WO2009070813A1

WO2009070813A1 - Up-flow filtration apparatus and method

Info

Publication number: WO2009070813A1
Application number: PCT/ZA2008/000106
Authority: WO
Inventors: Ronald Llewellyn Trollip
Original assignee: Ronald Llewellyn Trollip
Priority date: 2007-11-26
Filing date: 2008-11-11
Publication date: 2009-06-04
Also published as: MX2010005525A; CO6210694A2; AP2010005153A0; AP3065A; AU2008329598A1; ZA200908030B; AU2008329598B2; MY154038A

Abstract

The invention relates to an up-flow filtration apparatus and method of using such apparatus. The up-flow filtration apparatus comprises of a tank, a plurality of screens and a filtration medium containable between the screens. The filtration medium preferably has a specific density equal to or lower than the specific density of the liquid being filtered, so as to cause the filtration medium to float in the liquid. In use, liquid to be filtered rises upwardly in the tank through a lower screen via apertures defined therein and compresses the filtration medium, under a buoyancy force, against an upper screen. The liquid is forced upwardly through the interspaces between the filtration medium, causing impurities in the liquid to be trapped in the filtration medium. Filtered liquid passing through the filtration medium passes through apertures defined in the upper screen and out of the tank via an outlet. The filtration apparatus is cheap to build and to operate, is modular and is erectable at or near the location at which the filtered liquid is required.

Description

UP-FLOW FILTRATION APPARATUS AND METHOD

BACKGROUND OF THE INVENTION

THIS invention relates to an up-flow filtration apparatus. More specifically, the invention relates to a modular and cost effective up-flow filtration apparatus and method of using such apparatus.

Many different types of filtration systems, particularly for filtering water for human consumption, are generally well known. Up-flow filtration and down-flow sand filtration systems are the most commonly used systems for filtering water. Typically, these systems are utilised in large scale filtration plants that service whole communities at a time.

However, many disadvantages of large scale purification plants exist, namely:

(i) they are very expensive to construct, costing anywhere between ZAR 2.5 million and

ZAR 3.5 million for a plant capable of providing one million litres of filtered water per day; (ii) they are very time consuming to construct. A plant of the aforesaid capacity can take anywhere from 6 to 12 months to construct and commission; (iii) they are labour intensive to operate. This contributes to high operating costs and the risk of downtime in the event of the labour force downing tools; (iv) they are generally inefficient and outdated. Many of these plants are no longer capable of supplying the required capacity of filtered water, and do not lend themselves to modular construction and accordingly, to increase the capacity of the existing plant is not easily achieved; (v) they are remote from the location where the filtered water is required. This is particularly relevant where the continuous and reliant supply of filtered water is paramount to continued production in an operation; and (vi) they require large amounts of service water (approximately 8 to 15% bed volume) for flushing.

It is accordingly an object of the present invention to provide a modular and cost-effective up- flow filtration apparatus and method of using such apparatus that addresses the disadvantages of the abovementioned systems.

SUMMARY OF THE INVENTION

According to the invention there is provided an up-flow filtration apparatus for filtering liquid including:

a tank;

a lower screen located near a bottom end of the tank and an upper screen located near a top end of the tank, the lower and upper screens defining a plurality of apertures for allowing the passage of liquid therethrough;

a filtration media containable between the lower and upper screens, the filtration media having a specific density equal to or lower than that of the liquid being filtered and sized larger than the apertures defined by the lower and upper screens;

such that impurities in the liquid being filtered are captured by the filtration media while the liquid passes therethrough during a filtration cycle, the filtration media being compressible against the upper screen by the upwardly flowing liquid, thereby increasing the filtration efficiency of the filtration media.

The tank may be an opened topped tank or a closed tank. Generally, the tank defines a primary inlet, located beneath or above the lower screen, for introducing liquid to be filtered into the tank and a primary outlet, located above the upper screen, for removing filtered liquid from the tank. Preferably, the primary inlet is located beneath the lower screen. More preferably, the primary inlet and outlet are connectable to a primary inlet line and primary outlet line respectively. More preferably, the filtration media occupies 50% to 90% of the volume of the tank defined between the lower and upper screens. One or more intermediary screens may be located between the lower and upper screens for containing layers of filtration media having different specific densities and sizes therebetween. Preferably, the filtration media has a specific density equal to or less than the liquid to be filtered so as to allow the filtration media to float on the liquid. Typically, the liquid to be filtered is water and the specific density of the filtration media is 1 or less. Preferably, the filtration media comprises a plurality of bead or pellet type units. More preferably, the filtration media is made from a polyethylene or other type of synthetic material.

The apertures in the screens may be in the form of nozzles.

The filtration apparatus may further include a means for agitating the filtration media during an agitation cycle, the agitating means causing impurities captured in the filtration media during the filtration cycle to be dislodged therefrom. Generally, the agitating means is a fluid pump for pumping a gaseous fluid into the tank, thereby agitating the filtration media. Typically, the tank defines a secondary inlet through which the gaseous fluid is introducible into the tank. Preferably, the secondary inlet is located beneath the lower screen and is in fluid communication with the fluid pump via a secondary inlet line. More preferably, the secondary inlet line comprises a one way valve allowing flow in a direction from the fluid pump to the tank only. Most preferably, the fluid pump is in the form of a blower, fan or compressor and the gaseous fluid is air.

The tank may define a secondary outlet, located beneath the lower screen, for allowing liquid in the tank to be drained therefrom during a drainage cycle. Generally, the secondary outlet is connectable to a secondary outlet line for routing liquid during the drainage cycle away from the tank. Typically, the primary inlet and the secondary outlet are integral, the interchangeable use of which being controllable by the operation of one or more valves on the primary inlet and/or secondary outlet lines.

Also, the tank may further define a tertiary outlet, located above the upper screen for allowing water to exit the tank therethrough during a rinse cycle. Preferably, the tertiary outlet is connectable to a tertiary outlet line for routing liquid during the rinse cycle away from the tank. Generally, the primary outlet and the tertiary outlet are integral, the interchangeable use of which being controllable by the operation of one or more valves on the primary outlet and/or tertiary outlet lines. Typically, the operational cycles of the filtration apparatus are manually controllable on the warning of timing devices and/or pressure sensors, which provide an indicator to a manual operator to open and/or close the relevant valves, and to switch the agitation means on and/or off. Preferably, the operational cycles of the filtration apparatus are automatically controllable via a series of timing devices and/or pressure sensors, which devices and/or sensors actuate the relevant valves into their open and/or closed positions, and switch the agitation means on and off, on the occurrence of predetermined time and/or pressure parameters.

The filtration apparatus may be capable of providing at least about 30 and 37 cubic metres of clean water per square metre of cross sectional area of the tank. Typically, liquid to be filtered, and not filtered, municipal or other clean water, is usable to rinse or flush the filtration apparatus during the rinse cycle. Preferably, the volume of liquid required to rinse or flush the filtration apparatus during the rinse cycle is between 1.1 to 1.9 times the volume of the tank defined between the lower and upper screens. More preferably, the volume of liquid required to rinse or flush the filtration apparatus during the rinse cycle is about 1.3 times the volume of the tank defined between the lower and upper screens. Most preferably, the liquid to be filtered, used for rinsing or flushing the filtration apparatus is raw water.

The filtration system may be modular in that additional filtration apparatuses are connectable to one another as the requirement for greater volumes of filtered liquid increases. Preferably, the apparatus is erectable near or at the location at which the filtered liquid is required.

According to a second aspect of the invention, there is provided a method of operating an up- flow filtration apparatus as described above comprising the steps of:

(A) during the filtration cycle, opening the primary inlet and primary outlet while keeping the secondary and tertiary outlets closed and the agitation means switched off, thereby causing the liquid to be filtered entering the tank via the primary inlet to rise through the lower screen, the compressed filtration media, the upper screen and out of the primary outlet;

(B) during the agitation cycle, switching the agitation means on while keeping the primary inlet and the primary, secondary and tertiary outlets closed, thereby causing the gaseous fluid entering the tank through the secondary inlet to agitate the filtration media and dislodge impurities trapped therein;

(C) during the drainage cycle, opening the secondary outlet while keeping the primary inlet and the primary and tertiary outlets closed and the agitation means switched off, thereby allowing the liquid and impurities dislodged from the filtration media to drain from the tank via the secondary outlet; and

(D) during the rinse cycle, opening the primary inlet and tertiary outlet while keeping the primary outlet and secondary outlet closed and the agitation means switched off, thereby allowing the liquid to be filtered entering the tank via the primary inlet to rise through the lower screen, the compressed filtration media, the upper screen and out of the tertiary outlet for a predetermined amount of time, the lapse of which causing the filtration apparatus to revert back to the filtration cycle.

During the filtration cycle, chemicals for assisting the filtration and purification of the liquid to be filtered may be added thereto, at any location on the primary inlet line connected to the primary inlet. Preferably, the inlets and outlets are opened and closed, and the agitation means is switched on and off, automatically via the timing devices and/or pressure sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a side view of the filtration apparatus in accordance with the invention during a filtration cycle;

Figure 2 shows a side view of the filtration apparatus during an agitation cycle;

Figure 3 shows a side view of the filtration apparatus during a drainage cycle; and

Figure 4 shows a side view of the filtration apparatus during a rinse cycle. DESCRIPTION OF THE PREFERRED EMBODIMENT

An up-flow filtration apparatus according to a preferred embodiment of the invention is designated generally with the reference numeral 10. The up-flow filtration apparatus 10 includes a tank 12, a lower screen 14, an upper screen 16 and filtration media 18.

With specific reference to figure 1 , the lower screen 14 and the upper screen 16 divide the tank into a lower chamber 12A, a middle chamber 12B and an upper chamber 12C. The screens 14, 16 are located within the tank 12 between flanges 20, 22 respectively. The screens 14, 16 comprise a plurality of apertures (not shown), typically in the form of nozzles, sized large enough to allow the passage of liquid to be filtered threthrough, but small enough to prevent the passage of the filtration media 18 therethough.

As indicated above, the filtration media 18 is in the form of beads or pellets each bead or pellet being of a dimension large enough to prevent it from passing through any of the apertures defined by the screens 14, 16. Although not necessary, it is preferable that the filtration media 18 is manufactured from a synthetic material having a specific density equal to or less than the specific density of the liquid being filtered. Accordingly, where water is being filtered, the specific density of the filtration media must be 1 or less. The efficiency and capacity of the filtration apparatus 10 is dependent in the amount of filtration media 18 used. Preferably, the filtration media 18 occupies between 50% and 90% of the volume of the middle chamber 12B of the tank 12.

The tank 12 includes an inlet/outlet 24 through which liquid to be filtered (for example raw water) can be introduced into the lower chamber 12A of the tank 12 during a filtration cycle (as indicated by the arrows in figure 1), or through which water in the tank 12 can be drained therefrom during a drainage cycle (as indicated by the arrows in figure 3). The inlet/outlet 24 is in the form of a T-piece connecting a primary inlet line 26 and a secondary outlet line 28 to the tank 12. Although the inlet/outlet 24 has been illustrated as an integral component to both the primary inlet line 26 and a secondary outlet line 28, it will be appreciated that the lower chamber 12A may comprise a separate inlet and outlet for connecting the primary inlet line 26 and the secondary outlet line 28 to the tank 12 respectively. The tank 12 further includes a secondary inlet line 30 for, during an agitation cycle, introducing a gaseous fluid (as indicated by the arrows in figure 2), such as air, forced into the lower chamber 12A by an agitation means 32 in the form of an air blower. The secondary inlet line 30 further consists of a non-return valve 31 (or other ordinary valve), so as to allow flow in the direction from the blower 32 to the tank 12 only.

The upper chamber 12C of the tank 12 further includes a primary outlet line 34, for allowing filtered water during the filtration cycle to exit the tank 12 therethrough, and a tertiary outlet line 36, for allowing rinsing water during a rinse cycle (as indicated by the arrows in figure 4) to exit the tank 12 therethrough. The operational cycles making up the operation of the filtration apparatus consist of a filtration cycle (figure 1), a agitation cycle (figure 2), a drainage cycle (figure 3) and a rinse cycle (figure 4).

With specific reference to figure 1, the filtration cycle is initiated by opening the primary inlet valve 38 thereby allowing raw water to flow into the lower chamber 12A of the tank 12. During the filtration cycle, secondary and tertiary outlet valves 40, 42 are closed and the blower 32 is switched off. The raw water rises upwardly through the lower screen 14 into the middle chamber 12B of the tank 12.

As the raw water rises upwardly through the middle chamber 12B, the filtration media 18 is compressed, under the force of buoyancy, against the upper screen 16, thereby reducing the number and interspaces between the filtration media 18. As the raw water passes through the interspaces in the filtration media 18, impurities in the raw water are trapped in the filtration media 18. Clean water then rises upwardly through the upper screen 16, into the upper chamber 12C of the tank 12 until it exits the tank 12 via the primary outlet line 34. Clean water exiting the tank 12 via the primary outlet line 34 is preferably routed to a holding tank (not shown) for later use.

Once the filtration media 18 has become saturated with impurities from the water, it is necessary to switch the filtration apparatus to the agitation cycle, as best illustrated in figure 2. During the agitation cycle, with the primary inlet valve 38, the secondary outlet valve 40 and the tertiary outlet valve 42 in their closed positions, the blower 32 is switched on. The air from the blower 32 is forced upwardly through the lower screen 14 and into the middle chamber 12B of the tank 12. The air agitates the filtration media 18, allowing impurities trapped therein to dislodge from the filtration media 18.

Thereafter, the filtration apparatus 10 is switch over to the drainage cycle, wherein the blower 32 is switched off and all valves, except the secondary outlet valve 40, are maintained in the closed position The water remaining in the tank 12, now also containing the impurities dislodged from the filtration media 18 during the agitation cycle, is drained from the tank 12 via the inlet/outlet 24 and the secondary outlet line 28.

Once all of the water is drained from the tank 12, the filtration apparatus is switched over to the rinse cycle, wherein the secondary outlet valve 40 is closed, and the primary inlet valve 38 and the tertiary outlet valve 42 are opened. Raw water rises up through the tank 12 much in the same way as in the filtration cycle, and out through the tertiary outlet line 36. Once the water exiting the tank 12 via the tertiary outlet line 36 appears to be clean and potable, the filtration apparatus is switched back over to the filtration cycle by closing valve 42. The operational cycles are repeated in the aforementioned order either manually or automatically. Where the filtration apparatus 10 is operated automatically, the opening and closing of valves and the switching on and off of the blower 32 are actuated by timing devices (not shown) and/or pressure sensors (not shown). The timing devices actuate the relevant components on the lapse of predetermined amount of time, whereas the pressure sensors actuate the relevant components on the pressure rising above or falling below a predetermined band of pressures.

The advantages of the up-flow filtration apparatus 10 as described above are many, namely:

(i) cost effectiveness. A filtration apparatus 10 with a capacity of one million litres of filtered water per day costing in the region of ZAR 300,000; (ii) short time of construction. A filtration apparatus 10 of the aforesaid capacity can be built and operation within about 21 days; (iii) fully automated operation; (iv) modular construction. Further filtration apparatuses 10 can be connected to one another to increase the overall capacity of the system as and when the need further greater capacity arises; (v) location. The filtration apparatus 10 can be constructed at or near the location at which the filtered water is required; (vi) flow rate. The filtration apparatus 10 is capable of delivering 30 and 37 cubic metres of clean water per square metre of cross sectional area of the tank, as compared to about 14 cubic metres with conventional systems; and (vii) rinse water required. The filtration apparatus 10 uses raw water rather than expensive filtered, municipal or other clean water to rinse the apparatus 10 during the rinse cycle. Also, the rinse cycle only requires a volume of water equivalent to about 1.1 to 1.9 times, but generally about 1.3 times, the volume of the middle chamber 12B of the tank 12 to rinse the apparatus 10 during the rinse cycle. This translates to a reduction in required rinse water, as compared to existing systems, of between about 7 to 13%

Although the invention has been described above with reference to a preferred embodiment, it will be appreciated that many modifications or variations of the invention are possible without departing from the spirit or scope of the invention. For example, one or more intermediary screens may be located between the lower and upper screens for containing a plurality of layers of filtration media having different specific densities and sizes therebetween, so as to increase the filtration efficiency of the filtration apparatus 10.

Claims

1. An up-flow filtration apparatus for filtering liquid including:

a tank;

2. An up-flow filtration apparatus according to claim 1 , wherein the tank defines a primary inlet, located beneath the lower screen, for introducing liquid to be filtered into the tank and a primary outlet, located above the upper screen, for removing filtered liquid from the tank.

3. An up-flow filtration apparatus according to claim 2, wherein the primary inlet and primary outlet are connectable to a primary inlet line and primary outlet line respectively.

4. An up-flow filtration apparatus according to any one of claims 1 to 3, wherein the filtration media occupies 50% to 90% of the volume of the tank defined between the lower and upper screens.

5. An up-flow filtration apparatus according to any one of claims 1 to 4, wherein one or more intermediary screens are located between the lower and upper screens for containing layers of filtration media having different specific densities and sizes therebetween.

6. An up-flow filtration apparatus according to any one of claims 1 to 5, wherein the liquid to be filtered is raw water and the filtration media is of a specific density of 1 or less.

7. An up-flow filtration apparatus according to any one of the preceding claims wherein the filtration media comprises a plurality of bead or pellet type units.

8. An up-flow filtration apparatus according to any one of the preceding claims wherein the filtration media is made from a polyethylene or other type of synthetic material, or natural material.

9. An up-flow filtration apparatus according to any one of the preceding claims wherein the apertures in the screens are in the form of nozzles.

10. An up-flow filtration apparatus according to any one of the preceding claims wherein the filtration apparatus further includes a means for agitating the filtration media during an agitation cycle, the agitating means causing impurities captured in the filtration media during the filtration cycle to be dislodged therefrom.

11. An up-flow filtration apparatus according to claim 10, wherein the tank defines a secondary inlet through which a gaseous fluid is introducible into the tank, the agitation means being in the form of a fluid pump connectable to the secondary inlet via a secondary inlet line.

12. An up-flow filtration apparatus according to claim 11 , wherein the gaseous fluid is air and the secondary inlet is located beneath or above the lower screen.

13. An up-flow filtration apparatus according to claim 12, wherein the secondary inlet line comprises a valve for controlling flow from the agitation means into the tank.

14. An up-flow filtration apparatus according to claim 13, wherein the valve on the secondary inlet line is a one way valve allowing flow in the direction from the agitation means to the tank only.

15. An up-flow filtration apparatus according to any one of claims 11 to 14, wherein the fluid pump is in the form of a blower, fan or compressor.

16. An up-flow filtration apparatus according to any one of the preceding claims wherein the tank defines a secondary outlet, located beneath the lower screen, for allowing liquid in the tank to be drained therefrom during a drainage cycle, the secondary outlet being connectable to a secondary outlet line for routing liquid being drained away from the tank.

17. An up-flow filtration apparatus according to claim 16, wherein the primary inlet and the secondary outlet are integral, the interchangeable use of which being controllable by the operation of one or more valves on the primary inlet line and/or secondary outlet line.

18. An up-flow filtration apparatus according to any one of the preceding claims wherein the tank further defines a tertiary outlet, located above the upper screen and for allowing water to exit the tank therethrough during a rinse cycle, the tertiary outlet being connectable to a tertiary outlet line for routing liquid during the rinse cycle away from the tank.

19. An up-flow filtration apparatus according to claim 18, wherein the primary outlet and the tertiary outlet are integral, the interchangeable use of which being controllable by the operation of one or more valves on the primary outlet line and the tertiary outlet line.

20. An up-flow filtration apparatus according to claim 19, wherein the operational cycles of the filtration apparatus are manually controllable on the warning of timing devices and/or pressure sensors, which provide an indicator to a manual operator to open and/or close the relevant valves, and to switch the agitation means on and/or off.

21. An up-flow filtration apparatus according to claim 20, wherein the operational cycles of the filtration apparatus are automatically controllable via a series of timing devices and/or pressure sensors, which actuate the relevant valves into their open and/or closed positions, and switch the agitation means on and off, on the occurrence of predetermined time and/or pressure parameters.

22. An up-flow filtration apparatus according to any one of the preceding claims wherein the filtration apparatus is capable of providing at least about 30 and 37 cubic metres of clean water per square metre of cross sectional area of the tank.

23. An up-flow filtration apparatus according to any one of claims 18 to 22, wherein liquid to be filtered and not filtered, municipal or other clean water is usable to rinse or flush the filtration apparatus during the rinse cycle.

24. An up-flow filtration apparatus according to claim 23, wherein the volume of liquid required to rinse or flush the filtration apparatus during the rinse cycle is between 1.1 to 1.9 times the volume of the tank defined between the lower and upper screens.

25. An up-flow filtration apparatus according to claim 24, wherein the volume of liquid required to rinse or flush the filtration apparatus during the rinse cycle is about 1.3 times the volume of the tank defined between the lower and upper screens.

26. An up-flow filtration apparatus according to any one of the preceding claims wherein the filtration system is modular in that additional filtration apparatuses are connectable to one another as the requirement for greater volumes of filtered liquid increases.

27. An up-flow filtration apparatus according to any one of the preceding claims wherein the apparatus is erectable near or at the location at which the filtered liquid is required.

28. An up-flow filtration apparatus according to any one of claims 3 to 27, wherein chemicals for assisting the filtration and purification of the liquid to be filtered are introducible into the liquid via at a location along the primary inlet line.

29. A method of operating an up-flow filtration apparatus according to claims 1 to 28 comprising the steps of:

(C) during the drainage cycle, opening the secondary outlet while keeping the primary inlet and the primary and tertiary outlets closed and the agitation means switched off, thereby allowing the liquid and impurities dislodged from the filtration media to drain from the tank; and

30. A method according to claim 29, wherein the inlets and outlets are opened and closed, and the agitation means is switched on and off, manually or automatically or indication of or via the timing devices and/or pressure sensors.

31. A method according to claim 29 or claim 30, wherein chemicals for assisting the filtration and purification of the liquid to be filtered are introducible thereto at any location on the primary inlet.

32. An up-flow filtration apparatus substantially as herein described with reference to any one of the illustrated embodiments.

33. A method of operating an up-flow filtration apparatus substantially as herein described with reference to any one of the illustrated embodiments.