GB1573429A - Treatment of effluents - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE TREATMENT OF EFFLUENTS (71) We, SIMON-HARTLEY LIM ITED, a British Company, of Etruria Works, Stoke-on Trent, Staffordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns the treatment of effluents.

A commonly practised step in the treatment of both sewage and industrial effluent is the well-known activated sludge process wherein the effluent material is aerated in the presence of bacteria, which destroy various impurities by their metabolic processes.

It is known that the surfaces of the live bacteria cells in activated sludge have a covering of polymeric materials such as, for example, mucopolysaccharide. These materials are produced by the cells and may have varying properties including, for example, molecular weights, depending upon the environment in which the cells develop.

The present invention is based upon an appreciation of the possibility of using these naturally formed polymeric materials as a flocculating agent in the treatment of the effluent material.

According to the present invention there is provided a method of treating effluent material comprising the steps of collecting polymeric materials from the surfaces of the cells of the bacteria population in activated sludge by subjecting the sludge to shear forces, allowing the bio-mass to settle and decanting the supernatant liquid which contains the polymeric material in suspension and adding same to the effluent material as a flocculating agent.

The invention will be further apparent from the following description with reference to the single figure of the accompanying drawing which shows, by way of example only, a flow diagram for the treatment of municipal sewage effluent by a process incorporating both aspects of the invention.

Referring now to the drawing, it will be seen that raw sewage, after screening and grit removal, is passed through a line 10 to a primary sedimentation tank 11. The effluent from the primary sedimentation tank 11 is passed through a line 12 to an aeration tank 13 equipped with a rotary surface aerator for practising the well-known activated sludge treatment process. The effluent from the tank 13 is passed to a secondary sedimentation tank 15. The final effluent flows from the tank 15 through a line 16 for discharge. In known manner a portion of the sludge collected from the tank 15 is returned to the aeration tank 13 via a line 17. The remainder of the sludge is passed through a line 18 two a plant for separating the polymeric material from the surfaces of the live bacteria cells contained within the sludge. This is achieved by subjecting the sludge to high shear forces by passing it under high pressure through extremely fine nozzles in the apparatus at 19 This causes separation of the polymeric material from the cell surfaces and the biomass is allowed to settle out in a tank 20. The bio-mass from the tank 20 is passed through a line 21 to conventional sludge digesting or de-watering plant as required. The supernatant liquor containing the polymeric material in suspension is drawn from the tank 20 via line 22 and may be fixed to mix with the incoming raw sludge as a flocculating agent to assist primary sedimentation. Alternatively or additionally - the supernatant liquor may be mixed by line 23 with the liquid passing from the aeration tank 13 to the secondary sedimentation tank 15 again as a flocculating aid.

Alternatively or additionally a portion of the supernatant liquor may be led off through line 24 and used as a flocculating agent in other processes, such as certain tertiary treatment processes for example.

If desired the supernatant liquor from the vessel 20 may be filtered so that the polymeric material is collected in solid form.

It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible without departing from the scope thereof.

WHAT WE CLAIM IS:- 1. A method of treating effluent material comprising the steps of collecting polymeric materials from the surfaces of the cells of the bacteria population in activated sludge by subjecting the sludge to shear forces, allowing the bio-mass to settle and decanting the supernatant liquid which contains the polymeric material in suspension and adding same to the effluent material as a flocculating agent.

2. A method according to claim 1, wherein the polymeric material is added to raw sewage as a flocculating agent to assist primary sedimentation.

3. A method according to claim 1, wherein the polymeric material is added to effluent liquor after treatment thereof by the activated sludge treatment process as a flocculating agent to assist secondary sedimentation.

4. A method according to claim 1, wherein the polymeric material is used as a flocculating agent in the tertiary treatment of effluent material.

5. A method according to any preceding claim wherein the activated sludge is subjected to shear forces by passing same under pressure through nozzles.

6. A method according to any preceding claim wherein the decanted supernatant liquid is filtered to collect the polymeric material in solid form.

7. A method of treating effluent material substantially as described herein with reference to and as illustrated by the single figure of the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. occur to one skilled in the art, being possible without departing from the scope thereof. WHAT WE CLAIM IS:-

1. A method of treating effluent material comprising the steps of collecting polymeric materials from the surfaces of the cells of the bacteria population in activated sludge by subjecting the sludge to shear forces, allowing the bio-mass to settle and decanting the supernatant liquid which contains the polymeric material in suspension and adding same to the effluent material as a flocculating agent.

2. A method according to claim 1, wherein the polymeric material is added to raw sewage as a flocculating agent to assist primary sedimentation.

3. A method according to claim 1, wherein the polymeric material is added to effluent liquor after treatment thereof by the activated sludge treatment process as a flocculating agent to assist secondary sedimentation.

4. A method according to claim 1, wherein the polymeric material is used as a flocculating agent in the tertiary treatment of effluent material.

5. A method according to any preceding claim wherein the activated sludge is subjected to shear forces by passing same under pressure through nozzles.

6. A method according to any preceding claim wherein the decanted supernatant liquid is filtered to collect the polymeric material in solid form.

7. A method of treating effluent material substantially as described herein with reference to and as illustrated by the single figure of the accompanying drawing.