Wastewater treatment method comprising decantation and fine screening stages

• US 7,981,297 B2
• Filed: 11/02/2006
• Issued: 07/19/2011
• Est. Priority Date: 11/14/2005
• Status: Active Grant

• Current Assignee: Veolia Water Solutions & Technologies Support
• Original Assignee: OTV SA SA
• Inventors: Dahl, Claus Poulsen, Sauvignet, Philippe
• Primary Examiner(s): Hruskoci; Peter A
• Application Number:
  US12/093,524
• Publication Number:
  US 20080296228A1
• Time in Patent Office: 1,720 Days
• Field of Search: 210/665
• US Class Current: 210/666
• CPC Class Codes: B01D 21/0012 Settling tanks making use of filters, e.g. by floating layers of particulate material
• CPC Class Codes: B03D 3/02 Coagulation
• CPC Class Codes: B03D 3/06 Flocculation
• CPC Class Codes: C02F 1/004 using large scale industrial sized filters
• CPC Class Codes: C02F 1/28 by sorption using ion-exchange C02F1/42; sorbent compositions B01J
• CPC Class Codes: C02F 1/32 with ultraviolet light
• CPC Class Codes: C02F 1/44 by dialysis, osmosis or reverse osmosis general membrane separation processes B01D61/00, membrane modules B01D63/00, electrodialysis C02F1/4693, combination of membrane modules and bioreactors C02F3/1268
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 2209/40 Liquid flow rate
• CPC Class Codes: C02F 2303/04 Disinfection
• CPC Class Codes: C02F 2303/24 Separation of coarse particles, e.g. by using sieves or screens
• CPC Class Codes: C02F 2305/12 Inert solids used as ballast for improving sedimentation C02F3/1226 takes precedence

Abstract

A method for removing helminth egg and other suspended solids from a wastewater stream includes directing the wastewater to a ballasted flocculation system and adding a coagulation agent, flocculation agent and a ballast into the wastewater. Sludge is settled from the wastewater in a settling tank at a rate of at least 10 meters per hour. The method further includes removing helminth egg by filtering the effluent through a fine screen having a mesh diameter of approximately 5 micrometers to approximately 25 micrometers. After passing through the fine screen, the filtered effluent has less than one helminth egg per liter.

Claims

1. A method for removing helminth egg and other suspended solids from a wastewater stream, the method comprising:

directing the wastewater to a ballasted flocculation system and adding a ballast, a coagulation agent and a flocculation agent into the wastewater to form sludge in the wastewater;

settling the sludge in the wastewater in a settling tank at a rate of at least 10 meters per hour and producing an effluent; and

removing helminth egg from the effluent by filtering the effluent through a fine screen having a mesh diameter of approximately 8 micrometers to approximately 12 micrometers, such that the filtered effluent has less than 1 helminth egg per liter.

2. The method of claim 1 further comprising:

settling the sludge in the wastewater in the settling tank at a rate of at least 20 meters per hour;

the effluent through a fine screen having a mesh diameter of approximately 8 micrometers to approximately 12 micrometers;

removing suspended solids from the effluent by adding activated carbon in granular form, activated carbon in powder form or ion exchange resin to the effluent upstream from the fine screen; and

disinfecting the effluent by adding an oxidizing reagent to the effluent downstream from the settling tank, but upstream from the fine screen, wherein the oxidizing reagent comprises chlorine, sodium hypochlorite, chlorine dioxide or ozone.

3. The method of claim 2 further including further disinfecting the effluent with UV radiation, chlorination or ozonation downstream from the fine screen.

4. The method of claim 1 further comprising:

settling the sludge in the wastewater in the settling tank at a rate of at least 20 meters per hour;

the effluent through a fine screen having a mesh diameter of approximately 8 micrometers to approximately 12 micrometers;

removing suspended solids from the effluent by adding activated carbon in granular form, activated carbon in powder form or ion exchange resin to the effluent upstream from the fine screen; and

disinfecting the effluent with UV with radiation, chlorination or ozonation downstream from the settling tank, but upstream from the fine screen.

5. A method of treating water having helminth egg and other suspended solids, the method comprising:

directing water into a settling tank and settling the suspended solids in the water at a rate of at least 10 meters per hour and producing an effluent; and

downstream from the settling tank, filtering the effluent through a fine screen having a mesh diameter of approximately 8 micrometers to approximately 12 micrometers.

6. The method of claim 5 further comprising settling the sludge in the wastewater in the settling tank at a rate of at least 20 meters per hour.

7. The method of claim 5 further comprising treating the effluent by adding activated carbon in granular form, activated carbon in powder form or ion exchange resin to the effluent and adding an oxidizing reagent into the effluent upstream from the fine screen, wherein the oxidizing reagent comprises chlorine, sodium hypochlorite, chlorine dioxide or ozone.

8. The method of claim 7 further including disinfecting the effluent with UV radiation, chlorination or ozonation downstream from the fine screen.