The facultative membrane bioreactor (FMBR) is a biological wastewater treatment process that removes carbon, nitrogen and phosphorus simultaneously in a single reactor. It encourages a natural microbial competition, maximizes activity of the mixed biomass consortium, saves energy, and meets nutrient discharge limits with simple controls. It is a breakthrough technology for the utility of the future that enables simultaneous removal of C, N, and P, reduces operating costs with less carbon emission, and requires only very low periodic biosludge wasting. It also provides a benefit of emerging contaminant removal. FMBR is a cost effective and reliable system that has been developed by Jiangxi JDL Environmental Protection Co., Ltd. It has been used in practice and improved over the past 10 years.