Method and plant for thickening sludge derived from water treatment by flocculation-decantation with ballasted floc

• US 20050218056A1
• Filed: 05/25/2005
• Published: 10/06/2005
• Est. Priority Date: 02/09/2001
• Status: Active Grant

• Current Assignee: OTV S.A.
• Original Assignee: OTV S.A.
• Inventors: Binot, Patrick
• Granted Patent: US 7,083,715 B2
• Time in Patent Office: Days
• US Class Current: 210/207
• CPC Class Codes: B01D 21/0039 Settling tanks provided with contact surfaces, e.g. baffles, particles
• CPC Class Codes: B01D 21/0045 Plurality of essentially parallel plates
• CPC Class Codes: B01D 21/01 using flocculating agents for purifying water C02F1/52; for liquid radioactive waste G21F9/10
• CPC Class Codes: B01D 21/08 provided with flocculating compartments
• CPC Class Codes: B01D 21/2427 The feed or discharge opening located at a distant position from the side walls
• CPC Class Codes: B01D 21/2488 bringing about a partial recirculation of the liquid, e.g. for introducing chemical aids
• CPC Class Codes: B01D 21/2494 provided with means for the removal of gas, e.g. noxious gas, air
• CPC Class Codes: B01D 21/34 Controlling the feed distribution; Controlling the liquid level ; Control of process parameters
• CPC Class Codes: C02F 1/20 by degassing, i.e. liberation of dissolved gases degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D
• CPC Class Codes: C02F 1/38 by centrifugal separation
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 1/5281 Installations for water purification using chemical agents
• CPC Class Codes: C02F 11/147 using organic substances C02F11/148 takes precedence
• CPC Class Codes: C02F 2001/007 Processes including a sedimentation step
• CPC Class Codes: C02F 2103/001 Runoff or storm water
• CPC Class Codes: C02F 2305/12 Inert solids used as ballast for improving sedimentation C02F3/1226 takes precedence

Abstract

A method is provided for thickening sludge produced through a ballasted flocculation process. The sludge and granular material from the ballasted flocculation process are directed to a sludge separator where the sludge is separated from the granular material. Thereafter the separated sludge is sent to a degassing area and the sludge is degassed. A flocculating agent is mixed or injected into the sludge. The sludge is directed to a sludge thickener with a load at a sill calculated on the surface of the thickener greater than 200 kgMIS/m²/day. This process produces a thickened sludge having a concentration greater than 10 gm/l.

Claims

1. A lamellar sludge thickening system for thickening sludge produced from at least one wastewater or water treatment unit by the decantation flocculation with floc ballasted with micro-sand or other granular material, comprising:

at least one degassing zone having a minimum surface corresponding to a degassing speed of 100 m/hr relative to the flow rate of an entering sludge;

a flocculation zone adapted to enable at least one flocculation agent to be mixed with the sludge to be thickened;

at least one sludge thickener settler including a lamellar decantation zone including a series of plates, a thickening zone disposed under the plates, an extraction device associated with the thickener settler for extracting thickened sludge, and a clarified water zone above the plates, and wherein the surface at the sill of said thickener is less than that obtained by dividing the flow of the matter in suspension to be thickened expressed in kg MIS/day by a minimum admissible load of 200 kgMIS/m²/day.

2. The sludge thickening system of claim 1 including a coagulating zone disposed upstream of the flocculating zone.

3. The sludge thickening system of claim 1 wherein the maximum total surface of the degassing zone corresponds to a degassing speed of 60 m/hr relative to the flow rate of entering sludge.

4. The sludge thickening system of claim 1 wherein the flocculation zone includes an agitation tank.

5. The sludge thickening system of claim 1 wherein the plates are of a length of approximately 0.5 to 3 meters and are spaced apart approximately 5 to 15 cm;

and wherein the plates are disposed at an angle relative to a horizontal reference line of approximately 55; and

wherein the thickener settler includes a sludge raking device and at least one sensor for monitoring the height of the sludge blanket within the thickener settler.

6. The sludge thickening system of claim 1 including a recirculation loop extending between the thickener settler and the flocculation zone.