Patent ID: 8110116

Claim:
A method for cleaning a filter layer of a water treatment apparatus comprising the steps of: providing an apparatus comprising: a raw water supply tube; at least one mixed raw water stream jet nozzle having at least one air inlet tube, wherein each said at least one mixed raw water stream jet nozzle fluidically communicates at one end thereof with said raw water supply tube and having at the other end thereof a raw water outlet from which a mixed stream of raw water and air is jetted out; a filtering tank housing a filter layer disposed below said at least one mixed raw water stream jet nozzle with a predetermined distance between the surface of the filter layer and the raw water outlet of the mixed raw water stream jet nozzle or nozzles; a filtered water takeout tube provided in the filtering tank for taking out water filtered through the filter layer; a reverse stream cleaning water supply tube provided in the filtering tank for supplying reverse stream of cleaning water to the filter layer, a plurality of filter layer cleaning jet nozzles each fluidically communicating at one end thereof with a filter layer cleaning water supply tube and having at the other end thereof a cleaning water outlet from which cleaning water is jetted out, said filter layer cleaning jet nozzles being disposed at a predetermined circumferential interval above the filter layer in such a manner that the cleaning water outlets are located in the vicinity of the surface of the filter layer; and an overflow outlet provided in the filtering tank above the filter layer; flowing water through said cleaning jet nozzles to form a swirling stream in the water above the surface of the filter layer, thereby cleaning said filter layer.