METHODS OF CLEANING MEMBRANE MODULES
First Claim
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1. A method of backwashing a membrane filtration system including a vessel, a membrane module, piping, and a manifold comprising:
- filtering a feed liquid through pores in walls of membranes of the membrane filtration system to produce a liquid permeate;
withdrawing the permeate from lumens of the membranes and through the manifold, a portion of the piping, and a valve while filtering the feed liquid;
stopping the filtration process;
to isolating the lumens of the membranes, the manifold, the portion of the piping, and a gas inlet when the filtration process is stopped, the lumens of the membranes, the manifold, and the portion of piping upstream of the valve during filtration, wherein the lumens of the membranes, the manifold, and the portion of piping consist of those through which permeate is withdrawn while filtering the feed liquid;
scouring surfaces of the membranes by flowing bubbles of a first gas past surfaces of the membranes;
supplying a second gas through a second gas inlet at a pressure less than a bubble point of the membranes;
applying the second gas to a portion of liquid permeate present in the isolated lumens, manifold, and portion of piping by introducing the second gas through the second gas inlet into the filtration system on a side of the valve in direct fluid communication with the membrane module;
directing the portion of liquid permeate into the membrane module through a first end of the membrane module and through a second end of the membrane module;
backwashing the membranes by displacing at least some of the portion of liquid permeate through pores in walls of the membranes, the second gas not penetrating into the membrane pores;
discharging backwash waste from the vessel;
refilling the vessel with feed liquid;
venting the second gas from the isolated lumens, manifold, and portion of piping; and
resuming filtration.
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Accused Products
Abstract
A method and apparatus for backwashing a membrane filtration system wherein permeate remaining present in the filtration system wherein permeate remaining present in the filtration system when the filtration process is stopped or suspended is used to provide liquid for backwashing the membrane pores during a backwashing process.
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Citations
14 Claims
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1. A method of backwashing a membrane filtration system including a vessel, a membrane module, piping, and a manifold comprising:
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filtering a feed liquid through pores in walls of membranes of the membrane filtration system to produce a liquid permeate; withdrawing the permeate from lumens of the membranes and through the manifold, a portion of the piping, and a valve while filtering the feed liquid; stopping the filtration process; to isolating the lumens of the membranes, the manifold, the portion of the piping, and a gas inlet when the filtration process is stopped, the lumens of the membranes, the manifold, and the portion of piping upstream of the valve during filtration, wherein the lumens of the membranes, the manifold, and the portion of piping consist of those through which permeate is withdrawn while filtering the feed liquid; scouring surfaces of the membranes by flowing bubbles of a first gas past surfaces of the membranes; supplying a second gas through a second gas inlet at a pressure less than a bubble point of the membranes; applying the second gas to a portion of liquid permeate present in the isolated lumens, manifold, and portion of piping by introducing the second gas through the second gas inlet into the filtration system on a side of the valve in direct fluid communication with the membrane module; directing the portion of liquid permeate into the membrane module through a first end of the membrane module and through a second end of the membrane module; backwashing the membranes by displacing at least some of the portion of liquid permeate through pores in walls of the membranes, the second gas not penetrating into the membrane pores; discharging backwash waste from the vessel; refilling the vessel with feed liquid; venting the second gas from the isolated lumens, manifold, and portion of piping; and resuming filtration. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of filtering solids from a liquid suspension comprising:
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immersing filtration membranes in the liquid suspension; filtering the liquid suspension through pores in walls of the filtration membranes; producing a liquid permeate within lumens of the filtration membranes; drawing off liquid permeate from the lumens; withdrawing the permeate from the lumens and through a manifold and a valve; periodically suspending the filtration process; isolating the lumens, the manifold, a gas inlet, and a portion of piping when the filtration process is suspended, the lumens, the manifold, and the portion of piping upstream of the valve during filtration, wherein the lumens, the manifold, and the portion of piping consist of those through which permeate is withdrawn; directing liquid permeate present in the isolated manifold and portion of piping into the lumens through a first end of the filtration membranes and through a to second end of the filtration membranes; and applying a gas at a pressure below a bubble point of the filtration membranes to the liquid permeate to displace at least some of the liquid permeate through the pores in the walls of the filtration membranes in a direction opposite to that of filtration, the gas not penetrating into the membrane pores. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A method of filtering solids from a liquid suspension comprising:
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applying the liquid suspension to lumens of filtration membranes; filtering the liquid suspension through pores in walls of the filtration membranes; forming liquid permeate on a shell side of a pressure vessel in which the filtration membranes are mounted; drawing off liquid permeate from the shell side of the pressure vessel; periodically suspending the filtration process; and applying a gas at a pressure below a bubble point of the filtration membranes to liquid permeate remaining within the shell side of the pressure vessel, the liquid permeate remaining within the shell side of the pressure vessel consisting of the liquid permeate formed on the shell side of the pressure vessel, to displace at least some of the liquid permeate through the filtration membrane pores in a direction opposite to that of filtration, the gas not penetrating into the membrane pores.
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Specification