Characteristics of a Self-Forming Dynamic Membrane Coupled with a Bioreactor in Application of Anammox Processes

A novel anammox self-forming dynamic membrane bioreactor (SFDMBR) was proposed to achieve an efficient anammox process with high biomass retention and cost-effective operation. The cake layer formed on nylon mesh (pore size, 20-25 μm) was referred to as a dynamic membrane (DM). The high permeability of the DM layer contributed to low transmembrane pressure (TMP), which kept below 10 kPa for 50 days in one filtration cycle of 82 days. Compared to the high TMP (mainly > 20 kPa) in the MBR using polyvinylidene fluoride (PVDF) microfiltration membrane, energy can be significantly conserved in the SFDMBR. Besides, the mature DM layer achieved efficient biomass retention comparable to that of PVDF membrane, which favored anammox bacteria enrichment. Concomitantly, an appropriate microenvironment for autotrophic anammox bacterial growth with well-controlled extracellular polymeric substances (EPS) concentration (33.22 mg·g^-1 VSS) was achieved in SFDMBR. According to specific filtration resistance (SFR) analysis, reducing the EPS concentration in the bulk sludge improves sludge filterability and alleviate fouling, which was achieved in the SFDMBR system with a low SFR of 1.47 × 10¹² m^-1·kg^-1. Our results show that the cost-effective operations and technical merits make anammox SFDMBRs promising for practical applications.