Sludge fermentation liquid addition attained advanced nitrogen removal in low C/N ratio municipal wastewater through short-cut nitrification-denitrification and partial anammox

Biological nitrogen removal of wastewater with low COD/N ratio could be enhanced by the addition of wasted sludge fermentation liquid (SFL), but the performance is usually limited by the introducing ammonium. In this study, the process of using SFL was successfully improved by involving anammox process. Real municipal wastewater with a low C/N ratio of 2.8-3.4 was treated in a sequencing batch reactor (SBR). The SBR was operated under anaerobic-aerobic-anoxic (AOA) mode and excess SFL was added into the anoxic phase. Stable short-cut nitrification was achieved after 46d and then anammox sludge was inoculated. In the stable period, effluent total inorganic nitrogen (TIN) was less than 4.3 mg/L with removal efficiency of 92.3%. Further analysis suggests that anammox bacteria, mainly affiliated withCandidatus_Kuenenia, successfully reduced the external ammonia from the SFL and contributed approximately 28%-43% to TIN removal. Overall, this study suggests anammox could be combined with SFL addition, resulting in a stable enhanced nitrogen biological removal. (c) Higher Education Press 2020

Automated summary

The study successfully improved the process of enhancing biological nitrogen removal of wastewater with low COD/N ratio by involving anammox process, achieving stable removal efficiency of TIN with the contribution of anammox bacteria in reducing external ammonia. The combination of anammox with SFL addition resulted in a stable enhanced nitrogen biological removal.