Insights into the roles of anammox bacteria in post-treatment of anaerobically-treated sewage

Complete anaerobic treatment of sewage has the potential to achieve net energy production via capturing the energy of organics in sewage, but not nitrogen, which remains a concern. Anaerobic ammonium oxidation (anammox) is potential for energy-efficient nitrogen removal from anaerobically-treated sewage. Given the sensitivity of anammox bacteria and the challenge of the low ammonium-bearing influent with reduced compounds such as volatile fatty acids, methane, and sulfide, this article critically reviewed and analyzed, using thermodynamic computation as a tool, the potential interactions of anammox bacteria with other microbes induced by the reduced compounds in anaerobically-treated sewage. The dynamics of anammox bacteria to cooperate with these microbes that metabolize non-ammonium pollutants and to outcompete for the common substrate, i.e., nitrite, are extensively discussed. The versatile metabolism of anammox bacteria on volatile fatty acids and iron, which would help facilitate the treatment efficiency, was also reviewed. The information offered in this review will be beneficial to researchers and engineers in controlling process stability, enhancing total nitrogen removal, and achieving better effluent quality in post-treatment of anaerobically-treated sewage by anammox-based processes.