PURPOSE: To separate the dissolved impurities like as SS, heavy metal ion, etc., through the adsorption, to remove the clogging SS through the back washing, and to smooth the desorption and regeneratio through the acid washing, by employing the carbonaceous solid substance of specified particle size for the filter medium, at treating the sewage including SS, etc.

CONSTITUTION: The sewage 1, including SS and dissolved heavy metal ion, is introduced into the filter 2 including the packed zone 3 being packed with the carbonaceous solid substance (charcoal, lignite, brown coal for instance) of particle size above 1mm, suitably about 3W60mm. The SS, included in the sewage, is deposited mainly in the upper space 4 of the packed zone 3, and the dissolved heavy metal ion is adsorbed by the packed zone 3, and the cleaned water 5 is discharged. Next, if the SS fills up the space 4 causing clogging, the clean water pipe is closed, and the back washing water is introduced from the pipe 6 into the filter 2 for back washing, and the back wash water is sent to the SS treater through the pipe 7. After that, the sewage is again passed and cleaned, and if the clogging occurs, the back washing is again operated. When the heavy metal adsorption approaches the saturation point, the back washing is operated; after that, the acid is introduced from the pipe 8 and is passed through the filter 2 backward for desorbing the heavy metal, and is taken out through the pipe 9.