Wastewater treatment systems are disclosed. A wastewater treatment system includes a wastewater conduit disposed in a wastewater treatment vessel, a pump comprising an intake and an outlet connectable to the at least one opening of the wastewater conduit, and an adapter comprising a first end and a second end. The adapter is configured, in a treatment mode, to provide a flow path for wastewater from the wastewater treatment vessel through the adapter and pump to the wastewater conduit. The adapter is further configured to, in a backflush mode, provide a flow path for wastewater through the plurality of nozzles of the wastewater conduit and through the adapter and pump for discharge into the wastewater treatment vessel. Methods of treating wastewater using the system and adapter are disclosed. Methods of retrofitting a wastewater treatment system by providing the adapter are disclosed.