Performance and microbiome of an anammox biofilter for treating secondary wastewater: Effect of organic matter, low-strength nitrogen, and temperature

To broaden the application of anammox processes, this study investigated the implementation of an anammox biofilter using Filtralite (R) as support material for treating real secondary effluent characterized by low strength. The biofilter operated at optimal anammox temperatures (35 degrees C) and environmental temperatures (24.9 +/- 1.5 degrees C) to achieve nitrogen removal under stress conditions. The nitrogen removal efficiencies exceeded 50 %, with nitrogen removal rates greater than 60 g N center dot m(-3)center dot d(-1)under all operational conditions, including the presence of organic matter (COD similar to 90 mg O-2:L-1) and the low-strength nitrogen (41.1 mg-N center dot L-1). The presence of organic matter resulted in a reduction of less than 10 % of the total inorganic nitrogen removal efficiency during specific period compared to the control reactor. Additionally, the increased concentration of NH4+ in the influent enhanced nitrogen performance. The Denitratisoma genus was ubiquitous in all reactors, while anammox bacteria were predominantly represented by Candidatus Kuenenia at 35 degrees C and Candidatus Brocadia at environmental temperature. Comammox Nitrospira was the dominant phylotype at 35 degrees C. The dominant phylotypes of archaeal communities were taxonomically affiliated with Methanomicrobiales and Methanothrix, which demonstrated competitiveness by their persistence in the biofilm. This study demonstrates that anammox biofilter technology is a viable system for treating real low-strength urban wastewater, being particularly suitable for implementation at environmental temperatures due to its low-cost requirements and high nitrogen removal efficiency.