Nitrogen Removal from Actual Wastewater by the Coupled Thiosulfate-Driven Denitrification and Anammox Process

The coupled thiosulfate-driven denitrification and anammox (TDDA) process is an energy-efficient biotechnology for nitrogen removal from wastewater, but further studies are still needed in the substrate control during the sulfur-nitrogen cycle bioprocesses and in scaling up. In this study, the TDDA process was established and optimized in an up-flow anaerobic sludge blanket reactor using synthetic wastewater in 60 days, and its reliability was then verified with actual wastewater in the next 80 days. TThe anammox bacteria, dominated by Candidatus_Brocadia, were the primary contributor to TN removal, and the sulfur-oxidizing bacteria (SOB), dominated by Thiobacillus and Rhodanobacter, played a secondary role in TN removal. Maximizing the contribution of anammox by manipulating substrate composition led to higher treatment efficiency, more stable synthesis of extracellular polymeric substances (EPS), as well as higher abundance of functional genes (napA, nirS, hzs, soxXA, soxYZ, etc) and the corresponding species. In contrast, the TDDA process had a suboptimal performance when hiosulfate was added in excess to increase the contribution of SOB to TN removal. These findings revealed the mechanisms of TN removal by the functional microbes in TDDA in processing actual wastewater.