Study on low-temperature treatment of nitrogen-containing wastewater by anaerobic biological filter with alkali-treated loofah-based filler

In this study, a new type of anaerobic biological filter (ABF) packed with alkali-treated loofah filler and a filler-free suspension growth control group (SBR) were used to cultivate the inoculated activated sludge to improve the activity and low temperature tolerance of the enriched anaerobic ammonia oxidation bacteria in the reactor. The results show that ABF and SBR were acclimated and started quickly, and the total nitrogen removal rate was maintained at 70.9% and 63.7%, respectively. Under the low temperature operating conditions, the total nitrogen removal rate of ABF maintained 59.9%, which was 16.5% higher than that of SBR. The detected EPS in the biomass of ABF and SBR increased by 100% and 272%, respectively, under low temperatures (15°C). Metagenomic testing revealed that the anammox bacteria (Candidatus Brocadiae) were the dominant functional populations both in ABF and SBR systems, and their relative abundances were 22.5% and 11.38%, respectively. In addition, it is found for the first time that anammox bacteria and denitrifying bacteria were the main contributors to EPS synthesis, which is important to the stable operation of the reactor at low temperature