Reducing energy consumption or running cost associated with the membrane bioreactor (MBR) process is a serious challenge that needs to be addressed in treating sewage. The addition of anaerobic ammonium oxidation bacteria (AnAOB) to a running MBR has the potential to lower the aeration rate, thus decreasing the running cost in treating sewage. The results obtained showed that owing to addition of AnAOB, TN and NH4+-N removal rates increased by 9.8% and 1.13%, respectively, while the aeration rate decreased by 50%. Additionally, high throughput sequencing and isotope experiments showed that both AnAOB and heterotrophic denitrification bacteria could survive simultaneously and play an important role in nitrogen removal, with AnAOB having a significantly greater contribution. It can be concluded that the addition of AnAOB reduced the running cost of MBR in treating sewage.

The offshore oil extraction process generates copious amounts of high-salinity oil-bearing wastewater; at present, treating such wastewater in an efficient and low-consumption manner is a major challenge. In this study, a flat ceramic membrane bioreactor (C−MBR) process combining aerobic microbial treatment technology and ceramic membrane filtration technology was used to treat oil-bearing wastewater. The pilot test results demonstrated the remarkable performance of the combined sequential batch reactor (SBR) and C-MBR process, wherein the chemical oxygen demand (COD) and ammonia nitrogen (NH4+−N) removal rates reached 93% and 98.9%, respectively. Microbial analysis indicated that the symbiosis between Marinobacterium, Marinobacter, and Nitrosomonas might have contributed to simultaneously removing NH4+−N and reducing COD, and the increased enrichment of Nitrosomonas significantly improved the nitrogen removal efficiency. Cleaning ceramic membranes with NaClO solution reduces membrane contamination and membrane cleaning frequency. The combined SBR and C−MBR process is an economical and feasible solution for treating high-salinity oil-bearing wastewater. Based on the pilot application study, the capital expenditure for operating the full-scale combined SBR and C−MBR process was estimated to be 251,717 USD/year, and the unit wastewater treatment cost was 0.21 USD/m3, which saved 62.5% of the energy cost compared to the conventional MBR process.