An upper layer cleaning apparatus of a water treatment apparatus, the water treatment apparatus comprising a raw water supply pipe, one or a plurality of raw water special air mixing nozzles, one end portion each thereof communicating with the raw water supply pipe and at the other end portion each thereof being provided a raw water ejection outlet ejecting raw water as an air-mixed jet water stream of raw water and air;
- a filtering tank in circular shape in plan view, the tank housing a filter layer comprising two layers of an upper layer and a lower layer, the upper layer comprising a filter medium with a smaller specific gravity and a larger particle size than a filter medium of the lower layer;
- a filtered water removal pipe provided in the filtering tank to remove water filtered by the filter layer;
- a reverse cleaning water supply pipe provided in the filtering tank to supply reverse cleaning water to the filter layer;
- a drainage trough or a drainage outlet provided above the filter layer in the filtering tank;
- and an upper layer cleaning apparatus cleaning the upper layer while loosening the filter medium of the upper layer by an upward stream by introducing reverse cleaning water from the reverse cleaning water supply pipe at an upper layer cleaning speed, the raw water special air mixing nozzles being arranged at a predetermined interval above the filter layer or the drainage trough between the raw water ejection outlets and a surface of the filter layer or a bottom surface of the drainage trough, characterized in that the upper layer cleaning apparatus comprises:
- an upper layer cleaning pipe support member communicating with an upper layer cleaning water supply pipe and arranged in a radial direction above the filter layer;
- an upper layer cleaning water pipe comprising a center cleaning water pipe communicating with the upper layer cleaning pipe support member and rotatably attached to the support member and extending vertically and a pair of horizontal cleaning water pipes connected to a lower end portion of the center cleaning water pipe so as to communicate with the center cleaning water pipe and extending horizontally on both sides of a radial direction from the connected portion;
- a plurality of surface-cleaning special air mixing nozzles, an ejection outlet of each thereof protruding from the pair of horizontal cleaning water pipes diagonally downward in a circumferential direction of the filtering tank, a direction of the ejection outlets of the nozzles of one of the horizontal cleaning water pipes being opposite to a direction of the ejection outlets of the nozzles of the other one thereof;
- at least one air suction pipe fixed to the center cleaning water pipe and extending vertically;
- and
- a pair of horizontal air pipes connected to the air suction pipe so as to communicate with the air suction pipe and extending horizontally along the horizontal cleaning water pipes to be fixed to the horizontal cleaning water pipes,
- the horizontal air pipes communicating with each of the surface-cleaning special air mixing nozzles by a connection pipe and an upper end portion of the air suction pipe being open to an atmosphere and arranged upper than the drainage trough or the drainage outlet.