Supported biofilm process

• US 7,303,677 B2
• Filed: 02/21/2006
• Issued: 12/04/2007
• Est. Priority Date: 02/13/2003
• Status: Expired due to Term

• Current Assignee: Zenon Technology Partnership
• Original Assignee: Zenon Technology Partnership
• Inventors: Cote, Pierre Lucien, Behmann, Henry, Husain, Hidayat
• Primary Examiner(s): Barry; Chester T.
• Application Number:
  US11/357,051
• Publication Number:
  US 20060163157A1
• Time in Patent Office: 651 Days
• Field of Search: 210/615, 210/619
• US Class Current: 210/615
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 63/021 Manufacturing thereof
• CPC Class Codes: B01D 63/022 Encapsulating hollow fibres
• CPC Class Codes: B01D 63/0233 forming the bundle
• CPC Class Codes: B01D 63/034 Lumen open in more than two directions
• CPC Class Codes: B01D 63/04 comprising multiple hollow fibre assemblies
• CPC Class Codes: B01D 69/084 Undulated fibres
• CPC Class Codes: B01F 33/4062 with means for modifying the gas pressure or for supplying gas at different pressures or in different volumes at different parts of the bottom
• CPC Class Codes: C02F 2103/005 Black water originating from toilets
• CPC Class Codes: C02F 2103/008 Originating from marine vessels, ships and boats, e.g. bilge water or ballast water
• CPC Class Codes: C02F 3/102 Permeable membranes
• CPC Class Codes: C02F 3/103 Textile-type packing
• CPC Class Codes: C02F 3/208 Membrane aeration C02F3/201 takes precedence
• CPC Class Codes: C02F 3/30 Aerobic and anaerobic processes
• CPC Class Codes: C02F 3/302 Nitrification and denitrification treatment C02F3/308 takes precedence
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

A membrane supported biofilm reactor uses modules having fine, hollow fibres, for example, made from melt spun thermoplastic polymers treated after spinning to increase their permeability to oxygen, used, for example, in tows or formed into a fabric. In one module, one or more sheets of the fabric are potted into a module to enable oxygen containing gas to be supplied to the lumens of the hollow fibres. Various reactors and processes, for example to treat wastewater, using such modules are described. In one process, oxygen travels through fibers, optionally through an attached biofilm, to oxygenate surrounding water. Mechanical, chemical and biological methods, for example endogenous respiration, are used to control the thickness of the biofilm.

Claims

1. A process for treating a liquid comprising the steps of:

a) contacting an apparatus having a port in communication with one or more inner surfaces of a gas permeable biofilm support medium with the liquid, the medium comprising a membrane having openings of up to about 40 Angstroms in size;

b) providing a gas to the port of the apparatus, the gas permeating to outer surface(s) of the medium to support a biofilm growing on the outer surface(s); and

c) providing air bubbles in the liquid.

2. The process of claim 1 wherein the liquid comprises wastewater.

3. The process of claim 1 wherein the gas comprises oxygen.

4. The process of claim 1 performed in a septic tank or shipboard system or to treat a wastewater taken generally directly from one or more houses or businesses or parts of a ship.

5. The process of claim 1 wherein the biofilm is maintained at a thickness between 0.05 mm and 2 mm, more preferably between 0.1 mm and 1 mm.

7. The process of claim 1 wherein step (b) comprises steps of providing an oxygen bearing gas to the port, the oxygen traveling to the outer surface(s) of the medium and into the liquid.

8. The process of claim 7 further comprising growing a biofilm on the outer surface(s) of the medium, the oxygen traveling through the biofilm and into the substrate.

9. The process of claim 8 further comprising maintaining the biofilm under endogenous respiration.

10. The process of claim 7 wherein the apparatus has an exhaust port, the gas is air, and gases flow through the apparatus from the port to the exhaust port.

11. The process of claim 10 wherein the exhaust gas has a higher concentration or mass flow rate of carbon dioxide than the inlet gas.

12. The process of claim 8 further comprising performing nitrification in the biofilm.

13. The process of claim 7 wherein at least 100 mg/h of oxygen per liter of substrate is transferred.

14. The process of claim 8 wherein the biofilm has a thickness of at least 20 microns.

15. The process of claim 8 wherein the biofilm performs one or more of:

(a) nitrification (removal of ammonia); and

,

(b) removal of COD.

16. The process of claim 8 further comprising maintaining the substrate at a low soluble COD concentration and air scrubbing the biofilm to maintain the biofilm under a certain thickness.

17. The process of claim 1 wherein the air bubbles do one or more of

(a) add additional oxygen to the liquid;

(b) mix the liquid;

or,

(c) maintain bacteria in suspension in the liquid.

18. The process of claim 7 wherein the liquid is water within a suspended growth bioreactor.

19. The process of claim 7 wherein the biofilm support medium comprises hollow fibers made of a melt spun thermoplastic polymer subjected to thermal or mechanical treatment after spinning to have at least an annular region of increased permeability to oxygen without permitting a flow of liquid water through the walls of the fibers from the outer surfaces of the fibers to the lumens.

21. The process of claim 1 wherein the air bubbles in the liquid are sufficiently gentle to leave the biofilm on the outer surface(s) of the medium.

22. The process of claim 1 comprising using the air bubbles in the liquid to maintain biomass in suspension.

23. The process of claim 1 wherein the biofilm support medium comprises a plurality of membranes, each membrane supporting a layer of biofilm thereon, the air bubbles gently mixing the liquid between adjacent layers of biofilm.

6. A process for treating a liquid comprising the steps of:

a) contacting an apparatus having a port in communication with one or more inner surfaces of a gas permeable biofilm support medium with the liquid; and

,

b) providing a gas to the port of the apparatus, the gas permeating to outer surface(s) of the medium to support a biofilm growing on the outer surface(s); and

,

c) maintaining a least a portion of the biofilm so that its thickness alternately increases and decreases, the biofilm increasing in thickness over first periods of time and, between the first periods of time, reducing the thickness of the biofilm.

20. The process of claim 6 wherein the thickness of the biofilm is reduced by providing the air bubbles in the liquid.