Abstract: There is disclosed a method for the removal of impurities, particularly organic impurities from granular solids, having its greatest immediate application for the regeneration of spent adsorbents which are used to purify waste water. The spent activated carbon is immersed in an aqueous bath which preferably contains a surface active agent, and water is circulated over the activated carbon while ultrasonic vibration is applied to the aqueous bath at a frequency from about 1 to about 100 kHz to desorb the organic adsorbate from the activated carbon. The desorbed organic compounds are washed from the activated carbon by the circulating water stream and are decomposed by introducing ozone into the water stream and, most preferably, while subjecting the water stream to ultraviolet radiation, thereby producing a wash water which can be safely discharged to the environment.