GB2355712A

GB2355712A - Sewage plant

Info

Publication number: GB2355712A
Application number: GB0015410A
Authority: GB
Inventors: Stephen Ferenc Mate; Timothy Cumming
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-06-26
Filing date: 2000-06-26
Publication date: 2001-05-02
Also published as: GB9914888D0; GB0015410D0

Abstract

A sewage plant 10 comprises a biological filter stage illustrated generally at 12. The filter stage 12 is in the form of a removable module. The sewage plant 10 preferably comprises an enclosed housing having an access opening 66 through which the filter module 12 can be removed and installed.

Description

2355712 Sewaize Plant The present invention relates to sewage plants and

in particular, to sewage plants which provide biological treatment of sewage.

Buildings which are not connected with mains sewage, such as houses in remote locations, are conventionally provided with a sewage treatment plant which is buried near the building to receive and treat sewage from the building, breaking this down to a sludge which must periodically be removed. In one conventional arrangement, bacteria are used as part of the treatment process. However, as living organisms, they are vulnerable to mis-use of the system, particularly if waste which is toxic to them is put through the system. If the bacteria are killed or badly depleted in this manner, the plant will then treat sewage inadequately or not at all. However, some conditions can arise in which the bacteria grow excessively, causing a long stringy mass (known as humus) which can clog the filter. In conventional systems, the performance and reaction of the bacteria can be difficult to predict and control. In the event that the filter becomes clogged by bacterial strings, or the bacteria are killed off, it becomes necessary to dig out the plant for cleaning and maintenance. This operation can be extremely expensive (effectively as expensive as installing a new plant).

The present invention provides a sewage plant comprising a biological filter stage in the form of a removable module.

The plant preferably comprises an enclosed housing within which sewage treatment occurs, the housing having a closable access opening through which the filter module may be installed, removed or replaced.

The filter module preferably comprises a main chamber for biological growth medium. The filter module may have inlet and outlet openings communicating with the main chamber. The inlet and outlet openings are preferably relatively high and relatively low in the main chamber when oriented 2 for use, whereby fluid must pass down through the main chamber to pass through the module.

Preferably the inlet opening is located to receive influent from a primary settlement stage within the plant. The filter module preferably comprises an inlet baffle extending downwardly, in use, from the inlet opening, to define an upwardly directed path from the primary settlement stage to the inlet opening, whereby fluid entering the main chamber is drawn from beneath the uppermost level of the fluid in the primary settlement stage.

Preferably the outlet opening supplies a final settlement stage within the plant.

The outlet opening preferably communicates with a duct which defines a fluid path having a first leg rising from the outlet, and a second leg which extends downwardly to be located between the upper and lower levels of a final settlement tank.

The module preferably further comprises support means by which the biological growth medium is supported above the outlet opening to define a settlement zone.

The filter module preferably comprises first coupling means for coupling with a pump arrangement of the plant to allow settled material to be pumped from the settlement zone. The filter module preferably also comprises second coupling means for coupling with an air supply of the plant, to direct aerating air to the biological growth medium.

The invention also provides a removable filter module for use in a sewage plant as set out above.

An embodiment of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying 3 drawings, in which:

Fig. 1 is a highly schematic plan view of a sewage plant according to the invention; Fig. 2 is a highly schematic vertical section through the plant of Fig. 1; Fig. 3 is a simple vertical section through a baffle arrangement of the plant; and Fig. 4 is a vertical section through a housing for the filter module of the plant.

Fig. 1 shows a sewage plant 10 comprising a biological filter stage illustrated generally at 12. The filter stage 12 is in the form of a removable module, as will be described in more detail below.

Before describing the filter module 12 in more detail, it is convenient first to describe the overall arrangement and operation of the plant 10.

The plant 10 is contained within an external housing 14 which should be completely impervious to water and sewage when closed, to ensure a long service life. The housing 14 is preferably made of a synthetic plastics material, such as polypropylene. The plant 10 is intended to be buried to receive waste from a nearby building or the like. This enters the housing through an inlet 16 from which it passes into a primary settlement stage 18. During primary settlements, gross solids (primary sludge) settle to the bottom of the stage 18, where they will remain until the tank is desludged periodically (perhaps annually in a typical arrangement). Other material may initially float to the top of the primary stage 18, forming a crust.

The primary stage 18 is in two parts 18a,18b separated by a wall 20. Communication between the first and second parts 18a,18b is provided as 4 shown highly schematically in Fig. 3. A slot 22 formed in the wall 20 defines the upper level in the settlement parts 18a,18b. In the part 18a, a baffle 24 extends down from the slot 22 to provide an opening at 26 below the upper level 28 defined by the slot 22. When new material is introduced to the part 18a through the inlet 16, an equivalent volume of material will be displaced through the slot 22 into the second part 18b, but this material will have been drawn from below the level 28, up through the opening 16, behind the baffle 24, to the slot 22. Consequently, the depth to which the baffle 24 extends can be set to encourage relatively clear liquid from the middle of the tank to be displaced, rather than the crust at 28 or settled solids at the bottom of the part 18a.

Further settlement occurs in the second part 18b, from where material can then pass into the filter stage 12.

The filter stage 12 comprises a filter housing 30 (Fig. 4) which has an inlet 32 toward the top of the housing 30, and an outlet 34, toward the bottom of the housing 30. The inlet 32 communicates with the second primary settlement part 18b through the inlet 32 and an inlet baffle 36 which together act in a manner similar to the arrangement illustrated in Fig. 3, to draw material into the housing 30 from a mid-height in the primary settlement part 18b.

The outlet 34 is in communication with a vertical duct 38 which extends almost to the level 28 and then communicates with a vertical pipe 34 which extends down to an outlet at mid-level, within a final settlement tank 42. The purpose of this route is to encourage solid settlement at the bottom of the housing 30, and in the final settlement tank 42, particularly encouraging material arising from excessive bacterial growth (known as humus) to settle in the housing 30.

The final outlet of the plant 10 is at 44, high in the final settlement tank 42. When the plant 10 is operating correctly, liquid displaced from the outlet 44 will be sufficiently clean for discharge to a water course, soak-away or the like.

Pipework 46 is provided for drawing sludge from the bottom of the housing 30 and final settlement tank 42, for re-circulating back to the primary settlement tank 18, preferably into the first part 18a. This movement is driven by a compressor 46, shown mounted within the housing 14, but which could be located remotely. The pipework is shown schematically in Figs. 1 and 2, and is differently oriented in these drawings, in the interests of enhancing clarity of the drawings, without affecting the functional relations between the features illustrated.

The filter stage 12 can now be described in more detail. The inlet 32, which has been described more fully above, opens into the main chamber SO of the housing 30. This contains the media 52 for bacterial growth, supported on a suspended floor S4 which is in turn supported by lugs 56, a little above the outlet 34.

The media 52 are many thousands of small plastic elements, conventional in themselves, randomly packed into the main chamber SO, to provide surfacearea on which sewage treatment bacteria can grow.

The suspended floor 54, which is mesh to allow liquid to pass through, defines below it a settlement zone S8 which also houses aerating outlets 60, through which air may be provided to bubble up through the media 52 to maintain the growth conditions for the bacteria.

It is important to note that the outlet 44 is below the suspended floor S4, so that liquid leaving the outlet 44 must have passed through the column of media S2 and thus must have been treated by the bacteria. In practice, the hydraulics of the arrangement and the effect of the aeration will cause liquid to have passed the media 52 several times before leaving the outlet 44.

Aerating air for the outlets 60 is conveniently provided by power from 6 the compressor 48.

It is apparent from the above description that the filter stage 12 has four functional connections with the rest of the plant 10. These are the inlet at 32, the outlet at 34, the re-circulation pipework 46, and air supply to the outlets 60. in accordance with the invention, the filter stage 12 is formed as a removable module which can be removed and replaced to restore these connections. The inlet 32 and outlet 34 are provided by the location of the formations of the filter stage 12 and do not require couplings with components of the plant 10. However, appropriate couplings, illustrated schematically at 62, are provided to allow connection with the pipework 46 and an air supply illustrated schematically at 64.

A manhole cover 66 or other closable opening is provided above the location of the filter stage 12, to allow access into the plant 10 for removal and replacement of the filter stage 12. Handles, or attachment points for lifting gear are preferably provided on the module, to facilitate removal and installation through the manhole cover 66.

Forming the filter stage 12 as a removable module, as described, has a number of significant advantages, as follows. First, it becomes a relatively easy task to monitor the correct operation of the stage, during routine maintenance, because the filter stage 12 can readily be removed, inspected and replaced. In the event that the filter stage 12 has failed in some way, for instance the bacteria have been killed by toxins, a new filter stage 12 can be introduced readily. Furthermore, if the rating of the plant 10 needs to be changed, particularly if the rating needs to be increased as a result of the number of occupants of the associated building increasing, the filter stage 12 can readily be replaced with a new stage having a larger volume of media 52, and thus a greater throughput capacity. All of these operations can be achieved by access through the manhole cover 66, without digging up the complete plant 10. This avoids the bulk of the cost of equivalent maintenance tasks on conventional arrangements and allows the operations to be conducted much more quickly.

7 Very many variations and modifications can be made to the apparatus described above, without departing from the scope of the invention. In particular, the layout of the various stages of the plant 10 can be changed and the number of stages could be changed, according to the processing requirements for the plant 10. The physical form of the filter stage 12 could be changed according to other design choices within the plant 10. The filter stage 12 and other components could have various shapes, such as being rounded or squared. Various materials could be used for manufacturing the stage 12 and other components of the plant 10. However, it is envisaged that virtually the whole unit (with the exception of the compressor) could be manufactured from a synthetic plastics material such as polypropylene, for longevity and robustness.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

8

Claims

1. A sewage plant comprising a biological filter stage in the form of a removable module.

2. A plant according to claim 1, comprising an enclosed housing within which sewage treatment occurs, the housing having a closable access opening through which the filter module may be installed, removed or replaced.

3. A plant according to claim I or 2, wherein the filter module comprises a main chamber for biological growth medium.

4. A plant according to claim 3, wherein the filter module has inlet and outlet openings communicating with the main chamber.

S. A plant according to claim 4, wherein the inlet and outlet openings are relatively high and relatively low in the main chamber when oriented.

6. A plant according to claim 4 or 5, wherein the inlet opening is located to receive influent from a primary settlement stage within the plant.

7. A plant according to claim 6, wherein the filter module comprises an inlet baffle extending downwardly, in use, from the inlet opening, to define an upwardly directed path from the primary settlement stage to the inlet opening, whereby fluid entering the main chamber is drawn from beneath the uppermost level of the fluid in the primary settlement stage.

8. A plant according to any of claims 4 to 7, wherein the outlet opening supplies a final settlement stage within the plant.

9. A plant according to claim 8, wherein the outlet opening communications with a duct which defines a fluid path having a first leg rising from the outlet, and a second leg which extends downwardly to be located 9 between the upper and lower levels of a final settlement tank.

10. A plant according to any of claims 3 to 9, wherein the module further comprises support means by which the biological growth medium is supported above the outlet opening to define a settlement zone.

11. A plant according to claim 10, wherein the filter module comprises first coupling means for coupling with a pump arrangement of the plant to allow settled material to be pumped from the settlement zone.

12. A plant according to claim 11, wherein the filter module comprises second coupling means for coupling with an air supply of the plant, to direct aerating air to the biological growth medium.

13. A removable filter module for use in a sewage plant as set out above.

14. A sewage plant substantially as described above, with reference to the accompanying drawings.

15. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.