Abstract: A wastewater treatment unit (10) including a recirculation chamber (32), a dosing chamber (34) having no direct fluid connection to the recirculation chamber (32), and at least two filter layers (28, 30) in a single tank (12). Each filter layer (28, 30) containing filter media (56) and being located above the recirculation (32) and dosing chambers (34). The wastewater treatment unit (10) also including an influent pipe (50), a recirculation pump (72) located in the recirculation chamber (32), and an effluent discharge pipe (88) connected to the dosing chamber (34).