A wastewater treatment system includes a contact tank having a first inlet configured to receive wastewater to be treated, a second inlet configured to receive activated sludge, and an outlet, a dissolved air flotation unit having an inlet in fluid communication with the outlet of the contact tank, a biological treatment unit having a first inlet in fluid communication with an effluent outlet of the dissolved air flotation unit and an outlet, an anaerobic digester having an inlet and an outlet, a floated solids conduit providing fluid communication between the solids outlet of the dissolved air flotation unit and the inlet of the anaerobic digester, and a thickener having an inlet in fluid communication with the outlet of the anaerobic digester, a first outlet in fluid communication with the inlet of the anaerobic digester, and a second outlet.