Water Treatment Method Comprising a Rapid Settling Step Followed by a Filtration Step Directly on Micro- or Ultra-filtration Membranes, and Corresponding Device

• US 20080217244A1
• Filed: 09/25/2006
• Published: 09/11/2008
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Veolia Water Solutions & Technologies Support
• Original Assignee: OTV SA SA
• Inventors: Gaid, Abdelkader
• Granted Patent: US 8,419,947 B2
• Time in Patent Office: Days
• US Class Current: 210/636
• CPC Class Codes: B01D 21/0012 Settling tanks making use of filters, e.g. by floating layers of particulate material
• CPC Class Codes: B01D 21/01 using flocculating agents for purifying water C02F1/52; for liquid radioactive waste G21F9/10
• CPC Class Codes: B01D 21/2488 bringing about a partial recirculation of the liquid, e.g. for introducing chemical aids
• CPC Class Codes: B01D 2311/04 Specific process operations in the feed stream; Feed pretreatment
• CPC Class Codes: B01D 2311/12 Addition of chemical agents
• CPC Class Codes: B01D 2311/2642 Aggregation, sedimentation, flocculation, precipitation or coagulation
• CPC Class Codes: B01D 2321/16 Use of chemical agents
• CPC Class Codes: B01D 61/025 Reverse osmosis; Hyperfiltration
• CPC Class Codes: B01D 61/027 Nanofiltration
• CPC Class Codes: B01D 61/145 Ultrafiltration
• CPC Class Codes: B01D 61/147 Microfiltration
• CPC Class Codes: B01D 61/16 Feed pretreatment
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: C02F 1/24 by flotation C02F1/465 takes precedence
• CPC Class Codes: C02F 1/32 with ultraviolet light
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 1/5236 using inorganic agents
• CPC Class Codes: C02F 1/56 Macromolecular compounds
• CPC Class Codes: C02F 1/722 Oxidation by peroxides
• CPC Class Codes: C02F 1/76 : with halogens or compounds of halogens C02F1/4674 takes precedence
• CPC Class Codes: C02F 1/78 : with ozone C02F1/4672 takes precedence
• CPC Class Codes: C02F 2001/007 : Processes including a sedimentation step
• CPC Class Codes: C02F 2305/12 : Inert solids used as ballast for improving sedimentation C02F3/1226 takes precedence
• CPC Class Codes: Y02A 20/131 : Reverse-osmosis

Abstract

A method for treating water includes directing the water to a ballasted flocculation system and mixing a coagulant, flocculant and a ballast with the water. Solids are separated from a clarified effluent at a speed greater than 15 m/h. The method further includes filtering the clarified effluent with one or more microfiltration membranes or ultrafiltration membranes to produce filtered water. Thereafter directing the filtered water to an RO unit or a nanofiltration membrane or membranes and subjecting the filtered water to filtration by the RO unit or the nanofiltration membrane or membranes.

Claims

1-22. -22. (canceled)

23. A method of treating water, comprising:

directing the water to a ballasted flocculation system;

mixing a coagulant with the water;

mixing a flocculent with the water;

adding a ballast to the water;

mixing the ballast with the water and wherein the ballast forms floc in the water;

forming a liquid-solid separation at a speed greater than 15 m/h where the floc settle in a settling tank and an effluent liquid is produced;

filtering the effluent liquid with one or more micro filtration membranes or ultra filtration membranes and producing filtered water; and

directing the filtered water to an RO unit or a nano filtration membrane and subjecting the filtered water to filtration by the RO unit or the nano filtration membrane.

24. The method of claim 23 wherein the ballast is sand.

25. The method of claim 23 wherein the floc form sludge and wherein the sludge is recycled and mixed with the water to be treated by the ballasted flocculation system.

26. The method of claim 23 including declogging the micro or ultra filtration membranes and producing declogging water and recycling the declogging water to a point upstream from where the liquid-solid separation occurs.

27. The method of claim 23 including injecting at least one oxidizing reagent into the water at a point between the liquid-solid separation and the filtration that occurs because of the micro or ultra filtration modules.

28. The method of claim 27 including selecting the oxidizing reagent from the group including ozone, chlorinated oxidants, and hydrogen peroxide.

29. The method of claim 23 including exposing the water to ultraviolet (UV) energy at a point between the liquid-solid separation and where the liquid effluent is filtered by the micro or ultra filtration membranes.

30. The method of claim 23 including injecting active carbon powder into the water downstream from the liquid-solid separation and upstream from the filtration by the micro or ultra filtration membranes.

31. The method of claim 23 wherein the filtered water includes a silt density index no greater than 4.

32. A water treatment system for treating water, comprising:

a ballasted flocculation system including a settling tank and a flocculation tank and including an injection site for injecting a coagulant and a ballast into the water;

the settling tank configured to operate at a speed greater than 15 m/h;

a first membrane filtration device located downstream of the ballasted flocculation system, the first membrane filtration device including one or more micro filtration membranes or one or more ultra filtration membranes for filtering a liquid effluent produced by the ballasted flocculation system, and wherein the micro filtration membranes or ultra filtration membranes produce filtered water; and

a second membrane filtration device located downstream from the first membrane filtration device for filtering the filtered water produced by the first membrane filtration device, the second membrane filtration device including one or more RO filtration units or one or more ultra filtration membranes.

33. The water treatment system of claim 32 wherein the settling tank includes a sludge outlet and wherein there is provided a recirculation path that connects the sludge outlet and which recycles sludge to a point upstream from the settling tank.

34. The water treatment system of claim 32 including at least one flotation tank associated with at least one micro bubble production device.

35. The water treatment system of claim 32 including an injector associated with the first membrane filtration device or the second membrane filtration device for injecting declogging water for declogging the membrane or membranes of the first or second membrane filtration device.

36. The water treatment system of claim 35 including a recirculation line for recirculating the declogging water to a point upstream of the settling tank of the ballasted flocculation system.

37. The water treatment system of claim 32 including an oxidation reactor disposed downstream from the ballasted flocculation system and upstream of the first membrane filtration device for oxidizing the effluent produced by the ballasted flocculation system.

38. The water treatment system of claim 32 including an ultraviolet (UV) reactor disposed downstream of the ballasted flocculation system and upstream from the first membrane filtration device for exposing the effluent produced by the ballasted flocculation system to ultraviolet energy.