Study on enhanced denitrification using particulate organic matter in membrane bioreactor by mechanism modeling

• Enhanced denitrification was obtained without soluble carbon source in MBR.
• Considerable particulate organic matter (POM) remained in the MBR sludge.
• A kinetic method was proposed to evaluate denitrification with the residual POM.
• Post-anoxic configuration can display highest POM denitrification efficiency in MBR.
• Prolonging POM retention time via sludge reduction can enhance denitrification.

Particulate organic matter (POM) in wastewater is a potential denitrification carbon source, while the optimal operational mode using denitrification mechanism with POM is still unclear in wastewater treatment plants. In this work, we investigated the denitrification rates (DNRs) in a full-scale membrane bioreactor (MBR) coupled with two-stage pre-anoxic (pre-AN), and then evaluated the POM denitrification efficiency using mechanism modeling. The results indicate that POM related fraction accounted for the majority of the obtained specific DNR of 1.39 ± 0.46 mg N g−1 MLVSS h−1 in the second pre-AN without available soluble carbon source. The modeling approaches with calibration and validation procedures estimated a high residual POM concentration of 0.17 g COD g−1 MLVSS in the activated sludge, which provided specific DNR of 1.14 mg N g−1 MLVSS h−1. High POM retention time in the reactor was the result of high solid retention time used in the MBR. In particular, post-AN of high biomass concentration could provide the highest POM denitrification efficiency in MBR. The MBR process combined with additional sludge reduction technology could further enhance denitrification by POM.