Identification of optimal parameters for treatment of high-strength ammonium leachate by mixed communities of heterotrophic nitrifying/aerobic denitrifying bacteria.

Heterotrophic nitrifying and aerobic denitrifying bacteria (HNADB) are important for partial nitrification treatment of high strength ammonium leachate. However, conditions for their optimal performance in mixed reactor systems have yet to be determined. In this study, optimal parameters were identified and included free ammonia (FA) concentrations below 40 mg/L, a dissolved oxygen concentration of 1.2 mg/L, a carbon to nitrogen ratio of 5 and a reflux ratio of 4. These conditions were applied to a continuous anoxic/oxic membrane moving biofilm reactor treating raw incineration leachate with high total ammonium nitrogen (TAN = 1400 mg/L). Ammonium conversion and nitrogen removal efficiencies of 99% and 86% were achieved. Autotrophic ammonia oxidizing bacteria were inhibited at FA concentrations above 25 mg/L. HNADB, particularly Paracoccus species, contributed to ammonium conversion at high FA (25-40 mg/L). These results show that leachate with high TAN and FA can be treated using parameters that support the growth of HNADB.