GB2072647A - Biological reactor - Google Patents

Abstract

A biological reactor comprises a medium filled rotatable drum arranged with its axis horizontal and means for ensuring a constant liquid level in the drum so that it is more than half-filled. Longitudinal partitions or a helical blade divides the medium into portions which are intermittently submerged in liquid under treatment followed by the passage of air thereover, each submerged portion of media being effectively sealed from the air in another portion.

Description

SPECIFICATION Improved biological reactor The present invention concerns an improved biological reactor and a process especially but not exclusively for aerobic and anaerobic treatment of organic waste waters. The apparatus and process of the invention may be used as a reactor for other biological and chemical processes.

The reactor of the present invention is intended especially but not exclusively for use in the treatment of screened organic waste water (sewage and industrial effluent).

Processes presently employed for the treatment of screened organic wastewater involve conventional sewage treatment beds or activated sludge apparatus. Conventional beds require relatively large land areas and their construction involves considerable civil engineering works in that they include, inter alia large reinforced concrete troughs and tanks. Furthermore conventional plants operate at ambient temperatures and hence their efficiency is decreased if, for example, the temperature drops below a predetermined value. When a conventional plant requires repair or replacement considerable outlay is often involved, especially if replacement is required as this involves expensive and time consuming demolition and rebuilding.

Activated sludge plants avoid some of the disadvantages of conventional plants, however, the power required to operate them is considerable and consequently their operating costs are high.

It is an object of the present invention to obviate or mitigate the disadvantages inherent in the plants described above.

According to the present invention there is provided a biological reactor having a container including a medium for assisting in the biological reaction, means in the container for causing liquid under treatment to intermittently cover portions of said medium, those portion of medium not covered being exposed to the gas within the chamber, means being provided in the container to prevent gas flow from one liquid covered portion of medium to another, means being provided for admitting and discharging liquid to the container and means being provided for admitting and exhausting gas for the reaction to and from the container.

Preferably the container is a circular drum divided into segmental compartments each including a portion of medium.

Preferably partitions are provided to define said compartments, the partitions extending in a substantially radial direction from a point spaced from the centre of rotation of the drum to the inner surface thereof. Baffle means are provided at the centre of the drum to direct liquid under treatment from one compartment to its neighbouring compartment.

Alternatively the container is a circular drum having a central tube therethrough, a helical partition being arranged in the annular space between the tube and container wall, said portions of medium being conained in said annular space and each portion being delimited by corresponding facing submersed sections of the vane and the level of liquid under treatment therebetween.

Baffle means in the form of longitudinal radially extending plates are arranged on the tube to protrude part of the way into the annular space, the height of each plate being suficient to ensure that its free edge projects above the liquid level in the drum when it occupies its uppermost position.

Preferably the ends of the helical partition are closed off by a mesh screen to define a cylindrical chamber at each end of the drum.

Preferably the drum is mounted on driven trunnions.

Preferably fluid inlet and outlet cylinders to which liquid to be treated and treated liquid respectively are introduced and exhausted are provided at each end of the drum in communication with said compartments of annular space.

Inlet and outlet chambers are provided in communication with said cylinders, said outlet chamber including a weirto maintain a predetermined liquid level in the chambers, cylinders and drum. Sealing means are preferably provided between the chambers and cylinders to permit relative rotation therebetween.

Inlet vent pipes are provided to permit liquid and gas communication between each compartment of the container and the inlet cylinder and are so located that in operation as a compartment of the container is discharging its liquid to another compartment communication is provided between the interior of the compartment and a gas space above the liquid to be treated in the inlet cylinder. A gas supply pipe is provided to replenish gas in said gas space of the inlet cylinder.

Preferably a similar arrangement of outlet vent pipes is provided at the other end of the container from that provided with inlet vent pipes, said outlet vent pipes allowing for the exhaust of gas from a compartment which is being filled from another compartment and the discharge of treated liquid from the container.

Preferably the exhaust vent pipes when exhausting gas from the container communicate with a gas space above the liquid in the exhaust cylinder and an exhaust pipe allows passage of exhaust gas from said gas space directly to atmosphere or to atmosphere by way of filters, sterilising or other apparatus.

Preferably the container is dividld into four compartments by partitions which are convex when viewed in the direction of rotation of the drum, the partitions extending along the length of the drum.

Futher according to the present invention there is provided a method of biologically treating a liquid comprising introducing a liquid to be treated into a first compartment of a container having a plurality of compartments each including a treatment medium, transferring said liquid to a further compartment while preventing the passage of gas from said one to said further compartment, introducing a fresh charge of gas to said emptying compartment and exhausting gas from said filling compartment.

Still further according to the present invention there is provided a method of biologically treating a liquid comprising introducing the liquid to be treated into a helical compartment containing a treatment medium, introducing liquid into said compartment to partially fill same to submerge portions of the medium, said portions being separated from neigh bouring portions by further portions of the compart ment containing only gas forthe reaction and rotating the compartment to progress the liquid along the helix.

Preferably means are provided for recirculating liquid under treatment from the exit to the inlet of the helix.

Preferably said transfer of said liquid from one compartment to another is achieved by rotating the container.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows an elevation of a biological reactor; Figure 2 shows a sectional end elevation on the line A - A of Figure 1; Figure 3 shows a diagrammatic end elevation in the direction of arrow B of Figure 1; Figure 4 shows a sectional elevation on the line C Con Figure 1; Figure shows a similar view but with the drum of the reactor rotated through 450 from the Figure 4 position; Figure 6shows a section on the line D - D of Figure 4; Figure 7shows a section on the line E - E of Figure 5;; Figures shows a view similar to Figure 1 of a modified reactor and Figure 9 shows a sectional end elevation on the line IX - IX of Fiure 8 A biological reactor comprises a cylindrical drum 10 provided with circumerential runners 12 mounted on driven trunnions 14. The drum is divided into four equal compartments 16 by partitions 18 which extend for the length of the drum, are slightly curved and all extend radially inwards from the inner surface of the drum to terminate at a point spaced from the axis of rotation of the drum. A cruciform baffle having four similar arms 20 is arranged with the line of intersection of its arms coincident with the drum axis in such a way that the arms 20 divide the gap between the inner ends of adjacent partitions 18 equally in two, the arms 20 projecting into the compartments 16 defined by neighbouring partitions.

Liquid to be treated is introduced into the container, in a manner to be described hereunder, such that the liquid level L is high enough to ensure that the inner ends of the partitions 18 are submerged at all rotational positions of the drum.

It will be realised therefore and appreciated parti cularlyfrom Figures 4 and 5 that as the drum rotates, anticlockwise as viewed in the drawings, liquid flows from one emptying compartment between the gap defined by the partitions ends into the next adjacent compartment, the arms 20 of the baffle ensuring that little if any liquid passes into other compartments. It will be observed also that since the ends of the baffles are always submerged there is no possibility of air from the space above the liquid in an emptying compartment passing into an adjacent compartment.

To permit the emptying and filling of compartments 16 and to permit the flow of liquid through the drum, liquid and air filling and exhausting means are required and thse are provided by vent pipes arranged at each end of the drum, there being four inlet vent pipes 22, one for each comparment 16, and four exhaust vent pipes 24, again one for each compartment 16. The vent pipes each communicate with a compartment 16 through a passage in the end walls 26,28 of the drum, the other end of the pipes communicating with inlet and exhaust cylinders 30, 32 mounted co-axially on the drum ends 26,28 respectively. Each cylinder 30,32 is provided with a bearing pipe 34 which is rotatably mounted in a corresponding bearing pipe 36 of a stationary inlet or outlet chamber 38,40 respectively an O-ring 41 being provided to seal the joint between the bearing pipes 34 and 36.

Outlet chamber 40 is provided with a weir 42 the height of which determines the liquid level L within the drum 10.

It will be appreciated that in order to ensure that fresh air is introduced to an emptying compartment and is thereafter discharged from that compartment as it is refilled without the air passing through any other compartments, the location of the passages in the drum ends 26, 28 communicating with the inlet and exhaust vent pipes 22,24 is important. The positioning of said passages is best observed in Figures 3 and 4. Figure 3 shows that the passage to which the inlet vent pipes are connected are each located near the outer circumference of the drum and 26 and adjacent a partition 18 at the leading end of the compartment 16 in the direction of rotation R.

With this arrangement the first zone of a compartment 16 to be rotated above the liquid level Lwill be provided with a passage communicating with an inlet vent pipe 22 so that as liquid flows from said compartment into the next adjacent compartment the space previously occupied by the liquid will be filled with fresh air from the air space 44 in the inlet cylinder 30. Fresh air is supplied to said air space 44 by a supply pipe 46 which passes from said inlet cylinder 30, and through said inlet chamber 38.

When certain of the inlet vent pipes are providing airto emptying chambers it will be realised that the remaining vent pipes 22 provide liquid communication between compartments below liquid level L and the inlet cylinder 30. Liquid to be treated supplied to the inlet chamber 38 causes a difference in head between the inlet and outlet chambers and correspondingly a flow of liquid through the drum.

A similar arrangement is provided on the other drum end 28 to permit exhaust of air from compartment 16 and outlet of treated liquid. The arrangement of exhaust vent pipes 24 is best illustrated in Figure 2. The passages through the drum end 28 communicating with the exhaust vents are arranged at the outer cicumference of said drum end and adjacent the partitions 18 at the trailing end of each compartment 16 in the direction of rotation R. Thus as the drum 10 rotates and liquid from one compart ment flows into another, due to this rotation, air in this filling compartment is allowed to exhaust through the exhaust vent pipe 24 into the exhaust air space 46 above the liquid in the exhaust cylinder 42.

Exhaust air from the exhaust air space 48 may escape to atmosphere or to a filtration and/or sterilisation device by way of a J-pipe 50. When one exhaust pipe is venting exhaust air from a compartment 16 at least one other exhaust pipe is providing liquid communication between a compartment containing liquid and the exhaust cylinder 32, this permitting flow of liquid through the drum.

In view of the arrangement of baffles, liquid level and passages through the drum end 26 it will be realised that air can only be drawn into a compartment 16 by way of its inlet vent pipe 22. Similarly air can only be exhausted from the compartment 16 by way, of its exhaust vent pipe 24.

In operation liquid to be treated, for example screened organic waste water, is supplied to the supply chamber 38 until liquid in the drum reaches level L. Each compartment is prefilled with a medium manufactured from a plastics material of random pack or of tubular or modular construction which provides a greatly increased surface area such that liquid thereon may be subjected to the maximum air exposure As the drum rotates, typically at a speed of 1 revolution every 2 to 8 minutes, the liquid circulates continuously from compartment to compartment through the media therein. Due to this low rotational speed the liquid level L in the drum remains relatively static and a constant supply of fresh air is passed over the liquid wetted medium.

As the power required to rotate the drum is effectively only that required to rotate the self weight of the drum and not the weight of the liquid therein, the power requirement of the driving means for the trunnions is relatively low and further, in view of the construction if the drum, it can be regarded as a portable unit which is readily removable for repairing, or replacement, may be factory fabricated and involves only a minimum of civil construction, for example a concrete foundation.

Various modifications can be made without departing from the scope of the invention. For example any arrangement providing for the transference of liquid to be treated from one compartment to another and the presentation to emptying compartments of a continuing flow of fresh air will suffice.

Means may be provided for enriching the oxygen content of air supplied to the drum, the drum may be lagged or heated. The inlet and exhaust compartments may be modified such that the treatment process is anaerobic rather than aerobic as described above.

Another modification is illustrated in Figures 8 and 9 in which components similar to those described with reference to Figures 1 to 7 have been given the same reference numerals and, for simplicity will not be described in detail again.

The container in this modification is in the form of an enclosed drum 10 with an internal open ended concentric tube 60 along the axis of the drum. A screw blade 62 the outer limits of which are shown by broken lines of approximately 11/2 - 2 pitches is fitted in the annulus formed by the outer drum 10 and central tube 60, the joints between the screw blade 62 and the outer drum 10 and inner tube 60 being watertight. Radial arms 63, six in number are fitted along the length of the centre tube between the screw blade flights.

The annulus between the outer drum and the inner tube is filled with plastic media 64 of random pack, tubular, modular or sponge construction and is restrained at each end of the central tube by means of a mesh screen 66 which covers the area of the annulus at both ends.

As before, the drum is mounted on rollers trunnions 14 just clear of the floor with its axis horizontal.

The inlet and exhaust cylinders 30, 32 are of a generally similar construction to those shown in Figure 1 as are the inlet and outlet chambers 38,40 and they operate in the same manner. It is noticeable, however, that the inlet and exhaust gas spaces 46,48 communicaate with chambers 68,70 defined at the ends of the drum 10 by the mesh screens 66.

The reactor shown in Figures 8 and 9 operates with a liquid level L slightly above the top of the central tube 60. Incoming liquid raises the level in the inlet chamber 38 and liquid flows into the drum through the tube 34.

Discharge of effluent is by flow over the weir 42 in the outlet chamber 40 which regulates the drum through-flow.

The drum rotates about its axis at 1 revolution every 2-8 minutes in either direction.

The reactor acts as a liquid displacement device, the liquid trapped in each submerged portion between facing sections of the blade 62 being positively propelled through the drum. Liquid movement to an upstream submerged portion is prevented by means of the central tube 60 with attached radial arms 63. Air trapped in the upper portions above the submerged portions is propelled along the drum by movement of the liquid and is positively passed through the medium and induced into and expelled from the drum.

As the drum rotates, the liquid level in the drum remains relatively static due to the low rotational speed of the drum.

The liquid displacement of the screw pump effect is in excess of the liquid through-flow.

Consequently, a head differential occurs between the outlet and inlet end of the drum which induces recirculation of flow through the central tube 60 to the inlet end of the drum.

The helix angle of the screw 62 is designed to propel sludge dislodge from the media to the media free zones or chambers 68,70 at either end of the drum.

Scoops (not shown) constructed on the inside face of the drum end plates 26,28 collect the sludge during each rotation of the drum and deposit the sludge into appropriate chutes (not shown) connected to sludge ports (again not shown) of the inlet/outlet tubes 34.

During forward rotation of the drum, sludge is discharged externally through the sludge port for disposal.

During reverse rotation of the drum, sludge is discharged internally into the incoming liquid to provide sludge recirculation.

Variation of periods of alternate rotatation would regulate the amount of sludge in the system.

Variation in the speed of rotation provides great flexibility regarding recirculation rate, air passage.

Each complete rotation of the drum performs the following: a) The liquid in the drum has been in direct contact with the total media volume in the drum. (Total surface area of the media has been utilized).

b) High recirculation rate has been achieved.

c) Positive movement of air through the drum, in direct contact with total surface area of the media.

Claims (23)

1. A biological reactor having a container including a medium for assisting in the biological reaction, means in the container for causing liquid under treatment to intermittently cover portions of said medium, those portions of medium not covered being exposed to the gas within the chamber, means being provided in the container to prevent gas flow from one liquid covered portion of medium to another, means being provided for admitting and discharging liquid to the container and means being provided for admitting and exhausting gas for the reaction to and from the container.

2. A reactor as claimed in claim 1, in which the container is a circular drum divided into segmental compartments each including a portion of medium.

3. A reactor as claimed in claim 2, in which partitions are provided to define said compartments, the partitions extending in a substantially radial direction from a point spaced from the centre of rotation of the drum to the inner surface thereof.

4. A reactor as claimed in claim 3, in which baffle means are provided at the centre of the drum to direct liquid under treatment from one compartment to its neighbouring compartment.

5. A reactor as claimed in claim 1, in which the container is a circular drum having a central tube therethrough, a helical partition being arranged in the annular space between the tube and container wall, said portions of medium being contained in said annular space and each portion being delimited by corresponding facing submersed sections of the vane and the level of liquid under treatment therebetween.

6. A reactor as claimed in claim 5, in which baffle means in the form of longitudinal radially extending plates are arranged on the tube to protrude part of the way into the annular space, the height of each plate being sufficient to ensure that its free edge projects above the liquid level in the drum when it occupies its uppermost position.

7. A reactor as claimed in claim 5 or claim 6, in which the ends of the helical partition are closed off by a mesh screen to define a cylindrical chamber at each end of the drum.

8. A reactor as claimed in any one of claims 2 to 7, in which the drum is mounted on driven trunnions.

9. A reactor as claimed in any one of claims 2 to 8, in which fluid inlet and outlet cylinders to which liquid to be treated and treated liquid respectively are introduced and exhausted are provided at each end of the drum in communication with said compartments or annular space.

10. A reactor as claimed in claim 9, in which inlet and outlet chambers are provided in communication with said cylinders, said outlet chamber including a weirto maintain a predetermined liquid level in the chambers, cylinders and drum.

11. A reactor as claimed in claim 10, in which sealing means are provided between the chambers and cylinders to permit relative rotation therebetween.

12. A reactor as claimed in any one of claims 9 to 11, when dependent upon any one of claims 2 to 4, in which inlet vent pipes are provided to permit liquid and gas communication between each compartment of the container and the inlet cylinder and are so located that in operation as a compartment of the container is discharging its liquid to another compartment communication is provided between the interior of the compartment and gas space above the liquid to be treated in the inlet cylinder.

13. A reactor as claimed in claim 12, in which a gas supply pipe is provided to replenish gas in said gas space of the inlet cylinder.

14. A reactor as claimed in claim 12 or claim 13, in which a similar arrangement of outlet vent pipes is provided at the other end of the container from that provided with inlet vent pipes, said outlet vent pipes allowing for the exhaust of gas from a compartment which is being filled from another compartment and the discharge of treated liquid from the container.

15. A reactor as claimed in claim 14, in which the exhaust vent pipes when exhausting gas from the container communicate with a gas space above the liquid in the exhaust cylinder and an exhaust pipe allows passage of exhaust gas from said gas space directly to atmosphere or to atmosphere by way of filters, sterilising or other apparatus.

16. A reactor as claimed in any one of claims 2 to 4 and 8 to 15, in which the container is divided into four compartments by partitions which are convex when viewed in the direction of rotation of the drum, the partitions extending long the length of the drum.

17. A biological reactor substantially as hereinbefore described with reference to Figures 1 to 7 or Figures 8 and 9 of the accompanying drawings.

18. A method of biologically treating a liquid comprising introducing a liquid to be treated into a first compartment of a container having a plurality of compartments each including a treatment medium, transferring said liquid to a further compartment while preventing the passage of gas from said one to said further compartment, introducing a fresh charge of gas to said emptying compartment and exhausting gas from said filling compartment.

19. A method of biologically treating a liquid comprising introducing the liquid to be treated into a helical compartment containing a treatment medium, introducing liquid into said compartment to partially fill same to submerge portions of the medium, said portions being separated from neighbouring portions by further portions of the compartment containing only gas for the reaction and rotating the compartment to progress the liquid along the helix.

20. A method as claimed in claim 19, in which means are provided for recirculating liquid under treatment from the exit to the inlet of the helix.

21. A method as claimed in any one of claims 18 to 20, in which said transfer of said liquid from one compartment to another is achieved by rotating the container.

22. A method of biologically treating a liquid substantially as hereinbefore described with refer pence to Figures 1 to 7 or to Figures 8 and 9 of the accompanying drawings.

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