Modeling of enhanced denitrification capacity with microbial storage product in MBR systems

• A model based on storage product for enhanced denitrification in MBR is proposed.
• High anoxic and aerobic storage yields (0.52 and 0.64) of the MBR sludge are obtained.
• The model can fit enhanced denitrification characteristic in full-scale MBRs.
• Storage products only contribute main nitrogen removal in pre-denitrification system.

Although the product of microbial storage is a potential denitrification carbon, it is often overlooked in conventional wastewater treatment processes, particularly in membrane bioreactors (MBR). The current study aims to develop a kinetic model to investigate enhanced denitrification driven by microbial storage products. This model has been considered for improving nitrogen removal efficiency in full-scale MBRs. The model can describe simultaneous storage, utilization of storage product, and growth of heterotrophic bacteria. The parameter calibration procedures were conducted in groups of batch tests that represent different MBR system configurations, including pre- and post-denitrification. A high agreement between actual measurement and model simulation for enhanced denitrification was obtained in a full-scale MBR system. Storage yields of 0.64 and 0.52 under aerobic and anoxic conditions were observed, respectively. High microbial storage yields were essential in increasing the denitrification rate, which mainly contributed the enhanced denitrification capacity in pre-denitrification. However, the enhancement was mainly associated with endogenous respiration in post-denitrification.