Abstract: A treatment system for a wastewater influent containing having a facultative tank with a vertically disposed lower anaerobic treatment zone, a middle microaerophilic treatment zone and an upper aerobic treatment zone. A baffle extends vertically in the tank in at least portions of said upper and middle zones to define a vertically extending influent section to receive the influent and an effluent section. The heavier biosolid components of the wastewater received in the influent section drop from the bottom thereof into the lower anaerobic zone for treatment and the lighter components exiting from the influent section flow into the effluent section to rise therein and be treated as they flow upwardly through said microaerophilic and aerobic zones. A lift tube for an inlet above the anaerobic zone and lifts liquid and lighter solid components into the air for aeration and flow back into the influent section. To improve efficiency, biosolids are added to the wastewater.