An apparatus provides for treatment of primary effluent from residential and commercial establishments to allow subsurface or surface disposable of wastewater. A single tank includes dosing and recirculation chambers 28, 30 having no direct fluid communication therebetween and divided by a vertical chamber wall 32. A filter layer 26 is positioned atop both chambers such that wastewater that is filtered therein then flows into both the dosing and recirculation chambers. The position of the wall 32 determines the proportion of filtered wastewater that flows into each chamber by gravity.