Portable reverse osmosis unit for producing drinking water

• US 6,120,688 A
• Filed: 02/09/1998
• Issued: 09/19/2000
• Est. Priority Date: 02/25/1997
• Status: Expired due to Term

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Environmental Incorporated
• Inventors: Hauschild, Martin J., Daly, Frederick J., Behmann, Henry, Deutschmann, Ake
• Primary Examiner(s): FORTUNA, ANA M
• Application Number:
  US09/020,726
• Time in Patent Office: 953 Days
• Field of Search: 210/636, 210/650, 210/195.2, 210/257.2, 210/333.1, 210/333.01, 210/805, 210/85, 210/89, 210/106, 210/100, 210/108, 210/321.69
• US Class Current: 210/650
• CPC Class Codes: B01D 2311/04 Specific process operations in the feed stream; Feed pretreatment
• CPC Class Codes: B01D 2311/16 Flow or flux control
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/2066 Pulsated flow
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 61/04 Feed pretreatment
• CPC Class Codes: B01D 61/147 Microfiltration
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 2103/08 Seawater, e.g. for desalination
• CPC Class Codes: Y02A 20/131 Reverse-osmosis

Abstract

A method of purifying impure water to provide drinking water using an apparatus, the method comprising the steps of providing a microfiltration unit, a reverse osmosis unit and a CIP (clean-in-place) tank containing retentate interconnected to permit backflushing the microfiltration filter with retentate and continued or uninterrupted operation of the reverse osmosis unit by directing retentate thereto.

Claims

1. A method of purifying impure water to provide drinking water, the method comprising the step of:

(a) providing a microfiltration unit in fluid communication with an impure water source and with an air source, the microfiltration unit comprised of;

(i) a tank for containing said impure water;

(ii) a microfiltration membrane positioned in said tank to filter said impure water to provide a concentrate, the microfiltration membrane comprised of an array of hollow tubular membranes having an inside surface and an outside surface;

(iii) an air diffuser located in said tank for diffusing air past said tubular membranes for inducing water movement around said tubular membranes;

(b) directing water from said impure water source into said tank;

(c) drawing filtered water through said tubular membranes to provide purified water and simultaneously therewith rejecting impurities to provide said concentrate;

(d) permitting excess concentrate to flow from said tank;

(e) pumping said purified water to a high pressure side of a reverse osmosis module wherein water is permeated through a membrane to a low pressure side of said reverse osmosis module to provide said drinking water and wherein impurities are concentrated in said high pressure side to provide a retentate;

(f) returning retentate from the high pressure side of said reverse osmosis module to a CIP (clean-in-place) container;

(g) periodically backflushing said hollow tubular membranes with said retentate from said CIP container, said retentate directed to the inside surfaces of said membranes to dislodge foulants from the outside surfaces of said membranes; and

(h) continuing production of drinking water during said backflushing by directing flow of retentate to the high pressure side of said reverse osmosis module and recovering drinking water on said low pressure side.

2. The method in accordance with claim 1 including providing said hollow tubular membrane in a pore size in the range of 0.05 to 1.2 μ

m.

3. The method in accordance with claim 1 including the step of pumping said impure water into said container.

4. The method in accordance with claim 1 including recovering about 20 to 80% of said impure water as purified water.

5. The method in accordance with claim 1 including the step of backflushing said hollow tubular membranes at least once every two hours.

6. The method in accordance with claim 1 including the step of backflushing said hollow tubular membranes at least once every hour.

7. The method in accordance with claim 1 including the step of backflushing said hollow tubular membranes for a period of about 5 to 60 seconds.

8. The method in accordance with claim 1 including the step of permitting excess retentate to overflow from said CIP container.

9. A method of purifying impure water to provide drinking water, the method comprising the step of:

(a) providing a microfiltration unit in fluid communication with an impure water source, the microfiltration unit comprised of a microfiltration module positioned in said impure water, the microfiltration membrane comprised of an array of hollow tubular membranes having an inside surface and an outside surface;

(b) drawing filtered water through said tubular membranes to provide purified water and simultaneously therewith rejecting impurities;

(c) pumping said purified water to a high pressure side of a reverse osmosis module wherein water permeate is passed through a membrane to a low pressure side of said reverse osmosis module to provide said drinking water and wherein impurities are concentrated in said high pressure side to provide a retentate;

(d) returning retentate to a CIP (clean-in-place) container;

(e) backflushing said hollow tubular membranes with said retentate at least once every two hours, said retentate directed to the inside surfaces of said membranes to dislodge particles from pores in said membranes;

(f) continuing production of drinking water during said backflushing by directing flow of retentate to the high pressure side of said reverse osmosis module and recovering drinking water on said low pressure side.

10. A method of purifying impure water to provide drinking water using a portable apparatus, the method comprising the step of:

(a) providing a microfiltration unit in fluid communication with an impure water source and with an air source, the microfiltration unit comprised of;

(i) a tank for containing said impure water;

(ii) a microfiltration membrane positioned in said tank to filter said impure water to provide a concentrate, the microfiltration membrane comprised of an array of hydrophilic hollow thydrophilic hollow tubular membranes having an inside surface and an outside surface;

(iii) a diffuser located in said tank for inducing water movement around said tubular membranes;

(b) pumping water from said impure water source into said tank;

(c) drawing filtered water through said tubular membranes to provide purified water and simultaneously therewith reject impurities to provide said concentrate to recover about 20 to 80% of said impure water introduced to said tank;

(d) permitting excess concentrate to overflow from said tank;

(e) directing said purified water to a high pressure side of a reverse osmosis module wherein water permeates through a membrane to a low pressure side of said reverse osmosis module to provide said drinking water and wherein impurities are concentrated in said high pressure side to provide a retentate;

(f) returning said retentate to a CIP (clean-in-place) container;

(g) backflushing said hollow tubular membranes with said retentate from said CIP container at least once every two hours, said backflushing being for a period of 5 to 60 seconds, said retentate directed to the inside surfaces of said membranes to dislodge particles from the surfaces of said membranes;

(h) continuing production of drinking water during said backflushing by directing flow of retentate to the high pressure side of said reverse osmosis module and recovering drinking water on said low pressure side.

11. A system for purifying impure water to provide drinking water, the system comprised of:

(a) a microfiltration unit for fluid communication with an impure water source, the microfiltration unit comprised of;

(i) a tank for containing said impure water;

(ii) a microfiltration membrane positioned in said tank to filter said impure water to provide a concentrate, the microfiltration membrane comprised of an array of hollow tubular membranes having an inside surface and an outside surface;

(iii) an air diffuser located in said tank for diffusing air past said tubular membranes for inducing water movement around said tubular membranes;

(b) an air pump in fluid communication with said diffuser for pumping air thereto;

(c) a first pump for pumping said impure water into said tank;

(d) a second pump for drawing filtered water through said tubular membranes to provide purified water and simultaneously therewith reject impurities to provide said concentrate;

(e) an overflow in said tank for permitting excess concentrate to overflow from said tank;

(f) a reverse osmosis module having a high pressure side and a low pressure side separated by a membrane;

(g) a third pump in fluid communication with said second pump for receiving purified water therefrom and for directing said purified water to said high pressure side of said reverse osmosis module to permeate water therethrough to said low pressure side to provide said drinking water and to concentrate impurities in said high pressure side to provide a retentate; and

(h) a CIP (clean-in-place) container in fluid communication with said high pressure side of said reverse osmosis module for receiving retentate therefrom, said CIP container

(i) in fluid communication with said microfiltration membranes for periodically backflushing said hollow tubular membranes with said retentate directed to the inside surfaces of said membranes to dislodge particles from the outside surfaces of said membranes; and

(ii) in fluid communication with said high pressure side of said reverse osmosis membrane for directing flow of said retentate to the high pressure side of said reverse osmosis module to continue production of drinking water from said retentate during said backflushing.

12. The system in accordance with claim 11 in combination therewith a programmable logic controller for opening second and third solenoid valves and closing a first solenoid valve for directing retentate from said CIP tank to both said reverse osmosis module for continued production of drinking water and to said inside surfaces of said tubular membranes for backflushing and dislodging foulants therefrom.

13. The system in accordance with claim 12 wherein said programmable logic controlled is adapted for closing said second and third solenoid valves and opening said first valve to direct purified water from said microfiltration membrane to said high pressure side of said reverse osmosis module.

14. A system for purifying impure water to provide drinking water, the system comprised of:

(a) a microfiltration unit for fluid communication with an impure water source, the microfiltration unit comprised of;

(i) a tank for containing said impure water;

(ii) a microfiltration membrane positioned in said tank to filter said impure water to provide a concentrate, the microfiltration membrane comprised of an array of hollow tubular membranes having an inside surface and an outside surface;

(iii) an air diffuser located in said tank for diffusing air past said tubular membranes for inducing water movement around said tubular membranes;

(b) an air pump in fluid communication with said diffuser for pumping air thereto;

(c) a first pump for pumping said impure water into said tank;

(d) a second pump for drawing filtered water through said tubular membranes and through a first solenoid valve to provide purified water and simultaneously therewith reject impurities to provide said concentrate;

(e) an overflow in said tank for permitting excess concentrate to overflow from said tank;

(f) a reverse osmosis module having a high pressure side and a low pressure side separated by a membrane;

(g) a third pump in fluid communication with said second pump for receiving purified water therefrom and for directing said purified water to said high pressure side of said reverse osmosis module to permeate water therethrough to said low pressure side to provide said drinking water and to concentrate impurities in said high pressure side to provide a retentate;

(h) a CIP (clean-in-place) container in fluid communication with said high pressure side of said reverse osmosis module for receiving retentate therefrom, said CIP container

(i) in fluid communication through second and third solenoid valves with said microfiltration membranes for periodically backflushing said hollow tubular membranes with said retentate directed to the inside surfaces of said membranes to dislodge particles from the outside surfaces of said membranes; and

(ii) in fluid communication through said second solenoid valve with said high pressure side of said reverse osmosis membrane for directing flow of said retentate to the high pressure side of said reverse osmosis module to continue production of drinking water from said retentate during said backflushing; and

(i) a programmable logic controller for opening said second and third solenoid valves and closing said first valve for directing retentate from said CIP tank to both said reverse osmosis module for continued production of drinking water and to said inside surfaces of said tubular membranes for backflushing to dislodge foulants therefrom.

15. A portable apparatus for purifying impure water to provide drinking water, the apparatus comprised of:

(a) an air pump for pumping air to provide an air source;

(b) a filter for filtering impure water to provide filtered impure water;

(c) a microfiltration unit in fluid communication with said filtered impure water and said air source, the microfiltration unit comprised of;

(i) a tank for containing said filtered impure water;

(ii) a microfiltration membrane positioned in said tank to filter impure water and reject impurities in said filtered impure water to provide a concentrate, the microfiltration membrane comprised of an array of hydrophilic hollow tubular membranes having an inside surface and an outside surface; and

(iii) an air diffuser in fluid communication with said air source, said diffuser located in said tank adapted for diffusing air past said tubular membranes for inducing water movement around said tubular membranes;

(d) a process pump in fluid communication with said hollow fiber membranes for inducing a lower pressure on said inside surface than on said outside surface of said hollow fiber membranes to draw water into said hollow fibers to provide purified water and simultaneously therewith reject impurities to provide said concentrate;

(e) a reverse osmosis module having a high pressure side and a low pressure side, the high pressure side being in fluid communication with said process pump to receive purified water therefrom, said process pump capable of maintaining said water pressure in said high pressure side to produce water permeate on said low pressure side and water retentate on the high pressure side, said reverse osmosis module adapted to deliver water permeate to a water storage tank; and

(f) a CIP (clean-in-place) tank in fluid communication with said high pressure side of said reverse osmosis module adapted to receive water retentate from said reverse osmosis module;

in a backflush mode, said CIP (clean-in-place) tank in fluid communication with said inside surfaces of said hollow tubular membranes to deliver water retentate to said hollow tubular membranes to dislodge particles from outside surfaces thereof;

during said backflush mode, said CIP (clean-in-place) tank adapted to supply water retentate to said reverse osmosis module to permit continued operation of said reverse osmosis module during said backflush mode.

16. The portable apparatus in accordance with claim 15 in combination therewith a programmable logic controller for opening second and third solenoid valves and closing a first solenoid valve for directing retentate from said CIP tank to both said reverse osmosis module for continued production of drinking water and to said inside surfaces of said tubular membranes for backflushing and dislodging foulants therefrom.

17. The portable apparatus in accordance with claim 16 wherein said programmable logic controlled is adapted for closing said second and third solenoid valves and opening said first valve to direct purified water from said microfiltration membrane to said high pressure side of said reverse osmosis module.