Treatment using fixed film processes and ballasted settling
A system and method is provided for water and wastewater treatment. The system comprises a fixed film biological process and a ballasted flocculation process.
1. A method for treating wastewater, comprising:
introducing a source of wastewater to a fixed film biological reactor to provide a fixed film effluent;
adding a magnetic ballast to the fixed film effluent to provide a ballasted effluent;
separating the ballasted effluent into a treated effluent and ballasted solids in a clarifier;
magnetically separating the ballasted solids into recovered ballast and ballast-free solids;
adding at least a portion of the ballast-free solids to the source of wastewater; and
adding at least a portion of the recovered ballast to the fixed film effluent,
wherein no cleaning solution is used for ballast recovery.
2. The method of claim 1 , further comprising adding a flocculant to the ballasted effluent.
3. The method of claim 1 , further comprising adding a coagulant to the fixed film effluent to provide a coagulated effluent.
4. The method of claim 3 , further comprising adding a portion of the ballast-free solids to at least one of the fixed film effluent, and the coagulated effluent.
5. The method of claim 3 , further comprising adding a portion of the ballasted solids to at least one of the source of wastewater, the fixed film effluent, and the coagulated effluent.
6. The method of claim 1 , wherein the fixed film effluent comprises 50 mg/l to 300 mg/l of biological solids.
7. The method of claim 1 , wherein the ballast comprises magnetite.
8. The method of claim 1 , wherein the wastewater is treated at a rate of between 200 gallons per day per square foot of a surface area of the clarifier to 6,000 gallons per day per square foot of the surface area of the clarifier.
9. The method of claim 1 , wherein the magnetic ballast has a particle size of less than 40 μm.
10. The method of claim 9 , wherein the magnetic ballast has a particle size of less than 20 μm.
11. The method of claim 1 , wherein the magnetic ballast is added in a dry or powdered form.
12. The method of claim 1 , further comprising subjecting the ballasted solids to mechanical shearing prior to magnetic separation.
13. The method of claim 1 , wherein at least one of a coagulation tank, a ballast feed tank, and a flocculation tank is integrated into the clarifier.
14. The method of claim 1 , further comprising bypassing the fixed film biological reactor during a high flow event.
15. The method of claim 1 , further comprising subjecting the wastewater to clarification upstream of the fixed film biological reactor.