Patent ID: 7662277

Claim:
A wastewater treatment apparatus comprising: a tank; a recirculation chamber located in the tank; a dosing chamber located in the tank, the dosing chamber having no direct fluid connection to the recirculation chamber; a porous filter underdrain located above the recirculation chamber and the dosing chamber; at least one recirculation filter layer containing a filter media, the at least one recirculation filter layer being located on the porous filter underdrain above the recirculation chamber; at least one dosing filter layer containing a filter media, the at least one dosing filter layer being located on the porous filter underdrain above the dosing chamber; an influent pipe configured to direct wastewater entering the tank into the recirculation chamber; at least one recirculation pump in communication with the recirculation chamber, the at least one recirculation pump pumping the wastewater from the recirculation chamber onto the recirculation and dosing filter layers, the wastewater flowing through the filter media of the recirculation and dosing filter layers, through the underdrain, and into the recirculation chamber and the dosing chamber, respectively; and a discharge flow control system including at least one dosing pump in communication with the dosing chamber, a treated effluent tank return pipe having a first end coupled to the at least one dosing pump and a second end in communication with the recirculation chamber, and an effluent discharge pipe coupled to the at least one dosing pump, the discharge flow control system selectively controlling flow of wastewater from the dosing chamber back to the recirculation chamber through the tank return pipe for additional treatment and through the discharge pipe out of the tank.