To effectively remove impurities adsorbed on a filter medium such as filter sand from the filter sand in a short time and by the use of a small quantity of purifying water by providing a filter medium floating area with an ultrasonic oscillator for generating ultrasonic waves.
At the time of treating sewage by a filter type water treating device 11, the sewage is poured in a washing filter basin 12 to make it penetrate into a deposited bed 13 of filter sand and adsorb impurities in the sewage by the filter sand. After that, the water from which the impurities have been removed is taken out from the bottom part of the filter basin 12. On the other hand, in the case of washing the filter sand to remove the impurities adsorbed by the filter sand from the filter sand, backward washing water is poured upward from the bottom part of the filter basin 12 from a backward washing pipe 15, and also surface washing water is poured toward a deposited bed 13 from the upper side of the deposited bed 13 from a surface washing pipe 16. Ultrasonic waves are oscillated from an ultrasonic oscillator 17 to generated ultrasonic waves in a filter sand floating area 14. Eventually, the ultrasonic waves are applied to the filter sand floating on the deposited bed 13 to make the impurities adsorbed by the filter sand easily be removed and to easily remove them by the force of water.
SANEMORI AKIRO
NAKAHORI ICHIRO
SAKAGUCHI ISAO
OSAKA PREFECTURE