Spatial denitrification performance and microbial community composition in an up-flow immobilized biofilter for nitrate micro-polluted water treatment

Nitrates in secondary effluent need further removal to ensure water quality and protect the aquatic ecosystem. A lab-scale continuous up-flow immobilized biofilter (I-BF) (15L) based on polyurethane foams (PUFs) carriers immobilized bacterial consortia was constructed for treating nitrate micro-polluted water (14-18mgN/L). The results showed that a low effluent total nitrogen concentration of 0.68 +/- 0.11 mg/L and a high denitrification rate of 198.40 +/- 4.50g/(m(3).d) were obtained under a short hydraulic residence time (HRT) (1.8h). Shortening HRT decreased I-BF operating performance with a slight extent but enlarged the vertical spatial discrepancy in denitrification ability significantly. The high-throughput sequencing analysis revealed that Acidovorax belonging to beta-proteobacteria was the dominant genus involving in denitrification in this sodium acetate-fed immobilized biofilter. The spatial community structure has changed as HRT decreased. The different microbial composition along the height of I-BF at short HRT could respond to vertical differentiation in denitrification performance, and meanwhile enable the strong resistance ability of I-BF to high load impact. The research on both the I-BF operating performance and the dynamic characteristics of the microbial community in the vertical spaces of the biofilter is likely to provide a foundation for the biofilter denitrification process in practice. (C) 2020 Elsevier Ltd. All rights reserved.