LOW PRESSURE BACKWASH
First Claim
1. A method of backwashing a membrane filtration system comprising at least one permeable hollow membrane, the method comprising the step of applying a low-pressure gas to the permeate remaining present in the filtration system when the filtration process is stopped or suspended to provide liquid for backwashing pores of the membrane during a backwashing process, wherein the low-pressure gas is at a pressure in the range of about 30 kPa to about 150 kPa.
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Accused Products
Abstract
A method of backwashing a membrane filtration system comprising at least one permeable hollow membrane, the method comprising the step of applying a low-pressure gas to the permeate remaining present in the system when the filtration process is stopped or suspended to provide liquid for backwashing the pores of the membrane during a backwashing process.
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Citations
25 Claims
- 1. A method of backwashing a membrane filtration system comprising at least one permeable hollow membrane, the method comprising the step of applying a low-pressure gas to the permeate remaining present in the filtration system when the filtration process is stopped or suspended to provide liquid for backwashing pores of the membrane during a backwashing process, wherein the low-pressure gas is at a pressure in the range of about 30 kPa to about 150 kPa.
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3. (canceled)
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5. A method of filtering solids from a liquid suspension comprising:
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(i) providing a pressure differential across the walls of permeable, hollow membranes immersed in the liquid suspension, said liquid suspension being applied to the outer surface of the (porous) permeable hollow membranes to induce and sustain filtration through the membrane walls wherein; (a) some of the liquid suspension passes through the walls of the membranes to be drawn off as permeate from the hollow membrane lumens, and (b) at least some of the solids are retained on or in the hollow membranes or otherwise as suspended solids within the liquid surrounding the membranes, (ii) periodically backwashing the membrane pores using the permeate remaining within the lumens by applying low pressure gas at a pressure below the bubble point of the membrane to said liquid permeate to displace at least some of the liquid permeate within the lumens through the membrane pores resulting in removal of the solids retained on or in the hollow membranes, wherein the low-pressure gas is at a pressure in the range of about 30 kPa to about 150 kPa. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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6. A method of filtering solids from a liquid suspension in a filtration system comprising:
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(i) providing a pressure differential across the walls of permeable, hollow membranes having a liquid suspension applied to the inner surface of the permeable hollow membranes to induce and sustain filtration through the membrane walls wherein; (a) some of the liquid suspension passes through the walls of the membranes to be drawn off as permeate from the outer surface of said membranes, and (b) at least some of the solids are retained on or in the hollow membranes or otherwise as suspended solids within the membranes, (ii) stopping or suspending the filtration process; (iii) periodically backwashing the membrane pores using the permeate remaining in the system after the suspension of the filtration process by applying a low pressure gas at a pressure below the bubble point of the membrane to said liquid permeate to displace at least some of the liquid permeate through the membrane pores resulting in removal of the solids retained on or in the hollow membranes wherein the low-pressure gas is at a pressure in the range of about 30 kPa to about 150 kPa.
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13. A filtration system for removing fine solids from a liquid suspension comprising:
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(i) a vessel for containing said liquid suspension; (ii) a plurality of permeable, hollow membranes within the vessel; (iii) means for providing a pressure differential across walls of said membranes such that some of the liquid suspension passes through the walls of the membranes to be drawn off as permeate; (iv) means for withdrawing permeate from the membranes; and (v) means for applying low pressure gas at a pressure below the bubble point to the liquid permeate within the system and the membrane lumens to cause a discharge of at least some of the liquid permeate in the lumens through the membrane walls to dislodge any solids retained therein and displace the removed solids into the liquid suspension surrounding the membranes, wherein the low-pressure gas is at a pressure in the range of about 30 kPa to about 150 kPa. - View Dependent Claims (14, 15, 16, 17, 20, 21)
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18-19. -19. (canceled)
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22. A method of backwashing a membrane filtration system comprising at least one permeable hollow membrane, the method comprising the step of applying a low-pressure gas to the permeate remaining present in the filtration system when the filtration process is stopped or suspended to provide liquid for backwashing pores of the membrane during a backwashing process, wherein the low-pressure gas is provided by one or more gas pressure pulses.
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23. A method of filtering solids from a liquid suspension comprising:
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(i) providing a pressure differential across the walls of permeable, hollow membranes immersed in the liquid suspension, said liquid suspension being applied to the outer surface of the permeable hollow membranes to induce and sustain filtration through the membrane walls wherein; (a) some of the liquid suspension passes through the walls of the membranes to be drawn off as permeate from the hollow membrane lumens, and (b) at least some of the solids are retained on or in the hollow membranes or otherwise as suspended solids within the liquid surrounding the membranes, (ii) periodically backwashing the membrane pores using the permeate remaining within the lumens by applying low pressure gas at a pressure below the bubble point of the membrane to said liquid permeate to displace at least some of the liquid permeate within the lumens through the membrane pores resulting in removal of the solids retained on or in the hollow membranes, wherein the low-pressure gas is provided by one or more gas pressure pulses.
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24. A method of filtering solids from a liquid suspension in a filtration system comprising:
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(i) providing a pressure differential across the walls of permeable, hollow membranes having a liquid suspension applied to the inner surface of the permeable hollow membranes to induce and sustain filtration through the membrane walls wherein; (a) some of the liquid suspension passes through the walls of the membranes to be drawn off as permeate from the outer surface of said membranes, and (b) at least some of the solids are retained on or in the hollow membranes or otherwise as suspended solids within the membranes, (ii) stopping or suspending the filtration process; (iii) periodically backwashing the membrane pores using the permeate remaining in the system after the suspension of the filtration process by applying a low pressure gas at a pressure below the bubble point of the membrane to said liquid permeate to displace at least some of the liquid permeate through the membrane pores resulting in removal of the solids retained on or in the hollow membranes, wherein the low-pressure gas is provided by one or more gas pressure pulses.
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25. A filtration system for removing fine solids from a liquid suspension comprising:
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(i) a vessel for containing said liquid suspension; (ii) a plurality of permeable, hollow membranes within the vessel; (iii) means for providing a pressure differential across walls of said membranes such that some of the liquid suspension passes through the walls of the membranes to be drawn off as permeate; (iv) means for withdrawing permeate from the membranes; and (v) means for applying low pressure gas at a pressure below the bubble point to the liquid permeate within the system and the membrane lumens to cause a discharge of at least some of the liquid permeate in the lumens through the membrane walls to dislodge any solids retained therein and displace the removed solids into the liquid suspension surrounding the membranes, wherein the low-pressure gas is provided by one or more gas pressure pulses.
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Specification