Energy efficient wastewater treatment for nitrogen and phosphorus removal
First Claim
1. In a liquid side of a sewage treatment system for treating wastewater, a biological nutrient removal (BNR) configuration of high efficiency with minimal aeration requirements, comprising:
- at least four tanks or zones arranged for successive treatment of the wastewater, including simultaneous nitrification/denitrification, aerobic, anoxic and aerobic stages in sequence in the respective tanks or zones,a first simultaneous nitrification/denitrification stage being maintained essentially at less than 1 ppm oxygen, and with the oxygen level adjusted to maintain simultaneous nitrification/denitrification, so that ammonia is broken down to produce nitrate, and nitrate is broken down to release nitrogen gas, within a single tank or zone and simultaneously,a first aerobic stage being maintained essentially at greater than 1 ppm oxygen to promote nitrification,an anoxic stage after the first aerobic stage, being maintained essentially at less than 1 ppm oxygen, and with the oxygen level adjusted to maintain an anoxic condition at least in part of the wastewater or part of the time, to break down nitrate to release nitrogen gas, anda second aerobic stage being maintained essentially at greater than 1 ppm oxygen to promote nitrification.
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Abstract
In a wastewater treatment plant, the liquid side of the plant has preferably four stages for nitrification and/or denitrification, prior to further treatment such as a clarifier. Energy requirements are reduced by reducing aeration requirements. Four or more tanks/zones comprise serial anoxic and aerobic stages, but in the anoxic stages simultaneous nitrification/denitrification takes place in accordance with the known process of U.S. Pat. No. 5,906,746. By this arrangement the system can achieve a volume ratio of about 20% aerobic tankage to the total tankage volume, as compared to a much higher ratio in a typical prior art system of serial aerobic/anoxic stages, and greatly reducing aeration requirements.
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Citations
20 Claims
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1. In a liquid side of a sewage treatment system for treating wastewater, a biological nutrient removal (BNR) configuration of high efficiency with minimal aeration requirements, comprising:
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at least four tanks or zones arranged for successive treatment of the wastewater, including simultaneous nitrification/denitrification, aerobic, anoxic and aerobic stages in sequence in the respective tanks or zones, a first simultaneous nitrification/denitrification stage being maintained essentially at less than 1 ppm oxygen, and with the oxygen level adjusted to maintain simultaneous nitrification/denitrification, so that ammonia is broken down to produce nitrate, and nitrate is broken down to release nitrogen gas, within a single tank or zone and simultaneously, a first aerobic stage being maintained essentially at greater than 1 ppm oxygen to promote nitrification, an anoxic stage after the first aerobic stage, being maintained essentially at less than 1 ppm oxygen, and with the oxygen level adjusted to maintain an anoxic condition at least in part of the wastewater or part of the time, to break down nitrate to release nitrogen gas, and a second aerobic stage being maintained essentially at greater than 1 ppm oxygen to promote nitrification. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In a sewage treatment process, a method for high efficiency biological nutrient removal (BNR) for wastewater treatment, with minimal aeration requirements, comprising:
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providing at least four tanks or zones arranged for successive treatment of the wastewater, including simultaneous nitrification/denitrification, aerobic, anoxic and aerobic stages in succession in the respective tanks or zones, establishing a flow of wastewater through the stages in succession, maintaining the first simultaneous nitrification/denitrification anoxic stage substantially at less than 1 ppm oxygen, and adjusting the oxygen level to maintain simultaneous nitrification/denitrification, so that ammonia is broken down to produce nitrate, and nitrate is broken down to release nitrogen gas, within a single tank or zone and simultaneously, maintaining the first aerobic stage essentially at greater than 1 ppm oxygen to promote nitrification whereby ammonia is broken down to produce nitrate, maintaining the anoxic stage substantially at less than 1 ppm oxygen, and adjusting the oxygen level to maintain an anoxic condition at least in part of the wastewater or part of the time, to break down nitrate to release nitrogen gas, maintaining the second aerobic stage substantially at greater than 1 ppm oxygen to promote nitrification whereby ammonia is broken down to produce nitrate, and performing the above steps without recycle of sludge from any of the stages back to any previous stage. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. In a sewage treatment process, a method for high efficiency biological nutrient removal (BNR) for wastewater treatment, with minimal aeration requirements, comprising:
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providing at least four tanks or zones arranged for successive treatment of the wastewater, including simultaneous nitrification/denitrification, aerobic, anoxic and aerobic stages in succession in the respective tanks or zones, establishing a flow of wastewater through the stages in succession, maintaining the first simultaneous nitrification/denitrification anoxic stage substantially at less than 1 ppm oxygen, and adjusting the oxygen level to maintain simultaneous nitrification/denitrification, so that ammonia is broken down to produce nitrate, and nitrate is broken down to release nitrogen gas, within a single tank or zone and simultaneously, maintaining the first aerobic stage essentially at greater than 1 ppm oxygen to promote nitrification whereby ammonia is broken down to produce nitrate, maintaining the anoxic stage substantially at less than 1 ppm oxygen, and adjusting the oxygen level to maintain an anoxic condition at least in part of the wastewater or part of the time, to break down nitrate to release nitrogen gas, maintaining the second aerobic stage substantially at greater than 1 ppm oxygen to promote nitrification whereby ammonia is broken down to produce nitrate, and removing clean water with a membrane bioreacter positioned at the end of the stages. - View Dependent Claims (20)
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Specification