WO2014180481A1

WO2014180481A1 - A biological purification device and a method for cleaning individual filtering elements

Info

Publication number: WO2014180481A1
Application number: PCT/DK2013/050131
Authority: WO
Inventors: Ole Enggaard Pedersen
Original assignee: Aquatech Solutions A/S
Priority date: 2013-05-08
Filing date: 2013-05-08
Publication date: 2014-11-13

Abstract

Disclosed is a biological purification device (1) for biological purification of water. The purification device comprising a filtering tank (2) for holding the water and a plurality of individual filtering elements (3) floating in the water in the filtering tank (2), wherein the filtering elements (3) forms a floating filtering bed (4). The biological purification device (1) also includes one or more injector tubes (5) comprising injector means (6) arranged at a top surface (7) of the floating filtering bed (4) and the injector tubes (5) also includes tubular guide means (8) extending from the injector means (6) and downwards through the floating filtering bed (4). The injector tubes (5) also comprises pump means (9) for creating an injector flow from the injector means (6) and down through the tubular guide means (8), wherein the tubular guide means (8) comprise one or more inlet openings (10) for allowing the injector flow to draw filtering elements (3) directly into the tubular guide means (8) from the floating filtering bed (4) and wherein the inlet openings (10) are arranged at the injector means (6). A method for cleaning individual filtering elements (3) and use of a biological purification device (1) is also disclosed.

Description

A BIOLOGICAL PURIFICATION DEVICE AND A METHOD FOR CLEANING INDIVIDUAL

FILTERING ELEMENTS

Field of the Invention

The present invention relates to a biological purification device for biological purification of water and a method for cleaning individual filtering elements floating in a filtering tank and forming a floating filtering bed of a biological purification device for biological purification of water. Furthermore the invention relates to use of a biological purification device.

Background of the Invention

Biological filters typically consists of a bed of filter material through which sewage or other wastewater flows and causes a layer of microbial slime (biofilm) and suspended solids to accumulate, covering the filter material in the bed. Aerobic conditions are typically maintained by creating some sort of air flow through the bed.

After a period of time the efficiency of the filter is reduces if the biofilm and suspended solids is not removed from the filter material and from US 5,573,671 it is therefore known to form the top of a filtering tank conically to lead the floating granular filter material up to an outlet arranged at the apex of the tank and into a jet pump, which will accelerate and thereby wash the granular material while and when it is returned at the bottom of the tank, where the removed biofilm and suspended solids will sediment at the bottom of the tank, while the cleaned granular material will float upwards and join the bed of floating granular material.

However, particularly in relation with water from fish farms the biofilm and suspended solids build-up on the granular material has a tendency form an interconnected layer that may clog the filter. Furthermore, the complex piping and tank design makes this solution both complex and expensive. Thus, from DE 195 33 632 CI it is known to place an injector in a pipe extending down through a bed of floating granular material. At the top of the bed one or more suction arms comprising several openings are extending radial from the pipe. A motor rotates the pipe and thus the suction arm is rotated through the top layer of the floating granular material and granular material is sucked into the arm and further into and down through the pipe to be released at the bottom of the tank.

However, for biofilm and suspended solids to build up and be retained on the floating filter material it is important that the filter material is not agitated too much and although the device disclosed in DE 195 33 632 CI will reduce the risk of filter clogging it also constantly stirs up the upper part of the filtering bed and thus hinders that biofilm and suspended solids can build up on in the upper part of the biological bio filter bed. It is therefore an object of the present invention to provide an advantageous technique for cleaning the filtering elements in a biological purification device.

The invention

The invention relates to a biological purification device for biological purification of water. The purification device comprising a filtering tank for holding the water and a plurality of individual filtering elements floating in the water in the filtering tank, wherein the filtering elements forms a floating filtering bed. The biological purification device also includes one or more injector tubes comprising injector means arranged at a top surface of the floating filtering bed and the injector tubes also includes tubular guide means extending from the injector means and downwards through the floating filtering bed. The injector tubes also comprises pump means for creating an injector flow from the injector means and down through the tubular guide means, wherein the tubular guide means comprise one or more inlet openings for allowing the injector flow to draw filtering elements directly into the tubular guide means from the floating filtering bed and wherein the inlet openings are arranged at the injector means. By making the injector means suck the filtering elements directly into the tubular guide means at the injector means is advantageous in that this will cause very little commotion in the filtering bed and thus ensure that biofilm continues to build up on the filtering elements - even in the top layer and even close to the tubular guide means.

Furthermore, this injector tube and tank design is simple and thus less expensive and easier to install and maintain.

In an aspect of the invention, said tubular guide means substantially encloses said injector means.

Making the tubular guide means enclose the injector means is advantageous in that it increases the injector effect of the injector means and reduces the risk of unwanted commotion and turbulence in the filtering bed.

In an aspect of the invention, said tubular guide means is rigidly fixed in relation to said filtering tank.

Connecting the tubular guide means rigidly directly or indirectly to the filtering tank is advantageous in that it ensures a simple and easy installation process and a rigid fixation will ensure that the tubular guide means remains stationary and avoid that the tubular guide means causes unwanted motion in the filtering bed.

In an aspect of the invention, said one or more inlet openings are formed as orifices in a side wall of said tubular guide means.

Forming the inlet openings as orifices in the side wall of the tubular guide means is advantageous in that it provides for a simple and inexpensive design and in that it reduces the risk of the tubular guide means and/or the inlet openings causing unwanted motion in the filtering bed.

In an aspect of the invention, said tubular guide means are formed as a substantially straight pipe.

The flltering elements have a density smaller than water and are thus buoyant. Thus, the injector means have to create a significant downwards injector flow to ensure that the flltering elements actually reached the bottom end of the tubular guide means and leaves the tube. If the tubular guide means comprises bends or curves it will take even more energy to create an injector flow of sufficient strength. Furthermore, a straight pipe is the most inexpensive design and ensures simple manufacturing and installation. In an aspect of the invention, said filtering elements have a maximum external measurement of at least 4 mm, preferably at least 6 mm, and most preferred at least 8 mm.

If the flltering elements are too big the total surface area per cubic meter becomes too small and the biological purification device will either be very large or less effective. In a preferred embodiment the maximum external measurement of the filtering elements is therefore at least 100 mm, preferably 70 mm and most preferred 40 mm.

However, if the filtering elements becomes too small it becomes difficult to clean them properly and particularly in relation to cleaning water from fish farms the biofilm and suspended solids build-up on small filtering elements can entail that the biofilm and the filtering elements together forms a more or less solid gel that will reduce the efficiency of the biological purification device. In an aspect of the invention, said filtering elements are formed as pipes having internal and/or external lamellas. Forming the filtering elements as pipes provides a desired open structure suitable for biofilm build-up and capturing of suspended solids and it enables a simple manufacturing process e.g. in the form of extrusion. Designing the pieces of pipes with internal and/or external lamellas is also advantageous in that it increases the filtering elements total surface area.

In an aspect of the invention, said one or more inlet openings have a maximum external measurement of between 10 and 200 mm, preferably between 20 and 140 mm, and most preferred between 30 and 100 mm.

If the inlet openings are too small the risk of the filtering elements blocking the inlet openings is increased and if the inlet openings are too big, the water flow created by the injector will incur so low water speed through the openings that none or too little filter material will move into the in the pipe . The present size ranges therefore provides for an advantageous relationship between operational reliability and efficiency.

In an aspect of the invention, said filtering tank comprises two or more injector tubes and wherein said injector flow in said two or more injector tubes is created by common pump means.

Feeding several injector tubes by means of the same common pump means is advantageous in that it reduces the overall cost of the biological purification device and simplifies the design of the individual injector tubes.

The invention also relates to a method for cleaning individual filtering elements floating in a filtering tank and forming a floating filtering bed of a biological purification device for biological purification of water. The method comprises the steps of: creating a downwards directed injector flow through a stationary tubular guide mean extending down through the filtering bed,

sucking filtering elements from the floating filtering bed directly into the tubular guide means through one or more inlet openings arranged in the tubular guide means,

transporting the filtering elements down through the tubular guide mean and emitting the filtering elements from a bottom end of the tubular guide mean.

Hereby is provided an efficient method for cleaning the filtering elements without causing too much motion in the filtering bed - thus, increasing the efficiency of the biological purification device.

In an aspect of the invention, said injector flow is formed by impure water being lead to said biological purification device to be biological purified.

Pumping at least a part of the "dirty" inflow water through the tubular guide means to form the injector flow is advantageous in that the risk of unwanted motion in the filtering bed - at a possible inlet for the injector pump means - is eliminated and in that further sources can be avoided.

In an aspect of the invention, said method is a method for cleaning filtering elements of a biological purification device according to any of the previously mentioned biological purification devices.

Hereby is achieved an advantageous embodiment of the invention.

Even further, the invention relates to use of a biological purification device according to any of the previously mentioned biological purification devices for biological purification of water from a fish farm. Filtering elements in the form of granulate material having a size of 2 mm or less as disclosed in US 5,573,671 and DE 195 33 632 CI is generally used in relation with traditional sewage water purification. However, in relation with cleaning water from fish farms such granulate material cannot capture and accumulate sufficient amounts of suspended solids and is not particularly suited in that the biofilm created in relation with fish farm water is particularly coherent and the risk of filter clogging or at least reduced efficiency is therefore more profound.

Figures

The invention will be explained further herein below with reference to the figures in which:

Fig. 1 shows a cross section through a biological purification device, as seen from the front,

Fig. 2 shows the biological purification device disclosed in figure 1, as seen in perspective,

Fig. 3 shows a cross section through an injector tube, as seen from the front,

Fig. 4 shows the injector tube shown in figure 3, as seen in perspective,

Fig. 5 shows a layout of a fish farm and biological purification device, as seen from the top,

Fig. 6 shows an embodiment of a filtering element, as seen from the top, and

Fig. 7 shows the filtering element disclosed in fig. 6, as seen from the side.

Detailed description Figure 1 shows a cross section through a biological purification device 1, as seen from the front.

In this embodiment a number of injector tubes 5 are arranged in three neighbouring filtering tanks 2. Each tank 2 is provided with a top grate 15 arranged to ensure that the filtering bed 4 formed by buoyant filtering elements 3 are kept at a specific level so that the filtering elements 3 are sucked into the injector tubes 5 through the inlet openings 10 at the top surface 7 of filtering bed 4. The injector tubes 5 extend down through the filtering bed 4 so that filtering elements 3, sucked into the injector tubes 5 through the inlet openings at the top, will be blown out of the bottom end 13 of the tubular guide means 8 - by the water flow generated in the injector tube 5 - at the bottom of the tank 2, where the loose biofilm and suspended solids will settle at the bottom of the tank 2 while the substantially clean filtering elements will float upwards and joint the bottom of the filtering bed 4. New filtering elements 3 will occasionally or continuously be sucked into the injector tubes 5 and these will occasionally or continuously join the bottom of the filtering bed 4 so that the filtering elements 3 are substantially constantly and slowly moving upwards in the filtering bed 4. However, this motion is so relatively slow and protracted that it does not influence the build-up of biofilm and capturing and accumulation of suspended solids on the filtering elements 3 in the filtering bed 4. Thus, all the filtering elements 3 in the filtering bed 4 are substantially constantly active and efficient regarding biofilm build-up and capturing and accumulation of suspended solids from when they join the bottom of the bed 4 and until they are sucked into the inj ector tube 5.

In this embodiment the bottom of the tanks 2 are formed with a V-shaped design to enable that the loose biofilm and suspended solids settle in the bottoms of the Vs. Thus, in this embodiment the bottoms of the V's are provided with sludge removing means 16, which in this embodiment is formed as a pipe with upwards facing holes. When vacuum is established in the pipe - at appropriate times - the sludge is sucked out of the tank 2. The sludge can then e.g. be used as fertilizer e.g. in a dried-out state or it can undergo further purification.

In this embodiment the tanks 2 are also provided with water inlets 17 through which un-purified water may enter the tanks 2 and the tanks 2 are provided with aeration means 18 which in this embodiment are formed as perforated pipes through which air or oxygen is pumped into the tanks 2 and released under the filtering beds 4 to feed the aerobic process in the filtering bed 4. Fig. 2 shows the biological purification device 1 disclosed in figure 1, as seen in perspective. To enhance the understanding of the layout of the present biological purification device 1, the device 1 is in this embodiment shown without the filtering bed 4 and most of the top grate 15 is cut away. In this embodiment the biological purification device 1 comprises three more or less individual filtering tanks 2. However, the overflow of each tank 2 is in this embodiment connected to the same channel, which leads the clean water back to the system from which it came i.e. in this case back to a fish farm. In this embodiment all the injector tubes 5 in all the tanks 2 are all connected to the same common pump means 9 however in another embodiment only some of the injector tubes 5 would be connected to one or more common pump means 9 or some or all the injector tubes 5 could be provided with individually operated pump means e.g. arranged at the injector tubes 5 so that these can be installed without complicated piping.

In this embodiment the pump means 9 draws water from the un-purified water being lead to the biological purification device 1 i.e. the same water that flows out of the water inlets 17 discussed in relation to fig. 1. However, in another embodiment the water could be drawn from the tank 2 or from another source. Fig. 3 shows a cross section through an injector tube 1, as seen from the front and fig. 4 shows the injector tube 5 shown in figure 3, as seen in perspective.

In this embodiment the injector tube 1 comprises a valve 20 in the form of a turn valve to block the flow through the individual injector tubes 5. The valve 20 is in this embodiment succeeded by a manometer 21 to visually monitor the pressure in the individual injector tubes 5. In another embodiment the pressure could be electronically monitored e.g. from a central location. The water is now lead trough the injector means 6 which in this case comprises a main pipe 22 leading the water down to a nozzle 23 which due to the decreased diameter will force the water out at relatively high speed and thus create a downwards directed injector flow strong enough the clean the filtering elements 3 and lead them all the way down to the bottom of the injector tube 5. The injector means 6 will also create a vacuum inside the tubular guide means 8 at the inlet openings 10, which will draw water and filtering elements 3 into the tubular guide means 8.

In a preferred embodiment the pressure in the injector means 6 is between 1,000 and 1,000,000 Pa, preferably between 4,000 and 100,000 Pa and most preferred between 8,000 and 60,000 Pa.

If the pressure is too high, the injector tubes 5 will create too much motion in the filtering bed 4 and thus reduce the overall efficiency of the biological purification device 1 and if the pressure is too low the injector means 6 might not create an injector flow that is strong enough to transport the floating filtering elements 3 all the way to the bottom of the injector tube 5 or the injector flow will not be efficient at cleaning the filtering elements 3. In another embodiment the different parts of the injector tube 5 could be arranged differently such as in different order or at other locations and/or some - e.g. valve 20 and/or manometer 21 - could be common for several injector tubes 5 or one or more of the parts could be omitted in certain configurations.

In this embodiment the injector means 6 is enclosed in a tubular guide mean 8 which extends from the injector means 6 and all the way down to the bottom of the tank 2 as illustrated in fig. 1.

In this embodiment the tubular guide means 8 is formed as a straight cylindrical pipe having a constant diameter, however in another embodiment the tubular guide means 8 could have a different shape, such as oval, rectangular, square, polygonal or other, the tubular guide means 8 could comprise one or more bends and the inner and/or outer width of the pipe could vary along the extend of the pipe.

In another embodiment the tubular guide means 8 could also be provided with bends, chicane, obstacles or other to induce turbulence and e.g. ensure that the filtering elements are thoroughly cleaned down through the tubular guide means 8.

In this embodiment the tubular guide means 8 are provided with two inlet openings 10 arranged opposite each other at the injector means 6, so that the vacuum created by the injector means 6 in the tubular guide means 8 will draw water and filtering elements 3 from the filtering bed 4 outside the injector tube 5 into the tubular guide means 8. In this embodiment the inlet openings 10 are formed as two circular bores in the wall of the tubular guide means 8 but in another embodiment the inlet openings 10 could be formed with a different shape, the injector tube 5 could comprise another number of inlet openings 10 such as one, three, four, five or more and/or the inlet openings could be distributed differently in the wall of the tubular guide means 8. In an embodiment the inlet opening 10 could in principle also be formed as a gap at the upper end of the tubular guide means 8 or even the entire opening at the upper end of the tubular guide means 8 i.e. in another embodiment the upper end of the tubular guide means 8 could be moved downwards so that e.g. only the nozzle 23 of the injector means 6 was encircled by the tubular guide means 8 so that the filtering elements 3 would enter the tubular guide means 8 through the gap between the upper side wall 11 of the tubular guide means 8 and the nozzle 23. Or the tubular guide means 8 could be arranged to extend from the exit opening of the nozzle 23 or even so far down that a vertical gap is arranged between the injector means 6 and the upper end of the tubular guide means 8 so that the jet flow created by the injector means 6 will draw filter elements 3 down into the tubular guide means 8 and create an injector flow down through the tubular guide means 8 that will clean the filtering elements 3 and deliver them out of the bottom end 13 of the tubular guide means 8.

In this embodiment the tubular guide means 8 is formed as an approximately 090 mm PVC pipe having a length of nearly 4 meters and a material thickness of about 5- 6 mm but in another embodiment the diameter, the thickness and/or the length could be both greater or smaller e.g. in accordance with the specific task, a specific tank 2 or other. In this embodiment the inlet openings 10 have a maximum external measurement MI of around 063 mm but in another embodiment the size could vary between 10 and 200 mm, preferably between 20 and 140 mm, and most preferred between 30 and 100 mm. Since the filtering elements 3 enters the injector tubes 5 through the inlet openings 10 in the wall of the tubular guide means 8 directly from the filtering bed 4, the "reach" of each injector tube 5 might not be all that long and in this embodiment the injector tubes disclosed in fig. 1 and 2 is therefore arranged with a mutual distance of around 1500 mm to ensure that all or at least substantially all the filtering elements 3 - even at the top surface 7 - eventually in drawn into the injector tubes 5 to be cleaned. However, in another embodiment the injector tubes 5 could be arranged closer or more apart e.g. in accordance with the capacity of the injector tubes 5, the design of the filtering elements 3 or other. In this embodiment the tubular guide means 8 is provided with an connection flange 24 enabling that the tubular guide means 8 - by means of connection means such as screws, bolts, rivets, adhesive, welding or other - can by rigidly fixed to the top grate 15, which in turn is fixed in relation to the tank 5. However in another embodiment the tubular guide means 8 could be rigidly fixed in relation to the tank 2 in other ways, such as by means of dedicated brackets, by means of the piping supplying the injector tube 5, by means of connections arranged on other parts of the injector tube 5 or in another way.

Fig. 5 shows a layout of a fish farm 14 and biological purification device 1, as seen from the top.

In this embodiment a pipe leads unclean water from a fish farm 14 to a biological purification device 1 according to the present invention in which some of the water is pumped down through the injector tubes 5 by means of the pump means 9 to clean the filtering elements in the tank 2. The overflow of the biological purification device 1 is in this embodiment connected to an outlet pump which pumps the clean water back into the fish farm 14 in a substantially closed circuit.

Fig. 6 and 7 shows an embodiment of a filtering element 3, as seen from the top and the side.

The present filtering elements 3 are shown simplified but in this embodiment the elements 3 are formed as a cylindrical tube comprising different lamellas 12 arranged on the inside of the tube. However, in another embodiment the elements 3 could be formed with another shape and it could be form with lamellas 12 also on the outside or without lamellas 12.

In this embodiment the filtering elements 3 has a maximum external measurement MF - i.e. a diameter in this case - of around 16 mm and a height of around 9 mm but in another embodiment the maximum external measurement MF of the elements 3 could be both bigger or smaller such as 10 mm, 12 mm, 14 mm, 18 mm, 20 mm or bigger and the elements 3 could be both shorter or longer such as 6 mm, 8 mm, 11 mm, 13 mm or longer or any combination thereof.

In this embodiment the filtering elements 3 are formed circular to ensure that the element 3 does not pack up and to ensure water passage between the elements 3. Furthermore, the tubular design enables that the filtering elements 3 can be manufactured by means of protrusion thus reducing production cost. Also, in this embodiment the elements 3 are provided with an open inside structure ensuring easy water flow through the elements 3 and thus increasing the efficiency of the biological purification device 1.

Filtering elements of this type is particularly suited for cleaning water from a fish farm in that even though these elements 3 provides a very large surface on which the biofilm can develop these elements 3 also ensures that water and air substantially at all times may pass through and around the elements 3, thus reducing the risk of clogging and increasing the overall efficiency of the biological purification device 1.

In the foregoing, the invention is described in relation to specific embodiments of biological purification devices 1, injector tubes 5, filtering element 3 and other as shown in the drawings, but it is readily understood by a person skilled in the art that the invention can be varied in numerous ways within the scope of the appended claims.

Biological purification device

Filtering tank

Filtering element

Filtering bed

Injector tube

Injector means

Top surface

Tubular guide means

Pump means

Inlet opening

Side wall of tubular guide means

Lamella

Bottom end of tubular guide means

Fish farm

Top grate

Sludge removing means

Water inlet

Aeration means

Overflow

Valve

Manometer

Main pipe

Nozzle

Connection flange

Maximum external measurement of filtering element Maximum external measurement of inlet opening

Claims

1. A biological purification device (1) for biological purification of water, said purification device comprising a filtering tank (2) for holding said water, a plurality of individual filtering elements (3) floating in said water in said filtering tank (2), wherein said filtering elements (3) forming a floating filtering bed (4), and one or more injector tubes (5) comprising injector means (6) arranged at a top surface (7) of said floating filtering bed (4), said injector tubes (5) also includes tubular guide means (8) extending from said injector means (6) and downwards through said floating filtering bed (4) and pump means (9) for creating a injector flow from said injector means (6) and down through said tubular guide means (8), wherein said tubular guide means (8) comprise one or more inlet openings (10) for allowing said injector flow to draw filtering elements (3) directly into said tubular guide means (8) from said floating filtering bed (4) and wherein said inlet openings (10) are arranged at said injector means (6).

2. A biological purification device (1) according to claim 1, wherein said tubular guide means (8) substantially encloses said injector means (6).

3. A biological purification device (1) according to claim 1 or 2, wherein said tubular guide means (8) is rigidly fixed in relation to said filtering tank (2).

4. A biological purification device (1) according to one or more of the preceding claims, wherein said one or more inlet openings (10) are formed as orifices in a side wall (11) of said tubular guide means (8).

5. A biological purification device (1) according to one or more of the preceding claims, wherein said tubular guide means (8) are formed as a substantially straight pipe.

6. A biological purification device (1) according to one or more of the preceding claims, wherein said filtering elements (3) have a maximum external measurement (MF) of at least 4 mm, preferably at least 6 mm, and most preferred at least 8 mm.

7. A biological purification device (1) according to one or more of the preceding claims, wherein said filtering elements (3) are formed as pipes having internal and/or external lamellas (12).

8. A biological purification device (1) according to one or more of the preceding claims, wherein said one or more inlet openings (10) have a maximum external measurement (MI) of between 10 and 200 mm, preferably between 20 and 140 mm, and most preferred between 30 and 100 mm.

9. A biological purification device (1) according to one or more of the preceding claims, wherein said filtering tank (2) comprises two or more injector tubes (5) and wherein said injector flow in said two or more injector tubes (5) is created by common pump means (9).

10. A method for cleaning individual filtering elements (3) floating in a filtering tank (2) and forming a floating filtering bed (4) of a biological purification device (1) for biological purification of water, said method comprises the steps of:

• creating a downwards directed injector flow through a stationary tubular guide mean (8) extending down through said filtering bed (4),

• sucking filtering elements (3) from said floating filtering bed (4) directly into said tubular guide means (8) through one or more inlet openings (10) arranged in said tubular guide means (8), • transporting said filtering elements (3) down through said tubular guide mean and

• emitting said filtering elements (3) from a bottom end (13) of said tubular guide means (8).

11. A method according to claim 10, wherein said injector flow is formed by impure water being lead to said biological purification device (1) to be biological purified.

12. A method according to claim 10 or 11, wherein said method is a method for cleaning filtering elements (3) of a biological purification device (1) according to any of claims 1-9.

13. Use of a biological purification device (1) according to any of 1-9 for biological purification of water from a fish farm (14).