WO2004052796A1

WO2004052796A1 - Rotating biological contactor

Info

Publication number: WO2004052796A1
Application number: PCT/GB2003/005294
Authority: WO
Inventors: Bryan Nigel Victor Parsons
Original assignee: Copa Limited
Priority date: 2002-12-10
Filing date: 2003-12-04
Publication date: 2004-06-24
Also published as: AU2003288425A1; GB0228820D0

Abstract

A rotating biological contactor (20) has a plurality of media plates (15) for biological growth, the media plates (15) being arranged in a radial rotationally symmetric array, around a central cylinder (10), in to a generally cylindrical assembly, the radial shape of the media plates (15) being formed to an involute curve, so that the gap between adjacent media plates (15) remains substantially constant through out the assembly.

Description

Rotating Biological Contactor

This patent application relates to water purification apparatus and in particular to rotating biological contactors.

A rotating biological contactor is a device in which algae is encouraged to grow on a substrate, utilizing the effluent contaminating the water as a food or fertiliser. The substrate is half submersed and rotated in the polluted water and is thus continuously being immersed then exposed to atmospheric oxygen. Detritus falls from the substrate and collects at the bottom of the containment vessel and is mechanically removed, periodically.

According to one aspect current invention the rotating biological contactor comprises a plurality of media plates for biological growth arranged in a radial rotating symmetric array, around a central cylinder, in to a generally cylindrical assembly, wherein the profile of the media plates is formed to the same involute curve shape.

The involute curve is a mathematically defined shape representing the locus of a point attached to a taut string unwrapping from a cylinder. Using the involute curve for the profile ensures that the gap between adjacent media plates remains substantially constant through out the assembly.

Preferably the rotational biological contactor assembly is manufactured from a number of flat sheets of material joined to the central cylinder, equi-spaced around the cylindrical surface, with a constant thickness spacers placed between all the adjacent sheets, and the sheets are then wound around the central cylinder until the spacers bridge the gap between the sheets along the whole length, to form the involute profile for the media plates. Spacers may be positioned at spaced intervals across the width of the contactor, so as to divide the space between adjacent plates into a series of discrete channels. According to a preferred embodiment, spacers are provided along the side edges of the plates, the spacers terminating short of the edge of the plates attached to the cylinder, so as to provide an outlet for water flowing through the channels.

According to a preferred embodiment the rotating biological contactor is mounted horizontally within a vessel, means being provided for the entry and exit of the polluted water, such that the proportion of plate immersed in the water is approximately half the total area plates and wherein buoyant chambers within the central cylinder provide support for the cylindrical assembly.

According to a further preferred embodiment the outer edge of the media plates in the cylindrical assembly is formed to create a bucket of a waterwheel so that power to drive rotational components is derived from water power acting directly upon the contactor. The contactor in this embodiment is shaped to co-operate with a flow of water to provide the drive torque in the manner of the water wheel. The water power could be generated by a submersible pump sited within the containment vessel. The speed of rotation might be controlled by a mechanical or electrical escapement. Alternatively the rotor might be driven by air bubbling from beneath causing the buckets to be buoyant. A combination of both air and water drives might also be applied.

Alternatively the contactor may be driven by a motor, through a suitable drive mechanism.

Preferably the complete water purification plant will comprise a series of such sections of the rotating biological contactor. Different arrangements for the substrate would be used depending on the position of the rotating biological contactor section in the series comprising the complete water treatment plant.

In a further embodiment the containment vessel in which the rotating biological contactor is housed could be made removable for the purposes of cleaning and emptying. In an alternative arrangement the containment vessel might be fitted with a detachable lining which might be removed for cleaning purposes and ensuring adequate contact time for the biomass on the media plates to treat the sewage.

Various embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, in which;

Figures 1 a and 1 b illustrates diagramatically a single media plate formed to an involute profile in isometric and end elevation for a rotating biological contactor in accordance with the present invention;

Figure 2 illustrates diagramatically a rotating biological contactor assembly designed for drive by water;

Figure 3 illustrates diagramatically a water treatment plant comprising a rotating biological contactor in a tank;

Figures 4a and 4b illustrates diagramatically a method of construction for the media plates of the rotating biological contactor;

Figure 5 shows a part sectional perspective view of a rotating biological contactor in accordance with the present invention; and

Figure 6 shows a drive mechanism for the rotating biological contactor shown in figure 5. In figure 1 a and 1 b a single media plate 1 5 is shown attached along one edge to the central cylinder 10. The media plate 15 is shaped to conform to the involute curve. A small portion of the media plate is bent through a right angle at the outer peripheral end 16. Figurel a is an isometric view showing the longitudinal join of the media plate 1 5 with the central cylinder 10.

In Figure 2 the media plates 15 have been formed around the central cylinder 10 to form a rotating biological contactor 20. Flanges 25 interconnect the outer peripheral ends 16 of adjacent media plates 15 to form closed troughs or buckets 21 around the outer periphery of the contactor. A containing strap 28 wraps around the circumference of the assembly to hold the contactor together. The interior of the central cylinder 10 is hollow and water tight to form a buoyant support for the assembly.

In figure 3 a containment vessel 32 has an inflow pipe 12 and an outflow pipe 13 and contains polluted water for treatment. The media plates 15 attached to the central cylinder 10 are floating within the containment vessel 32. The media plates 15 are shaped so that water from water pipe 35 collects in troughs or buckets 21 formed at the peripheral edges of the media plates 1 5 and provides a torque due to the weight of the water tending to rotate the assembly about its centre. Alternatively or additionally air from air pipe 36 rises through the water in containment vessel 32 to be caught in the upturned buckets 21 , which provides a buoyant torque to the assembly and thus cause rotation.

Figure 4a shows the media plates 15 as being initially flat with a small portion at the outer peripheral end 1 6 turned at a right angle. The media plates 15 are attached longitudinally along one edge and are equally spaced around the central cylinder 10 and splay out radially. Figure 4b shows the media plates 1 5 partly wound down to demonstrate a manufacturing process.

In the rotating biological contactor 20 illustrated in figure 5, constant thickness spacers 50, 52, 54 are located between adjacent media plates 15 and extend longitudinally thereof. Spacers 50 are located adjacent the side edges of the media plates 15, spacers 52 are located centrally of the media plates and spacers 54 are located intermediate of spacers 50 and 52. The media plates 15 are wrapped down onto the spacers 50, 52 and 54 along the full length of the spacers 50, 52, 54 so as to maintain constant spacing between the media plates 1 5 and divide the gap between the media plates 15 into four discrete channels 56. As illustrated in figure 5, outer spacers 50 are terminated short of the ends of the media plates 15 attached to the cylinder 10, so as to provide on outlet 58 for water flowing through the channels 56. The central spacers 52 may extend to the inner ends of the media plates 15 and the intermediate spacers 54 preferably extend to a radial position between the outer spacers 50 and inner spacers 52.

Figure 6 shows an electric motor drive for the rotating biological contactor 20 illustrated in figure 5, the rotating biological contactor assembly being omitted for clarity. A pair of end plates 70 are secured one to each of the ends of cylinder 10. The end plates 70 are interconnected by three tie rods 72 which are located symmetrically of the end plates 70 in bores 74 formed adjacent the outer circumference of the end plates 70. A support shaft 76 is rotatably mounted in central bores 78 in the end plates and is located axially thereof in suitable manner (not shown).

The tie rods 72 extend at one end, through the end plate 70 to form journals 80. A drive plate 82 is drivingly connected to an electric motor 84, via a gear box (not shown), at a level above the axis of rotation of the cylinder 10. The drive plate 82 has three pins 86 located symmetrically of the rotational axis of the drive plate 82, the pitch circle diameter of the pins 86 being the same as that of the journals 80. Each pin 86 is connected to a corresponding journal 80 by means of a link 88, the pins 86 and journals 80 being mounted in bearings 90 adjacent opposite ends of the links 88. In this manner, rotation of the drive plate will be transmitted to the cylinder 10 and rotating biological contactor 20 formed thereon. The offset of the electric motor 84 from the axis of rotation of the cylinder 10 allows the motor to be mounted in a containment vessel, above the level of water therein.

A crank 90 is non-rotatably secured to the end of the support shaft 76 at the end remote from the drive plate 82, externally of the end plate 70. The end of the crank 90 remote from the support shaft 76 has a pin 92 which engages a bearing mounted on a support structure. The pin 92 is mounted so that it is coaxial with the drive plate 82, so that the cylinder 10 may swing about the common axis of the pin 92 and drive plate 82, to find its buoyant level.

In an alternative embodiment flanges may be provided on the central cylinder 10, the flanges having involute grooves which support side edges of the media plates 15, along at least a part of their lengths. The flanges will be provided at the extremities of the cylinder 10. Additional flanges may be provided at spaced locations, between the extremities of the cylinder 10.

Apertures are provided in the flanges, to provide outlets for water flowing between the media plates 15.

The media plates may be secured to the cylinder and/or the flanges. Alternatively tie rods may be secured adjacent the inner periphery of the flanges, so that they extend across the flanges parallel to the cylinder, the inner edges of the media plates 1 5 being secured to the tie rods by, for example, being wrapped around the tie rods and welded.

A series of rotating biological contactor tanks can be arranged so that the outfall of the first feeds the inlet of the second. All of the rotors can be fed by their own water source. In the event of failure of one rotor the remaining rotors will continue to work. Replacing a rotor might be achieved without stopping the remaining working rotors.

Claims

1 . A rotating biological contactor (20) comprising a plurality of media plates (15) for biological growth, the media plates (15) being arranged in a radial rotationally symmetric array, around a central cylinder (10), in to a generally cylindrical assembly, characterised in that the radial shape of the media plates (15) is formed to an involute curve so that the gap between adjacent media plates (1 5) remains substantially constant through out the assembly.

2. A rotating biological contactor (20) as claimed in claim 1 , characterised in that spacers (50,52,54) are located between adjacent media plates (15) in order to maintain uniform spacing between the media plates (15).

3. A rotating biological contactor (20) as claimed in claim 2, characterised in that spacers (50) extend longitudinally of the media plates, adjacent the side edges of the media plates (15).

4. A rotating biological contactor (20) as claimed in claim 3, characterised in that the spacers (50) terminate short of the edge of the media plates (15) attached to the central cylinder (10) in order to provide an outlet from the channel (56) defined between adjacent media plates (15).

5. A rotating biological contactor (20) as claimed in any one of claims 2 to 4, characterised in that a plurality of spacers (50,52,54) are spaced across the media plates (15), so as to divide the gap between adjacent media plates (15), into a plurality of channels (56).

6. A rotating biological contactor (20) as claimed in any one of the preceding claims, characterised in that flanges are provided on the central cylinder (10), the flanges having involute grooves which support the side edges of the media plates along at least a portion of their length.

7. A rotating biological contactor (20) as claimed in any one of the preceding claims, characterised in that the rotating biological contactor (20) is mounted horizontally within a vessel (32), the vessel (32) being provided with an inlet (12,35) to for polluted water and an outlet (13) for treated water, so that the level of water in the vessel (32) will be sufficient to immerse the rotating biological contactor (20), so that approximately half the total area of media plates is immersed, buoyant chambers being provided in the central cylinder (10) to provide support for the rotating biological contactor (20).

8. A rotating biological contactor (20) as claimed in any one of the preceding claims, characterised in that the outer edges (16) of the media plates (15) are formed to create buckets (21 ) of a waterwheel, so that power to drive the rotating biological contactor (20) is derived from water power acting directly upon the rotating biological contactor (20).

9. A rotating biological contactor (20) as claimed in claim 8 characterised In that water power to rotate the rotating biological contactor (20) is derived from a submersible pump.

10. A rotating biological contactor (20) as claimed in claim 9 characterised in that the water pump is submersed in the container (32) associated with the unit.

1 1 . A rotating biological contactor (20) as claimed in any one of the preceding claims characterised in that the outer edges (16) of the media plates (15) are formed to create a buoyancy buckets (21 ), so that power to drive rotating biological contactor (20) is derived from trapping air bubbled from an inlet (36) located directly beneath the rotating biological contactor (20).

12. A rotating biological contactor (20) as claimed in any one of the preceding claims characterised in that the speed of rotation rotating of the rotating biological contactor (20) is governed by a mechanical escapement mechanism.

13. A rotating biological contactor (20) as claimed in any one of claims 1 to 1 1 characterised in that the speed of rotation rotating of the rotating biological contactor (20) is governed by an electrical escapement mechanism.

14. A rotating biological contactor (20) as claimed in any one of claims 1 to 7 characterised in that the rotating biological contactor (20) is driven by means of a motor (84) the axis of the motor (84) being offset from the axis of rotation of the rotating biological contactor (20).

15. A rotating biological contactor (20) as claimed in claim 14 characterised in that the motor (84) is drivingly connected to the rotating biological contactor (20) by means of a crank link mechanism (82,86,88,80).

16. A rotating biological contactor (20) as claimed in claim 15 characterised in that the motor is drivingly connected to a drive plate (82), three pins (86) are symmetrically mounted on the drive plate (82), the pins (86) connected to three correspondingly located journals (80) provided on the rotating biological contactor (20) symmetrically of the axis of rotation thereof, by means of links (88).

17. A rotating biological contactor (20) as claimed in claim 16 characterised in that the rotating biological contactor (20) is rotatably mounted on a support shaft (76), the support shaft (76) being mounted for rotation about the axis of the driven plate.

18. A rotating biological contactor (20) as claimed in any one of the preceding claims characterised in that there is provided a removable liner to the vessel (32) to facilitate cleaning.

19. A rotating biological contactor (20) as claimed in Claim 18 characterised in that the liner is a disposable fabric.

20. A plurality of rotating biological contactors (20) as claimed in any one of the preceding claims characterised in that the flow from one rotating biological contactor (20) flows to the next rotating biological contactor (20) to provide a progressive water treatment process.

21 . A method of manufacture for the rotating biological contactor (20) characterised in that a plurality of media plates (15) in the form if flat sheets of material are joined to a central cylinder (10), the media plates (15) being equi-spaced around the cylindrical surface, a constant width spacer (50,52,54) placed between adjacent media plates (15), and the media plates (15) being wound around the central cylinder (10) until the spacers (50,52,54) bridge the gaps between adjacent media plates (15) along the whole length of the spacer (50,52,54), to form the involute profile for the media plates (16).