Method and system for filtration and filtration cake layer formation

Patent metadata

Field	Value
Publication number	US-10486089-B2
Application number	US-201214009621-A
Country	US
Kind code	B2
Filing date	Mar 27, 2012
Priority date	Apr 5, 2011
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

The present invention relates to a method of filtering a feed and waste water treatment system using the filtration method. The method utilizes a filtration cake for the filtration, which filtration cake is formed by elements contained in a liquid having a different composition than the feed to the filtered. The invention relates in particular to a method for filtering a liquid containing solid particles of different sizes which utilizes a filtration cake formed at least partly and preferably only from particles contained in said liquid containing solid particles of different sizes. The particles of the filtration cake are deposited on a filtration cake support and the method involves separation of the liquid containing solid particles of different sizes into two fractions: one fraction containing solid particles above a certain size and one containing smaller particles, and filtering the fraction containing smaller particles through the filtration cake. According to preferred aspects of the invention, the feed to be filtered is activated sludge supernatant and the filtration cake is formed from floes of an activated sludge mixed liquor.

First claim

The invention claimed is:

1. A method for filtering an untreated waste water liquid or an activated sludge mixed liquor liquid, which contains solid particles of different sizes, comprising:
establishing a filtration cake at least partly from activated sludge flocs contained in said untreated waste water liquid or said activated sludge mixed liquor liquid, wherein said activated sludge flocs are deposited on a filtration cake support being a porous member that allows liquid to flow through the filtration cake so as to provide a filtrate,
separating the untreated waste water liquid or said activated sludge mixed liquor liquid containing solid particles of different sizes into fractions, wherein one fraction contains solid particles above a certain size and one fraction consisting essentially of smaller solid particles, wherein the fraction containing solid particles above a certain size comprises the activated sludge flocs, and,
providing a flow of the fraction consisting essentially of the smaller solid particles towards and through the formed filtration cake in a direction towards and through the cake support, thereby providing a filtering of the fraction consisting essentially of the smaller solid particles.

2. The method according to claim 1 , wherein the filtration cake is made by deposition of particles on the filtration cake support from the untreated waste water liquid or said activated sludge mixed liquor liquid containing solid particles of different sizes.

3. The method according to claim 1 , wherein the filtration cake is made by deposition of particles on the filtration cake support from the fraction of the untreated waste water liquid or said activated sludge mixed liquor liquid containing solid particles of different sizes, which contains solid particles above a certain size.

4. The method according to claim 1 , wherein the untreated waste water liquid or said activated sludge mixed liquor liquid containing solid particles of different sizes is activated sludge mixed liquor and the fraction consisting essentially of the smaller solid particles is activated sludge supernatant.

5. The method according to claim 4 , wherein the activated sludge mixed liquor is activated sludge mixed liquor from a biological waste water treatment process.

6. The method according to claim 4 , wherein the activated sludge supernatant is provided by settling an activated sludge mixed liquor or a biologically treated municipal or industrial waste water present in a system treating municipal or industrial waste water.

7. The method according to claim 4 , wherein the filtration cake is provided by the activated sludge flocs contained in the activated sludge mixed liquor and coagulated substances provided by adding a coagulant to the sludge.

8. The method according to claim 1 , wherein the filtration cake is formed on a backing layer on the cake support, wherein the backing layer comprises a paper or a net, having a pore size that allows filtrate to pass through while allowing build-up of the filtration cake, and wherein the cake is removed together with the backing layer.

9. The method according to claim 1 , further comprising removal of the filtration cake, wherein the removal comprises providing a flow of liquid through the cake support directed towards the filtration cake.

10. The method according to claim 1 , further comprising removal of the filtration cake or residues thereof by: a mechanical action, a chemical action, a flow of air bubbles, a thermal action, or a sonication with ultrasound or by a means for separating the cake from the support.

11. The method according to claim 9 , further comprising returning the removed filtration cake to a process tank containing activated sludge mixed liquor.

12. A method according to claim 1 , wherein establishing the filtration cake comprises:
providing a flow of untreated waste water liquid or said activated sludge mixed liquor liquid towards the filtration cake support, wherein the untreated waste water liquid or said activated sludge mixed liquor liquid comprises solid particles of different sizes or the untreated waste water liquid or said activated sludge mixed liquor liquid is a fraction that contains solid particles above a certain size; and
providing a pressure difference across the filtration cake support and the activated sludge flocs when deposited thereon, so as to provide a flow of untreated waste water liquid or activated sludge mixed liquor liquid through the filtration cake support and the activated sludge flocs deposited thereon until a filtration cake has been formed.

13. The method according to claim 12 , wherein establishing the filtration cake further comprises:
flushing a region in front of the filtration cake by the fraction consisting essentially of the smaller solid particles thereby removing the untreated waste water liquid or said activated sludge mixed liquor liquid used during establishing the filtration cake in order to prevent further cake growth.

14. The method according to claim 12 , wherein the pressure difference across the filtration cake support and the activated sludge flocs when deposited thereon during establishing the filtration cake is below 1 bar.

15. The method according to claim 12 , wherein the pressure difference during establishing the filtration cake is constant over time, or the flow of untreated waste water liquid or said activated sludge mixed liquor liquid through the filtration cake and filtration cake support during establishing the filtration cake is constant over time, or both flow and pressure change over time according to a predefined profile.

16. The method according to claim 12 , wherein the filtration cake is defined to have been formed when the mass of solids per unit area of the cake support has reached between 0.05 to 10 kg dry solids per square meter.

17. The method according to claim 12 , wherein the pressure difference across the filtration cake support and the activated sludge flocs when deposited thereon during establishing the filtration cake is increased over time.

18. The method according to claim 17 , wherein the filtration cake is defined to have been formed, when the pressure difference has reached a preselected level.

19. The method according to claim 1 , further comprising determining, one or more parameters, selected from the group consisting of turbidity, suspended solids concentration, total bacteria count, total organic carbon concentration, and chemical oxygen demand (COD) of the untreated waste water liquid or said activated sludge mixed liquor liquid having passed through the cake support and the filtration cake, wherein the determining is done by measuring and/or calculating.

20. The method according to claim 1 , further comprising capturing the filtration cake or the particles thereof after it has been used for filtering the fraction consisting essentially of the smaller solid particles and removing it, from a waste water treatment system as surplus activated sludge.

21. The method according to claim 1 , wherein the method of filtration comprises a cyclic repetition of:
establishing the filtration cake,
filtering of the fraction consisting essentially of the smaller solid particles, and
removal of the filtration cake.

22. The method according to claim 1 , wherein the method forms part of a waste water treatment system.

23. The method of claim 1 , wherein establishing the filtration cake comprises providing:
a flow of liquid toward the filtra

Assignees

• Dominiak Dominik Marek
• Jæger Tom Bjerregaard
• Grundfos Holding As

Inventors

• Dominiak Dominik Marek
• Jæger Tom Bjerregaard

Classifications

• C02F2209/10

  Solids, e.g. total solids [TS], total suspended solids [TSS] or volatile solids [VS] · CPC title

• C02F2209/11

  Turbidity · CPC title

• C02F2209/44

  Time · CPC title

• C02F2209/03

  Pressure · CPC title

• B01D29/03 Primary

  self-supporting · CPC title