Tapping the potential of anammox upgrading in full-scale wastewater treatment plants through biofilm-enhanced anammox and denitrification

Abstract

Implementing the Anammox process at a large scale remains a significant challenge. However, this study presents a potential approach for upgrading full-scale wastewater treatment plants (WWTPs) to incorporate the Anammox process in treating ammonium-rich wastewater. The research focuses on a WWTP at a duck breeding farm that utilizes an anaerobic/microaerobic/anoxic/oxic (A/M/A/O) process. With 83% removal of total nitrogen, the contribution of anammox and denitrification nitrogen removal in the entire process was 52% and 31%, respectively. The study tracks the changes in water quality and analyzes the potential of simultaneous Anammox-denitrification processes to mitigate nitrate accumulation. Porous carriers were introduced into the primary anaerobic tank (Anaerobic T1) and the primary microaerobic tank (Microaerobic T1) and were harvested on the 90th day. The results revealed that the specific Anammox activity (SAA) of the microaerobic biofilm reached 252.06 mg N/g VSS·d, which was 6.0 times and 3.7 times higher than that of suspended sludge and anaerobic biofilm, respectively. The microaerobic biofilm demonstrated the capacity for simultaneous Anammox-denitrification, with anammox and denitrification rates of 65.35 and 36.3 nmol N/g·h, respectively. These rates were significantly higher than those observed in the anaerobic biofilm and suspended sludge. Furthermore, the main partial denitrification bacteria identified were Ignavibacterales UTCHB1 (57.75%) and Trichococcus (5.12%), which contributed nitrite to Candidatus Brocadia (1.54%). The findings highlight the importance of creating a suitable microenvironment using porous carriers, which facilitates the Anammox pathway for nitrogen removal in biofilms. This approach presents a potential retrofitting and upgrading strategy for existing WWTPs.