Waste water treatment

Patent Pending PROBLEM TO BE SOLVED: To provide a method for treating waste water, in which heavy metal ions in waste water are removed. ; SOLUTION: The method for treating waste water comprises the steps of: arranging a diffuser connected to a gas-liquid two-phase whirling type micro bubble generator and an immersion type ultrasonic vibrator connected to an ultrasonic transmitter in a flocculation/precipitation tank for coprecipitating heavy metals in industrial waste water; and generating micro bubbles in the whole waste water, in which flocks of hydroxides such as iron hydroxide produced by coprecipitating heavy metals are dispersed, from the diffuser and crystallizing flocks of hydroxides by effects of the hot spot/micro jet to be formed by bursting micro bubbles by the sound pressure of an ultrasonic wave transmitted from the ultrasonic vibrator to promote the sedimentation/separation of the crystallized flocks.