GB2372715A

GB2372715A - Combined Sewer Overflow device

Info

Publication number: GB2372715A
Application number: GB0202301A
Authority: GB
Inventors: Gerald Parker; Peter Charles Wall
Original assignee: SOAR ENGINEERING
Current assignee: SOAR ENGINEERING
Priority date: 2001-02-02
Filing date: 2002-01-31
Publication date: 2002-09-04
Also published as: GB0202301D0; GB0102697D0

Abstract

A screen module (1) for a combined sewer overflow (CSO) comprises a mesh floor (3), having at least one sloped surface, the floor being located in a frame (2) having means to connect one module to another. The mesh floor preferably has the general shape of a 'W' forming peaks (5) and troughs (6). The frame may comprise walls having holes (9) for the reception of connection means, for example a nut (10) and bolt (8), by which the modules may be releasably connected together. A reinforcing rod (7) may be used to maintain the inclination of the sloped surfaces. The modules are preferably smaller than that of a manhole so that they can be accessed and removed easily for maintenance. A combined sewer overflow is preferably comprised of at least two modules in which the mesh floors may be different. The mesh floor is preferably made of wedge shaped wire and the frame made from stainless steel sheet.

Description

COMBINED SEWER OVERFLOW DEVICE The invention relates to a combined sewer overflow device.

A combined sewer overflow (CSO) is a device adapted to cope with excess flow of water (and contained solids) from drains into rivers, and is the subject of the regulations such as the Urban Waste Water Treatment (England & Wales) Regulations 1994. The device comprises a chamber in a side weir or a stilling pond. The chamber may have different configurations, e. g. circular, triangular, square or rectangular cross-sectional shape. The chamber may have a screen adapted to allow water to flow through but hold back the solids. Two of the major problems with the screen are the need for access via manholes and the like to retrofit into existing chambers and the like, and the need for maintenance.

It is an object of the invention to provide a screen system for a CSO which will perform in accordance with the regulations, be installed easily and be easily maintained.

According to the invention in one aspect a there is provided a screen module for a combined sewer overflow, the module comprising a mesh floor having at least one ramp surface, the floor being located in a frame which has means whereby one module may be connected to another module.

The mesh floor may be in the form of perforated metal or the like. Preferably the mesh floor is formed of wires arranged to form the mesh. Preferably the wire IS of wedge shape as seen in section. According to the invention in another aspect there is provided a combined sewer overflow incorporating at least two modules of the invention.

Preferably the screen has a'W'or inverted"W"configuration, as seen in end view.

Preferably the frame comprises walls having holes for the reception of connection means by which one module may be connected to another such module. It is a preferred feature of the invention that the connection means is releasable. In one convenient form the connection means is a bolt and nut connection. It is an advantageous feature that the holes are located In both the upper and lower portions of the frame walls.

A reinforcing rod may be present to maintain the inclination of the ramp surface.

The modules may be of any suitable size. It is preferred that the area of the module IS less than that of a manhole whereby the module may be passed through the manhole to reach a chamber requiring or containing the CSO.

The mesh floor screening properties of one module may differ from those of the second module. Several modules may be present The chamber of the CSO may be of any known type and incorporate known components, e. g. a scumboard, a vortex arrangement, a hydrodynamic separation system, or the like. In order that the invention may be well understood it will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 is a plan view of an overflow screen made up of four modules of the invention;

Figures 2A and 2B are vertical sections taken on lines 11-)I and I)--I t respectively on Figure 1, showing different shapes of module Figures 3A and 3B are partial perspective views of the modules of Figures 2A and 2B; and Figure 4 is an enlarged view of a module mesh floor.

The screen S is set into the chamber of a CSO and comprises a number of modules 1 each generally square or rectangular in shape. Each module comprises an outer frame 2 made from stainless steel sheet. Each module contains a screen mesh floor 3 made of preferably wedged shaped wire 11 having apertures 4 which are substantially square in section. As shown in Figure 2A, the mesh floor can be bent or folded to assume a generally'W'configuration or, as shown in Figure 2B, a generally inverted'W'or an'M' section to provide one or more ramp surfaces. As a result each module has peaks 5 and valleys 6. A reinforcing rod 7 is welded to a peak 5 to maintain the shape. The frame 2 stand slightly proud of the mesh floor 3 it contains. Bolts 8 pass through holes 9 in the frame 2 to unite adjacent modules to form a screen system. Nuts 10 may be present to hold the bolts in place. In one example, the outer frame 2 is made from 3.00 mm stainless steel sheet. In a typical module the mesh area measures 0.32 m2 for a planar area of 0 25m2. Each individual aperture 4 measures 6 mm by 6 mm or as required by regulation or application. The wedge wire 11 is typically 1.6 mm on its flat surface and the cross rod 12 is typically 3 mm wide. The screen sits In the chamber of any type of CSO. In the event of an overflow the level of liquid rises up through the mesh floor and flows out of the CSO exit duct via the apertures 4 of the screen. Solid particles in fluids leaving through the CSO exit duct are retained beneath the mesh floor if they are of size greater than the apertures. The retained particles which remain on the underside of the screen are washed off when the water level (risen because of a storm) falls, as there is a backwash action through the screen caused by the height of the frame 2 around each module.

Because there are separate modules the overall screen size may be modified to fit the particular CSO process requirements. Where access is restricted it is easy to insert any required number of modules through, e. g. a manhole, to reach a chamber below If any of the modules is damaged it is simple to replace one module, so avoiding the need and cost of replacing the whole screen. The modular construction allows the apertures within any given module to be varied within a total screen to meet any special process requirements. The mesh of one module may differ from another, e. g. in aperture size and mesh type filter medium.

The screen is useful in a combined storm overflow, a sewage works overflow, a water pumping station overflow; and the like.

Use of a screen system of the invention will offer other advantages. Because of the increased efficiency and maintenance it may be possible to reduce the overall size of the chamber. The invention is not limited to the embodiments shown. The mesh floor may be extended to form frame walls. The reinforcing rod may be omitted.

Claims

CLAIMS 1. A screen module for a combined sewer overflow, the module comprising a mesh floor having at least one ramp surface, the floor being located in a frame having means whereby one module may be connected to another module.
2. A module according to Claim 1, wherein the mesh floor has the general shape of a'W'as seen in the end view.
3 A module according to Claim 1 or 2, wherein the frame comprises walls having holes for the reception of connection means by which one module may be connected to another such module.
4. A module according to any of Claims 1 to 3, wherein the connection means is releasable.
5. A module according to Claim 4, wherein the connection means is a bolt and nut connection.
6. A module according to Claim 3,4 or 5, wherein bolt-receiving holes are located in the upper portion and/or lower portion of the frame walls.
7. A module according to any preceding Claim, including a reinforcing rod to maintain the inclination of the ramp surface.
8. A module according to any preceding Claim, wherein the surface area is less than that of a manhole associated with the combined sewer outlet whereby the module may be passed through the manhole to reach a chamber containing the combined sewer overflow.
9. A combined sewer overflow (CSO) incorporating at least two modules according to any preceding Claim.
10. A CSO according to Claim 9, wherein the mesh floor of one module differs from that of the second module.