Water treatment process and plant using ballasted flocculation and settling

摘要

A method for treating wastewater using a ballasted flocculation technique includes continuously measuring the concentration of suspended solids, organic matter or other impurities in the water to be treated prior to directing the water to be treated to a flocculation tank. Based on this measurement, the amount of ballast necessary to obtain treated water of a predetermined quality is then calculated. In the flocculation tank, ballast and a flocculating reagent are added to the water to form a water-floc mixture. The water-floc mixture is directed to a settling tank where a sludge-ballast mixture is settled. The sludge-ballast mixture is directed to a mixing tank and then to a separator to separate the ballast from the sludge. The separated ballast is directed to the flocculation tank. The separated sludge is directed to the mixing tank when the level of sludge-ballast mixture in the mixing tank is lower than a predetermined level.