WO2002085487A1 - Procede et dispositif pour filtrer un liquide - Google Patents

Procede et dispositif pour filtrer un liquide Download PDF

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Publication number
WO2002085487A1
WO2002085487A1 PCT/SE2002/000786 SE0200786W WO02085487A1 WO 2002085487 A1 WO2002085487 A1 WO 2002085487A1 SE 0200786 W SE0200786 W SE 0200786W WO 02085487 A1 WO02085487 A1 WO 02085487A1
Authority
WO
WIPO (PCT)
Prior art keywords
sheet
filtering
layer
filtering particles
particles
Prior art date
Application number
PCT/SE2002/000786
Other languages
English (en)
Inventor
Nils-Ake Persson
Original Assignee
Hydrotech Nils-Ake Persson Aktiebolag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hydrotech Nils-Ake Persson Aktiebolag filed Critical Hydrotech Nils-Ake Persson Aktiebolag
Publication of WO2002085487A1 publication Critical patent/WO2002085487A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D24/00—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof
    • B01D24/02—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration
    • B01D24/10—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration the filtering material being held in a closed container
    • B01D24/12—Downward filtration, the filtering material being supported by pervious surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D24/00—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof
    • B01D24/46—Regenerating the filtering material in the filter
    • B01D24/4631—Counter-current flushing, e.g. by air

Definitions

  • the present invention relates to a device for filtering a liquid, comprising a layer of filtering particles, according to a first and a second aspect of the invention.
  • the invention further relates to a method for filtering a liquid, comprising the steps of conducting, during filtration, the liquid to be filtered in a filtering direction through a layer of filtering particles, and intermittently backwashing the layer of filtering particles by conducting a backwash fluid in a direction of backwashing opposite to the filtering direction according to a first and a second aspect of the invention.
  • the invention also concerns a system for filtering a liquid.
  • a relatively simple and inexpensive type of filter for removing particles from a liquid is the sand filter.
  • a sand filter uses one or more layers of granular mate- rial in the form of sand or the like to remove particles and other impurities.
  • the liquid to be cleaned by filtering is passed through the sand layer and filtered by the particles and other impurities being trapped in the sand layer.
  • For cleaning it is common to wash the sand filter at regular intervals, or when necessary, by conducting a backwash fluid (usually water or air) in a direction of backwashing opposite to the filtering direction.
  • the particles that have been filtered off from the liquid and intercepted by the sand layer are removed from the sand layer by this backwashing or reverse flushing, and the 'sand filter is then ready to be used again.
  • An ordinary sand filter of this type comprises a grate with pebbles or coarse gravel supported thereon. A number of layers of filtering particles of different sizes are provided on top of this base.
  • One drawback of these sand filters is that large quantities of backwash fluid are required during the backwashing process, and since this backwash fluid is not clean but has to be cleaned afterwards the large quantity used considerably reduces the filtration capacity of the sand filter.
  • the large quantity of filtering particles in the sand filter also makes the sand filter expensive to build and to maintain, on the one hand because racks and sur- rounding parts must support heavy weights in the form of thick sand filter layers and, on the other hand, because it is expensive to replace the relatively large quantity of sand since used sand often has to be deposited at a high environmental control charge .
  • a sand filter it is usually the top layer of sand that is first clogged by particles, partly because the top layer of filtering particles comprises the finest particles and partly because the liquid to be filtered is introduced from above. As soon as the top layer of filtering particles has become clogged to a non-acceptable level the sand filter has to be backwashed or the top layer replaced.
  • the full filtration potential of the filter is not being used since the filter has to be backwashed or the filtering particles replaced too frequently.
  • SE 365,945 discloses a conventional sand filter where an attempt has been made to make better use of the various sections of the sand filter than has previously been possible.
  • this sand filter the filtering direc- tion and the direction of backwashing have been inverted so that the liquid to be filtered is introduced into the filter from below and pressed upwardly through the sand filter.
  • the result is that coarse particles are trapped in the layers consisting of large filtering particles and the fine particles are trapped in the layers of the sand filter consisting of small particles. This means that filtration can be carried out for a longer period of time before the filter is clogged.
  • the construction required is expensive, particularly since the entire construction has to be pressurised to ensure that the water to be cleaned is passed upwardly through the sand filter.
  • the construction presents the same drawback as conventional sand filters during backwashing, since considerable quantities of backwash liquid are required to clean all the filter layers. Nor does it offer any solution to the problem of the high costs for replacing the sand in the filter.
  • NO 147,639 is an attempt to solve similar problems by superposing a number of trays or cassettes containing a filter medium.
  • the liquid to be filtered is conducted through the top cassette and is then passed downward through each of the different cassettes.
  • the purpose of using different kinds of filter media in the various cassettes is to remove the large particles in the upper cassette or cassettes and then to remove the small particles in the lower cassettes .
  • This allows the use of a filter medium that is easy to clean in the top cassette, in this case mineral wool, and, in the lower cassettes, a filter medium that provides better cleaning but that does not necessarily have to be as easy to clean.
  • this design is complicated and space-requiring.
  • the design requires the cassettes to be replaced once they have become clogged. Thus, either equipment for cleaning the different cassettes have to be supplemented or the cassettes containing filter media have to be deposited at a considerable cost. Conse- quently, this design does not provide a solution to the problems stated above.
  • An object of the present invention is to provide a solution to the problems stated above.
  • One particular object is to provide a device in which the degree of utilization of the layer of filtering particles is high, i.e. in which only a small quantity of filtering particles is required and in which said particles can be used for an extended period of time before they need replacing.
  • a further object of the invention is to provide a method in which an adequate filtration capacity is achieved while ensuring that the filtering particles can be used for an extended period of time and the backwashing can be kept at a minimum.
  • Another object of the invention is to provide a system for filtering a liquid, which provides a large filtration capacity on a small floor space.
  • the device comprises a first sheet-like element and a second sheet-like element, which are essentially parallel and located a first distance from each other, the layer of filtering particles being located between said two sheetlike elements, which are permeable to liquid and which retain the filtering particles, the layer of filtering particles having a thickness which during filtration is less than 90% of the distance between the sheet-like ele- ments, and the layer of filtering particles having a thickness during filtration of less than 300 mm.
  • the filtration layer is so thin, the height of the device is small and the weight low, which allows several filter devices to be arranged one on top of the other. In this way, a large filtration surface can be obtained using only a small floor space.
  • filtration of liquid takes place in a filtering direction along which the liquid to be filtered is conducted through the first sheet-like element, through the layer of filtering particles and out through the second sheet-like element.
  • This design gives a construc- tion where the first sheet-like element can be used to prevent too large particles from being passed through the layer of filtering particles, which allows the time interval between consecutive backwashings to be extended and makes it possible to prevent an accumulation of large foreign particles in the layer of filtering particles.
  • the layer of filtering particles is adapted to be cleaned by back- washing, during which a fluid is conducted in a direction of backwashing opposite to the filtering direction trough the second sheet-like element, through the layer of filtering particles and out through the first sheet-like element.
  • a construction that can be backwashed in an efficient manner without the loss of filtering particles is obtained.
  • the first sheet-like element effectively retains the filtering particles, but permits the backwash fluid to pass.
  • the layer of filtering particles has a thickness during filtration which is less than 85%, preferably 80%, of the distance between the two sheetlike elements. Owing to these preferred distances there is more space available for the fluidisation of the layer of filtering particles and, thus, in many cases an even more efficient backwashing of the layer of filtering particles will be obtained.
  • the second sheet-like element is adapted to support the layer of filtering particles during fil- tration, which means that the layer of filtering particles will be safely kept in the right position.
  • the first sheet-like element is adapted to retain the filtering particles during backwashing, which ensures that the filtering particles will be retained in the device also in the event of intensive flushing.
  • the first sheet-like element has through holes whose total area amounts to more than 25% of the total area of the sheet- like element, thereby allowing a suitable flow capacity through the plate to be obtained.
  • the presence of the plate ensures adequate distribution of the liquid to be passed through the layer of filtering particles, which in turn means that local, directly penetrating flows through the layer of filtering particles and local clogging of certain portions of the layer of filtering particles can be avoided. Adequate distribution of the liquid to be filtered is important in order to ensure a long-term use of the filtration layer.
  • the second sheet-like element has through holes whose to- tal area amounts to less than 15% of the total area of the shee -like element, the latter area supporting the layer of filtering particles.
  • the filtering particles have a grain size of 0.4-0.8 mm. This size ensures a satisfactory filtration capacity while being relatively easy to handle.
  • the two sheet-like elements are essentially hori- zontal, which allows a very simple construction since the layer of filtering particles naturally will strive to assume a horizontal position.
  • the filtering direction extends downward.
  • the force of gravity is used to achieve a natural flow through the layer of filtering particles, which makes the construction extremely simple.
  • the device comprises at least one brush which extends across the upper side of the first sheet-like element and which is displaceable along the upper side of the first sheet-like element for cleaning the first sheet-like element.
  • any fouling of the first sheet-like element can easily be removed.
  • the device comprises a sheet-like element, the layer of fil- tering particles is supported by said sheet-like element, the sheet-like element has through holes whose total area amounts to less than 15% of the total area of the sheet- like element, the latter area supporting the layer of filtering particles, and the layer of filtering particles has a thickness during filtration of less than 300 mm.
  • a device for filtering a liquid is obtained in which the layer of filtering particles can be made very thin and by means of which an adequate filtration capacity can still be achieved.
  • the sheet-like element having the through holes of said area, adequate distribution of liquid is obtained both during filtration and during backwashing.
  • the inventive method of the type mentioned by way of introduction is characterised in that, during filtration, the liquid to be filtered is passed through a first sheet-like element, the layer of filtering particles and a second sheet-like element, that, during filtration, the second sheet-like element supports the layer of filtering particles, and that, during backwashing, the first sheetlike element retains the filtering particles.
  • a satisfactory filtration is obtained while allowing a relatively thin layer of filtering particles to be used.
  • the two sheet-like elements distribute the flow evenly through the layer of filtering particles both during filtration and during backwashing. Since the first sheet-like element retains the filtering particles during backwashing, no filtering particles have to be added to maintain the desired thickness of the layer.
  • the layer of filtering particles located between the two sheet-like elements fluidises during backwashing. Excellent cleaning of filtering particles is thus obtained.
  • the fluidisation means that the layer of filtering particles is evenly distributed over the second sheet-like element.
  • the layer of filtering particles has a thickness during filtration which is less than 85%, preferably 80%, of a distance between the two sheet-like elements, which are essentially parallel and located a distance from each other. This means that excellent fluidisation of the layer of filtering particles is ob- tained, which in turn results in excellent cleaning of the filtering particles.
  • the second sheet-like element distributes the backwashing fluid by means of through holes provided therein whose total area amounts to less than 15% of the total area of the sheetlike element, the latter area supporting the layer of filtering particles. A satisfactory distribution of the backwash fluid is thus obtained, thereby avoiding the risk of local flows that could have a detrimental effect on the cleaning of the filtering particles and on the redistribution of the layer of filtering particles after backwashing .
  • a method according to a second aspect of the invention which method is characterised in that, during filtration, the liquid to be filtered is passed through the layer of filtering particles and a sheet-like element, that, during filtration, the sheet-like element supports the layer of filtering particles, and that, during backwashing, the sheet-like element distributes the backwashing fluid by means of through holes provided therein whose total area amounts to less than 15% of the total area of the sheet- like element, the latter area supporting the layer of filtering particles.
  • This method affords excellent filtration while maintaining a thin layer of filtering particles.
  • the fact that the sheet-like element distributes the backwash fluid during backwashing prevents the backwash fluid from flowing locally through only certain portions of the layer of filtering particles. An adequate distribution of the backwashing fluid is essential in order to obtain a uniform and efficient cleaning of the filtering particles and to obtain even distribution of filtering particles once the backwashing is terminated.
  • the layer of filtering particles flu- idises on the sheet-like element during backwashing. Satisfactory cleaning of the filtering particles is thus obtained as is even distribution of the filtering particles across the sheet-like element once the backwashing is terminated.
  • Fig. 1 is a basic sketch illustrating the flow during filtration of a liquid.
  • Fig. 2 is a basic sketch illustrating the flow during backwashing.
  • Fig. 3 is a side view of a device according to the invention.
  • Fig. 4 is a front view of the device shown in Fig. 3.
  • Fig. 5 is a top plan view of a sheet-like element.
  • Fig. 6 is a perspective view of a device according to the invention.
  • Fig. 7 is a longitudinal cross-sectional view of a filter system according to the invention. Description of Preferred Embodiments
  • filtration of a liquid is carried out by the liquid being supplied through an inlet 1 and distributed as an even flow across a first sheet-like element 2.
  • the liquid to be filtered is then passed through a layer 3 of filtering particles such as sand or the like. After the layer 3 of filtering particles, the liquid is conducted through a second sheet-like element 4 and out through two outlets 5A, 5B.
  • the liquid to be filtered is intended to be supplied through the inlet 1 at such a rate that, when the flow through the layer 3 of filtering particles is normal, the water surface will be located slightly above the first sheet-like element 2.
  • the flow resistance of the layer 3 will increase causing the water surface to rise.
  • the liquid surface reaches a certain predetermined level, monitored for example by means of a level indicator 13, the supply of liquid to be filtered is cut off.
  • the outlets 5A, 5B are kept open, which means that a large part of the liquid that, during filtration, is located above and in the layer 3 is drained off.
  • the backwashing is initiated (see Fig. 2) .
  • the backwashing fluid or liquid is conducted through the outlets 5A, 5B and upwards through the second sheet-like element 4.
  • the second sheet-like element 4 distributes the backwashing liquid over the whole layer 3 of filtering particles.
  • the flow through the second sheet-like element 4 and the layer 3 of filtering particles is such that the layer 3 fluidises and thus expands extending towards or all the way to the first sheet-like element 2.
  • the backwashing fluid is then conducted through the first sheet-like element 2 and out through the inlet 1.
  • the layer 3 of filtering particles consists of sand with a grain size of 0.4-0.8 mm and has a thickness during filtration of about 12 cm. The distance between the two sheet-like elements is about 16 cm and, during backwashing, the layer 3 will fluidise to about this level .
  • the first sheet-like element comprises a thin metal plate provided with a large number of through holes (see Fig. 5) .
  • the plate has a thickness of about 0.5 mm and the holes are round and have a diameter of about the same size, i.e. about 0.5 mm. However, the size of the holes is slightly smaller than the size of the selected fil- tering particles.
  • the total area of the holes i.e. the free area, amounts to about 25-30% of the total area. Alternatively, it is conceivable to have a free area amounting to about 50%.
  • the second sheet-like element 4 also consists of a thin metal plate provided with a large number of small holes.
  • the plate has a thickness of about 0.5 mm and the holes are round and have a diameter of about the same size, i.e. about 0.5 mm.
  • the second sheet-like element 4 has a free area which amounts to about 5%, in any case less than 10%.
  • Figs 3 and 4 show a device according to an embodiment that uses the basic function shown in Fig. 1 and Fig. 2.
  • the filtering device comprises a tank 6 in which the first sheet-like element 2, the layer 3 of filtering particles, and the second sheet-like element 4 are con- tained.
  • the device further comprises a space 7 which is adapted to receive a liquid and which is located above the first sheet-like element 2, and a second space 8 which is adapted to receive a liquid and which is located below the second sheet-like element 4.
  • the liquid is supplied through the inlet 1 to the quantity of liquid present in the space 7 and falls down through the first sheet-like element 2, the layer 3 of filtering particles and through the second sheet-like element 4 to the liquid present in the space 8. Since there are no sealed portions, it is actually one and the same column of water that extends from the bottom of the space 8 to the liquid surface level in the space 7.
  • the device has a layer 3 of filtering particles with a thickness of 120 mm.
  • the layer 3 has a thickness during fil- tration of less than 300 mm. In most cases, a layer thickness of 100-150 mm may be used.
  • the device will be light and have a small height, which makes it possible to superpose as much as ten sand filters . A large filtration capacity is thus obtained without the filter device being particularly space-requiring.
  • the construction shown is intended for the arrangement of modules and comprises, for this purpose, a frame that encloses the lower space 8, a frame that encloses the layer 3 of filtering particles and a frame that encloses the upper space 7.
  • the outer edges of the sheet- like elements 2, 4 are placed between said frames, and the whole arrangement is then clamped together by means of a number of transverse upper 9 and lower 10 sectional elements, which are then pulled together by means of a number of tie bars 11.
  • tie bars 11 By designing the device in this manner, it is conceivable to superimpose a large number of such units and to pull them together by means of tie bars.
  • the first 2 and the second 4 sheet-like elements are provided with gaskets which extend along the circumference thereof and which- are adapted to be clamped between the above frames.
  • each of the filtering units has its own inlet 1 and its own outlets 5A, 5B, all the inlets 1 being interconnected and all the outlets 5A, 5B being interconnected.
  • the filtering units are thus separated from one another. Accordingly, in this system, the filtering units are connected in parallel, as opposed to the units in NO- 147,639, mentioned above, which are connected in series.
  • a constan -level tank (not shown) is connected to respectively the interconnected inlet conduits and the interconnected outlet conduits.
  • a constan -level tank (not shown) is connected to respectively the interconnected inlet conduits and the interconnected outlet conduits.
  • the brushes 14 have bristles made of a plastic material and are operated by an actuator 15 in the form of, for example, a pneumatic piston, a motor- operated rack and pinion drive or a manual drive along the upper side of the first sheet-like element 2.
  • the role of the brushes 14 is to brush off any deposits, for example in the form of biological fouling, from the upper side of the sheet-like element 2 and also to remove any deposits in the through holes of the sheet-like element 2. If the sheet 2 is made really thin, the bristles of the brush 14 will reach far enough down the holes to remove most of the fouling that may occur.
  • the underside of the sheet 2 is cleaned by the filtering particles as the filtering layer 3 fluidises during backwashing.
  • the filtering particles may, to a certain extent, penetrate the holes and in this way scrape off any fouling.
  • brushes to clean the sheet 2
  • the brushes 14 are not in operation, they are removed from the sheet 2 so that their bristles are not unnecessarily deformed. So far there is nothing that suggests that it is necessary to use brushes on the second sheet-like element 4 or on the single sheet-like element 4 in the device according to the second aspect of the invention. Should any fouling of the sheet-like element 4 occur, however, it is of course possible to provide brushes also on the underside of the sheet-like element 4, as shown in the example described.
  • the brushes allow environmentally sound cleaning of the sheet-like element 2, since no chemicals are needed to remove the deposits, if any.
  • the filtering device is provided with inspection covers 12 made, for example, of plexiglass. By using these inspection covers 12, it is possible to verify, for instance, that the fluidisation process during backwashing is correct .
  • the sheet-like elements may, for example, be inclined and the sand may be continuously exchanged by more or less falling down between the sheet-like elements.
  • the sheet-like elements may comprise continuous belts of filter cloth which are stretched between two rollers and which rotate either in the direction of motion of the filtering particles or in the opposite direction.
  • any optional type of material may be used to obtain the desired distribution effect and retaining effect of the sheet-like elements.
  • a micro filter cloth mounted on a more rigid frame may be used, for example .
  • the holes may be of other shapes, such as quadratic, oblong or any other shape, as long as it is impossible for the filtering particles to pass through the opening .

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Filtering Materials (AREA)
  • Filtration Of Liquid (AREA)

Abstract

L'invention concerne un procédé et un dispositif permettant de filtrer un liquide (A), comprenant une couche (3) de particules filtrantes, un premier élément (2) sous forme de feuille (2) et un second élément (4) sous forme de feuille, qui sont essentiellement parallèles et situés à une première distance (C) l'un l'autre. Cette couche (3) de particules filtrantes se trouve entre les deux éléments sous forme de feuilles (2, 4), qui sont perméables au liquide et retiennent les particules filtrantes. Pendant la filtration, l'épaisseur (D1) de la couche est inférieure à 90 % de la distance (C) entre les éléments sous forme de feuilles. Pendant la filtration, l'épaisseur (D1) de la couche (3) de particules filtrantes est inférieure à moins de 300 mm.
PCT/SE2002/000786 2001-04-23 2002-04-23 Procede et dispositif pour filtrer un liquide WO2002085487A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0101407-5 2001-04-23
SE0101407A SE0101407D0 (sv) 2001-04-23 2001-04-23 Anordning samt förfarande för filtrering av en vätska

Publications (1)

Publication Number Publication Date
WO2002085487A1 true WO2002085487A1 (fr) 2002-10-31

Family

ID=20283835

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE2002/000786 WO2002085487A1 (fr) 2001-04-23 2002-04-23 Procede et dispositif pour filtrer un liquide

Country Status (2)

Country Link
SE (1) SE0101407D0 (fr)
WO (1) WO2002085487A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8118175B2 (en) 2007-07-18 2012-02-21 Siemens Industry, Inc. Venting device for a disc filter
US8801929B2 (en) 2007-07-18 2014-08-12 Evoqua Water Technologies Llc Trash tolerant filter support for a disc filter
US9028692B2 (en) 2006-08-14 2015-05-12 Evoqua Water Technologies Llc High flow disc filter
US10857491B2 (en) 2014-06-05 2020-12-08 Evoqua Water Technologies Llc Filtering panel and method of making the same
US10888807B2 (en) 2016-08-12 2021-01-12 Evoqua Water Technologies Llc Disc filter pre-screen dual media disc filter

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE24543C1 (fr) * 1908-04-18
SE124147C1 (fr) * 1949-01-01
NO147639B (no) * 1980-08-12 1983-02-07 Fjeldhammer Brug As Anordning ved filterkum.
FR2576521A1 (fr) * 1985-01-30 1986-08-01 Projets Etu Const Engineering Dispositif pour filtrer l'eau d'une piscine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE24543C1 (fr) * 1908-04-18
SE124147C1 (fr) * 1949-01-01
NO147639B (no) * 1980-08-12 1983-02-07 Fjeldhammer Brug As Anordning ved filterkum.
FR2576521A1 (fr) * 1985-01-30 1986-08-01 Projets Etu Const Engineering Dispositif pour filtrer l'eau d'une piscine

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
KUFFERATH DR. A.: "Filtration und filter", CHEMISCH-TECHNISCHER VERLAG DR. G. BODENBENDER, 1953, BERLIN-LICHTERFELDE, pages 232 - 235 *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9028692B2 (en) 2006-08-14 2015-05-12 Evoqua Water Technologies Llc High flow disc filter
US10207210B2 (en) 2006-08-14 2019-02-19 Evoqua Water Technologies Llc High flow disc filter
US8118175B2 (en) 2007-07-18 2012-02-21 Siemens Industry, Inc. Venting device for a disc filter
US8801929B2 (en) 2007-07-18 2014-08-12 Evoqua Water Technologies Llc Trash tolerant filter support for a disc filter
US8808542B2 (en) 2007-07-18 2014-08-19 Evoqua Water Technologies Llc Disc filter
US9023208B2 (en) 2007-07-18 2015-05-05 Evoqua Water Technologies Llc Disc filter
US9339745B2 (en) 2007-07-18 2016-05-17 Evoqua Water Technologies Llc Trash tolerant filter support for a disc filter
US10857491B2 (en) 2014-06-05 2020-12-08 Evoqua Water Technologies Llc Filtering panel and method of making the same
US11660552B2 (en) 2014-06-05 2023-05-30 Evoqua Water Technologies Llc Filtering panel and method of making the same
US10888807B2 (en) 2016-08-12 2021-01-12 Evoqua Water Technologies Llc Disc filter pre-screen dual media disc filter

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