GB2143154A - Liquid treatment apparatus - Google Patents

Abstract

In a water treatment process and apparatus, the jets 21 (or 41) in the distributor arms 20 (or 40) of a percolating filter are kept clear from jamming by automatic actuation of plungers 27 (or 47) which enter the jets to dislodge any obstructions therein. The plungers may be mounted on individual brackets 24 associated with respective jets 21, or on a common axle 51 and actuated by a trailing dependent lever 50. <IMAGE>

Description

SPECIFICATION Liquid treatment apparatus This invention relates to liquid treatment apparatus and, more particularly, to distributor arms utilised in filtration plant.

Percolating filter plants for the treatment of aqueous effluents such as sewage are well known. They comprise a filter bed and a series of hollow liquid distributor arms disposed horizontally over the bed and mounted on a vertical shaft centrally of the bed. The shaft is rotated to move the arms to distribute the liquid over the bed from jets disposed in the distributor arms. One problem with these known arrangements is that the jets tend to clog up which results in an uneven distribution of the liquid over the filter. The jets have to be cleaned manually. To alleviate this problem, removable screens are sometimes installed in channels conveying primary tank effluent, but these too usually need clearing at least daily, and the screenings have to be disposed of.

It has been proposed to deal with this problem of jet blockage by providing, adjacent each jet, a plunger which intermittently is operable to enter the jet to clear any blocking debris. In such an arrangement, the plungers are mounted on a common axle and the axle is caused to turn, to move the plungers into their respective jets, and to return (to remove the plungers) by engagement of a lever with a trip mechanism. Thus, as the arm moves above the filter bed, the lever rides up over a trip and then returns to its starting position.

We have devised some improvements in this system whereby certain disadvantages therein can be reduced or overcome. We have found that, instead of mounting all the plungers on a common axle, it is instead advantageous to provide a separate mounting bracket for each plunger, adjacent the respective jet.

This can reduce capital costs, simplify the installation and reduce the resistance of the mechanisms to operation. This last point is important because the plunger operation is powered only by the movement of the distributor arm, and any excessive load may cause the arm to jam with serious consequences.

In one aspect, the invention provides a hollow distributor arm for a filtration plant, which arm comprises a plurality of jets mounted therein to distribute liquid, supplied through said arm, over a filter, wherein each jet has associated therewith a bracket mounted externally on the arm, which bracket pivotally supports a plunger movable into and out of said jet to keep the same clear of obstructions.

In the known arrangements of plunger mechanisms, the lever used to actuate the plunger operation has been relatively short and has required more mechanical effort than has been desirable. We have found that this problem can be overcome by ensuring that the axle is no lower than the axis of the distributor arm itself, and providing a lever dependent therefrom to a point below the arm, usually close to the surface of the filter bed itself.

In a further aspect of the present invention, therefore, there is provided a filtration unit which comprises a filter bed and at least one hollow liquid distributor arm mounted, at one end thereof, to lie generally horizontally above the filter bed and to be turned about a generally vertical axis to move over the filter bed, said arm having a plurality of jets therein, to distribute liquid supplied through said arm onto the filter bed as the arm is turned, each jet having associated therewith a plunger pivotally mounted externally of the arm and movable into and out of the respective jet to keep it clear of obstructions, wherein each said plunger is mounted on a common axle, and wherein a lever depends from a pivot, level with or above the arm, to a point below the arm where, as said arm is turned, said lever trails said arm and is periodically deflected by engagement with a trip, each said deflection causing rotation of said axle to move the plungers into and out of the jets.

This arrangement is particularly useful on relatively small reaction filters. The lever is long and is mounted behind the distributor arm and near the centre of the filter, and is connected to the operating axle or shaft by a mechanical linkage or gears.

In order that the invention may be more fully understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a view of a first known selfcleaning mechanism for the distributor arm of a percolating filter; FIGURE 2 is a section on the ll-ll of Figure 1; FIGURE 3 is a view of a second known selfcleaning mechanism for the distributor arm of a percolating filter; FIGURE 4 is a section on the line lV-lV of Figure 3; FIGURE 5 is a section through one embodiment of distributor arm of the invention; FIGURE 6 is a top plan view of the arrangement of Figure 5 (omitting the arm itself); FIGURE 7 is a section through a second embodiment of distributor arm of the invention; and FIGURE 8 is a section through a third embodiment of distributor arm of the invention.

Referring to the drawings, Figure 1 shows a distributor arm 1 mounted horizontally to extend radially of a shaft 2 which is at the centre of the filter surface. A portion of the outer wall 3 of the filter is shown. The arm 1 is hollow, its outer end being conventionally closed by a plate 4. It comprises a series of orifices or jets 5 from which (in use) the liquid (supplied internally of the arm) issues on to the filter surface.

To keep the jets clear, a series of plungers 6 are mounted on arms 7 each fixed to the axle 8 which has. at its outer end, an upstanding operating lever 9. A spring 10 is provided to maintain lever 9 upright.

Arm 1 is driven in the direction of arrow 11 and, at each complete revolution about the axis of shaft 2, lever 9 bears against a tripping arm 12 (which is fixed to wall 3). The lever is moved, against the bias of spring 10, in the direction of the arrow 13. This causes axle 8 to turn about its axis to cause plungers 6 to enter their respective jets 5. As distributor arm 1 moves on beyond tripping arm 12, lever 9 disengages therefrom (i.e. passes underneath) and is returned to the (illustrated) upright position by spring 10. This return motion withdraws the plungers from the jets.

Figure 2 shows, in full lines, the position of the plungers as in Figure 1, and in discontinuous lines the positions upon insertion of the plungers in the jets 5.

Figures 3 and 4 are similar to Figures 1 and 2 and like numerals have been used to indicate like parts. In Figures 3 and 4, however, it will be seen that axle 8 lies below the distributor arm 1, and the operating lever 9 extends downwardly (contrast Figures 1 and 2) to a trip arm just above the filter surface. Also, the lever 9 is at the inner end of distributor arm 1.

Figures 5 and 6, and Figure 7 show two embodiments in accordance with a first aspect of the invention. In both these embodiments, the plungers are not all mounted on a common axle but rather are individualiy mounted each on a bracket associated with the respective jet.

Referring to Figures 5 and 6, the distributor arm 20 has a series of orifices 20A therein (as in Figures 1 to 4), in each of which is a nozzle member 21. This is in the form of a bush comprising a cylindrical member 22 with an external collar 23. The inner end of the member 22 is screw-threadedly received in orifice 20A. As shown in Figure 5, cylindrical member 22 passes through a hole in the end of a bracket 24, and collar 23 of nozzle 21 bears against the bracket effectively to secure the bracket to arm 20 and mount it thereon. At the other end 25 of the bracket there is pivoted a plunger arm 26 having a plunger brush 27 mounted thereon. The position of the brush 27 relative to the arm 26 is adjustable via screws 28 and slide member 29. A bolt 30 secures the brush 27 to the arm 26.

As illustrated in full lines, brush 27 is entering the nozzle 21. Thus, arm 20 is moving in the direction of arrow 31, and plunger arm 26 is riding up over tripping arm 32. This forces the brushes 27 into the jets.

As the distributor arm 20 moves further on, the plunger arm 26 returns to the "at-rest" position shown in discontinuous lines (Figure 5), the brushes 27 being thus removed from the jets 21. Figure 6 shows a top plan view of the "at-rest" position (omitting the distributor arm 20).

As shown in Figure 5. tripping arm-32 is positioned on the filter surface 33.

The arrangement of Figure 7 is very similar to that of Figures 5 and 6 and like numerals indicate like parts. In Figure 7, a shorter plunger 27 (which is not a brush) is used, and the plunger arm 26 is of U-shape, the side 26A of the "U" receiving the plunger and including an adjustment screw 26B.

Figure 8 shows an embodiment of the invention in accordance with a second aspect thereof. This differs from the arrangements of Figures 5 to 7 in being especially suited to very low power operation. Referring to Figure 8, there is shown a distributor arm 40 having nozzles 41 therein (generally as in Figures 5 to 7 but excluding the bracket). Around arm 40 is a clamp 42 which attaches to the arm 40 a support plate 43. Adjustably mounted on support plate 43 is a bearing plate 44 which supports an axle 45 which extends the length of the distributor arm 40. Fixed to the axle 45, at intervals, are two-part plunger arms 46,46A, each having a plunger 47 positioned to enter a respective nozzle 41. (A screw 48 is provided for allowing adjustment between the parts 46 and 46A.) The arrangement includes a lever 50 pivoted at its upper end 51 which is well above the distributor arm 40.At its lower end. below arm 40, is a weight 52. The lever 50 is normally approximately vertical. At its upper end, it is fast with slotted member 53. Within slot 54 of member 53 is a pin 55 mounted on a plate 56 which moves with axle 45. In operation, the distributor arm 40 moves in the direction of arrow 57 (i.e. to the left of Figure 8). The lower tip 58 of lever 50 rides over a fixed trip 59 and lever 50 is thus pivoted about 51. This turning movement is relatively large, because of the length of lever 50, and is converted into a rotation of axle 45 to move the plungers 47 into respective jets 41. Thus, as lever 50 turns, so (via member 53 and pin 55) does plate 56 which causes axle 45 to rotate in an opposite direction to the pivoting of lever 50 about point 51.

Further movement of arm 40 draws the lower end 58 of lever 50 over trip 10, whereupon counterweight 52 causes lever 50 to swing to the vertical, thus causing axle 45 to rotate counterclockwise to withdraw the plungers 47 from the respective jets 41.

The self-cleaning mechanisms of the invention for the jets of distributer arms are especially useful in the biological filtration of finely-screened sewage. as described by G.

Hoyland and D. Ronald in a paper entitled "BIOLOGICAL FILTRATION OF FINELY SCREENED SEWAGE" presented to the IWPC, London, on 21st April, 1983, to which paper reference should be made for further details. In this process, there are used highvoidage plastics filter elements. The sewage to be treated is finely-screened to remove only the large materials, and is then distributed over a bed of the filter elements using distributer arms fitted with the cleaning mechanisms of the present invention.

Claims (11)

1. A hollow distributor arm for a filtration plant, which arm comprises a plurality of jets mounted therein to distribute liquid, supplied through said arm, over a filter, wherein each jet has associated therewith a bracket mounted externally on the arm, which bracket pivotally supports a plunger movable into and out of said jet to keep the same clear of obstructions.

2. A distributor arm according to claim 1, wherein each bracket is mounted on the arm by engagement of the bracket with a respective jet.

3. A distributor arm according to claim 2, wherein each jet comprises a cylindrical body having an external flange at one end, the said body passing through a hole in said bracket and being secured to said arm with said flange engaging said brackettomount it on said arm.

4. A distributor arm according to claim 1,2 or 3, wherein each said jet is screw-threadedly received in a corresponding orifice in said arm.

5. A filtration unit which comprises a filter bed and at least one hollow distributor arm as defined in any of claims 1 to 4.

6. A filtration unit which comprises a filter bed and at least one hollow liquid distributor arm mounted, at one end thereof, to lie generally horizontally above the filter bed and to be turned about a generally vertical axis to move over the filter bed, said arm having a plurality of jets therein, to distribute liquid supplied through said arm onto the filter bed as the arm is turned, each jet having associated therewith a plunger pivotally mounted externally of the arm and movable into and out of the respective jet to keep it clear of obstructions, wherein each said plunger is mounted on a common axle, and wherein a lever depends from a pivot, level with or above the arm, to a point below the arm where, as said arm is turned, said lever trails said arm and is periodically deflected by en gagement with a trip, each said deflection causing rotation of said axle to move the plungers into and out of the jets.

7. A unit according to claim 6, wherein said lever is mounted close to said axis.

8. A unit according to claim 6 or 7, wherein said lever has a weight at its lower end to assist its return after deflection.

9. A unit according to claim 6, 7 or 8, wherein a mechanical linkage is provided between said lever and said axle whereby, as said lever trails rearwardly upon engagement with a trip, said plungers are moved forwardly into said jets.

10. A method of biologically treating aqueous effluents wherein there is used a filtration unit as claimed in any of claims 5 to 9.

11. A method according to claim 10, wherein the filter bed is composed of high voidage plastics filter elements, and wherein the aqueous effluent is sewage.