Membrane system backwash energy efficiency
First Claim
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1. A method of filtering solids from a liquid suspension in a filtration system comprising:
- performing a filtration process including providing a pressure differential across a wall of a permeable hollow membrane to induce and sustain filtration through the wall of the permeable hollow membrane;
suspending the filtration process; and
periodically backwashing pores of the permeable hollow membrane using permeate remaining in the filtration system after suspending the filtration process, the backwashing of the pores dislodging fouling materials therefrom, the backwashing of the pores including;
measuring a characteristic of the permeable hollow membrane, the characteristic of the permeable hollow membrane being one of membrane permeability, membrane resistance, and an increase in membrane resistance over a filtration cycle;
making a determination of a gas pressure at which to apply backwash gas to the permeate remaining in the filtration system after suspending the filtration process, the determination made responsive to the measured characteristic of the permeable hollow membrane, the gas pressure being one of a high gas pressure below the bubble point of the permeable hollow membrane and a low gas pressure below the bubble point of the permeable hollow membrane, the low gas pressure being lower than the high gas pressure; and
applying the backwash gas at the determined gas pressure to the permeate remaining in the filtration system after suspending the filtration process.
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Abstract
A method of backwashing a membrane filtration system comprising at least one permeable membrane, preferably a hollow fiber membrane, the method comprising the step of applying a pressurized gas at a variable pressure to permeate remaining present in the system when filtration process is stopped or suspended to provide liquid for backwashing pores of the permeable membrane during a backwashing process. Also provided are methods of filtering solids from a liquid suspension using alternating liquid backwash pressures.
642 Citations
16 Claims
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1. A method of filtering solids from a liquid suspension in a filtration system comprising:
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performing a filtration process including providing a pressure differential across a wall of a permeable hollow membrane to induce and sustain filtration through the wall of the permeable hollow membrane; suspending the filtration process; and periodically backwashing pores of the permeable hollow membrane using permeate remaining in the filtration system after suspending the filtration process, the backwashing of the pores dislodging fouling materials therefrom, the backwashing of the pores including; measuring a characteristic of the permeable hollow membrane, the characteristic of the permeable hollow membrane being one of membrane permeability, membrane resistance, and an increase in membrane resistance over a filtration cycle; making a determination of a gas pressure at which to apply backwash gas to the permeate remaining in the filtration system after suspending the filtration process, the determination made responsive to the measured characteristic of the permeable hollow membrane, the gas pressure being one of a high gas pressure below the bubble point of the permeable hollow membrane and a low gas pressure below the bubble point of the permeable hollow membrane, the low gas pressure being lower than the high gas pressure; and applying the backwash gas at the determined gas pressure to the permeate remaining in the filtration system after suspending the filtration process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of filtering solids from a liquid suspension in a filtration system comprising:
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performing a filtration process including providing a pressure differential across a wall of a permeable hollow membrane to induce and sustain filtration through the wall of the permeable hollow membrane; suspending the filtration process; and periodically backwashing pores of the permeable hollow membrane using permeate remaining in the filtration system after suspending the filtration process, the backwashing of the pores including; measuring a net increase in membrane resistance of the permeable hollow membrane over several filtration cycles; making a determination of a gas pressure at which to apply backwash gas to the permeate remaining in the filtration system after suspending the filtration process, the determination made responsive to the measured net increase in membrane resistance of the permeable hollow membrane, the gas pressure being one of a high gas pressure below the bubble point of the permeable hollow membrane and a low gas pressure below the bubble point of the permeable hollow membrane, the low gas pressure being lower than the high gas pressure; and applying the backwash gas at the determined gas pressure to the permeate remaining in the filtration system after suspending the filtration process. - View Dependent Claims (14, 15, 16)
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Specification