Dynamic Control of Atomic Hydrogen for Electrochemical Nitrate Reduction Coupled with Anammox Autotrophic Nitrogen Removal

Anaerobic ammonium oxidation (anammox) is the most cost-effective and low-carbon biological nitrogen removal technology and is very sensitive to the ammonia/nitrite ratio. Bioinspired by the dissimilatory nitrate reduction process, for the first time, we built an electric field-driven dissimilatory nitrate reduction (eDNR) process coupled with anammox (eDNR-anammox) to achieve low-carbon and efficient nitrogen removal from nitrate-rich industrial wastewater. The eDNR process, utilizing a copper nanowire catalyst with abundant oxygen vacancies as a model catalyst, enables the potential-dependent provision of atomic hydrogen that facilitates nitrate reduction into tunable ratios of nitrite and ammonium. This tunability supports successful conversion of the formed nitrogen species into dinitrogen by the anammox process, with over 90% total nitrogen removal. Compared to the partial-denitrification-anammox process, the eDNR-anammox process reduces organic requirements by 100%, sludge production by 70%, and nitrous oxide emissions by 2 orders of magnitude.