Abstract: A vessel (10) for placement on a land site for sanitary treatment of wastewater, in which an inlet communicates wastewater and suspended solids through a mixing chamber (30) to an aeration zone (34) that receives air from nozzles (37) for biological digestion of the suspended solids and conversion to activated sludge. The activated sludge communicates through an airlift (70) to the mixing chamber (30) for facilitating treatment. The air from the nozzles (37) creates an upflow of wastewater and activated sludge to secondary clarifiers (42) having sludge receiving plates (48) on which the sludge settles, accumulates, and falls from resulting in treated water in the secondary clarifier (42). The treated water discharges in a trough (62) from the vessel (12, 92). A method of sanitary treating of wastewater is disclosed.