Wastewater treatment system
View Patent ↗A system and method for treating wastewater includes two or more biological reaction zones separated by chamber walls. The system and method for treating wastewater includes static recycle of a mixed liquor from a second biological reaction zone to a first biological reaction zone.
1. A process for treating wastewater, comprising the steps of:
introducing wastewater at an influent velocity through an inlet into an outer aerated anoxic zone wherein the wastewater undergoes nitrification/denitrification;
moving an activated sludge and forming a first mixed liquor having a height in the aerated anoxic zone;
allowing the first mixed liquor to flow into an inner aerobic zone through an outlet;
forming a second mixed liquor in the aerobic zone, the second mixed liquor having a height in the aerobic zone, wherein the height in the aerobic zone is lower than the height in the aerated anoxic zone;
statically redirecting a first portion of the second mixed liquor from the aerobic zone to the aerated anoxic zone through an opening at a flow rate of two to four times the influent velocity;
transferring a second portion of the second mixed liquor from the aerobic zone to a settling zone;
withdrawing an effluent stream from the settling zone;
measuring a total nitrogen content of the effluent stream;
comparing the measured nitrogen content to a target nitrogen content; and
recycling the effluent stream from the settling zone to the aerobic zone when the measured nitrogen content exceeds the target nitrogen content.
2. The process according to claim 1 , wherein the wastewater comprises a nitrogen-containing compound.
3. The process according to claim 1 , wherein the wastewater comprises a phosphorous-containing compound.
4. The process according to claim 1 , wherein the aerated anoxic zone and the aerobic zone are concentric.
5. The process according to claim 4 , wherein the aerated anoxic zone and the aerobic zone are in a racetrack configuration.
6. The process according to claim 4 , wherein the aerated anoxic zone and the aerobic zone are in a circular configuration.
7. The process according to claim 1 , further comprising providing an oxygen-containing gas to the aerated anoxic zone.
8. The process according to claim 7 , wherein the oxygen-containing gas is provided by an aerator.
9. The process according to claim 8 , wherein the aerator is a disc aerator.
10. The process according to claim 1 further comprising allowing a third portion of the second mixed liquor to flow into an anaerobic zone and forming a third mixed liquor.
11. The process according to claim 10 , further comprising statically redirecting at least a portion of the third mixed liquor to the aerobic zone.
12. The process according to claim 1 , further comprising placing a baffle at a predetermined location between the aerated anoxic zone and the aerobic zone.
13. The process according to claim 1 , further comprising withdrawing activated sludge from the second mixed liquor to form a settled sludge.
14. The process according to claim 13 , further comprising recycling at least a portion of the settled sludge to the aerated anoxic zone.
15. A process for recycling mixed liquor in an oxidation ditch having multiple adjacent moving biological reaction zones, the biological reaction zones sharing a common intermediate chamber wall, wherein the mixed liquor level of an outer aerated anoxic nitrification/denitrification zone is higher than the mixed liquor level of an inner aerobic zone such that the mixed liquor flows from the outer aerated anoxic nitrification/denitrification zone to the inner aerobic zone, the process comprising:
statically redirecting the flow of the mixed liquor in the aerobic zone to the aerated anoxic nitrification/denitrification zone at a fluid velocity of two to four times an influent flow rate;
transferring a portion of the mixed liquor from the aerobic zone to a settling zone;
withdrawing an effluent stream from the settling zone;
measuring a nitrogen content of the effluent stream; and
comparing the measured nitrogen content to a target nitrogen content.
16. The process according to claim 15 , wherein the aerated anoxic zone and the aerobic zone are concentric.
17. The process according to claim 16 , wherein the aerated anoxic zone and the aerobic zone are in a racetrack configuration.
18. The process according to claim 16 , wherein the aerated anoxic zone and the aerobic zone are in a circular configuration.
19. The process according to claim 15 , further comprising recycling the effluent stream from the settling zone to the aerobic zone when the measured nitrogen content exceeds the target nitrogen content.