Patent US3850797A successfully refreshed from Google Patents.
US3850797A
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Method of sterilizing reverse osmosis water treatment units
Assignee: Culligan International Co
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Filing: 1973-06-12
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Granted: 1974-11-26
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Expires: 1993-06-12
Abstract
Abstract The semi-permeable membrane of a reverse osmosis water treatment unit is treated during periods of ''''down time'''' with a solution having a pH preferably in the range of 4.5 and 6.0 and tending both to sterilize the membrane as well as to retard bacterial and fungal growth thereon. The method comprises: passing an aqueous solution of the desired pH and containing formaldehyde and an acid selected from the group consisting of acetic, formic, citric, fumaric and boric, into the water treatment unit and through the membrane thereof and maintaining said aqueous solution in the unit and in contact with the membrane during extended periods of unit ''''down time'''' to both sterilize the unit and extend the life of its membrane.
Inventors
- 👤 C Lyall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:23
CPC Classifications
B; B01; B01D; B01D65/00; B01D65/02; C; C02; C02F; C02F1/00; C02F1/50; B01D2321/00; B01D2321/16; B01D61/00; B01D61/02; B01D61/025
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
90 words
A METHOD OF TREATING A SEMI-PERMEABLE MEMBRANE IN A REVERSE OSMOSIS UNIT HAVING AN ACTIVATED PERIOD AND A DOWNTIME PERIOD TO STERILIZE SAID MEMBRANE AND EXTEND ITS USEFUL LIFE, WHICH COMPRISES: IMMERSING SAID MEMBRANE IN AN AQUEOUS SOLUTION HAVING A PH IN THE RANGE OF 4.5 TO 6, SAID SOLUTION COMPRISING A MIXTURE OF WATER, ACETIC ACID AND A BACTERIAL FUNGAL GROWTH INHIBITOR COMPATIBLE WITH SAID ACID; AND MAINTAINING SAID SOLUTION IN CONTACT WITH SAID MEMBRANE FOR AT LEAST A PORTION OF SAID DOWN-TIME PERIOD OF THE REVERSE OSMOSIS UNIT.
Claim 2
Independent Claim
90 words
A METHOD OF TREATING A SEMI-PERMEABLE MEMBRANE IN A REVERSE OSMOSIS UNIT HAVING AN ACTIVATED PERIOD AND A DOWNTIME PERIOD TO STERILIZE SAID MEMBRANE AND EXTEND ITS USEFUL LIFE, WHICH COMPRISES: IMMERSING SAID MEMBRANE IN AN AQUEOUS SOLUTION HAVING A PH IN THE RANGE OF 4.5 TO 6, SAID SOLUTION COMPRISING A MIXTURE OF WATER, ACETIC ACID AND A BACTERIAL FUNGAL GROWTH INHIBITOR COMPATIBLE WITH SAID ACID; AND MAINTAINING SAID SOLUTION IN CONTACT WITH SAID MEMBRANE FOR AT LEAST A PORTION OF SAID DOWN-TIME PERIOD OF THE REVERSE OSMOSIS UNIT.
Claim 3
Dependent Claim
15 words
A method according to claim 1, wherein said bacterial and fungal growth inhibitor is formaldehyde.
Claim 4
Dependent Claim
37 words
A method according to claim 2, wherein said aqueous solution contains acid in an amount between about 6 and 14 grains per gallon of solution and between about 0.5 and about 2.0 percent by weight of formaldehyde.
Claim 5
Dependent Claim
20 words
A method according to claim 1, wherein the pH of said aqueous solution is between about 5.0 and about 5.5.
Claim 6
Dependent Claim
32 words
A method according to claim 1, wherein said aqueous solution is maintained in said unit and in contact with said membrane for a period of between about 2 and about 5 hours.
Claim 7
Independent Claim
102 words
A method of treating a semi-permeable membrane in a reverse osmosis unit having an activated period and a down-time period to sterilize said membrane and extend its useful life, which comprises: immersing said membrane in an aqueous solution having a pH in the range of 4.5 to 6, said solution comprising a mixture of water, acetic acid in the amount of about 10 grains per gallon of solution and a bacterial and fungal growth inhibitor compatible with said acid; and maintaining said solution in contact with said membrane for at least a portion of said down-time period of the reverse osmosis unit.
Claim 8
Independent Claim
102 words
A method of treating a semi-permeable membrane in a reverse osmosis unit having an activated period and a down-time period to sterilize said membrane and extend its useful life, which comprises: immersing said membrane in an aqueous solution having a pH in the range of 4.5 to 6, said solution comprising a mixture of water, acetic acid in the amount of about 10 grains per gallon of solution and a bacterial and fungal growth inhibitor compatible with said acid; and maintaining said solution in contact with said membrane for at least a portion of said down-time period of the reverse osmosis unit.
Claim 9
Independent Claim
99 words
A method of treating a semi-permeable membrane in a reverse osmosis unit having an activated period and a down-time period to sterilize said membrane and extend its useful life, which comprises: immersing said membrane in an aqueous solution having a pH in the range of 4.5 to 6, said solution comprising a mixture of water, acetic acid in the amount of about 10 grains per gallon of solution and about 1 percent by weight of formaldehyde; and maintaining said solution in contact with said membrane for at least a portion of said down-time period of the reverse osmosis unit.
Claim 10
Independent Claim
99 words
A method of treating a semi-permeable membrane in a reverse osmosis unit having an activated period and a down-time period to sterilize said membrane and extend its useful life, which comprises: immersing said membrane in an aqueous solution having a pH in the range of 4.5 to 6, said solution comprising a mixture of water, acetic acid in the amount of about 10 grains per gallon of solution and about 1 percent by weight of formaldehyde; and maintaining said solution in contact with said membrane for at least a portion of said down-time period of the reverse osmosis unit.
References Cited (Backward Citations)
US3700591A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-25 | 1978-05-27 | 1978-11-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-25 | 1982-05-27 | 1982-11-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-25 | 1986-05-27 | 1986-11-26 | $7700.00 | Window Closed / Lapsed |