and 4.9 kg N m −3  d −1 , respectively, while the corresponding values of the control test were 64.7% and 4.1 kg N m −3  d −1 , respectively. Altogether, appropriate dosages of Cu 2+ , Ni 2+ and Fe 3+ can significantly enhance the SAA and improve the reactor capacity at ambient temperature.