Impacts of Biofilm Properties on the Start-Up and Performance of a Membrane Biofilm Reactor Performing Anammox and Nitrate/Nitrite-Dependent Anaerobic Methane Oxidation Integrated Processes: A Model-Based Investigation

Even though the membrane biofilm reactor (MBfR) performing the anammox and nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) integrated processes has been known to enable complete nitrogen removal, the effects of biofilm properties on such an MBfR are yet to be disclosed. In this work, a biofilm model was constructed to investigate the effects of the initial microbial composition of the biofilm, the initial biofilm thickness, the boundary layer thickness of the biofilm, and the diffusivity of solutes in the biofilm structure on the start-up process and steady-state performance of the MBfR performing anammox/n-DAMO. The results showed that the four biofilm properties would not affect the steady-state performance but would significantly regulate the start-up time of the MBfR. Unless the MBfR was operated under undesired operational conditions, inoculation of sludge comprised mainly of anammox bacteria or/and n-DAMO archaea to form a thin initial biofilm would accelerate the start-up process of the MBfR. Moreover, measures could be taken to reduce the boundary layer thickness and the diffusivity of solutes in the biofilm structure, the latter of which would also enhance methane utilization. This work would provide valuable practical guidance for the rapid establishment of the MBfR with a high-level treatment capacity based on anammox/n-DAMO.