With increased urbanization, wastewater resource recovery facilities face new challenges. When a conventional activated sludge wastewater treatment facility has reached its limit, Fluence's SUBRE can come to the rescue. Instead of enlarging current plants and building new basins, SUBRE modules are submerged in existing chambers, improving effluent quality, lowering the use of chemicals, saving energy and operational costs, and enlarging capacity. SUBRE upgrades WWTPs using membrane aerated biofilm reactor (MABR) modules. SUBRE is designed to upgrade existing basins with capacities of 2,000-100,000 m3/d (0.5-25 MGD) or improve effluent qualities to meet stringent nutrient regulations.