Abstract
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.
Highlights
In recent years, the process of Anaerobic Ammonia Oxidation (ANAMMOX) has attracted extensive attention and has been applied in the full-scale urban and industrial wastewater treatment plants[1], with its advantages of low requirement for aeration and carbon sources, and yields less wasted sludge[2].The enrichment of Anammox bacteria (AAOB) is the key to start the anammox process and improve their tolerance to cold environment rapidly
Studies have shown that the extracellular polymer secreted by AAOB may enhance their attachment to the biological filler and effectively alleviate the cell erosion phenomenon inside the
Loofah has the potential as good biological carrier filler [4] with various advantages, such as low cost, porous structure with high specific surface area, non-toxic and high affinity for microorganisms growth[5].The alkali-treated loofah material reduces the hydroxyl groups on the fiber surface and improves the fiber’s microbial corrosion resistance and the service life of the filler. In this experiment, a new type of alkali-treated loofah-based filler biological filter was used to enhance the enrichment of the bacterial population in the reactor by adding porous structure fillers, and to improve the biological denitrification efficiency of the reactor
Summary
The process of Anaerobic Ammonia Oxidation (ANAMMOX) has attracted extensive attention and has been applied in the full-scale urban and industrial wastewater treatment plants[1], with its advantages of low requirement for aeration and carbon sources, and yields less wasted sludge[2].The enrichment of Anammox bacteria (AAOB) is the key to start the anammox process and improve their tolerance to cold environment rapidly. Loofah has the potential as good biological carrier filler [4] with various advantages, such as low cost, porous structure with high specific surface area, non-toxic and high affinity for microorganisms growth[5].The alkali-treated loofah material reduces the hydroxyl groups on the fiber surface and improves the fiber’s microbial corrosion resistance and the service life of the filler. In this experiment, a new type of alkali-treated loofah-based filler biological filter was used to enhance the enrichment of the bacterial population in the reactor by adding porous structure fillers, and to improve the biological denitrification efficiency of the reactor. The research results can provide new ideas for maintaining the nitrogen removal efficiency of the anaerobic ammonia oxidation process under low temperature operation and improving the tolerance of the bacterial flora to low temperature environments
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