Layered media backwash with internal draft tube

Patent metadata

Field	Value
Publication number	US-2024246011-A1
Application number	US-202218563052-A
Country	US
Kind code	A1
Filing date	May 11, 2022
Priority date	May 25, 2021
Publication date	Jul 25, 2024
Grant date	—

Abstract

A wastewater filter includes a vessel having a bottom and a side wall that cooperate to define a filter space. A first filter media is positioned within the filter space to define a first media layer, and a second filter media different from the first filter media is positioned within the filter space above the first media layer to define a second media layer, the first media layer and the second media layer cooperating to define an interface plane. A draft tube is positioned within the second media layer and has a first end positioned a first non-zero distance above the interface plane, and a second end disposed a second non-zero distance from a top surface of the second media layer. A backwash fluid line is positioned to inject a backwash fluid into the first filter media, and a backwash gas line is positioned to inject a backwash gas into the draft tube.

First claim

What is claimed is:

1 . A wastewater filter comprising:
a vessel having a bottom and a side wall that cooperate to define a filter space; a first filter media positioned within the filter space to define a first media layer; a second filter media different from the first filter media positioned within the filter space above the first media layer to define a second media layer, the first media layer and the second media layer cooperating to define an interface plane; a draft tube positioned within the second media layer and having a first end positioned a first non-zero distance above the interface plane, and a second end disposed a second non-zero distance from a top surface of the second media layer; a backwash fluid line positioned to inject a backwash fluid into the first filter media; and a backwash gas line positioned to inject a backwash gas into the draft tube.

2 . The wastewater filter of claim 1 , wherein the vessel includes a cover that encloses the filter space, and wherein the filter space is operated at a pressure greater than atmospheric pressure.

3 . The wastewater filter of claim 1 , wherein the first filter media is finer and denser than the second filter media.

4 . The wastewater filter of claim 3 , wherein the first filter media has a first density that is between 120 percent and 300 percent of a second density of the second filter media

5 . The wastewater filter of claim 1 , wherein the second filter media includes one of walnut shells and a synthetic wood/plastic blend.

6 . The wastewater filter of claim 1 , wherein the first filter media includes one of sand and garnet.

7 . The wastewater filter of claim 1 , wherein the first media layer defines a depth between 10 and 15 inches (25.4-38.1 cm) and the first non-zero distance is less than 5 inches (12.7 cm).

8 . The wastewater filter of claim 1 , wherein the backwash fluid includes water and the backwash gas includes air.

9 . A wastewater filter comprising:
a vessel having a bottom and a side wall that cooperate to define a filter space; a first filter media positioned within the filter space to define a first media layer having a first density; a second filter media positioned within the filter space above the first filter media to define a second media layer having a second density that is less dense than the first density, the first media layer and the second media layer cooperating to define an interface plane; a draft tube positioned within the second media layer and having a first end positioned a first non-zero distance above the interface plane, and a second end disposed a second non-zero distance from a top surface of the second media layer; a backwash fluid line positioned to inject a backwash fluid into the first filter media; and a backwash gas line that extends through the first media layer and includes an outlet positioned within the draft tube to inject air into the draft tube.

10 . The wastewater filter of claim 9 , wherein the vessel includes a top that encloses the filter space, and wherein the filter space is operated at a pressure greater than atmospheric pressure.

11 . The wastewater filter of claim 9 , wherein the first filter media is finer and denser than the second filter media.

12 . The wastewater filter of claim 11 , wherein the first filter media has a first density that is between 120 percent and 300 percent of a second density of the second filter media.

13 . The wastewater filter of claim 9 , wherein the second filter media includes one of walnut shells and a synthetic wood/plastic blend.

14 . The wastewater filter of claim 9 , wherein the first filter media includes one of sand and garnet.

15 . The wastewater filter of claim 9 , wherein the first media layer defines a depth between 10 and 15 inches (25.4-38.1 cm) and the first non-zero distance is less than 5 inches (12.7 cm).

16 . A method of backwashing a wastewater filter that includes a draft tube, the method comprising:
positioning a first filter media in a filter space to define a first media layer, the first media layer being disposed a first non-zero distance below a first end of the draft tube; positioning a second filter media in the filter space on top of the first media layer to define a second media layer and an interface plane between the first media layer and the second media layer, the second media layer extending a second non-zero distance above a second end of the draft tube; injecting a backwash fluid into the first media layer, the backwash fluid having a first flow rate that is selected to mix and roll the first media layer and fluidize the second media layer without mixing the first media layer and the second media layer with one another; and injecting a backwash gas into the draft tube, the backwash gas having a second flow rate selected to draw a portion of the second filter media from a bottom portion of the second media layer to a top portion of the second media layer.

17 . The method of claim 16 , wherein the first filter media has a first density that is between 120 percent and 300 percent of a second density of the second filter media.

18 . The method of claim 16 , further comprising positioning a backwash gas tube such that an outlet of the backwash gas tube is positioned within the draft tube.

19 . The method of claim 16 , wherein the first media layer defines a depth between 10 and 15 inches (25.4-38.1 cm) and the first non-zero distance is less than 5 inches (12.7 cm).

20 . The method of claim 16 , wherein the first filter media includes one of sand and garnet, and wherein the second filter media includes one of walnut shells and a synthetic wood/plastic blend.

Assignees

• Siemens Energy Inc

Inventors

• Burclaff Philip A
• Cooley Curtis D

Classifications

• B01D24/105

  downward filtration without specifications about the filter material supporting means · CPC title

• B01D2101/04

  Sand or gravel filters · CPC title

• B01D2201/087

  using gas bubbles, e.g. air · CPC title

• B01D24/008 Primary

  arranged concentrically or coaxially · CPC title

• B01D24/4631 Primary

  Counter-current flushing, e.g. by air · CPC title