GB2306121A - Support base for deep bed filter - Google Patents

Abstract

A support base for a waste liquid filter, such as a deep bed sewage filter, comprises a plurality of metal trays 11 that are filled with concrete. The trays 11 are positioned over a channel 13 set in the filter base 14, with small gaps 16 between them to allow filtered liquid to flow through them into the channel 13. The trays 11 may be held in place by anchors 12.

Description

DEEP BED FILTER SUPPORT SYSTEM The present invention relates to a support base for a waste liquid filter, in particular, but not exclusively, a deep bed filter, and to a method of forming a support base for a waste liquid filter.

The deep bed filter was developed approximately 30 years ago to treat the effluent from steel mills. The rugged design was quickly appreciated and its use spread into all areas of waste water treatment. The deep bed filters role is to reduce the suspended solid load from the discharge of a waste water treatment. To this end it has been extensively used in both the initial design of plants, and as a retrofit to plants to improve existing effluent discharge performance.

Deep bed filters use a deep bed of coarse media to remove suspended solids from industrial and municipal waste waters. Effluent enters from the top and filters through media leaving filter at bottom. Air and water are fed from the base of the media bed during backwashing (cleaning) and the dirty backwash water overflows at the top of the filter.

The air and liquid feed are located in a channel in the base of the filter. The channel is covered by a support base which supports the media in the filter. The support base is made from a series of plates which are fitted in recesses along the base of the filter. The plates must be mechanically strong enough to support the weight of the media bed which is considerable. The plates must be accurately positioned in the recesses so that small pathways are left for the air and liquid feeds.

Due to the high cost of repair or replacement of the support base, it is important that the base does not fail during operation, which may last for many years e.g. 15 to 20. Furthermore, it is also important that the fluid pathways formed between adjacent plates of the support base do not become blocked.

In view of the above, the support base has been formed in one of two following. Either a thick steel sheet (about 25 mm thick) has been used to form the plates, or a thick precast concrete block e.g. (125 mm thick) has been used.

Whilst these plates provide the required strength, they are difficult to install because they are heavy. The present invention seeks to provide an alternative support base for waste liquid filter, in particular, but not exclusively, a deep bed filter, which is simpler to install.

According to a first aspect of the present invention there is provided a support plate for a deep bed sewage filter, comprising a metal tray formed from a base plate with lips extending upwardly from two opposed sides thereof, the tray being substantially filled by a non-metal solid material. Normally, the non-metal solid material would be concrete.

Advantageously, using the present invention, it is possible to provide a mechanically strong support plate which is much lighter than the corresponding solid steel construction or solid concrete construction of required dimension for the particular installation.

According to a second aspect of the present invention there is provided a method of forming a support base for the media of a deep bed sewage filter, including the steps of: (a) positioning metal trays over a channel in the base of the filter; (b) substantially filling the metal trays with a settable material.

With this method the support base is formed in a particularly advantageous manner as only the metal tray needs accurate positioning in the filter in one horizontal plane. The trays are clearly much lighter than the prior known base plates. Thus, it is particularly easy to accurately position the trays in the filter and secure them in their preset positions.

Subsequently, the settable material is poured into the trays to form the strong durable support base of the filter that is level and aligns accurately with the adjacent flow.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of the base of a filter with a row metal trays according to the present invention secured above a channel of the filter base; Figure 2 shows the perspective view of Figure 1 with the metal trays substantially filled with concrete to form the support base according to the present invention; Figure 3 shows a plan view of a filter base channel having two metal trays positioned thereover; Figure 4 shows an end view of an embodiment of the metal trays; Figure 5 shows a cross-sectional view along a channel during construction of the support base according to the present invention; Figure 6 shows a cross-sectional view in the line A-A of Figure 5;; Figure 7 shows a planned view of a partially constructed support base according to the present invention.

In Figure 1 a row of metal trays (11) are shown secured by anchors (12), e.g. resin anchors over a channel (13) of the filter base (14). A small gap (16) has been maintained between adjacent trays (11). The trays (11) are fitted into a recess provided at the top of the channel (13). The upstanding walls of the recess forming the end walls of the trough provided between side lips of each tray (11).

When the trough of each tray is filled with concrete, or other suitable material, as shown in Figure 2, the gap (16) is still maintained. This can be accomplished as shown in Figure 5 by inserting a temporary baton between adjacent trays, e.g. a wooden baton which is removed after the trough in the tray (11) has been substantially filled and set.

Of course, it would be possible to preset the concrete in the trays (11) before these are fitted over the channel (13). The support plates (10) would still be more manageable than a solid steel, or a solid concrete plate of suitable dimensions, and thus be easier to install.

The trays (11) are normally formed from a single U shaped member. Alternatively, as shown in Figure 4 can be formed from two L-shaped members which, in the illustrated embodiment, are not welded together. When the resin anchor (12) secure the two L shaped members in position over the channel (13) the tray (11) is securely formed.

The trays (11) must be accurately positioned over the channel (13) as explained hereinbefore. Typical arrangements are shown in Figures 3 and 7.

In order to install a support base according to the present invention the following procedure may be adopted: 1. Locate trough cover plates into filter floor rebate.

2. Ensure centre punch marks in line with air lateral connection in air headers.

3. Check that the gap between adjacent centre punch marks corresponds exactly with the predetermined amount.

4. Check that the gap between adjacent trays (10) corresponds to the predetermined amount.

5. Drill holes for the anchor bolts, e.g. resin anchor bolts.

6. Ensure gap between tray and filter base is free from all loose debris.

7. Fix the trays into position with the anchor bolts.

8. Temporarily fill the gap between adjacent trays using long wood batons to prevent ingress of concrete.

9. Fill trough in each tray with concrete tamp level with filter floor.

10. Remove wooden baton after initial set, check clean up gap between adjacent support plates.

As shown in Figure 5, the top edges of the rim of the metal tray (11) may protrude slightly above the level of the filter floor. This can help prevent the media of the filter filling the gaps between adjacent plates which form air and liquid passageways into the filter and allows for variation in levels of the previously formed concrete rebates into which the trough cover plates sit.

In a deep bed filter the effluent to be treated flows downward through a deep bed of filter media exiting the filters via the support media layers, between the plates and into a collection trough for discharging from the filter. The suspended solids are removed by the filtering properties of the media. Over a period of time these solids accrue within the deep bed filter and require to be removed.

Removal is achieved by backwashing the filter with previously filtered water, air and combination thereof.

The backwash water enters the filter at pressure along the bottom collection trough, through the gap between the plates into the support layers and media, exiting the filter at the top from outlet launder. The backwash air is introduced to the area below the filter media and follows the same upward route as the backwash water. This action cleans the media.

Claims (13)

CLAIMS:

1. A support plate for a deep bed sewage filter, comprising a metal tray having a base plate with lips extending upwardly from two opposed side edges thereof, the tray being substantially filled by a non-metal solid material.

2. The support plate according to claim 1, wherein the metal is steel.

3. The support plate according to claim 1 or claim 2, wherein the non-metal solid material is concrete or other settable material.

4. Use of one or more support plates according to any one of claims 1 to 3 to form a deep bed sewage filter support base.

5. A sewage filter such as a deep bed filter, having a media support base comprising one or more of the support plates of any one of claims 1 to 3.

6. A method of forming a support base for supporting the media of a deep bed sewage filter, including the steps of: (a) positioning metal trays over a channel in the base of the filter.

(b) then substantially filling the metal trays with a settable material.

7. The method according to claim 6, wherein in step (a) the trays are positioned in a row over the channel, with opposite end edges of each tray being supported in recesses at the top of the channel walls; the trays of the row being separated from adjacent trays by a preset amount.

8. The method according to claim 7, wherein a baton is placed in each gap between adjacent trays before step (b).

9. The method according to claim 8, wherein the baton is removed after step (b).

10. A support plate for a deep bed sewage filter as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

11. Use of a support plate as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

12. A filter such as a deep bed filter as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

13. A method of forming a media support base in a filter as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.