LAUSR

Abstract A pilot-scale anammox biofilter was set up and operated using reject water in order to investigate its nitrogen removal performance and the microbial community present at different stages of operation of this technology. A novel material “Filtralite” was used a support in order to achieve shorter start-up periods and obtain higher nitrogen load removal than other anammox technologies. Physico-chemical analysis demonstrated that nitrogen removal efficiency was higher than 70% from operational Day 100, reaching steady-stable total nitrogen removal and NH4+-N of 82% and 91%, respectively, this results suggest the robustness and adaptability of the technology to withstand changing nitrogen loads in the influent. Molecular analysis showed the presence of Nitrosomonas and Candidatus Brocadiales with relative abundance on different key days at around 2.5% of total relative abundance, although other phylotypes involved in the nitrogen cycle were also found. RT-PCR analysis showed that the pre-seed Filtralite used promoted the occurrence of anammox bacteria and other ammonia-oxidizing bacteria. The eukaryotic community oscillated greatly during operation and did not show any clear pattern. Both Prokarya and Eukarya showed high diversity and evenness, attributes which were very stable during operation. The biofilter performed robustly, despite changes in influent and nitrogen load, validating its suitability for treating industrial or urban effluent with high nitrogen loading in order to avoid damages in the environment in the save-cost way.