Prevention of biofouling of reverse osmosis membranes

• US 4,988,444 A
• Filed: 05/12/1989
• Issued: 01/29/1991
• Est. Priority Date: 05/12/1989
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Winters, Harvey, Erkenbrecher, Carl W. Jr., Applegate, Lynn E.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Shideler, Krisanne
• Application Number:
  US07/351,238
• Time in Patent Office: 627 Days
• Field of Search: 210/636, 210/639, 210/764, 210/754, 210/756, 210/757, 210/653, 422/28, 422/29, 422/37
• US Class Current: 210/636
• CPC Class Codes: A61L 2/18 Liquid substances or solutions comprising solids or dissolved gases
• CPC Class Codes: B01D 2311/04 Specific process operations in the feed stream; Feed pretreatment
• CPC Class Codes: B01D 2311/12 Addition of chemical agents
• CPC Class Codes: B01D 2321/168 Use of other chemical agents
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 61/04 Feed pretreatment
• CPC Class Codes: B01D 65/022 Membrane sterilisation
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/76 with halogens or compounds of halogens C02F1/4674 takes precedence
• CPC Class Codes: C02F 2303/185 The treatment agent being halogen or a halogenated compound
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

An improved process is disclosed for killing and inhibiting growth and reproduction (aftergrowth) of microorganisms comprising adding sufficient chloramine to kill the microorganisms without oxidizing high molecular weight organics, which are not easily assimilated by organisms that survive, into lower molecular weight ones, which are easily assimilated.

Claims

1. A process for preventing aftergrowth of microorganisms and the biofouling of equipment which equipment is adversely affected by chlorine, the equipment being fed by a liquid process feed stream containing chlorine degradable organic material that, when in degraded form, provides an energy/carbon food source that is assimilable by microorganisms and that, in the absence of chlorine, enables microorganisms to grow and reproduce comprising adding into the process feed stream an amount of a chloramine sufficient to kill at least 99 percent of microorganisms present and then dechloraminating prior to the process stream'"'"'s entering the equipment.

2. The process of claim 1 wherein the chloramine is made in situ by injecting NH₃ and chlorine in a means that produces chloramine before the chlorine degradable organic material is sufficiently degraded to provide an energy/carbon food source that is assimilable by any surviving microorganisms and that enables the surviving microorganisms to grow and reproduce after dechlorination.

3. The process of claim 1 wherein the amount of chloramine is an amount sufficient to kill at least 99 percent of the microorganisms present in the liquid process stream.

4. In the process for continuously purifying a liquid process stream by passing it through at least one reverse osmosis module comprising a core member having a semipermeable membrane positioned in a manner whereby the liquid permeates through the membrane producing flows of permeate and concentrate, the improvement which comprises inhibiting the growth of microorganisms in said liquid process stream and on the membrane by continuously adding into the process stream an amount of a chloramine sufficient to kill at least 99 percent of the microorganisms in the stream followed by adding sufficient reducing agent to dechloraminate prior to the process stream'"'"'s entering the reverse osmosis module.

5. The process of claim 4 wherein the chloramine is made in situ by injecting NH₃ and chlorine in a means that produces chloramine before the chlorine degradable organic material is sufficiently degraded to provide an energy/carbon food source that is assimilable by any surviving microorganisms and that enables the surviving microorganisms to grow and reproduce after dechlorination.

6. The process of claim 4 wherein the membrane is a polyamide membrane.