The invention relates to a method for removing impurities from an aqueous stream. The method includes 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. The aqueous stream and the adsorbent material is then directed to a ballasted flocculation zone where the adsorbent material is mixed with ballast to form sludge. The aqueous stream is then separated from the sludge to produce treated water and the sludge is settled in a settling zone. The ballast is then separated from the sludge and directed to the ballasted flocculation zone while the sludge and the adsorbent material are directed to a transition zone. In addition, the method requires 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.