Simultaneous Ferric Reduction with Ammonia Oxidation Phenomena in Activated Sludge in Anaerobic Environment

Abstract

In recent years, a few phenomena of ferric reduction and ammonia oxidation (Feammox) have been discovered in Paddy soil, lake sediments and wetland soil, but none was observed in activated sludge. Thus, the Feammox process and the dynamic response of corresponding microbial community in activated sludge were explored by conventional chemical analyses and microbial community denatured gradient gel electrophoresis (DGGE) technique. After 24 d of operation, ammonia transformation occurred. Nitrate and ferrous ion were detected in the reactor, indicating the existence of Feammox process in activated sludge with a reduction of nitrate and ferrous ion accompanied by a small amount of nitrogen gas. After 84 days of culture, the highest inversion of ammonia was 29.85 mg·L-1, the conversion rate of ammonia reached 59.7%, and the highest nitrate concentration of the reactor effluent was 24.56 mg·L-1. Feammox in activated sludge was a process that resulted in acid leading, which decreased the pH value. The structure of community bands changed during the whole incubation, some communities were retained and part of the dominant bacteria were enriched in the reaction of activated sludge.