GB2453149A

GB2453149A - A Reed Bed formed of Reed bed modules

Info

Publication number: GB2453149A
Application number: GB0718868A
Authority: GB
Inventors: Nigel Arthur Paston
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-09-27
Filing date: 2007-09-27
Publication date: 2009-04-01
Anticipated expiration: 2027-09-27
Also published as: GB2453149B; GB0718868D0

Abstract

A reed bed 1, adapted to extract pollutants such as ammonia from water 12, comprising an outer structure containing a plurality of reed bed modules 13. The outer wall is formed of a wall 2 and/or an excavation that is lined with a waterproof membrane 3. Each reed bed module 13 is formed of an open-topped container (15; fig 4) with apertures or holes (18, 20; fig 4) in the walls and/or floor which allow the passage of water 12, and contains a layer of support medium 16 on which a plurality of reeds 14 have been grown. Handle holes (21; fig 4) are provided for lifting and carrying the container (15; fig 4). The reed bed modules 13, containing reeds 14 already grown to a desired maturity, are installed in the reed bed 1 so that polluted water may be passed through the modules 13 and the root structure of the reeds 14 therein. The reed bed 1 may be divided into bays 10, each containing a plurality of reed bed modules 13, by baffles 8, 9 disposed to ensure that the water 12 passes through the root structure of the reeds 14 of each bay 10.

Description

1 2453149

REED BED

The present invention relates to equipment for cleaning pollutants from waste water and the like. More particularly, but not exclusively, it relates to equipment utilising wetland plants such as reeds to reduce the levels of ammonia in waste water.

A major issue in cleaning waste water is the removal, or reduction to acceptable levels, of dissolved ammonia. The waste water may be drainage from agricultural land, effluent from an industrial process, or partially treated sewage. In each case, an effective and economical solution may be the system known as a reed bed. Plants growing in shallow water, particularly reeds of the genus Phragmites, frequently have associated with their root systems bacteria that absorb ammonia and some other pollutants. The reeds themselves also absorb many pollutants. The complex structure of the reeds' root systems ensures that polluted water flowing through the reed bed must follow an indirect, prolonged route through the bed. This maximises the duration of contact between the water and the bed and ensures effective removal of a very high proportion of the pollutants from the water. Once an artificial reed bed has been set up, maintenance requirements are usually minimal.

Other shallow-water plants may be used for this purpose, besides reeds in the strict sense.

For the purposes of the present application, the term "reed" should be understood also to refer to such other plants.

However, the construction of a reed bed is in general a medium to long-term process. An excavation or an above-ground structure of sufficient area must be constructed, filled with suitable material in which the reeds may grow and flooded, and then the reeds themselves must be allowed to become established before the bed may be used. Typically, reeds are grown from rhizomes, generally horizontally by extending runners that produce generally vertical stems and roots at intervals along their length. It generally takes two years from initial planting of rhizome sections before an effective reed bed becomes established.

There will hence be many situations in which a conventional reed bed is not a viable option.

For example, there might be an unexpected need for pollutants to be cleaned up following a spillage. Also, a back-up reed bed might be required only for a short period, for example if an existing reed bed is damaged or is temporarily loaded beyond its capacity (e.g. by run-off after heavy rainfall). It is also possible that the need for a reed bed might simply not be recognised sufficiently early in a project for one to be constructed to a conventional schedule.

It is hence an object of the present invention to provide a reed bed or the like which can be constructed and bought into operation at short notice, obviating some or all of the above problems.

According to a first aspect of the present invention, there is provided a reed bed module adapted to extract pollutants such as ammonia from water, comprising open topped container means having floor means and/or wall means adapted for passage of water therethrough, a layer within said container means of substrate material adapted to support the growth of reeds as defined herein, and a plurality of said reeds growing from said substrate material.

Preferably, said module is dimensioned to be portable by no more than two persons, optionally to be portable by one person alone.

Advantageously, the module is provided with manually graspable handle means.

Preferably, the floor and/or wall means of said module are provided with a plurality of apertures adapted for water to flow therethrough.

Said wall and/or floor means may each comprise framework means defining one or more window means through which water may flow into or out of the reed bed module.

Preferably, said reeds are grown in the reed bed module prior to it being transported to a location at which extraction of pollutants is to occur.

The container means may comprise a moulding of plastics material, optionally a unitary moulding.

The substrate material to support the growth of reeds may comprise gravel.

Additionally or alternatively, said substrate material may comprise a porous particulate material.

Said porous particulate material may comprise pores adapted to support bacteria such as those associated with reed root systems.

According to a second aspect of the present invention, there is provided reed bed means for the extraction of pollutants such as ammonia from water, comprising an operatively interconnected plurality of reed bed modules as described in the first aspect above.

Preferably, said reed bed means comprises enclosure means having floor means and wall means impervious to water, each of said plurality of reed bed modules being located within said enclosure means.

Said enclosure means may comprise excavation means.

Alternatively or additionally, the wall means of said enclosure means may extend above an adjacent ground surface external of the enclosure means.

The enclosure means may be provided with water impermeable membrane means extending across floor and wall means thereof.

Preferably, said reed bed modules are disposed each adjacent at least one other reed bed module.

Advantageously, said reed bed modules are adjacently disposed in a regular array.

Optionally, said reed bed modules are disposed substantially in contact, each with its neighbours, such that water may flow directly between neighbouring modules.

Preferably, the reed bed means is filled, in use, with sufficient water that a water surface is above an upper surface of the substrate material in each reed bed module.

Advantageously, said water surface is above an upper rim of the container means of each reed bed module.

Preferably, the reed bed means is provided with water inlet means and water outlet means located remotely from the water inlet means.

Said water inlet and outlet means may each be located partway up a wall means of the enclosure means.

Preferably, the reed bed means is divided by partition means into a sequence of bays through which water may successively flow.

Advantageously, said partition means comprise a series of baffle means, so disposed that water may flow over or under alternate baffle means of the series.

Thus, water may flow sequentially through each bay alternately generally upwardly or generally downwardly.

Each said bay may contain at least one, preferably an array of reed bed modules, so arranged that water passing through the bay must pass through at least one reed bed module.

An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-sectional elevation of a reed bed embodying the present invention, taken along a medial plane; Figure 2 is a schematic plan view of the reed bed shown in Figure 1; Figure 3 is a schematic perspective view of an individual module separated from the reed bed shown in Figures 1 and 2; and Figure 4 is a schematic cross-sectional elevation of a container of the module shown in Figure 3.

Referring now to the Figures and to Figure 1 in particular, a reed bed 1 embodying the present invention comprises a rectangular wall 2, here comprising a plurality of horizontally-extending baulks of wood, but in practice constructed from any convenient strong material.

(Other shapes of bed are possible; a rectangle is merely a form that will be widely convenient). A waterproof membrane 3 is laid on a ground surface within the wall 2, forming a floor of the reed bed 1. This membrane 3 also extends sufficiently far up the wall 2 to render the reed bed I watertight. (NB: the reed bed 1 may instead be built in an excavation, in which case the membrane 3 is laid across the floor and walls of the excavation.

The bed may also combine a shallower excavation with above-ground walls 2).

A layer of gravel 4 or the like is spread across the floor of the reed bed 1, and containers holding growing reeds are laid on top of the gravel 4 (these containers and the reeds themselves are omitted from Figure 1 for clarity, but are described below). In use, the reed bed 1 is filled with sufficient water 5 to cover the roots of the reeds (see Figure 4 for details).

A water inlet 6 is provided partway up the wall 2, at a level above the layer of gravel 4 but below a surface (in use) of the water 5. A water outlet 7 is provided partway up the wall 2, at a similar height to and at a point remote from the water inlet 6. This ensures that the reed bed I is kept wet, but over-filling and flooding can be avoided.

A plurality of vertical baffles 8, 9 are provided, each extending completely across the reed bed I so as to divide the reed bed 1 into a series of sections or treatment bays 10. Upper baffles 8 alternate with lower baffles 9. Each upper baffle 8 extends from above the surface of the water 5, downwardly into the gravel layer 4, while stopping short of the floor of the reed bed 1. Each lower baffle 9 extends upwardly from the floor, completely through the gravel layer 4, into the water 5, but stops short of the surface of the water 5.

When the reed bed 1 is in use, contaminated water is introduced through the water inlet 6 into a first bay 11, which acts as a distributor. The contaminated water may only leave the first distributor bay 11 by flowing through the gravel 4 beneath a first upper baffle 8 into an adjacent first treatment bay 10. From this treatment bay 10, the water may only leave by flowing over the top of a first lower baffle 9 into the adjacent second treatment bay 10. Thus, the water must flow generally upwardly through the first treatment bay 10, then generally downwardly through the second treatment bay 10, exiting through the gravel 4 beneath a second upper baffle 8. As shown by arrows 12, the contaminated water must thus flow generally upwardly and generally downwardly through successive treatment bays 10 until it reaches the water outlet 7. Figure 1 shows four treatment bays 10, but any convenient number may be used. A final collector bay (not shown) may be provided immediately before the water outlet 7, if desired.

This arrangement ensures that the contaminated water undergoes multiple passages through the root system of the reeds in the bed 1, and so maximises the contact time between the contaminated water and the root system and its associated bacteria.

Figure 2 shows how the reed bed I is made up of a plurality of individual modules 13. The distributor bay II adjacent the water inlet 6 contains no reeds, but the remainder of the reed bed I is packed with a regular array of reed bed modules 13. The distributor bay 11 is straightforward to hose down, for example if solids are fed to the bed I in error. Each module 13 contains a plurality of reeds 14 (only a representative sample of the reeds 14 are shown, for clarity).

The reeds 14 are grown in the modules 13 before the reed bed I itself is constructed. An appropriate number of modules 13 containing reeds 14 of the requisite degree of maturity are then transported from the site at which they were grown to the reed bed 1, and simply placed on top of the layer of gravel 4 within the wall 2. Since this does not disturb the reeds 14 and their root system, the reed bed I will be operable almost immediately.

A single reed bed module 13 is shown schematically in Figure 3. The module 13 comprises an open-topped container 15, shown in cross-section in Figure 4. A layer of a support medium 16 for growing reeds is held in a lower part of the container 15. The support medium 16 preferably comprises a mixture of materials including gravel and "imploded glass". This is a fine particulate glass material that has been found to be beneficial for growing reeds for reed beds. It is believed that it comprises or creates pores in the layer 16 having a suitable size to support the bacteria usually associated with reed root systems but not supporting harmful bacteria, such as are known occasionally to attack reed beds and their bacterial load. Thus, not only do the desired bacteria grow in the root system itself, but throughout the layer of support medium 16, leading to a higher concentration of contaminant-processing species in the bed.

Sections of reed root rhizome are planted in the support medium 16 and grow horizontally, producing downwardly-extending roots and upwardly-extending reed stems 14 at intervals.

After about two years, a complex, stable root structure will have formed, and the module 13 may then be picked up, transported and simply plugged into a reed bed 1 as shown above. It is also possible to remove modules 13 from an existing reed bed I, for example if their reeds 14 should be harmed by an influx of an inappropriate pollutant or if the passage of water therethrough is blocked for any reason. Once a module 13 has been removed, it may be washed or back-washed, and then replaced in the bed 1. Alternatively, one may simply insert fresh modules 13.

Reed bed modules 13 may also be added to a conventional reed bed, either to replace existing reeds or to extend the area of the bed at short notice.

A preferred form of container 15 for the reed bed modules 13 is shown in Figure 4. This is a rectangular open-topped crate, roughly 70cm long, 50cm wide and 30cm in height, formed as a unitary plastics moulding. Each wall 17 of the container 15 is provided with one or more windows 18, through which water may flow. A floor 19 of the container 15 is provided with a plurality of smaller openings 20, also for passage of water therethrough. Conveniently, at least two handle holes 21 are provided in opposite walls 17 of the container 15, just below its rim 22, so that the container 15 may easily be grasped, lifted, carried and dropped into place in the reed bed 1. This size of container 15 may be handled by one man.

The windows 18 and openings 20 allow water to pass freely into and out of the container 15, both while the reeds 14 are being grown in the module 13, and when in use in the reed bed 1.

The container 15 thus allows contaminated water full access to the reed root system.

In any case, the reed bed I will usually be operated as shown in Figure 3. A surface 23 of the water S in the bed I should be higher than the rim 22 of the container 15 of each module 13.

Thus, containers 15 with fewer or even no windows 18 could also be used. All that should be needed is that the containers 15 provide at least one route for water to pass upwardly or downwardly through each module 13 and the reed root systems therein.

Claims

II CLAIMS

1. A reed bed module adapted to extract pollutants such as ammonia from water, comprising open topped container means having floor means and/or wall means adapted for passage of water therethrough, a layer within said container means of substrate material adapted to support the growth of reeds as defined herein, and a plurality of said reeds growing from said substrate material.

2. A reed bed module as claimed in claim 1, dimensioned to be portable by no more than two persons, optionally to be portable by one person alone.

3. A reed bed module as claimed in either claim I or claim 2, wherein the floor and/or wall means thereof are provided with a plurality of apertures adapted for water to * ..

flow therethrough. *1SS * * ****

4. A reed bed module as claimed in any one of the preceding claims, comprising reeds * grown therein prior to the module being transported to a location at which extraction **** * I...

*:*. of pollutants is to occur.

5. A reed bed module as claimed in any one of the preceding claims, wherein the substrate material comprises a porous particulate material.

6. A reed bed module as claimed in claim 5, wherein said porous particulate material comprises pores adapted to support bacteria such as those associated with reed root systems.

7. A reed bed module substantially described herein with reference to the Figures of the accompanying drawings.

8. A reed bed means adapted for extraction of pollutants such as ammonia from water, comprising an operatively interconnected plurality of reed bed modules as claimed in any of the preceding claims.

9. Reed bed means as claimed in claim 8, comprising enclosure means having floor means and wall means impervious to water, each of said plurality of reed bed modules being located within said enclosure means.

*:*::*

10. Reed bed means as claimed in claim 9, wherein said enclosure means comprises excavation means. **S. * I * SS* I...

11. Reed bed means as claimed in either claim 9 or claim 10, wherein the wall means of *.. *

said enclosure means extends above an adjacent ground surface external of the ****

S *.*.

*:*. enclosure means.

12. Reed bed means as claimed in any one of claims 9 to 11, wherein the enclosure means is provided with water impermeable membrane means extending across floor and wall means thereof

13. Reed bed means as claimed in any one of claims 8 to 12, wherein each said reed bed module is disposed adjacent at least one other reed bed module.

14. Reed bed means as claimed in any one of claims 8 to 13, wherein said reed bed modules are adjacently disposed in a regular array.

15. Reed bed means as claimed in any one of claims 8 to 14, wherein the reed bed means is adapted to be filled, in use, with sufficient water that a water surface is above an upper surface of the substrate material in each reed bed module, optionally above an upper rim of the container means of each reed bed module of the reed bed means.

16. Reed bed means as claimed in any one of claims 8 to 15, divided by partition means into a sequence of bays through which water may successively flow.

17. Reed bed means as claimed in claim 16, wherein said partition means comprise a * ** series of baffle means, so disposed that water may flow over or under alternate baffle *I** * * S.. S means of the series. *5*S * SS S. S

S *5S

18. Reed bed means as claimed in either claim 16 or claim 17, wherein each said bay *SSS contains at least one, preferably an array of reed bed modules, so arranged that water passing through the bay must pass through at least one reed bed module.

19. Reed bed means substantially as described herein with reference to the Figures of the accompanying drawings.

20. A method of extracting pollutants from water, comprising the steps of providing at least one reed bed module as claimed in any one of claims I to 7, transporting said at least one reed bed module and the reeds grown therein to a location at which extraction of pollutants is to occur, incorporating said at least one reed bed module into reed bed means and passing polluted water therethrough. * ** * V S * ** **.* * * * S S.,., * ** ** S

S S..

S *SSS

S * S S * 55