A water treatment system for aeration of water in a treatment tank includes at least one bridge extending above an upper surface of the water in the tank; a retrievable mounting frame assembly, including a frame, a plurality of aeration elements, a plurality of mounting brackets to secure the aeration elements to the frame, a control arm having secured to the frame at the first end, and a first air distribution conduit coupled to the aeration elements for supplying an air flow to the aeration elements; at least one guide rail system secured to the bridge assembly and extending to the floor of the tank, the guide rail system having at least one or multiple parallel guide rails, a second air distribution conduit coupled to the first air distribution conduit, and an actuatable push-rod positioned between the guide rails and connected to the control arm's second end. The hold-down rod, when actuated, moves the mounting frame assembly along the guide rails from a first position above the upper surface of the water and into a second position on the floor of the tank for aeration of the water. A transport device and a transferrable lifting crane for positioning the frame assembly are moveable along the length of the bridge along guide tracks provided in the bridge.