Denitrification performance and microbial diversity of immobilized bacterial consortium treating nitrate micro-polluted water.

A heterotrophic denitrification process using bacterial consortium immobilized by polyurethane foams carriers to treat nitrate micro-polluted water was investigated. Nitrate reduction and nitrite accumulation were studied under several factors including initial COD/NO3--N concentration ratio, initial pH, initial NO2--N/NO3--N concentration ratio and inlet NO3--N concentration. Batch denitrification experiments showed that nitrate was completely removed at 5 h without nitrite accumulation under the optimum conditions of COD/NO3--N concentration ratio of 5.0-5.5 and initial pH of 7.2 ± 0.1. High initial NO2--N/NO3--N ratio enhanced denitrification rate mainly by accelerating nitrite reduction. Denitrification processes followed zero-order reaction kinetics at different initial NO3--N concentrations and obtained higher denitrification rate at higher inlet nitrate. High-throughput sequencing results showed that microbial community structure differed between the surface and interior space of polyurethane foams carriers while the dominant population in the inner zone of carriers was Pseudoxanthomonas.