Performance and mechanism of modified biological nutrient removal process in treating low carbon-to-nitrogen ratio wastewater

For solving the challenge of difficult nutrient removal, high running cost and CO2 emission at low carbon-to -nitrogen (C:N) ratio, Bi-Bio-Selector for nitrogen and phosphorus removal (BBSNP) process was developed. Under parallel operation conditions, full-scale BBSNP was less influence by low C:N ratio (3.5-2) than Anaerobic-anoxic-aerobic (AAO) and achieved better nitrogen removal performance. The mechanism of performance advantage in BBSNP was analyzed by mass balance and high throughout sequencing. It demonstrated BBSNP developed unique microbial community at C:N ratio of 2. Higher abundance of Saccharibacteria, Ferruginibacter, Ottowia, Dokdonella, Candidatus_Nitrotoga and Nitrospira in BBSNP was responsible for better chemical oxygen demand (COD) utilization efficiency, denitrification, denitrifying phosphorus removal and nitrification. Mean-while, under low C:N ratio, BBSNP could save 10% organic carbon and 15% oxygen requirement, reduce 53% running cost and 21% CO2 emission, which had practical value in relieving energy crisis and carbon emission of wastewater treatment plants (WWTPs).

Automated summary

To address the challenges of difficult nutrient removal, high running cost, and CO2 emission at low carbon-to-nitrogen (C:N) ratio, the Bi-Bio-Selector for nitrogen and phosphorus removal (BBSNP) process was developed. Compared to the Anaerobic-anoxic-aerobic (AAO) process, full-scale BBSNP showed less sensitivity to low C:N ratio (3.5-2) and achieved better nitrogen removal performance. The superiority of BBSNP was attributed to the development of a unique microbial community at C:N ratio of 2, which resulted in improved chemical oxygen demand (COD) utilization efficiency, denitrification, denitrifying phosphorus removal, and nitrification. Under low C:N ratio, BBSNP could also save organic carbon, oxygen requirement, running cost, and reduce CO2 emission, providing practical value in addressing energy crisis and carbon emission in wastewater treatment plants (WWTPs).