Simultaneous Sulfur-Driven Autotrophic Denitratation and Anammox Process for Treating Nitrogen-Laden Saline Wastewater in a Single Reactor

A novel bioprocess integrating sulfur-driven autotrophic denitratation with anammox (SdADAx) was developed and operated in a single anaerobic reactor for nitrogen removal from ammonia-laden and carbon-deficient saline wastewater in this study. During the 169-d operation, total nitrogen removal of up to 99% was achieved with a 2.2 S/N mass ratio in the influent, in which most (∼98%) was contributed by the anammox process. Most of the influent nitrate was reduced into nitrite in the sulfur-driven autotrophic denitratation (SdAD), resulting in an expected NH4+-to-NO2– mole ratio of about 1:1 for the subsequent anammox process. Compared to nitritation by promoting ammonia-oxidizing bacteria and suppressing nitrite-oxidizing bacteria, SdAD is more stable and easier to achieve, particularly in ammonia-laden saline wastewater. High-throughput sequencing analysis indicates that marine anammox bacteria (22.8%) and sulfur-oxidizing bacteria (10.7%) are the dominant microbes coexisting in the SdADAx reactor. The functional enzymes for the anammox process (hydrazine dehydrogenase and hydrazine synthase) and nitrate reduction (nitrate reductase) were highly detected, while nitrite reductase was at a low gene level based on metagenomic analysis. Finally, the underlying mechanism was also proposed to improve our understanding of the SdADAx process. The novel SdADAx process indicates a new direction for nutrient removal from ammonia-laden and carbon-deficient saline wastewater.