# US 10,118,131 B2 · Method for preventing microbial growth on a filtration membrane

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- Number: US 10,118,131 B2
- Document ID: US10118131B2
- Status: Granted
- Kind: B2
- Application number: 14/369,727
- Filed: 2012-12-19
- Published: 2014-12-18
- Granted: 2018-11-06
- Earliest claimed: 2011-12-30
- Applicants: Kemira Oyj
- Inventors: Jussi Salonen; Marko Kolari; Mehrdad Hesampour; Kaj Jansson
- Web page: https://patentgrep.com/patent/US10118131B2

## CPC

- B01D 65/08: Prevention of membrane fouling or of concentration polarisation
- B01D 61/025: {Reverse osmosis; Hyperfiltration}
- B01D 61/04: Feed pretreatment
- C02F 1/441: {by reverse osmosis}
- B01D 2321/162: Use of acids
- C02F 2303/16: Regeneration of sorbents, filters
- Y02A 20/131: Reverse-osmosis
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## Abstract

The present invention relates to a method for preventing microbial growth on a filtration membrane during desalination process. The method comprises that the membrane is exposed to a low concentration of performic acid by continuously or intermittently introducing performic acid to the membrane surface. When performic acid is added according to the present invention to the water flow, there is no significant reduction in the water flux through the membrane.

## Claims

### Claim 1

A method for prevention of microbial growth on a filtration membrane in a desalination system during a desalination process of sea water or brackish water, the method consists of exposing the filtration membrane to performic acid by continuously or intermittently introducing 0.4-1 mg/l performic acid to a sea water or a brackish water flow contacting a membrane surface of the filtration membrane at the same time as the desalination system is functioning without interruption, wherein a water flux through the membrane remains greater than 85% of an original water flux throughout the desalination process.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the membrane is exposed to performic acid by continuously introducing performic acid to the sea water or the brackish water flow contacting the membrane surface for at least 12 hours.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the sea water comprises total dissolved solid from 30 to 50 g/l and the brackish water comprises total dissolved solid from 0.5 to 30 g/l.

### Claim 4

A method for prevention of microbial growth on a filtration membrane in a desalination system during a desalination process of sea water or brackish water, the method consists of exposing the filtration membrane to performic acid by continuously or intermittently introducing 0.4-1 mg/l performic acid to a sea water or a brackish water flow contacting a membrane surface of the filtration membrane at the same time as the desalination system is functioning without interruption, wherein a saline water flux through the membrane remains greater than 85% of an original water flux throughout the desalination process, and wherein performic acid does not damage the filtration membrane.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the membrane is exposed to performic acid by continuously introducing performic acid to the sea water or the brackish water flow contacting the membrane surface for at least 12 hours.

### Claim 6 (depends on 4)

The method according to claim 4, wherein the sea water comprises total dissolved solid from 30 to 50 g/l and the brackish water comprises total dissolved solid from 0.5 to 30 g/l.

### Claim 7 (depends on 1)

The method of claim 1, wherein the desalination process is not interrupted for filtration membrane cleaning.