Method and system for utilizing activated sludge in a ballasted flocculation process to remove BOD and suspended solids
A method and system for treating water or wastewater to remove both soluble BOD and suspended solids. The method entails a ballasted flocculation process where a flocculant and insoluble granular material is added to the water or wastewater to be treated causing solids in the water or wastewater to aggregate around the granular material to form ballasted floc particles. In a settling zone, ballasted floc particles form settled sludge and the settled sludge is separated from clarified effluent. At some point in the process, activated sludge, in the form of return activated sludge or mixed liquor, is mixed with the water or wastewater being subjected to the ballasted flocculation process. The addition of activated sludge enables the process to remove soluble BOD.
1. A wastewater treatment system, comprising:
an activated sludge system including at least one reactor, a clarifier and a return activated sludge line for conveying return activated sludge from the clarifier to the reactor to form mixed liquor;
a ballasted flocculation system having one or more tanks and a settling zone and disposed is a non-series relationship with the activated sludge system; and
a mixed liquor supply line connected between the activated sludge system and the ballasted flocculation system for transferring at least a portion of the mixed liquor directly to the ballasted flocculation system.
2. A method of treating wastewater utilizing an activated sludge system and a ballasted flocculation system to remove soluble BOD from the wastewater being treated, the method comprising:
directing the wastewater into and through an activated sludge system having at least one reactor and a clarifier;
returning activated sludge from the clarifier to the reactor and mixing the activated sludge with the wastewater to form mixed liquor;
directing a portion of the mixed liquor through the activated sludge system and to the clarifier where the clarifier produces a first clarified effluent;
directing another portion of the mixed liquor from the activated sludge system to a ballasted flocculation system disposed in parallel relationship with the clarifier of the activated sludge system;
directing the other portion of the mixed liquor through the ballasted flocculation system wherein the ballasted flocculation produces a second clarified effluent;
wherein substantially all of the wastewater that forms a part of the mixed liquor that is treated in the ballasted flocculation passes through at least a part of the activated sludge system prior to entering the ballasted flocculation system; and
wherein the clarifier of the activated sludge system and the ballasted flocculation system clarifies the wastewater being treated, and wherein the activated sludge that forms a part of the mixed liquor is effective to remove soluble BOD from the wastewater that forms a part of the mixed liquor that passes through both the activated sludge system and the ballasted flocculation system therein.
3. The method of claim 2 including producing sludge in the ballasted flocculation system and returning the produced sludge from the ballasted flocculation system to the activated sludge system.
4. The method of claim 3 wherein both the activated sludge produced in the activated sludge system and the sludge produced by the ballasted flocculation system are returned to at least one reactor in the activated sludge system and mixed with wastewater to form the mixed liquor.
5. A method of treating wastewater utilizing an activated sludge system and a ballasted flocculation system to clarify the wastewater and remove soluble BOO from the wastewater, the method comprising:
directing substantially all the wastewater to be treated into an activated sludge system having at least one reactor and a clarifier;
returning activated sludge from the clarifier to the reactor and mixing the activated sludge with the wastewater to form mixed liquor;
directing a portion of the mixed liquor through the activated sludge system and to the clarifier where the clarifier produces a first clarified effluent;
directing another portion of the mixed liquor from the activated sludge system to a ballasted flocculation system disposed in a non-series relationship with the activated sludge system;
clarifying the other portion of the mixed liquor in the ballasted flocculation system to produce a second clarified effluent; and
removing soluble BOD from the wastewater that passes through both the activated sludge system and the ballasted flocculation system.
6. The method of claim 5 including directing the other portion of the mixed liquor directly to the ballasted flocculation system.
7. The method of claim 5 wherein the other portion of mixed liquor is not mixed with other wastewater prior to entering the ballasted flocculation system.
8. The method of claim 5 wherein there is provided a mixed liquor line extending from the activated sludge system to the ballasted flocculation system and wherein the method entails directing the other portion of mixed liquor through the mixed liquor line into the ballasted flocculation system.
9. The method of claim 5 wherein substantially all of the wastewater to be treated is mixed with return activated sludge in the activated sludge system to form mixed liquor in the activated sludge system.
10. The method of claim 5 wherein the ballasted flocculation system includes at least one mixing tank and wherein the method entails directing the other portion of the mixed liquor directly to the mixing tank of the ballasted flocculation system.
11. The method of claim 10 wherein there is provided a line between the activated sludge system and the mixing tank of the ballasted flocculation system and wherein the method includes directing the other portion of the mixed liquor from the activated sludge system through the line to the mixing tank of the ballasted flocculation system.
12. The wastewater treatment system of claim 1 wherein the clarifier of the activated sludge system and the ballasted flocculation system are disposed in parallel relationship.