GB2451252A

GB2451252A - A Cleaning Apparatus

Info

Publication number: GB2451252A
Application number: GB0714429A
Authority: GB
Inventors: Martin Roche
Original assignee: Rockbourne Environmental Ltd
Current assignee: Rockbourne Environmental Ltd
Priority date: 2007-07-24
Filing date: 2007-07-24
Publication date: 2009-01-28
Also published as: GB0714429D0

Abstract

Apparatus for cleaning and/or refurbishing a reed bed comprises a body having an open end with the body defining a cavity having an internal volume, wherein the cavity is in fluid communication with silt and/or solids removal means. The silt removal means is a screen with apertures, such as a filter, and may include a suction means. The device may also include an agitation means in the form of a gas or air jet which is supplied to the apparatus by tubes or lances. In operation, the sludge, silt and solid waste is agitated by the gas jet and is sucked through the screen with water but the medium in which the reed bed is planted is not extracted. The cleaning apparatus can form part of a system with a filtration station to separate the solid waste and silt form the water such that the water is recycled and returned to the reed bed. A method of cleaning a reed bed by sucking water to be treated from the reed bed in various locations is also disclosed.

Description

CLEANING

The present invention relates to the cleaning and refurbishment of constructed wetlands and reed beds.

Reed beds play an important role in water treatment. They are used for the secondary and tertiary treatment of sewage, wastewaters, groundwaters, leachates, effluents, surface and storm waters.

A typical reed bed may comprise an essentially rectangular pool having a base with a shallow gradient across it, the pool optionally being lined with clay or an impermeable sheet material. On top of the base there is a layer of a medium, which is typically gravel but may be glass, shredded car tyres or soil etc. At the side of the pool at the higher end of the gradient there is an inlet distribution zone comprising large stones p..

in communication with the top of which zone is an inlet for to-be-treated water. At the side of the pool to the lower end of the gradient there is an outlet collection zone comprising large stones towards the bottom of which there is connected thereto an :: outlet pipe. Common reeds, e.g. phragmites australis, are distributed across the pool.

In use, to-be-treated water flows from the inlet into the reed bed through the inlet distribution zone. The large stones of the inlet distribution zone act to distribute water evenly as it enters the reed bed. The to-be-treated water flows slowly through the reed bed towards the outlet. En route, the water is treated by a complex combination of one or more of removing organic matter, oxidising ammonia, reducing nitrate and phosphorous and also filtration, sedimentation and chemical precipitation.

Over time, the pores or interstitial spaces in the medium can become clogged with silt and other solid matter, reducing the effectiveness of the reed bed. As a consequence, the hydraulic conductivity of the medium is reduced. Also, excessive solid matter can accumulate on the surface of the medium, which can cause the operating water level in the reed bed to rise above workable levels, potentially leading to an overflow of untreated water.

Consequently, reed beds require cleaning and refurbishing periodically.

It is known to refurbish a reed bed by taking the bed offline removing the surface sludge and sometimes digging out the medium. The old medium is disposed of, on site or by landfill. Replacement medium is brought in to fill the bed. In addition, the reeds are removed and then need to be re-planted. A typical reed bed of 500 to 1000 m2 can be offline for two to three weeks while this refurbishment procedure is 10..

undertaken. Thus, temporary replacement treatment facilities may have to be provided.

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: ,* This procedure also has several further disadvantages examples of which include: III.

*. the reed bed needing to be taken offline for a considerable length of time; landfilling the medium is costly and environmentally undesirable; replacement medium needs to be purchased; and the lining of the reed bed may be damaged during the digging out of the medium.

It is also known to dig out the medium and to wash it on site to remove the silts and other solids therefrom. The reed bed is then refilled with the washed medium.

Advantageously, this process negates the need to dispose of the medium and replace it with new medium. However, in addition to many of the disadvantages discussed above, this process also suffers from the fact that the apparatus used to wash the medium may be costly, requires space and consumes a lot of water.

Accordingly, it is a non-exclusive object of the invention to provide an apparatus for cleaning and/or refurbishing a reed bed which offers significant advantages over known techniques. A process using the apparatus and a system incorporating the apparatus are also provided.

It is a further object of the invention to reduce the environmental impact of reed bed refurbishment and to reduce the length of time that a reed bed needs to be taken offline for refurbishment and optionally provide for temporary water treatment to enable continuous discharge. I. * * * *** **.S

In a first aspect of the invention there is provided apparatus for cleaning and/or refurbishing a reed bed comprising a body having an open end, the body defining a cavity having an internal volume wherein the cavity is in fluid communication with silt : *** and/or solids removal means. ** S * S * * **

Alternatively or additionally, the silt and/or solids removal means may comprise a screen having apertures therein or a net located within the cavity.

The size of the apertures in the screen may be varied to suit the particle size of the medium. Typically, the apertures in the screen may be up to 6mm in diameter, for instance approximately 4 mm in diameter. Typically, the screen is made from metal, e.g. stainless steel, but may alternatively be made from plastic or be in the form of a net or wire gauze.

The silt and/or solids removal means may comprise suction means, the suction means being in fluid communication with the cavity.

The screen or net may preferably be located within the cavity between the open end of the body and the suction means, the screen or net thereby providing, in use, a permeable barrier.

The apparatus may further comprise agitation means.

The agitation means may be mechanical. Alternatively, the agitation means may comprise a source of air or other gas and/or means for delivering the gas to an intended site. The air or other gas may be compressed. *.I. * **IS

The means for delivering the air or other gas may comprise one or more tubes or lances. * ** * * * **S.

Preferably the means for delivering the air or other gas may comprise between 10 and 30, more preferably between 10 and 20, tubes or lances.

The tubes or lances may be connected to a supply of air or another gas.

The supply of air or another gas may be integral to, or separate from, the apparatus.

Advantageously, the apparatus may be portable from one site of use to the next.

In a second aspect of the invention there is provided a method of refurbishing a reed bed in situ, the method comprising: a) sucking to-be-treated water from a first location in the reed bed; b) repeating step a) at one or more further locations.

The length of time the cleaning apparatus remains at each location may be varied depending on the degree of silt, the depth and type of medium and the water and air flow rates.

For example, the medium may be gravel comprising particles of 10 to 20 mm in diameter, the gravel having a mean depth of between say 0.6m and O.75m. *S.. * * **..

The cleaning apparatus may remain at each location for up to 20 minutes, preferably between 2 and 10 minutes, more preferably between 2 and 5 minutes. * .. * * ****

** The method may further comprise the step of sending the water sucked from the reed bed to a filtration station.

The method may further comprise providing a screen or net to prevent any pieces of a medium from the base of the reed bed that is entrained with the water sucked from the reed bed from passing to the filtration station.

The method may further comprise recycling the water sucked from the reed bed subsequent to the water having passed through the filtration station by re-introducing the water to the reed bed.

The method may further comprise agitating the water and/or medium at the base of the reed bed. Agitation may be effected using mechanical means or by an air or gas stream. Agitation may or may not be continuous throughout the process and may be effected at any stage of the process.

According to a further aspect of the invention there is provided a system for the in situ refurbishment and/or cleaning of reed beds, the system comprising: * at least one cleaning apparatus, the apparatus comprising silt removal means; and * a filtration station in fluid communication with the cleaning apparatus. *SS. * * I...

Preferably, the at least one cleaning apparatus is movable from one site of use to the next within a reed bed and/or from one reed bed to another. * ** * * S *S** ** S

The system may further comprise a recycling line, the recycling line connecting the filtration station with an inlet to the reed bed to allow flushing of the reed bed with filtered water.

The system may further comprise a control chamber for receiving and assessing the quality of water that has passed through the reed bed. The control chamber may be connected by a recycling line to the filtration unit and/or be in fluid communication with means for discharge of treated wastewater.

As will be apparent to the person skilled in the art the present invention provides many improvements over known apparatus, methods and systems.

The present invention provides for in situ cleaning and/or refurbishment of the gravel medium, especially gravel, without the need for removal of the medium by excavation Compared with the prior art, the length of time that the reed bed is offline during refurbishment is greatly reduced. Moreover, because the present invention obviates the need for digging or excavation, the risk of damage to the lining of the reed bed is ameliorated. Also, there is no need to remove and re-plant the reeds. The present invention has less of an impact on the environment than known methods and also provides cost savings. The filtration station also enables treated water to be discharged without the need for temporary treatment facilities. **.* * S * *S.

The invention will now be described by way of example only in terms of a specific embodiment and with reference to the following Figures: * S. * S * *SS.

*. Figure 1 shows a cross sectional view of an apparatus according to the invention.

Figure 2 shows a plan view of a typical reed bed with the apparatus according to the invention.

Referring to Figure 1, there is shown in cross section a preferred embodiment of the apparatus according to the present invention. The apparatus 100 comprises a body 101 having an open end 102 at its intended bottom face. The body 101 comprises a cavity 103 having an inner volume. Connected to the intended upper surface of the body 101 and communicating with the cavity 103 is a tube 104 to which suction means, e.g. a pump (not shown), is attached. At its other end, the tube 104 is connected to a filtration station (not shown).

Located within the cavity 103 is a mesh-like screen 105. This screen 105 is positioned between the open end 102 of the body 101 and the tube 104, the screen has a plurality of apertures which are sized such that any gravel medium that becomes entrained with the water being sucked from the reed bed cannot pass through the screen, while allowing smaller silt and solid particles to pass through the screen. The screen is made from stainless steel and the apertures are approximately 4 mm in diameter. * *

The apparatus 100 also comprises a plurality of lances 106 for delivering air or another gas to a site of use. The lances 106 are connected to a supply of air or : .. another gas (not shown). **S. S. * S * S **

The lances 106 are located such that, in use, they deliver air or another gas to an area below the open end 102 of the body 101.

The mode of operation of the apparatus 100 will now be described.

The apparatus 100 is positioned at a first location in a reed bed, with at least the open end 102 ol the apparatus 100 within the water contained in the reed bed. The lances 106 are directed towards the medium at the base of the reed bed. Air is delivered through the lances 106 to agitate the silt and other solid material deposited on and within the medium. The air percolates upwards, helping to lift silt and other solid material to the water surface. Although it is highly variable, in some instances it has been found that delivering 20 cubic metres of air per hour can lift around 2 to 3 cubic metres of silt.

The suction means (not shown) are turned on to draw silt-containing water from the cavity 103.

The screen 105 located within the cavity 103 ensures that any medium that may be sucked up with the silt-containing water does not pass on to the tube and filtration station. The smaller silt and other solids particles entrained in the water are able to *... *

pass through the screen 105. *. * **.

The method of the invention will now be described with reference to Figure 2 which is : *. a plan view of a typical reed bed with the apparatus of the invention.

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Figure 2 shows wastewater for treatment 1 flowing to an inlet distribution zone 2 comprising distribution pipework, channels or troughs 3. On the opposite side of the reed bed from the inlet distribution zone 2 is a collection zone 7 comprising collection pipework 8. Collection pipework 8 leads to a control chamber 9. Control chamber 9 is connected by a first recycling line 10 to a filtration station 11. Control chamber 9 is also connected to a treated wastewater discharge 12. Filtration station 11 is in communication with a sludge storage and/or dewatering station 17. Filtration station 11 is also in communication with treated wastewater discharge 12. Filtration station 11 is connected to a second recycling line 13 which communicates with inlet zone 2.

At a position within the reed bed there is shown a cleaning apparatus 5. An air source 14 is connected to apparatus 5 by an air supply line 15. An extraction line 16 connects apparatus 5 with filtration station 11. An area of the reed bed in which the gravel has been cleaned 4 is marked, as is an area where the gravel has yet to be cleaned 6.

Water containing silt or other solids passes from the cleaning apparatus 5 to filtration station 11 via extraction line 16.

The filtration station 11 provides a high quality effluent containing few suspended solids. This effluent is transferred via second recycling line 13 to the inlet zone 2 and * * subsequently assists with further flushing and cleaning. * * * ***

Silt and solids retained by the filtration station 11 are discharged to sludge storage : .* and/or dewateririg station 17 for disposal of the silt and solids removed from the reed *** bed. These silt and solids may be useful in other industries, e.g. in the manufacture of compost. Incoming wastewater and recycled waters help to flush out any residual silt or solids towards the cleaning apparatus 5 and/or the collection zone 7.

Wastewater and recycled water which is not transferred to the filtration station 11 via cleaning apparatus 5 and extraction line 16 flows through the collection zone 7 and collection pipework 8 to the control chamber 9.

From the control chamber 9 the water is diverted along first recycling line 10 to the filtration station 11 and then may be discharged off site via wastewater discharge 12.

Typically, a sequential pattern is employed, whereby the cleaning apparatus 5 is moved from one location to a neighbouring location until the entire surface area of medium in the reed bed has been treated. Upon completion of this sequence, the cleaning apparatus can be removed, e.g. to be re-deployed in another reed bed.

The water is then recycled via the filtration station 11 at a high rate to help flush out any residual solids and silts from the reed bed for capture in the filtration station 11.

Any permanent pipework and chambers associated with the reed bed may be jet washed either contemporaneously or subsequently.

Flushing with recycled water may be carried out until the quality of the water reaching *... * *

the control chamber 9 meets a required standard, at which point the filtration station 11 and recycling lines 10, 13 may be disconnected and discharge from control chamber 9 to waste water discharge 12 may be re-established * ** * * *S*.

Alternatively, if no control chamber is present in the system, a temporary sump may be located within the reed bed. The temporary sump may also be present in the same system as the control chamber The person skilled in the art will appreciate that many changes can be made to the disclosure above without departing from the scope of the present invention.

For instance, while the invention has largely been described in terms of a single cleaning apparatus operating on a single reed bed at any particular time, it would be equally possible to use more than one cleaning apparatus operating in a reed bed at the same time, the more than one cleaning apparatuses being connected to either a single filtration station or each to its own filtration station. I. *. * I.. * * **... 0s * *..

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Claims

1. Apparatus for cleaning and/or refurbishing a reed bed comprising a body having an open end, the body defining a cavity having an internal volume wherein the cavity is in fluid communication with silt and/or solids removal means.

2. Apparatus according to Claim 1, wherein the silt and/or solids removal means comprises a screen having apertures therein.

3. Apparatus according to Claim 2, wherein the apertures in the screen are up to 6mm in diameter, say up to 4mm in diameter.

4. Apparatus according to any one of Claims 1, 2 or 3, wherein the silt and/or solids removal means further comprises suction means.

5. Apparatus according to Claim 4, wherein the suction means is in fluid communication with the cavity.

6. Apparatus according to Claim 4 or Claim 5, wherein the screen is located within the cavity between the open end of the body and the suction means.

7. Apparatus according to any preceding Claim, further comprising agitation means.

8. Apparatus according to Claim 7, wherein said agitation means comprises a source of gas.

9. Apparatus according to Claim 8, further comprising means for delivering the gas to an intended site.

10. Apparatus according to Claim 9, wherein the means for delivering the gas comprises one or more tubes or lances.

11. A method of refurbishing a reed bed in situ, the method comprising: Co a) sucking to-be-treated water from a first location in the reed bed; b) repeating step a) at one or more further locations. (0

12. A method according to Claim 11, wherein treatment at each location lasts for up to 20 minutes.

13. A method according to Claim 11 or Claim 12, wherein treatment at each location lasts for between 2 and 10 minutes, say for between 2 and 5 minutes.

14. A method according to any one of Claims 11 to 13, further comprising the step of sending the water sucked from the reed bed to a filtration station.

15. A method according to any one of Claims 11 to 14, further comprising recycling the water sucked from the reed bed subsequent to the water having passed through the or a filtration station by re-introducing that water to the reed bed.

16. A method according to any one of Claims 11 to 15, further comprising agitating the water and/or medium at the base of the reed bed.

17. A method according to Claim 16, wherein agitation is effected by using mechanical means.

18. A method according to Claim 16, wherein agitation is effected by a gas stream.

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19. A system for the in situ refurbishment and/or cleaning of reed beds, the system comprising: * at least one cleaning apparatus; and * a filtration station in fluid communication with the cleaning apparatus, wherein the apparatus comprises silt removal means.

20. A system according to Claim 19, wherein said at least one cleaning apparatus is moveable from one site of use to the next within a reed bed and/or from one reed bed to another. (0

21. A system according to Claim 19 or Claim 20, further comprising a recycling line.

22. A system according to Claim 21, wherein the recycling line connects the filtration station with an inlet to the reed bed.

23. A system according to any one of Claims 19 to 22, further comprising a control chamber for receiving and assessing the quality of water that has passed through the reed bed.

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24. A system according to Claim 23, wherein the control chamber is connected by a recycling line to the filtration unit and/or is in fluid communication with means for discharge of treated wastewater. (0

25. Apparatus as described herein with reference to the accompanying drawings.

26. A method of refurbishing a reed bed in situ as described herein.

27. A system for the in situ refurbishment and/or cleaning of reed beds as described herein.