Systems and methods for treating wastewater including a contact tank configured to mix influent wastewater with activated sludge to form a mixed liquor, a dissolved air flotation unit having an inlet and an outlet, the inlet of the dissolved air flotation unit in fluid communication with an outlet of the contact tank, and a membrane bioreactor including a biological treatment vessel having an inlet in fluid communication with the outlet of the dissolved air flotation unit and an activated sludge outlet in fluid communication with an inlet of the contact tank.