Dissimilatory nitrate reduction to ammonia in the natural environment and wastewater treatment facilities: A comprehensive review
Long Zhao, Jinyu Chen, Gongqi Shen, Yuan Zhou, Xianqing Zhang, Yijun Zhou, Zhanyang Yu, Juan Ma
Abstract
Dissimilatory Nitrate Reduction to Ammonium (DNRA), an essential nitrogen conversion pathway, is prevalent in soil, water ecosystems, and wastewater treatment facilities. DNRA facilitates the reduction of nitrate (NO₃⁻) to ammonium (NH₄⁺), thereby ensuring nitrogen remains in an available form in the environment, rather than being converted to gaseous nitrogen (N₂) through denitrification. This process is particularly efficient under specific conditions, including a high carbon-to-nitrogen ratio, low oxygen levels, and environments rich in sulfide or iron ions, effectively mitigating the emission of greenhouse gases such as nitrous oxide (N₂O). DNRA interacts with both nitrification and denitrification processes in wastewater treatment plants, influencing the ultimate fate of nitrogen. Additionally, anaerobic ammonium oxidizing bacteria can utilize internal carbon sources as electron donors and nitrate as electron acceptors to enhance nitrogen removal via the DNRA pathway. This article reviews the DNRA pathways present in natural habitats, sewage treatment facilities, and anaerobic ammonium oxidizing bacteria, while analyzing the key environmental factors that influence the DNRA process, with the goal of providing a foundation for optimizing nitrogen management and pollution control. • The challenges and potential applications of DNRA pathways have been discussed. • The DNRA pathways in WWTPs and the microorganisms involved have been identified. • The new metabolic pathways and induction methods of AnAOB have been described.