Anaerobic ammonium oxidation in marine environments: contribution to biogeochemical cycles and biotechnological developments for wastewater treatment

Microbial processes are responsible for most reactions involved in the nitrogen cycle in the oceans, which determine the fluxes of this crucial nutrient in these environments. The present review provides an overview of the contribution of anaerobic ammonium oxidation (Anammox) to marine biogeochemical processes. Besides the conventional Anammox process, anaerobic ammonium oxidation coupled to the microbial reduction of alternative electron acceptors, such as sulfate (Sulfammox), ferric iron (Feammox), and natural organic matter (NOM-dependent Anammox) is also described in the context of global marine biogeochemical cycles. Also, the complex interactions among the oceanic biogeochemical cycles of N, S and Fe are discussed at the light of the new findings available in the literature. The review also underlines the important role of the microbial processes performing the Anammox reaction in the development of wastewater treatment systems for the removal of nitrogen from saline effluents. Strategies to enrich and immobilize Anammox bacteria in different reactor configurations for the treatment of saline wastewaters are also described as well as future directions for novel biotechnological developments based on Anammox.