Patent ID: 7648637

Claim:
A method for removing impurities from an aqueous stream, the method comprising: directing the aqueous stream into an adsorbent contact zone and contacting the aqueous stream with an adsorbent material in the adsorbent contact zone so that impurities in the aqueous stream are adsorbed onto the adsorbent material; directing the aqueous stream containing the adsorbent material to a ballasted flocculation zone and mixing a ballast with the adsorbent material in the ballasted flocculation zone to form sludge containing ballast and the adsorbent material; separating the aqueous stream from the sludge to produce treated water and settling the sludge in a settling zone; separating ballast from the sludge, directing the separated ballast to the ballasted flocculation zone, and directing the sludge and the adsorbent material to a transition zone; measuring the concentration of the adsorbent material in the adsorbent contact zone; and adding adsorbent material to the aqueous stream if the value of the measured concentration of the adsorbent material in the absorbent contact zone is below a predetermined threshold value.