Anammox in a biofilter reactor to treat wastewater of high strength nitrogen

An anammox biofilter reactor (A-BFR) under high total nitrogen (TN) concentration and high nitrogen loading rate (NLR) was operated for 283 days and the biomass characteristics were investigated at the end of the experiment to discuss the origin of strong impact resistance of A-BFR. The result showed TN removal rate of A-BFR reached 81.76 % averagely under the influent concentration of 525 mg/L and the NLR of 6.30 kg N/m(3)/d. Furthermore, A-BFR was partitioned as the core zone and the polish zone spontaneously according to the water quality along the height of reactor due to the characteristics of plug flow. Although the core zone bore an actual NLR of 17.71 kg N/m(3)/d, and an average free ammonia (FA) concentrations of 13.35 mg/L as well as a mean free nitrous acid (FNA) concentrations of 36.89 mu g/L, it still obtained the TN removal of >80 %, which could be attributed to the high biomass of 30.67 gVSS/L comprised of biofilm and granular sludge aggregates, the high specific anammox activity up to 49.24 mg N/g VSS/d, and high extracellular polymeric substances of 148.69 mg/ gVSS. In addition, the enrichment of anammox bacteria in the core zone attained over 50 %, and the dominant bacteria were unclassified Candidatus Brocadiaceae and Candidatus Kuenenia after the operation of 283 days. These findings revealed the unique characteristics of biomass in the core zone decided the robust capacity of A-BFR to resist high NLR and the inhibition of FA and FNA from high TN concentration, which would enrich the knowledge and understanding of anammox with plug flow reactor under higher FA and FNA concentrations, implying BFR was a robust and resilient reactor for anammox.