Patent ID: 8454831

Claim:
A method for biologically treating wastewater, the method comprising: biologically treating the wastewater in a fixed-biomass biological reactor; directing the biologically treated wastewater to a ballasted flocculation system, and wherein a portion of the biomass from the biological reactor flows with the wastewater to the ballasted flocculation system; removing suspended solids from the wastewater by mixing the biologically treated wastewater with a ballast and a flocculant in the ballasted flocculation system to produce clarified wastewater and sludge, wherein the sludge contains suspended solids and the ballast having biomass accumulated thereon; separating the ballast having biomass accumulated thereon from the sludge; cleaning the ballast having biomass accumulated thereon by mixing the ballast with a cleaning solution; separating the cleaned ballast from the biomass; and recirculating the cleaned ballast to the ballasted flocculation system.