Nitrogen removal and functional bacteria distribution of ANAMMOX at ambient temperature

Abstract

In this study, an up-flow anaerobic biofilter (AF) was operated to investigate the efficiency of anaerobic ammonium oxidation (ANAMMOX) in treating low strength ammonia (46.5 mg/L) at ambient temperatures (20.3–23.2 °C). Microbial compositions and functional populations of the upper (140–190 cm), middle (40–140 cm), and lower (0–40 cm) parts of the biofilter were monitored using scanning electron microscopy, denaturing gradient gel electrophoresis (DGGE), clone and sequence. The results show that stable biofilter performance was achieved with an average nitrogen removal rate of 2.26 kg/(m3·d) and a total nitrogen removal efficiency of 75.9%. Approximately 67% of the ammonia and nitrite disappeared in the middle part of the biofilter. The spherical bacteria, similar to ANAMMOX bacteria, dominated the middle part of the biofilter. There were eight bacterial DGGE bands; clone and sequence results showed that they included Oxalicibacterium sp., Ignavibacterium album, Bacterium rJ15, Candidatus Kuenenia stuttgartiensis, Hippea maritima, Thioprofundum lithotrophica, and Rhodopseudomonas palustris. The genus of ANAMMOX bacterium remaining at constant levels in different parts of the biofilter was identified as Candidatus Kuenenia stuttgartiensis. The AF bioreactor maintained high activity due to the ANAMMOX bacteria's ability to adapt to ambient temperature and low matrix influent conditions.