A novel pure biofilm system based on aerobic denitrification for nitrate wastewater treatment: Exploring the feasibility of high total nitrogen removal under low-carbon condition

To improve the poor denitrification efficiency of traditional biological treatment for low-carbon wastewater, a novel pure biofilm moving bed biofilm reactor (PH-MBBR) based on heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria was proposed. The start-up of PH-MBBR inoculated with HN-AD bacteria and the operating performances and microbial community composition under various C/N ratios were studied. The results showed that at C/N ratio of only 4, the total nitrogen (TN) removal rate of 10.02 mg/(L·h) was achieved under aerobic conditions. Microbial analysis indicates that the synergistic effect of oligotrophic bacteria Thauera and Azoarcus was the main reason for the high pollutant removal at C/N ratio of 4. Furthermore, the analysis of functional genes and enzymes reveals that NorB and NosZ played important roles in nitrate metabolism in PH-MBBR, and aerobic denitrification pathway was NO3–-N → NO → N2O → N2. This study provides a practical and theoretical basis for low-carbon nitrate wastewater treatment.