To prevent a filter medium from being clogged up again with solid matter when washing and regenerating a filter medium bed loaded for a tank filter by discharging deposits in the bottom part before sending air and washing water from below the filter medium bed to wash the filter medium while agitating it.
When a filter medium bed 1 in a treating tank 3 is clogged with sludge or the like, the supply of raw water and the circulation of treated water are stopped and a treated water takeoff valve 2 is closed and deposits in the bottom part of the treating tank 3 are drawn off from a draw-off pipe 4. Next, a washing blower 5 is operated to supply air from an air nozzle 6 and agitate the filter medium through a draft tube 7. After that, while air supply from the air nozzle 6 is continued, washing water is supplied from a raw water supply pipe 10 through a washing water pipe 8 and a circulating pump 9 to discharge waste water containing excess sludge or the like removed from the filter medium from a drain pipe 13 through an overflow trough 11 and a treated water takeoff pipe 12. Next, the washing blower 5 is stopped and a circulating valve 14 is opened and a washing water valve 15 is closed to stop the washing water supply.
FUJIMURA SHIGEYUKI
YAMASHITA OSAMU
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