GB2367015A

GB2367015A - A waste water filtration tank with an automatic flushing mechanism

Info

Publication number: GB2367015A
Application number: GB0118725A
Authority: GB
Inventors: Anthony Cowan
Original assignee: G&K Valve Services Ltd
Current assignee: G&K Valve Services Ltd
Priority date: 2000-08-05
Filing date: 2001-07-31
Publication date: 2002-03-27
Anticipated expiration: 2021-07-31
Also published as: GB0118725D0; GB2367015B; GB0019209D0

Abstract

A waste water tank for the filtering of solids from effluent comprises an inlet 11, first and second outlets 10, 17, a filter screen 7 and a discharge means 13, 14, 15. The effluent passes from the inlet 11 to the first outlet 10 through the screen 7. When the screen 7 reaches a predetermined level of contamination, the discharge means 13, 14, 15 opens the second outlet 17 allowing effluent to flow directly out of the second outlet. As a result, the screen 7 is automatically backwashed as the level of effluent in the tank drops due to the open second outlet 17. No manual clearing of the screen 7 is therefore necessary.

Description

WASTE WATER FILTRATION TANK WITH AUTOMATIC FLUSHING MECHANISM The present invention relates to a waste water filtration tank for the treatment of waste water.

Before waste water can be passed to processing plants such as water treatment facilities, all the solid waste within the effluent must be removed. It is known to use filtration tanks in order to remove such material, with the waste material being separated from the water before the water is either passed on for further processing or else, in some instances, discharged back into the river or sea. Other known methods of treatment include sand filtration and chemical treatment of the liquid to remove impurities.

Filtration tanks which use float mechanisms to flush collected solids from the tank are known. These tanks use a float in the tank where the float is attached to a lever mechanism that opens and closes a

gate or valve when the level of liquid in the tank reaches a predetermined level. With the gate/valve open, the liquid is flushed from the tank and the float and attached lever lower with the level of the liquid, thus closing the gate/valve. However, this arrangement has been shown not to work effectively with high flow rates of over approximately 70 lis.

With known arrangements, the constant in-flow of liquid at such a rate into the tank can begin to lift the float again before the gate/valve is completely closed. Thus, the gate/valve can be stuck at least partially open so that liquid simply flows straight through the tank, rather than passing through the filters elsewhere in the tank.

It is the aim of the present invention to provide an automatic waste water flushing system which filters out solids from the effluent before automatically removing said solids from the tank, thereby allowing the filtration to be carried out with the minimum of supervision and also removing the need for the filtered solids to be discharged manually. It is a further aim of the present invention to remove the disadvantage of known float mechanisms as described above.

According to the present invention, there is provided a waste water tank for the filtering of solids from effluent, said tank having an inlet, first and second outlets, a first filtration means located between the inlet and first outlet, and discharge means, wherein

the second outlet is located on the same side of the first filtration means as the inlet, and the discharge means reverses the flow of effluent through said first filtration means when said first filtration means reaches a predetermined degree of contamination.

Preferably, said second outlet is adapted to move between open and closed states under the action of said discharge means.

Preferably, said tank further comprises a reservoir located between the inlet and second outlet, the tank being adapted such that the level of effluent in the reservoir will rise as the degree of contamination of the first filtration means increases. Preferably, said reservoir is provided with a dump valve.

Preferably, said reservoir is provided with a second filtration means.

Preferably, said discharge means comprises a sensor located in said reservoir, processing means, a gate covering said second outlet, a first actuator adapted to selectively open and close the gate, and a second actuator adapted to selectively operate said dump valve, wherein said sensor transmits a first signal to said processing means when the effluent level in said reservoir reaches a predetermined level, and said processing means transmits a second signal to each of said first and second actuators upon receipt of said first signal.

Preferably, said processing means sends a third signal to each of said first and second actuators a predetermined length of time after said second signals, said actuators closing said gate and dump valve upon receipt of said third signals.

Alternatively, said discharge means comprises a first float located within said reservoir, a gate covering said second outlet, and a hydraulic apparatus for the operation of said gate and said dump valve, wherein said first float actuates said hydraulic apparatus when the level of effluent in said reservoir rises above a predetermined level.

Preferably, said hydraulic apparatus is adapted to move said dump valve and said gate from closed to open positions when acted upon by said first float.

Preferably, said hydraulic apparatus comprises a pivotable beam member attached to said first float, and a first hydraulic cylinder, the hydraulic apparatus facilitating selective actuation of the cylinder by the beam member.

Preferably, said first hydraulic cylinder comprises a hydraulic valve and a piston, wherein the movement of the beam member selectively actuates said hydraulic valve. Preferably, an end of the piston is fixedly attached to the gate. Preferably, the cylinder further comprises biasing that which bias the piston

into a position where the gate is open. Preferably, said first hydraulic cylinder further comprises a fluid control valve.

Preferably said hydraulic apparatus further comprises a second hydraulic cylinder adapted to actuate said dump valve, wherein said hydraulic valve controls flow of hydraulic fluid between said first and second hydraulic cylinders, and wherein said apparatus is adapted to open and close said hydraulic valve under the action of said first float.

Preferably, said apparatus further comprises a second float located in said reservoir, wherein said second float is adapted to move said dump valve between closed and open positions when acted upon by said second cylinder.

Preferably, said effluent enters said inlet under atmospheric pressure.

Preferably, said first and second filtration means are mesh screens adapted to prevent solids of a predetermined size passing therethrough.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 shows a projected view of a first embodiment of a filtration tank according to the

present invention, the side wall of said tank having been removed for illustrative purposes ; Fig. 2 shows a side elevation of the tank, with fluid flow directions highlighted; Fig. 3 shows a plan view of the tank as seen in Fig. 2; Fig. 4 shows an end elevation of the inlet end of the tank shown in Figs. 2 and 3; Fig. 5 shows a cut-away side elevation view of the outlet end of the tank of the first embodiment; Fig. 6 shows an end elevation of the outlet end of the tank of the first embodiment; Fig. 7 shows a cut-away side elevation view of a second embodiment of a filtration tank in accordance with the present invention; Fig. 8 shows an end elevation of the outlet end of the tank of the second embodiment; Fig. 9 shows a circuit diagram of the control arrangement of the second embodiment; and Figs. 10 (a) and 10 (b) show schematic diagrams of combinations of tanks according to the present invention.

Referring to the drawings, Fig. 1 shows a filtration tank 1 for filtration of waste water or effluent, a side wall panel having been removed for illustrative purposes. The tank 1 has an inlet chamber 3, and a screen chamber 2 which contains a filtration means, in the form of a screen, 7. The unfiltered effluent flows into the inlet chamber 3 through an inlet flange 11. A head is generated by the flow of waste

water through the inlet 11. The effluent flow enters the inlet chamber 3 and a passageway 8 but is prevented from passing out of the tank 1 by a closed sluice gate 17. Therefore, the level of waste water in the tank 1 rises as the water continues to flow in through the inlet 11 until it reaches a predetermined level whereupon in begins to pass upwards through the screen 7 into the screen chamber 2. As the effluent rises through the screen 7, solid residue is trapped in the passageway 8 and cannot pass into the screen chamber 2. Because the sluice gate 17 remains closed, the level of filtered liquid both inside the tank 1 and in the inlet pipe (not shown) continues to rise. Within the tank 1, the liquid rises in the screen chamber 2 until it begins to overflow 9 from the screen chamber 2 into an overflow 4, as illustrated in Figs. 2 and 3. The filtered liquid then passes out of the overflow 4 via a first outlet 10 to be discharged for further treatment or else into a sea or river area.

The more solids that are filtered by the screen 7, the more blocked the screen 7 will become, thus restricting the rise of liquid through the screen 7 into the screen chamber 2. With the screen 7 becoming more clogged, a pressure drop will occur across the screen 7, leading to an increase in the level of waste water in a stilling chamber 5 connected to the passageway 8. As a result of the pressure drop, the level of effluent in the stilling chamber 5 will continue to rise independently of the

level in the screen chamber 2. As the screen 7 continues to clog, the level of waste water increases in the stilling chamber 5 until it begins to overflow into a reservoir 6. Solids are prevented from flowing from the stilling chamber 5 to the reservoir 6 by a further filtration means, or screen, 25.

The reservoir 6 contains a drum float 13 that will begin to rise as liquid enters. The float 13 is part of a discharge mechanism that controls the automatic operation of the sluice gate 17. This discharge mechanism alleviates the need to flush the tank 1, as the tank 1 automatically flushes itself when solids have blocked the screen 7 to a predetermined degree.

In one embodiment of the present invention, as shown best in Fig. 1, the discharge mechanism consists of a pivoting beam 14 to which the float 13 is attached.

Also attached to the beam 14 at the opposite end from the pivot are a primary rod member 15 and a secondary rod member 19. With the mechanism in the closed position, the base of the primary rod member 15 rests on top of a spring-biased piston 18 in a hydraulic cylinder 20. The piston 18 is connected to the sluice gate 17 so that upward movement of the piston under the action of the spring will lift, and therefore open, the gate.

As the rise in liquid within the reservoir 6 lifts the float 13, the float 13 raises the beam 14, which in turn lifts the primary rod member 15 and the

secondary rod member 19. As the secondary rod member 19 rises, it comes into contact with a striker pin (not shown) which controls a spool valve 16 and also holds the piston in position. The tripping of the striker pin by the secondary rod 19 opens the spool valve 16 and releases the piston 18 within the cylinder 20. In operation, the combination of the float 13 and beam 14 lift the secondary rod 19 to a predetermined level and a cam (not shown) on the rod 19 acts on the striker pin. The movement of the striker pin simultaneously allows pressurised hydraulic fluid in the cylinder 20 to flow out of the cylinder 20 via the spool valve 16 and releases the piston rod 18 and spring within the cylinder 20 which forces the fluid out through the spool valve 16. As the spring extends, the piston rod 18 rises swiftly, the rapid upward movement of the piston rod 18 also opening the sluice gate 17 at the same time, allowing the solid residue and fluid trapped in the passageway 8 to be discharged.

As the liquid in the passageway 8 flows out through the sluice gate 17, the head of liquid in the screening chamber 2 will flow back through the screen 7 and out the sluice gate 17, thus backwashing the screen 7 to remove any solids on the underside. At the same time as the sluice gate 17 opens, the hydraulic fluid from the cylinder 20 enters a pilot cylinder 22 via pipework 21. The resultant pressurisation within the pilot cylinder 22 pushes the piston of the pilot cylinder 22 into contact with

a lever 23 which holds a second float 36 located within the reservoir 6. When the hydraulic fluid pushes the pilot cylinder piston into contact with the lever 23, the lever 23 releases the second float 36, which then rises in the liquid within the reservoir 6. The rising of the second float 36 opens the dump valve, thus emptying the reservoir 6 at a controlled rate. As the reservoir 6 empties, the weight of the first float 13 causes both the first float 13 and beam 14 to lower. The lowering of the beam 14 recompresses the spring within the cylinder 20 by pushing the primary rod member 15 down against the piston rod 18. Primary rod member 15 acts upon the piston through the top of the cylinder 20, the top and bottom of the cylinder 20 having a suitable seals (not shown) provided so that no fluid may escape out of the cylinder 20. As the piston 18 and spring are recompressed, the sluice gate 17 closes against the flow of fluid through the passageway 8.

As the primary rod member 15 and secondary rod member 19 fall, the spool valve 16 is closed by the secondary rod 19 again acting on the striker pin, which in turn holds the recompressed spring and piston 18. The cylinder 20 is also provided with a fluid control valve 24 to control the flow of fluid through the system. Thus, when the piston 18 and spring are being recompressed, the control valve 24 allows fluid to flow out of the cylinder 20 so that no back pressure is created. The control valve 24 also restricts the speed of the piston action within

the cylinder 20 so that damage to the cylinder 20 or piston 18 is avoided during operation. As the piston and spring are recompressed, the hydraulic fluid flows from the cylinder 20 to the back side of the pilot cylinder piston. The fluid pushes the pilot cylinder piston back to its start position, which allows the lever 23 and dump valve float 36 to reset.

The mechanism then automatically resets and begins the filtration cycle again.

An alternative embodiment of the present invention is illustrated in Figs. 7 to 9. For simplicity, any components shared by the two embodiments are referred to using the same reference signs. The tank layout is identical to that of the first embodiment as illustrated in Fig. 1. However, the second embodiment uses an electrical system in place of the hydraulic system in order to flush the tank. The chamber 6 of the tank that contained the float in the first embodiment is instead here provided with a level control sensor 30 which monitors the level of liquid flowing into the chamber 6. The sensor 30 is positioned in the chamber at a predetermined height so that once the level of liquid in the chamber 6 reaches that height, the sensor 30 trips the circuit.

As seen in Fig. 9, the sensor 30 sends a first signal to a central processor 31. Once the first signal is processed, the processor 31 transmits second signals to both a dump valve actuator 32 and a sluice gate actuator 33. The dump valve actuator 32 operates a

lever 34 which is connected to a dump valve float 36.

Therefore, when the second signal is received from the central processor 31, the dump valve actuator 32 trips the lever 34 and the dump valve float 36 is released. As in the previous embodiment, once the float 36 is released, the dump valve opens and the chamber 6 is emptied.

At the same time as the processor 31 transmits to the dump valve actuator 32, the sluice gate actuator 33 also receives a signal from the processor 31. Upon receipt of the signal, the actuator 33 rotates a sluice gate spindle 35, which raises the sluice gate 17, thus allowing the waste water to flow out of the tank.

After a predetermined period of time sufficient to allow both the tank and chamber 6 to empty, the processor will then send a third signal to each actuator 32,33. These third signals are reset signals which instruct the actuators 32,33 to return the dump valve lever 34 and sluice gate 17 back to their original positions, closing the sluice gate 17.

The processor 31 then resets the system to await a new signal from the sensor 30.

Thus, the filtration tank 1 provides a filtration mechanism which filters the incoming effluent until such time as the filtering screen 7 becomes blocked.

Both of the embodiments described above provide filtration means that do not need to be operated

manually by an operator, as the mechanism will automatically discharge the filtered solids and begin the cycle again. Thus, the mechanism can operate with the minimum of supervision, and without the need for any manual intervention.

With the provision of the reservoir 6, the liquid in the passageway 8 and stilling chamber 5 does not directly act on the float arrangement described above. This arrangement eliminates the problem previously described in known tanks, where the float is acted upon directly by water entering the tank.

If this happens above a particular flow rate (appoximately 70 lis or above) in such known tanks, the gate or valve through which the flushing of the tank is facilitated will remain at least partially open at all times as the flow of liquid into the tank keeps the float at a relatively high level.

Introducing a separate float chamber eradicates this problem, allowing the tank to filter liquids flowing at up to approximately 150 lis.

It is intended that the tank of the present invention may be used by itself or else in combination with a number of other tanks. Figs. 10 (a) and 10 (b) show possible arrangements of a number of the tanks in a waste water treatment works or the like. Fig. 10 (a) shows a possible layout for secondary treatment of waste water, in which four tanks 40,50, 60,70 are used in series. Each tank has a screen with a smaller mesh size than the preceding screen. For example,

the first tank 40 may have a screen with a 6mm mesh, while the second tank 50 has a screen with a 4mm mesh, the third tank 60 a 2mm mesh, and the final tank 70 has a mesh measured in microns. Each of the tanks in this example has an inlet 100, an outlet 80 and an overflow 90. The waste water enters the tank through the inlet 100 and is treated in the manner previously described herein. The tank then discharges the filtered waste water through the outlet 80 to the next tank, whilst any overflow created by storm water or the like is transferred to a treatment works via overflow 90.

Fig. 10 (b) shows a possible arrangement of tanks 1 in an inlet works. The tanks 1 are arranged in parallel with waste water entering through inlets 100. As with the previous example, each tank 1 has an outlet 80 and an overflow 90 which transport treated and untreated water, respectively.

Modifications and improvements can be incorporated without departing from the scope of the invention.

Claims

CLAIMS :

1. A waste water tank for the filtering of solids from effluent, said tank having an inlet, first and second outlets, a first filtration means located between the inlet and first outlet, and discharge means, wherein the second outlet is located on the same side of the first filtration means as the inlet, and the discharge means reverses the flow of effluent through said first filtration means when said first filtration means reaches a predetermined degree of contamination.

2. The tank of Claim 1, wherein said second outlet is adapted to move between open and closed states under the action of said discharge means.

3. The tank of either Claim 1 or Claim 2, said tank further comprising a reservoir, the reservoir having a dump valve and being located between the inlet and second outlet, wherein the tank is adapted such that the level of effluent in the reservoir will rise as the degree of contamination of the first filtration means increases.

4. The tank of Claim 3, wherein the reservoir is provided with a second filtration means.

5. The tank of either Claim 3 or Claim 4, wherein the discharge means comprises a sensor located in said reservoir, processing means, a gate covering said second outlet, a first actuator adapted to

selectively open and close the gate, and a second actuator adapted to selectively operate said dump valve, wherein said sensor transmits a first signal to said processing means when the effluent level in said reservoir reaches a predetermined level, and said processing means transmits a second signal to each of said first and second actuators upon receipt of said first signal.

6. The tank of Claim 5, wherein the processing means sends a third signal to each of said first and second actuators a predetermined length of time after said second signals, said actuators closing said gate and dump valve upon receipt of said third signals.

7. The tank of either Claim 3 or Claim 4, wherein the discharge means comprises a first float located within said reservoir, a gate covering said second outlet, and a hydraulic apparatus for the operation of said gate and said dump valve, wherein said first float actuates said hydraulic apparatus when the level of effluent in said reservoir rises above a predetermined level.

8. The tank of Claim 7, wherein said hydraulic apparatus is adapted to move said dump valve and said gate from closed to open positions when acted upon by said first float.

9. The tank of either Claim 7 or Claim 8, wherein the hydraulic apparatus comprises a pivotable beam

member attached to said first float, and a first hydraulic cylinder, the hydraulic apparatus facilitating selective actuation of the cylinder by the beam member.

10. The tank of Claim 9, wherein the first hydraulic cylinder comprises a hydraulic valve and a piston, wherein the movement of the beam member selectively actuates said hydraulic valve.

11. The tank of Claim 10, wherein an end of the piston is fixedly attached to the gate.

12. The tank of Claim 11, wherein the first cylinder further comprises biasing means that bias the piston into a position where the gate is open.

13. The tank of any of Claims 10 to 12, wherein the first hydraulic cylinder further comprises a fluid control valve.

14. The tank of any of Claims 9 to 13, wherein the hydraulic apparatus further comprises a second hydraulic cylinder adapted to actuate said dump valve, wherein said hydraulic valve controls flow of hydraulic fluid between said first and second hydraulic cylinders, and wherein said apparatus is adapted to open and close said hydraulic valve under the action of said first float.

15. The tank of Claim 14, wherein the hydraulic apparatus further comprises a second float located

in said reservoir, wherein said second float is adapted to move said dump valve between closed and open positions when acted upon by said second cylinder.

16. The tank of any preceding claim, wherein the effluent enters said inlet under atmospheric pressure.

17. The tank of any preceding claim, wherein the first and second filtration means are mesh screens adapted to prevent solids of a predetermined size passing therethrough.

18. A waste water tank substantially as hereinbefore described with reference to the accompanying drawings.