High-temperature biofilm system based on heterotrophic nitrification and aerobic denitrification treating high-strength ammonia wastewater: Nitrogen removal performances and temperature-regulated metabolic pathways

Conventional autotrophic nitrification process is difficult to treat high-temperature wastewater with highstrength ammonia. In this study, a high-temperature (50 degrees C) biofilm system based on heterotrophic nitrification and aerobic denitrification (HNAD) was established. The results showed that the HNAD process was high temperature resistant, and the nitrogen removal performance, pathway and microbial mechanism varied remarkably at different temperatures. The high-temperature system showed excellent nitrogen and COD removal capacities at 50 degrees C. Ammonia oxidation was mainly undertaken by heterotrophic nitrification, while anoxic and aerobic pathways worked in concert for denitrification. High-throughput sequencing indicated that heterotrophic nitrifying bacteria (8.58%) and denitrifying bacteria (52.88%) were dominant at 50 degrees C. Metagenomic analysis further suggested that the carbon metabolism was up-regulated in response to the increasing temperature, so more energy was generated, thereby promoting the HNAD-related nitrogen removal pathways. The study revealed the microbial mechanism of HNAD at high temperature and provided new insights into hightemperature biological nitrogen removal.

Automated summary

The study demonstrated that the HNAD process at high temperature effectively removes nitrogen from wastewater, with heterotrophic nitrification being the main process for ammonia oxidation and both aerobic and anoxic pathways contributing to denitrification. High-throughput sequencing and metagenomic analysis revealed the dominant microbial species and metabolic pathways in the system, showing an up-regulation of carbon metabolism with increasing temperature which promoted nitrogen removal.