GB2397538A

GB2397538A - Filtration apparatus with automatic backflush

Info

Publication number: GB2397538A
Application number: GB0400757A
Authority: GB
Inventors: Anthony Cowan
Original assignee: G&K Valve Services Ltd
Current assignee: G&K Valve Services Ltd
Priority date: 2003-01-23
Filing date: 2004-01-14
Publication date: 2004-07-28
Also published as: GB0301496D0; GB0400757D0

Abstract

A sewerage filtration apparatus for filtering solids from overflow sewerage in the event of a storm surge or flood is disclosed. The sewerage filtration apparatus has a first chamber 10 and a second overflow chamber 16 which are fluidly linked by a weir 18. The first chamber has a first inlet (not shown) and a first outlet 14. The second chamber has second 28 and third outlets 20. The second chamber also has a filter screen 26 which is located between the weir and the second outlet. The second chamber also has flushing means 22 adapted for backflushing fluid through the filter screen and out through the third outlet when the third outlet is opened. The third outlet may be opened by a valve means 22 which opens when the fluid level in the first chamber drops below a predetermined level. During a storm the first chamber will fill and then overflow into the second chamber. As the second chamber fills the screen filters the solids contained in the fluid. When the storm finishes the fluid level in the first chamber will begin to decrease. Once the fluid level in the first chamber passes a certain point the valve means opens the third outlet and the fluid is backflushed into the first chamber. As this happens any filtered solids which have accumulated at the filter screen are removed from the screen. Advantageously, the filter screen does not need to be cleaned manually after every storm or flood event as it is cleaned automatically by the backflushing of the fluid in the second chamber.

Description

SEWERAGE FILTRATION APPARATUS

1 The present invention is directed to a filtration 2 apparatus for filtering solids from sewerage/waste 3 water in the event of a storm surge, flood or 4 similar event.

6 In the event of heavy rainfall over a short period 7 of time, such as commonly happens during a storm, 8 the water levels in rivers and the like in the area 9 of the rainfall will rise. If there is sustained rainfall over a longer period, this rise in water 11 levels can lead to flooding as the rivers burst 12 their banks. When such a rise in water levels 13 occurs, this has the effect of also increasing water 14 levels within sewerage systems. The rising levels in typical sewerage infrastructure such as, for 16 example, pumping stations or access manholes means 17 that water can rise to the point where it overflows 18 from the sewers untreated directly into a water 19 course or perhaps even into the streets. Indeed, the vast majority of damage caused during flooding 21 is not caused by water damage, but is in fact caused 1 by contamination due to sewerage overflow into the 2 floodwaters.

4 In order to attempt to prevent the leakage of sewerage during such events, filter screens can be 6 placed adjacent the top of pumping station wells or 7 access manholes to prevent solids of a certain size 8 from leaking from the well/manhole. However, the 9 disadvantage of such filter screens is that they must be cleaned manually to prevent excessive build 11 up of solids on the upstream side of the screen.

12 Furthermore, such screens hinder access through 13 manholes as they must be fixed in position to work 14 effectively. The present invention is directed to overcoming one or more of these disadvantages.

17 According to the present invention, there is 18 provided a sewerage filtration apparatus comprising: 19 a first chamber having a first inlet and a first outlet; 21 a second chamber in fluid communication with 22 the first chamber and having second and third 23 outlets; 24 a weir disposed between the first and second chambers; 26 a filter screen located in the second chamber 27 between the weir and the second outlet, the screen 28 having a second outlet side; and 29 a flushing means adapted to backflush fluid through the filtering screen from the second outlet 31 side and out through the third outlet when the third 32 outlet is opened.

2 Preferably, the third outlet is fluidly connected to 3 the first chamber, and wherein the flushing means 4 comprises a valve means adapted to control fluid flow from the third outlet into the first chamber, 6 wherein the valve means opens the third outlet when 7 the fluid level in the first chamber drops below a 8 predetermined level.

Preferably, the second chamber is disposed partially 11 within the first chamber. Alternatively, the second 12 chamber is disposed adjacent the first chamber.

14 Preferably, the valve means comprises a hinged flap adapted to close the third outlet, at least one 16 pivotable lever for engaging the flap, and a float 17 located in the first chamber and attached to the end 18 of the at least one lever remote from its pivot 19 point.

21 Preferably, the valve means further comprises a 22 locking means for locking the flap in a closed 23 position to prevent fluid flow through the third 24 outlet.

26 Preferably, the locking means is a recess on the 2 7 lever which engages the flap.

29 Alternatively, the locking means comprises a cam surface on the flap, and a cam follower attached to 31 the lever for engaging the cam surface.

1 Preferably, the valve means comprises a pair of 2 levers having a crossmember attached therebetween, 3 and the cam follower being provided on the 4 crossmember.

6 Preferably, the second chamber further comprises a 7 floor which slopes in the direction of the third 8 outlet.

Preferably, the second chamber further comprises a 11 barrier means adapted to direct fluid through the 12 filter screen before passing through the second 13 outlet.

Preferably, the second chamber further comprises a 16 floor which slopes in the direction of the third 17 outlet, and a barrier means adapted to direct fluid 18 through the filter screen before passing through the 19 second outlet, wherein the sloping floor, barrier means and filter screen are made from a plastics 21 material and are integrally formed with one another 22 from a single moulding.

24 Preferably, the second chamber further comprises a floor which slopes in the direction of the third 26 outlet, a barrier means adapted to direct fluid 27 through the filter screen before passing through the 28 second outlet, and a plastic liner which has one or 29 more of the weir, barrier means, filter screen and sloping floor integrally formed therewith.

1 Preferably, the first chamber is a pump well of a 2 pumping station. Alternatively, the first chamber 3 is a manhole of a sewerage system.

Preferred embodiments of the present invention will 6 now be described, by way of example only, with 7 reference to the accompanying drawings, wherein: 9 Figure l(a) is a vertical cross section through a sewerage overflow filtration apparatus when 11 installed at a pumping station; 12 Figure l(b) is a plan view of the apparatus of 13 Figure l(a); 14 Figure 2 (a) is a vertical cross section through the filtration apparatus of Figures l(a) and l(b) 16 when installed at an access manhole; 17 Figure 2(b) is a plan view of the apparatus of 18 Figure 2 (a); 19 Figures 3 (a) and 3 (b) show side elevations of a 2 0 valve used in the apparatus; 21 Figure 3 (c) shows a plan view of the valve 22 shown in Figures 3 (a) and 3 (b); 23 Figures 4(a)-(c) show side elevations of an 24 alternative embodiment of the valve used in the 2 5 apparatus; and 26 Figure 4 (d) shows a plan view of the valve of 2 7 Figures 4 ( a)-(c).

29 Figures l(a) and l(b) show views of a sewerage overflow filtration apparatus in accordance with the 31 present invention, which in this example is 32 installed at a pumping station. The pumping station 1 has a first chamber in the form of a well 10, in 2 which a pump 12 is located. Sewerage enters the 3 well 10 via an inlet (not shown) and in normal 4 operating conditions is then pumped out of the well 10 by the pump 12 through an outlet pipe 14 for 6 treatment.

8 With the present invention, a hole is dug adjacent 9 the well 10 so as to create a second, or overflow, chamber 16. Both the well 10 and overflow chamber 11 16 can be produced in a conventional manner, such as 12 excavating suitable holes and by then inserting one 13 or more pre-formed concrete rings to define the 14 walls of the excavations. The well 10 and overflow chamber 16 can fluidly communicate with each other 16 in two ways. Firstly, once the fluid in the well 10 17 rises to a sufficiently high level, it may pass into 18 the overflow chamber 16 by way of an overflow weir 19 18 located at the top of the well 10. Secondly, as will be explained in detail below, fluid may also 21 pass back from the overflow chamber 16 to the well 22 10 by way of flushing means, or pipe, 20 and 23 discharge valve 22 which controls fluid flow through 24 the pipe 20.

26 The overflow chamber 16 is provided with a barrier 27 means 25 and a mesh screen 26 in order to filter 28 solids from the sewerage. The barrier means 25 29 ensures that the sewerage flow into the overflow chamber 16 cannot bypass the screen 26. In 31 addition, the overflow chamber 16 may also have a 32 sloping floor 24 which slopes downward in the 1 direction of the discharge pipe 20. For 2 convenience, the floor 24, barrier means 25 and 3 screen 26 may be of moulded plastic and integral 4 with one another, so that they can simply be inserted as one component into the overflow chamber 6 16 once it is complete. The overflow chamber 16 is 7 also provided with an outlet 28 on the downstream 8 side of the screen 26 through which filtered 9 sewerage may leave the overflow chamber 16.

11 In the illustrated embodiment, the screen 26 has a 12 V-shaped profile. By making the screen 26 V-shaped, 13 the performance of the screen 26 is improved over 14 conventional flat screens. This is because the angle of the two parts of the screen 26 forces the 16 sewerage away from the base of the "V" where the two 17 parts of the screen 26 meet, thus spreading the 18 filtered solids over more of the surface area of the 19 screen 26 than normal during operation. Thus, clogging of the screen 26 takes longer than it would 21 with a flat screen. However, it should be 22 understood that the present invention is not 23 restricted to use of a V-shaped screen and that a 24 flat screen may be used instead if desired.

26 Figures 2 (a) and 2 (b) show the filtration apparatus 27 when the first chamber is an access manhole 30. The 28 manhole 30 gives direct access to a sewerage pipe 32 29 through which sewerage flows in normal conditions.

The components of the apparatus are the same as 31 those described in respect of the pumping station 32 and hence share the same reference numerals. As 1 each component has already been referred to above, 2 they will not be further described here.

4 Figures 3 (a)-(c) show a first embodiment of the discharge valve 22 that controls fluid flow from the 6 overflow chamber 16 into the well 10 or manhole 30.

7 Figure 3 (a) shows the valve 22 in its fully open 8 state, while Figure 3 (b) shows the valve 22 in its 9 closed state. The valve 22 comprises a hinged flap 40 which is secured to the top of the outlet of the 11 discharge pipe 20 located in the well 10 (or manhole 12 30). The flap 40 is secured to the pipe 20 by way 13 of a hinge 42. Secured to the base of the outlet of 14 the discharge pipe 20 is a pivotable lever 44 which has a float 48 attached thereto at the end of the 16 lever 44 remote from its pivot point 46. The pivot 17 point is provided on the pipe 20.

19 The weight of the flap 40 is such that it closes the outlet of the discharge pipe 20 when the apparatus 21 is not in operation. The end of the lever 44 22 proximate the discharge pipe 20 is provided with a 23 recess 50 which is shaped so as to secure the flap 24 40 in the closed position when the float 48 and lever 44 are acted upon by rising fluid levels in 26 the well/manhole 10, 30. This closed position is 27 shown in Figure 3 (b). Once the level of fluid in 28 the well/manhole 10, 30 has dropped, this will allow 29 the float 48 and lever 44 to lower, thus releasing the flap 40. The flap 40 can then simply be forced 31 into the open position shown in Figure 3 (a) under 32 the action of fluid flowing through the discharge 1 pipe 20 from the overflow chamber 16. For further 2 clarification, a plan view of the valve 22 looking 3 down into the well/manhole 10, 30 is shown in Figure 4 3(c).

6 An alternative embodiment of the discharge valve 22 7 is shown in Figures 4(a)-(d). In this alternative 8 embodiment, the flap 40' is secured to the base of 9 the discharge pipe 20, rather than the top. A hinge 42' secures the flap 40' to the pipe 20. With the 11 flap 40' hinged at the base, its weight causes the 12 flap 40' to lie in the open position, as shown in 13 Figure 4(a). A pair of levers 44' are also attached 14 to the discharge pipe 20 at a pair of pivot points 46' on opposite sides of the pipe 20. The levers 16 44' are identical to one another and each has first 17 and second sections which are at an angle to each 18 other. At the point on each lever 44' where the 19 first and second sections meet there is cross member 60 attached. An end of the cross member 60 is 21 attached to each lever 44' so as to prevent relative 22 movement between the levers 44'. Also attached 23 between the two levers 44' at the end of the levers 24 44' remote from the pipe 20 is a float 48'.

26 As best seen in Figures 4(c) and 4(d), the outer 27 surface of the flap 40' is provided with a 28 projecting cam surface 62. The cross member 60 is 29 provided with a cam follower 61, which may be a roller or the like and which follows the cam surface 31 62. As a result of the inclusion of the cam 32 arrangement, the flap 40' will not open until the 1 float 48' has dropped past its intermediate position 2 shown in Figure 4 (b). In the intermediate and 3 highest positions of the float 48' shown in Figures 4 4 (b) and 4 (c), respectively, the flap 40' remains closed due to the cam follower 61 still following 6 the cam surface 62. Only when the float 48' drops 7 below the intermediate position does the flap 40' 8 then open as the cam follower 61 leaves the cam 9 surface 62.

11 The general operation of the apparatus as shown in 12 both Figures 1 and 2 will now be described. During 13 a storm surge or flood, sewerage levels will rise in 14 the pump well 10 or manhole 30 due to either the pump 12 being unable to cope (Figure 1) or because 16 of the rising flood waters infiltrating the sewer 17 (Figure 2). When this happens, the rising sewerage 18 level will cause the float 48,48' to rise, thus 19 securing the flap 40,40' in the closed positions shown in Figures 3 (b) and 4 (c) by way of the 21 lever(s) 44,44' . If the sewerage level continues to 22 rise, it will eventually reach the overflow weir 18 23 and begin to flow into the overflow chamber 16.

With the float 48,48' holding the flap 40,40' closed 26 at this point, the sewerage flowing into the 27 overflow chamber 16 cannot pass through the 28 discharge pipe 20. The barrier means 25 ensures 29 that as the resultant head of fluid builds up in the overflow chamber, it must rise up through the screen 31 26 before flowing out of the outlet 28. Thus, l solids are caught by the screen 26 and only filtered 2 sewerage passes through the outlet 28.

4 Once the storm surge or flood water has abated, the sewerage level in the well 10 or manhole 30 will 6 begin to decrease. As this happens, the float 7 48,48' will begin to lower from the position in 8 which the flap 40,40' is closed. Once the float 9 48,48 ' has descended past the points shown in Figures 3 (b) and 4 (b), the flap 40,40' is not longer ll held closed by the lever(s) 44,44'. Thus, the flap 12 40,40' will then open under the force of the 13 sewerage still trapped in the overflow chamber 16 14 and discharge pipe 20, allowing the trapped sewerage to flow back through the pipe 20 into the well 10 or 16 manhole 30. This flow will be helped by the 17 provision of the sloping floor 24 in the overflow 18 chamber 16.

As the sewerage trapped in the overflow chamber 16 21 flows back into the well/manhole 10, 30, the head of 22 sewerage which is above the level of the screen 26 23 will flow back down through the screen 26 and out 24 through the discharge pipe 20. As it does so, it will backflush any filtered solids which have 26 accumulated on the underside of the screen 26. In 27 this way, the screen 26 does not need to be manually 28 cleaned after the storm or flood event as it has 29 been automatically backflushed by the head of sewerage held in the overflow chamber 16.

1 The present invention may be installed adjacent 2 existing sewerage infrastructure such as the 3 aforementioned pump wells and manholes 10, 30, or 4 else it may be installed when new wells or manholes are being created. In either case, to install the 6 present invention a suitable hole is first excavated 7 adjacent the well/manhole 10, 30. The hole 8 preferably should have a depth of between 9 approximately one third to one half the depth of the adjacent well/manhole 10, 30. Once dug, one or more 11 conventional pre-formed concrete rings are inserted 12 into the hole to form the outer walls of the 13 overflow chamber 16. Portions of the top of both 14 the well/manhole 10, 30 and the chamber rings are then drilled out to provide the overflow route 16 between the well/manhole 10, 30 and overflow chamber 17 16. A further drilling is made through the overflow 18 chamber 16 and well/manhole 10, 30 near the base of 19 the overflow chamber 16 so as to enter the well/manhole 10, 30 approximately halfway down.

21 This allows the discharge pipe 20 and discharge 22 valve 22 to be installed between the overflow 23 chamber 16 and well/manhole 10, 30. The final 24 drilling of the upper ring in the overflow chamber 16 produces the outlet 28 for filtered sewerage to 26 exit the apparatus.

28 The sloping floor 24, barrier 25 and screen 26 may 29 then be installed in the overflow chamber 16. As stated above, these items are preferably made of 31 plastic and moulded together as one insert.

32 Alternatively, the overflow chamber 16 may be 1 provided with a plastics liner with which the floor 2 24, barrier means 25 and screen 26 are integrally 3 formed. However, they may equally be provided and 4 installed into the overflow chamber 16 separately.

Indeed, the sloping floor 24 can also be provided by 6 way of a concrete casting in the base of the 7 overflow chamber 16, or may also be formed from a 8 suitably treated metal rather than a plastics 9 material.

11 If necessary these components, whether formed as a 12 single insert or not, can be provided with 13 additional fixing means so as to be secured in the 14 overflow chamber 16 at the correct height.

Conventional fixing means such as bolts or the like 16 would be suitable for the purpose. The apparatus is 17 then ready for operation.

19 The present invention provides a means for preventing unfiltered sewerage from entering a water 21 course or flooding out of sewers via manholes in the 22 event of a storm surge or flood. In addition, it 23 also provides a means for automatically cleaning the 24 filter screen of solids caught during the flood once the floodwaters have abated. In this way, no manual 26 cleaning of the screen is required. Furthermore, 27 the present invention can be installed relatively 28 simply either to adapt existing sewerage 29 infrastructure or else in conjunction with new excavations.

1 As previously explained, although a screen having a 2 V-profile offers performance advantages over 3 conventional flat screens, a flat screen could also 4 be used in the apparatus without departing from the scope of the present invention. Preferably, the 6 components of the discharge valve and overflow 7 chamber are manufactured from a plastics material 8 which is not susceptible to corrosion or degradation 9 in spite of the nature of the fluids passing through the apparatus. However, suitably treated metal 11 components may also be used for one or more of these 12 components if desired. Although it has already been 13 stated above that is desirable for the sloping 14 floor, barrier and screen of the overflow chamber to be formed as a single component with or without a 16 liner, that single component may also incorporate 17 the overflow weir if desired. Finally, in the 18 manhole application, an additional disc-shaped float 19 having the same surface area as the manhole cover may be loosely attached to the underside of the 21 cover so as to prevent any fluid leakage through the 22 cover during a storm surge or flood.

24 It should also be noted that the present invention may also operate without the need for a separate 26 overflow chamber being installed. Instead, assuming 27 that the well or manhole is of a suitable diameter, 28 an overflow chamber insert comprising the weir, 29 floor and walls, barrier and screen may be simply installed directly in the well/manhole, so that the 31 overflow chamber would then be at least partially 32 disposed within the well/manhole. If the overflow 1 chamber can be located entirely within the 2 well/manhole, then the invention would operate in 3 the same manner, yet would not require the 4 additional excavation of a chamber adjacent the well/manhole.

7 Furthermore, it should be noted that the filtration 8 apparatus illustrated in Figures l(a) and l(b) or 9 2(a) and 2(b) may include a cover or wire mesh, or the like, that covers the upper portions of both the 11 first and second chambers 10, 16 in order to prevent 12 items from entering the first or second chambers 10, 13 16, or for allowing access to the first or second 14 chambers 10, 16.

16 These and other modifications and improvements may 17 be incorporated without departing from the scope of 18 the present invention.

Claims

1 Claims 3 1. A sewerage filtration apparatus comprising: 4 a first

chamber having a first inlet and a first outlet; 6 a second chamber in fluid communication with 7 the first chamber and having second and third 8 outlets; 9 a weir disposed between the first and second chambers; 11 a filter screen located in the second chamber 12 between the weir and the second outlet, the screen 13 having a second outlet side; and 14 a flushing means adapted to backflush fluid through the filtering screen from the second outlet 16 side and out through the third outlet when the third 17 outlet is opened.

19 2. A sewerage filtration apparatus as claimed in Claim 1, wherein the third outlet is fluidly 21 connected to the first chamber, and wherein the 22 flushing means comprises a valve means adapted to 23 control fluid flow from the third outlet into the 24 first chamber, wherein the valve means opens the third outlet when the fluid level in the first 26 chamber drops below a predetermined level.

28 3. A sewerage filtration apparatus as claimed in 29 either Claim 1 or Claim 2, wherein the second chamber is disposed at least partially within the 31 first chamber.

1 4. A sewerage filtration apparatus as claimed in 2 either Claim 1 or Claim 2, wherein the second 3 chamber is disposed adjacent the first chamber.

5. A sewerage filtration apparatus as claimed in 6 any of Claims 2 to 4, wherein the valve means 7 comprises: 8 a hinged flap adapted to close the third 9 outlet; at least one pivotable lever for engaging the 11 flap; and 12 a float located in the first chamber and 13 attached to the end of the at least one lever remote 14 from its pivot point.

16 6. A sewerage filtration apparatus as claimed in 17 Claim 5, wherein the valve means further comprises a 18 locking means for locking the flap in a closed 19 position to prevent fluid flow through the third outlet.

22 7. A sewerage filtration apparatus as claimed in 23 Claim 6, wherein the locking means is a recess on 24 the lever which engages the flap.

26 8. A sewerage filtration apparatus as claimed in 27 Claim 6, wherein the locking means comprises: 28 a cam surface on the flap; and 29 a cam follower attached to the lever for engaging the cam surface.

1 9. A sewerage filtration apparatus as claimed in 2 Claim 8, wherein the valve means comprises a pair of 3 levers having a crossmember attached therebetween, 4 and the cam follower being provided on the crossmember.

7 10. A sewerage filtration apparatus as claimed in 8 any preceding claim, wherein the second chamber 9 further comprises a floor which slopes in the direction of the third outlet.

12 11. A sewerage filtration apparatus as claimed in 13 any preceding claim, wherein the second chamber 14 further comprises a barrier means adapted to direct fluid through the filter screen before passing 16 through the second outlet.

18 12. A sewerage filtration apparatus as claimed in 19 any of Claims 1 to 9, wherein the second chamber further comprises: 21 a floor which slopes in the direction of the 22 third outlet; and 23 a barrier means adapted to direct fluid through 24 the filter screen before passing through the second outlet, wherein the sloping floor, barrier means and 26 filter screen are made from a plastics material and 27 are integrally formed with one another from a single 28 moulding.

13. A sewerage filtration apparatus as claimed in 31 any of Claims 1 to 9, wherein the second chamber 32 further comprises: 1 a floor which slopes in the direction of the 2 third outlet; 3 a barrier means adapted to direct fluid through 4 the filter screen before passing through the second outlet; and 6 a plastic liner which has one or more of the 7 weir, barrier means, filter screen and sloping floor 8 integrally formed therewith.

14. A sewerage filtration apparatus as claimed in 11 any preceding claim, wherein the first chamber is a 12 pump well of a pumping station.

14 15. A sewerage filtration apparatus as claimed in any of Claims 1 to 13, wherein the first chamber is 16 a manhole of a sewerage system.

18 16. A sewerage filtration apparatus as herein 19 described with reference to the accompanying drawings.