Patent ID: 7323108

Claim:
A method of treating wastewater with both a biological system and a ballasted flocculation system, comprising: a. directing a first wastewater stream to the biological system and biologically treating the first wastewater stream; b. separating a first sludge from the wastewater in the biological system and producing a first effluent; c. directing a second wastewater stream to the ballasted flocculation system; d. transferring at least some of the first sludge from the biological system, and mixing the first sludge with the wastewater in the ballasted flocculation system to biologically treat the second stream of wastewater; e. in the ballasted flocculation system, separating a second sludge from the wastewater in the ballasted flocculation system to produce a second effluent; f. recycling the second sludge to a separator and separating ballast from the sludge; and g. maintaining the second sludge recycle rate such that the flow rate of the second sludge to the separator is 15% or more of the influent flow rate to the ballasted flocculation system.