A wastewater treatment system (100; 200; 300) comprising a first sub-system and a second sub-system operating in a parallel configuration, the first sub-system comprising: a wastewater conduit (106; 306) in fluid communication with a source of wastewater (105; 305), the wastewater conduit having a wastewater outlet and an overflow outlet, the overflow outlet configured to output overflow wastewater; a biological treatment unit (130; 330) having an inlet in fluid communication with the wastewater outlet, the biological treatment unit configured to biologically break down organic components of the wastewater to form a first mixed liquor; and a solids-liquid separation unit (140; 340) having an inlet in fluid communication with the biological treatment unit, the solids-liquid separation unit configured to separate solids from a portion of the first mixed liquor and form a first solids-lean effluent and a return activated sludge, and configured to output the first solids-lean effluent through an effluent outlet and output the return activated sludge through a return activated sludge outlet, and the second sub-system comprising: a contact tank (110; 310) having a first inlet in selective fluid communication with the overflow outlet, a second inlet in selective fluid communication with the return activated sludge outlet, the contact tank configured to mix the overflow wastewater with the return activated sludge to form a second mixed liquor; and a dissolved air flotation (120; 320) unit having an inlet in fluid communication with the contact tank, the dissolved air flotation unit configured to separate suspended matter from a portion of the second mixed liquor and form a second solids-lean effluent, floated solids, and waste solids, and configured to output the second solids-lean effluent through an effluent outlet of the dissolved air flotation unit, a flow meter coupled to the wastewater conduit and configured to measure a flow rate of the wastewater; an overflow valve positioned upstream from the contact tank in electrical communication with the flow meter, the overflow valve configured to selectively provide fluid communication between the overflow outlet and the contact tank responsive to the flow rate of the wastewater exceeding a first threshold flow rate; and a return activated sludge valve positioned upstream from the contact tank, the return activated sludge valve configured to selectively provide fluid communication between the return activated sludge outlet and the contact tank responsive to the flow rate of the wastewater exceeding a second threshold flow rate, a wastewater conduit (106; 306) in fluid communication with a source of wastewater (105; 305), the wastewater conduit having a wastewater outlet and an overflow outlet, the overflow outlet configured to output overflow wastewater; a biological treatment unit (130; 330) having an inlet in fluid communication with the wastewater outlet, the biological treatment unit configured to biologically break down organic components of the wastewater to form a first mixed liquor; and a solids-liquid separation unit (140; 340) having an inlet in fluid communication with the biological treatment unit, the solids-liquid separation unit configured to separate solids from a portion of the first mixed liquor and form a first solids-lean effluent and a return activated sludge, and configured to output the first solids-lean effluent through an effluent outlet and output the return activated sludge through a return activated sludge outlet, and a contact tank (110; 310) having a first inlet in selective fluid communication with the overflow outlet, a second inlet in selective fluid communication with the return activated sludge outlet, the contact tank configured to mix the overflow wastewater with the return activated sludge to form a second mixed liquor; and a dissolved air flotation (120; 320) unit having an inlet in fluid communication with the contact tank, the dissolved air flotation unit configured to separate suspended matter from a portion of the second mixed liquor and form a second solids-lean effluent, floated solids, and waste solids, and configured to output the second solids-lean effluent through an effluent outlet of the dissolved air flotation unit, a flow meter coupled to the wastewater conduit and configured to measure a flow rate of the wastewater; an overflow valve positioned upstream from the contact tank in electrical communication with the flow meter, the overflow valve configured to selectively provide fluid communication between the overflow outlet and the contact tank responsive to the flow rate of the wastewater exceeding a first threshold flow rate; and a return activated sludge valve positioned upstream from the contact tank, the return activated sludge valve configured to selectively provide fluid communication between the return activated sludge outlet and the contact tank responsive to the flow rate of the wastewater exceeding a second threshold flow rate,