Biofilter constructed of iron–carbon, ceramsite and biochar to synchronous removal of nitrate and phosphate: Treatment optimization and analysis of microbial community difference

Abstract

Ceramsite, iron–carbon (FeC) and modified biochar were selected to construct a biofilter with strains Aquabacterium sp. XL4 and Zoogloea sp. FY6 with ability of nitrate–dependent ferrous (Fe2+) oxidizing (NDFO). When the material filling rate was 50 % (v/v), the hydraulic retention time was 2.0, the carbon to nitrogen ratio was 1.5, the nitrate concentration was 20 mg L−1, the phosphate concentration was 5.0 mg L−1, and the influent pH was neutral, the denitrification performance can reach 97.6 %, the phosphate removal efficiency was 91.2 %, and the effluent nitrite accumulation was 1.05 mg L−1. In addition, the contaminant removal performance of biofilter was not affected by the more obvious colonies in the actual sewage. The iron source released in FeC micro–electrolysis process, the silicide, and aluminide in the ceramsite can both promote the denitrification of the biofilter. High–throughput data analysis found that strains XL4 and FY6 always had strong abundance values in the biofilter of the composite system, and the proportion of genes related to nitrate, iron redox cycle and phosphate conversion was also high. This study provides an idea for the deep treatment of low C/N ratio sewage.