Membrane bioreactor, process and aerator

• US 20050061725A1
• Filed: 09/28/2004
• Published: 03/24/2005
• Est. Priority Date: 12/05/2002
• Status: Active Grant

• Current Assignee: Zenon Environmental Incorporated
• Original Assignee: Zenon Environmental Incorporated
• Inventors: Cote, Pierre, Liu, Minggang, Husain, Hidayat, Pottinger, Ian
• Granted Patent: US 7,022,236 B2
• Time in Patent Office: Days
• US Class Current: 210/220
• CPC Class Codes: B01D 2311/2642 Aggregation, sedimentation, flocculation, precipitation or coagulation
• CPC Class Codes: B01D 2313/26 Specific gas distributors or gas intakes
• CPC Class Codes: B01D 2315/06 Submerged-type; Immersion type
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/16 Use of chemical agents
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 2321/40 Automatic control of cleaning processes
• CPC Class Codes: B01D 61/22 Controlling or regulating
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: C02F 2103/002 Grey water, e.g. from clothes washers, showers or dishwashers
• CPC Class Codes: C02F 2103/005 Black water originating from toilets
• CPC Class Codes: C02F 2209/42 Liquid level
• CPC Class Codes: C02F 3/1215 Combinations of activated sludge treatment with precipitation, flocculation, coagulation and separation of phosphates
• CPC Class Codes: C02F 3/1268 Membrane bioreactor systems
• CPC Class Codes: C02F 3/1273 Submerged membrane bioreactors
• 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
• CPC Class Codes: Y10S 210/903 Nitrogenous

Abstract

A reactor has an aerobic tank, an anoxic tank and a sealed membrane tank with conduits for circulating mixed liquor between them. Permeation starts when the mixed liquor reaches a high level and stops when the mixed liquor reaches a low level. A sensor, for detecting the mixed liquor level, may stop and start permeation. Pressure builds in the membrane tank when membrane air is on. Transmembrane pressure is also provided by gravity flow or siphon. Membrane air generates an air lift which drives the mixed liquor circulation. The total amount of air provided by an air source is divided and varied in time between the membrane aerator and the process aerator. The process aerator acts as a screening inlet to the conduit to the membrane tank. Chemical maintenance cleaning is provided by gravity flow.

Claims

1. An apparatus comprising,

a) one or more process tanks or zones for one or more of aerobic digestion, nitrification or denitrification;

b) an immersed membrane tank or zone;

c) a conduit or passage for mixed liquor to flow from the membrane tank or zone to the one or more process tanks or zones;

d) a conduit or passage for mixed liquor to flow from the one or more process tanks or zones to the membrane tank or zone;

e) an inlet for feed to enter into one or more of the tanks or zones;

f) an outlet for permeate to exit the membrane tank or zone; and

,

g) a level sensor for detecting a selected maximum mixed liquor level and a selected minimum mixed liquor level in one of the one or more process tanks or zones.

2. The apparatus of claim 1 wherein the level sensor is operatively connected to devices for one or more of (a) stopping and starting permeation, (b) increasing and decreasing the total air supply provided by an air supply or (c) altering a regime of cyclic aeration.

3. An aerator comprising,

a) an aerator body with holes for releasing bubbles from the aerator body or for allowing mixed liquor surrounding the aerator to enter the aerator body;

b) an inlet for air to enter the aerator body; and

,

c) an outlet for mixed liquor to exit the aerator body.

4. The apparatus of claim 3 wherein the outlet is connected to a mixed liquor conduit for removing mixed liquor from a tank or zone containing the aerator.

5. The apparatus of claim 4 wherein the inlet is connected to an aeration system which provides an airflow sufficient to create bubbles from at least some of the holes at some times and which allows mixed liquor to flow into the holes during at least some times.

7. The aeration system of claim 6 combined with the apparatus of claim 5 wherein the level sensor is operatively connected to the air supply to control when air is provided at the higher rate of flow and the lower rate of flow.

8. The aeration system of claim 7 wherein air is provided at the higher rate of flow whenever the level of mixed liquor is above a high level, the high level related to the need for the higher rate of flow to meet process air requirements.

9. The aeration system of claim 7 wherein air is provided at the higher rate of flow from the time that the mixed liquor reaches a maximum mixed liquor level to the time when the mixed liquor reaches a minimum mixed liquor level.

6. An aeration system comprising,

a) one or more process aerators;

b) one or more membrane aerators;

c) an air supply;

d) a process air line which provides a path for air from the air supply to the one or more process aerators;

e) a membrane air line which provides a path for air from the air supply to the one or more membrane aerators;

wherein the air supply is adapted to provide at least a higher flow rate of air and a lower flow rate of air.

10. The aeration system of claim 6 wherein the process aerator is a fine bubble aerator and the membrane aerator is a coarse bubble aerator.

11. A process of chemical cleaning comprising the step of providing a backwashing flow of a chemical cleaning solution followed by a period in which permeate is not withdrawn.