WO1996038387A1 - Method for biological cleaning of water, for the substrate culture of plants, and a filter and a filter unit therefor - Google Patents

Method for biological cleaning of water, for the substrate culture of plants, and a filter and a filter unit therefor Download PDF

Info

Publication number
WO1996038387A1
WO1996038387A1 PCT/NL1996/000214 NL9600214W WO9638387A1 WO 1996038387 A1 WO1996038387 A1 WO 1996038387A1 NL 9600214 W NL9600214 W NL 9600214W WO 9638387 A1 WO9638387 A1 WO 9638387A1
Authority
WO
WIPO (PCT)
Prior art keywords
filter
water
filter unit
filter material
mineral wool
Prior art date
Application number
PCT/NL1996/000214
Other languages
French (fr)
Inventor
Joseph Maria Elise Beaujean
Jacob Frank De Groot
Original Assignee
Rockwool/Grodan B.V.
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 Rockwool/Grodan B.V. filed Critical Rockwool/Grodan B.V.
Priority to AU58463/96A priority Critical patent/AU5846396A/en
Publication of WO1996038387A1 publication Critical patent/WO1996038387A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/10—Packings; Fillings; Grids
    • C02F3/103—Textile-type packing
    • 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
    • B01D24/105—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 downward filtration without specifications about the filter material supporting means
    • 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
    • B01D24/38—Feed or discharge devices
    • B01D24/42—Feed or discharge devices for discharging filtrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/01—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements
    • B01D29/05—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements supported
    • B01D29/07—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements supported with corrugated, folded or wound filtering sheets
    • B01D29/073—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements supported with corrugated, folded or wound filtering sheets with wound filtering sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/88—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor having feed or discharge devices
    • B01D29/92—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor having feed or discharge devices for discharging filtrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
    • B01D35/30—Filter housing constructions
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

  • the present invention relates to a method for bio ⁇ logical cleaning of water, to a method for the substrate culture of plants, and to a filter and a filter unit therefor.
  • organ ⁇ isms such as bacteria and other single-cell organisms which not only biologically convert organic substances present in the dirty water but also separate out, and even deactivate/destroy micro-organisms present in the dirty water, in particular fungi.
  • the systems used up to the present time for sand bed filtration comprise a first collection tank for dirty water, a tank connected thereto and provided with a sand bed, and finally a tank for clean water.
  • silos are required with a diameter of 3-6 metres.
  • the sand bed used is relatively high because the grain size in this sand bed changes over the height and because, as a result of the sand filter bed becoming clogged, the top layer must be continually removed, while the filter also has its greatest biological activity in this top layer.
  • rockwool has a filtering action on gases and liquids.
  • Rockwool acts partially as a sieve and the material for separation partially adheres to the surface of the rockwool fibres.
  • a biological environment can thus result with its own affinity for material for separation.
  • An important problem in making filters based on rockwool as filter material is to obtain sufficient homogeneity. This problem arises particularly in larger filters because leakage paths can therein occur round the used rockwool material. Such leakage paths occur when the rockwool is used as granulate and as coherent products.
  • the drawback occurs here relative to sand filters because the sand used in sand filters is pressed under the influence of its own specific weight and will thus tend to close off possible leakage paths.
  • the present invention has for its object to provide a different filter system for biological cleaning of water, wherein a notably higher cleaning efficiency is obtained which, under well-chosen conditions, even achieves an efficiency of more than 99.5% to even 100%.
  • the present invention is based on the insight that if mineral wool is chosen as filter material a markedly better biologically cleaning system is obtained because compared to sand the pore volume is at least 4 times greater and the suction forces acting during the filtra- tion are 3-4 times smaller, which means that when mineral wool is used as filter material such a biofilter has an action that is 4-16 times better, i.e. can be constructed 4-16 times more compactly in the same filtering condi ⁇ tions, wherein the problem of the dangers of the presence of leakage paths is resolved. Compared to sand mineral wool moreover has the advantage that it is a markedly lighter material with a larger internal surface, thus resulting in less danger of blockage and a lower pressure drop.
  • Such a biological mineral wool filtration system according to the invention generally operates at tempera ⁇ tures from 10°C to about a maximum of 29°C, while temper ⁇ atures far below zero (-10°C) can occur temporarily.
  • the filter system according to the invention could possibly operate such that in the mineral wool filter material a microflora, i.e. micro-organisms, in particu ⁇ lar bacteria, will form which not only remove organic materials but which also deactivate fungi.
  • a microflora i.e. micro-organisms, in particu ⁇ lar bacteria
  • a layer thickness of about 50 centimetres will generally be sufficient, while in the case of sand use must be made of a filter material thickness of 1-2 metres. Because operation takes place with a relatively small layer thickness the problem of leakage paths is particularly great and frequently even fatal.
  • the biological material for cleaning can be any material in which organic substances, and in particular harmful micro-organisms, occur, such as water which is supplied to biological treatment installations, but particularly water that has been in contact with plants and micro-organisms, such as water from aquariums.
  • the method according to the invention is particularly appli- cable in recirculation systems for the horticultural sector wherein water/nutrient water is supplied to the plants, collected again and recirculated in order to optimize the environmental impact and the cost of the system.
  • This filter material may consist of a rolled-up strip of mineral wool but the use is recommend ⁇ ed of filter material packages which consist of a longi ⁇ tudinal envelope of watertight material having therein either the rolled-up strip of mineral wool or the mineral wool granulate.
  • a filter material package can consist of a strip of mineral wool which is rolled up, wherein the rolled package practically covers sub- stantially the whole surface of the filter unit through which there is flow.
  • the filter material package instead of one filter material package it is possible to use a large number of filter material packages which cover substantially the whole surface of the filter unit through which there is flow.
  • the sealing material is preferably arranged between the packages and is in particular a sealing material which swells under the influence of water and contains for this purpose a water-swelling material preferably in combination with a carrier material.
  • a sealing material which swells under the influence of water and contains for this purpose a water-swelling material preferably in combination with a carrier material.
  • Trisoplast ® obtainable from General Industrial Development Benelux B.V. , Velddriel
  • the filter unit comprises a filter tank provided with a layer of filter material and having a dirty water inlet and a clean water outlet separated therefrom by the layer of filter materi ⁇ al, and an inlet for fresh water separated from the dirty water inlet by a flexible membrane.
  • a filter unit has the advantage that it can operate at a practically constant hydrostatic pressure because this pressure is determined by the height of the dirty water layer present in the filter unit which is separated by means of a flexible membrane from the cleaned water likewise present therein. A reduced supply of dirty water is then combined with more clean water being retained in the filter unit and vice versa.
  • the flexible membrane is preferably provided with non-return valves operating on the dirty water side.
  • the present invention relates to a method for the substrate culture of plants, wherein water op- tionally containing nutrients is recirculated and the recirculated water is purified with a filter unit accord ⁇ ing to the invention.
  • mineral wool is used as filter material.
  • the mineral wool can consist of rock- wool, glass wool, slag wool, ceramic wool and mixtures thereof. All known types of mineral wool can be applied in the fibre lengths and fibre diameter distributions known in the prior art .
  • a mineral wool is used in the form of a granulate having dimensions of 1 millimetre to 5 centimetres, in general about 6 milli ⁇ metres.
  • the mineral wool in the form of a package which can take the form of a shape-retaining mat or the form of a strip of mineral wool which is rolled up in the manner of a spiral or a plurality of mineral wool strips rolled up in the manner of a spiral which may optionally be provided on the outer side with a foil, whereby the flow through such rolled-up filter material packages takes place axially.
  • the filter material according to the invention it is possible to dispense with the origi ⁇ nal known filter systems which are also provided with a dirty water tank and a clean water tank. By making use of a membrane these dirty water and clean water tanks can even be integrated into the tank provided with the layer of filter material.
  • fig. 1, 2 and 5 each show a filter unit according to the invention
  • fig. 3 and 4 each show a different type of filter for use in a filter unit as shown in fig. 1, 2 and 5.
  • Fig. 1 shows a filter system 1 according to the invention.
  • This filter system 1 comprises a dirty water tank 3 with a dirty water inlet 5 provided with a pump 4.
  • the dirty water tank 3 is connected to a filter unit 8 according to the invention via a conduit 7 provided with a pump 6, wherein the dirty water inlet conduit 7 is separated from a filtered clean water outlet 9 by a layer of filter material 10 according to the invention.
  • Outlet 9 is provided with a pump 11 and connects onto a clean water tank 12 which drains the clean water out of the filter system 1 via the conduit 14 provided with a pump 13.
  • the filter system 1 can be used for multiple applica ⁇ tions but is particularly characterized by the use of the layer of filter material 10 consisting of mineral wool, in this example rolls 15 of mineral wool, which rolls are mutually separated by sealing material 16 which extends over the whole height of rolls 15 because these are not provided with a watertight longitudinal envelope.
  • Such a system can be used for cleaning water.
  • the filter unit 8 has a diameter of about 3 metres when the area amounts to about 1 hectare.
  • Fig. 2 shows a filter system 2 according to the invention, wherein the dirty water tank and the clean water tank 12 are now integrated into the filter unit 18 according to the invention.
  • Filter unit 18 is provided with a dirty water inlet 19 having upstream a pre-filter 20 for filtering out floating parts and larger particles, in addition to a unit 21 for supplying air/oxygen from the reservoir 22 and heat via the heat exchanger 23.
  • the pre-filter 20 can be switched on and off via a three-way tap 24.
  • Fig. 3 shows in more detail the filter material packages 26 which are enclosed in a plastic foil 18 wherein the interspaces are filled with sealing material 29.
  • These filter material packages 26 are manufactured for instance from a strip of mineral wool with a density of 25-50 kg/m 3 and have a height of about 50 centimetres and a diameter of 52 centimetres.
  • Fig. 4 shows a layer of filter material 37 which consists of a rolled-up strip 38 of mineral wool.
  • FIG. 5 shows a filter unit 40 which comprises a filter tank 41 with a dirty water inlet 42 which is separated from a clean water outlet 43 by a layer of filter material consisting of filter packages 44.
  • the packages are provided with a watertight longitudinal envelope 45 so that they are open to water at both end surfaces 46 and 47. Leakage paths are not possible on account of the sealing material as shown in fig. 2 ar ⁇ ranged between the packages and the tank.
  • the clean water outlet 43 is provided with a pump 48 which carries clean water 50 via a recirculation conduit 49 onto the flexible membrane 51 provided with non-return valves 52. Via a flexible hose 53 water can be drained to the substrate culture.
  • aerating means which comprise an air pump 54 and an air pipe 55 provided with holes and a turbulent flow is thus generated as according to the ovally round arrows 56 in the layer of water located between the filter material and the flexible membrane. Due to this turbulence with air oxygen is added to the water, which enhances the biological environment inside the filter.

Abstract

The invention relates to a method for biological cleaning of water, wherein the water is guided through a filter which comprises mineral wool as filter material, wherein the water has preferably been in contact with plants and/or organisms, to a filter for biological cleaning of water comprising a filter material of mineral wool, to a filter unit comprising a filter tank provided with a layer of filter material and having a dirty water inlet and a clean water outlet separated therefrom by the layer of filter material, and an inlet for fresh water which is separated from the dirty water inlet by a flexible membrane, and to a method for the substrate culture of plants, wherein water optionally containing nutrients is recirculated and the recirculated water is purified with such a filter unit.

Description

METHOD FOR BIOLOGICAL CLEANING OF WATER, FOR THE
SUBSTRATE CULTURE OF PLANTS, AND A FILTER
AND A FILTER UNIT THEREFOR
The present invention relates to a method for bio¬ logical cleaning of water, to a method for the substrate culture of plants, and to a filter and a filter unit therefor. In the biological cleaning of water it is important that the dirty water is guided over a layer of filter material, the top layer of which is provided with organ¬ isms such as bacteria and other single-cell organisms which not only biologically convert organic substances present in the dirty water but also separate out, and even deactivate/destroy micro-organisms present in the dirty water, in particular fungi.
Particularly in the market gardening sector use is made during the recirculation of water, in particular nutrient water, of sand bed filters which are however not wholly satisfactory in practice because with such a slow sand filtration the purification efficiency is not suffi¬ ciently high (that is, about 100%) . This means that a single diseased plant can infect an entire plant glass- house with the diseasing agent via the recirculation water since the germs are not all separated out by the filter.
Recourse is therefore often made to other cleaning techniques such as ultrafiltration, UV cleaning and pasteurization of the recirculated water.
The systems used up to the present time for sand bed filtration comprise a first collection tank for dirty water, a tank connected thereto and provided with a sand bed, and finally a tank for clean water. Depending on the number of hectares cultivated, silos are required with a diameter of 3-6 metres.
The sand bed used is relatively high because the grain size in this sand bed changes over the height and because, as a result of the sand filter bed becoming clogged, the top layer must be continually removed, while the filter also has its greatest biological activity in this top layer.
It is further known that rockwool has a filtering action on gases and liquids. Rockwool acts partially as a sieve and the material for separation partially adheres to the surface of the rockwool fibres. A biological environment can thus result with its own affinity for material for separation. An important problem in making filters based on rockwool as filter material is to obtain sufficient homogeneity. This problem arises particularly in larger filters because leakage paths can therein occur round the used rockwool material. Such leakage paths occur when the rockwool is used as granulate and as coherent products. The drawback occurs here relative to sand filters because the sand used in sand filters is pressed under the influence of its own specific weight and will thus tend to close off possible leakage paths. An additional danger of the use of the rockwool as filter material is the relatively small water-retaining capacity and capillary action of the rockwool. If there is insufficient water in the filter material there is the danger of drying and a deterioration or even disappear¬ ance of the biological environment prevailing therein. The present invention has for its object to provide a different filter system for biological cleaning of water, wherein a notably higher cleaning efficiency is obtained which, under well-chosen conditions, even achieves an efficiency of more than 99.5% to even 100%. The present invention is based on the insight that if mineral wool is chosen as filter material a markedly better biologically cleaning system is obtained because compared to sand the pore volume is at least 4 times greater and the suction forces acting during the filtra- tion are 3-4 times smaller, which means that when mineral wool is used as filter material such a biofilter has an action that is 4-16 times better, i.e. can be constructed 4-16 times more compactly in the same filtering condi¬ tions, wherein the problem of the dangers of the presence of leakage paths is resolved. Compared to sand mineral wool moreover has the advantage that it is a markedly lighter material with a larger internal surface, thus resulting in less danger of blockage and a lower pressure drop. Such a biological mineral wool filtration system according to the invention generally operates at tempera¬ tures from 10°C to about a maximum of 29°C, while temper¬ atures far below zero (-10°C) can occur temporarily.
The filter system according to the invention could possibly operate such that in the mineral wool filter material a microflora, i.e. micro-organisms, in particu¬ lar bacteria, will form which not only remove organic materials but which also deactivate fungi. In this re¬ spect it is relatively important that an optimum and constant temperature as well as an optimum oxygen concen¬ tration prevail in the filter material. A layer thickness of about 50 centimetres will generally be sufficient, while in the case of sand use must be made of a filter material thickness of 1-2 metres. Because operation takes place with a relatively small layer thickness the problem of leakage paths is particularly great and frequently even fatal.
The biological material for cleaning can be any material in which organic substances, and in particular harmful micro-organisms, occur, such as water which is supplied to biological treatment installations, but particularly water that has been in contact with plants and micro-organisms, such as water from aquariums. The method according to the invention is particularly appli- cable in recirculation systems for the horticultural sector wherein water/nutrient water is supplied to the plants, collected again and recirculated in order to optimize the environmental impact and the cost of the system. Another aspect of the invention relates to the use of a filter unit for biological cleaning of water, which filter unit comprises a filter tank with a dirty water inlet and a clean water outlet separated therefrom by a layer of filter material, wherein the filter material comprises mineral wool in the form of a rolled-up strip of mineral wool. This filter material may consist of a rolled-up strip of mineral wool but the use is recommend¬ ed of filter material packages which consist of a longi¬ tudinal envelope of watertight material having therein either the rolled-up strip of mineral wool or the mineral wool granulate. The use of the watertight envelope has the advantage that leakage paths can occur less frequent¬ ly as a result of water flowing sideways out of the package but also that the sealing between the packages on the one hand and the filter tank and/or the other packag¬ es on the other only need take place over a smaller part of the height of the package. A filter material package can consist of a strip of mineral wool which is rolled up, wherein the rolled package practically covers sub- stantially the whole surface of the filter unit through which there is flow. However, instead of one filter material package it is possible to use a large number of filter material packages which cover substantially the whole surface of the filter unit through which there is flow.
The sealing material is preferably arranged between the packages and is in particular a sealing material which swells under the influence of water and contains for this purpose a water-swelling material preferably in combination with a carrier material. According to the invention use can be made of the material Trisoplast® (obtainable from General Industrial Development Benelux B.V. , Velddriel) .
According to a preferred embodiment the filter unit comprises a filter tank provided with a layer of filter material and having a dirty water inlet and a clean water outlet separated therefrom by the layer of filter materi¬ al, and an inlet for fresh water separated from the dirty water inlet by a flexible membrane. Such a filter unit has the advantage that it can operate at a practically constant hydrostatic pressure because this pressure is determined by the height of the dirty water layer present in the filter unit which is separated by means of a flexible membrane from the cleaned water likewise present therein. A reduced supply of dirty water is then combined with more clean water being retained in the filter unit and vice versa.
The flexible membrane is preferably provided with non-return valves operating on the dirty water side. Thus achieved is that when the supply of dirty water stops for a longer period, cleaned water can pass through the flexible material via the non-return valves back to above the layer of filter material, whereby is achieved that the layer of filter material does not dry out or come under too great a pressure. It will be apparent that the filters according to the invention can also be used in the filter unit.
Finally, the present invention relates to a method for the substrate culture of plants, wherein water op- tionally containing nutrients is recirculated and the recirculated water is purified with a filter unit accord¬ ing to the invention.
According to the invention mineral wool is used as filter material. The mineral wool can consist of rock- wool, glass wool, slag wool, ceramic wool and mixtures thereof. All known types of mineral wool can be applied in the fibre lengths and fibre diameter distributions known in the prior art . In preference a mineral wool is used in the form of a granulate having dimensions of 1 millimetre to 5 centimetres, in general about 6 milli¬ metres. Instead of fibres or as granulate it is also possible however to use the mineral wool in the form of a package which can take the form of a shape-retaining mat or the form of a strip of mineral wool which is rolled up in the manner of a spiral or a plurality of mineral wool strips rolled up in the manner of a spiral which may optionally be provided on the outer side with a foil, whereby the flow through such rolled-up filter material packages takes place axially. By making use of the filter material according to the invention it is possible to dispense with the origi¬ nal known filter systems which are also provided with a dirty water tank and a clean water tank. By making use of a membrane these dirty water and clean water tanks can even be integrated into the tank provided with the layer of filter material.
Mentioned and other features of the method, the filter and the filter unit according to the invention will be further elucidated hereinbelow with reference to a number of embodiments which are only given by way of example without the invention being deemed as limited thereto.
In the drawing: fig. 1, 2 and 5 each show a filter unit according to the invention; and fig. 3 and 4 each show a different type of filter for use in a filter unit as shown in fig. 1, 2 and 5.
Fig. 1 shows a filter system 1 according to the invention. This filter system 1 comprises a dirty water tank 3 with a dirty water inlet 5 provided with a pump 4. The dirty water tank 3 is connected to a filter unit 8 according to the invention via a conduit 7 provided with a pump 6, wherein the dirty water inlet conduit 7 is separated from a filtered clean water outlet 9 by a layer of filter material 10 according to the invention. Outlet 9 is provided with a pump 11 and connects onto a clean water tank 12 which drains the clean water out of the filter system 1 via the conduit 14 provided with a pump 13. The filter system 1 can be used for multiple applica¬ tions but is particularly characterized by the use of the layer of filter material 10 consisting of mineral wool, in this example rolls 15 of mineral wool, which rolls are mutually separated by sealing material 16 which extends over the whole height of rolls 15 because these are not provided with a watertight longitudinal envelope.
Such a system can be used for cleaning water. In the case of use in horticulture the filter unit 8 has a diameter of about 3 metres when the area amounts to about 1 hectare.
Fig. 2 shows a filter system 2 according to the invention, wherein the dirty water tank and the clean water tank 12 are now integrated into the filter unit 18 according to the invention. Filter unit 18 is provided with a dirty water inlet 19 having upstream a pre-filter 20 for filtering out floating parts and larger particles, in addition to a unit 21 for supplying air/oxygen from the reservoir 22 and heat via the heat exchanger 23. The pre-filter 20 can be switched on and off via a three-way tap 24.
In the filter unit 18 the layer of filter material
25 consists of filter material packages 26. Each package
26 consists of a rolled-up strip 27 of mineral wool and is enclosed in a plastic foil 28. Spaces between the filter material packages 26 are filled with sealing material 29 which consists in this case of a combination of clay mineral and polymer as available in the form of Trisoplast®. The polymer, for example polyacrylamide, swells through contact with water to 10 times its original volume. An optimum sealing is thus created for the layer of filter material 25 between the dirty water inlet 19 and the clean water outlet 30. This outlet 30 carries the clean water via a pump 31 back into the filter unit 18, wherein dirty water 31 and clean water 32 are however mutually separated by a flexible membrane 33 manufactured for instance from EPDM rubber. Membrane 33 has a form such that when substantially no dirty water is being added the membrane can rest on the layer of filter material 25, while when all the clean water 32 is drained the membrane can lie practically on the upper edge of filter unit 18.
Fig. 3 shows in more detail the filter material packages 26 which are enclosed in a plastic foil 18 wherein the interspaces are filled with sealing material 29. These filter material packages 26 are manufactured for instance from a strip of mineral wool with a density of 25-50 kg/m3 and have a height of about 50 centimetres and a diameter of 52 centimetres.
Fig. 4 shows a layer of filter material 37 which consists of a rolled-up strip 38 of mineral wool.
Although not shown in fig. 2, air/oxygen can not only be added to the dirty water but also directly before or after the layer of filter material. The activity of the filter can be determined by measuring the oxygen content in the clean water. Fig. 5 shows a filter unit 40 which comprises a filter tank 41 with a dirty water inlet 42 which is separated from a clean water outlet 43 by a layer of filter material consisting of filter packages 44. The packages are provided with a watertight longitudinal envelope 45 so that they are open to water at both end surfaces 46 and 47. Leakage paths are not possible on account of the sealing material as shown in fig. 2 ar¬ ranged between the packages and the tank. The clean water outlet 43 is provided with a pump 48 which carries clean water 50 via a recirculation conduit 49 onto the flexible membrane 51 provided with non-return valves 52. Via a flexible hose 53 water can be drained to the substrate culture. Arranged between the membrane and the layer of filter material are aerating means which comprise an air pump 54 and an air pipe 55 provided with holes and a turbulent flow is thus generated as according to the ovally round arrows 56 in the layer of water located between the filter material and the flexible membrane. Due to this turbulence with air oxygen is added to the water, which enhances the biological environment inside the filter. In addition, floating plant parts (plankton remnants, algae and the like) are kept circulating so that aerobic bacteria and fungi which are present in this water layer can mineralize such floating parts and there¬ fore prevent precipitation occurring on the end surfaces of the filter packages, whereby the filter package could become clogged. It has been found that by making use of the filter units according to the invention all manner of germs can be removed from drain water from the substrate culture of plants which grow not only on mineral wool but also on all kinds of other substrates such as peat and plastic substrates as well as mixtures thereof. It has been found possible to remove phytophthora spores, phytium for more than 98% and even for more than 99.5% to more than 99.9% and therefore about 100%. If complete certainty must be obtained it is possible to still subject the clean water leaving the filter unit 8 or 18 according to the inven¬ tion to a disinfection, for instance an UV-disinfection.
*****

Claims

1. Filter unit comprising a filter tank with a dirty water inlet and a clean water outlet separated therefrom by a layer of filter material, wherein the filter materi¬ al comprises mineral wool in the form of a rolled-up strip of mineral wool .
2. Filter unit as claimed in claim 1, wherein the filter material comprises at least one filter material package of a rolled-up strip of mineral wool which is provided with a longitudinal envelope of watertight material such as a plastic foil.
3. Filter unit as claimed in claim 1, wherein the filter material comprises at least one filter material package which comprises mineral wool granulate arranged in a longitudinal envelope.
4. Filter unit as claimed in claims 1-3, wherein space between the filter tank and the filter material is sealed with a material swelling under the influence of water.
5. Filter unit as claimed in claim 4, wherein a plurality of filter material packages forms the layer of filter material and intermediate space between the filter material packages is sealed with a material swelling under the influence of water.
6. Filter unit as claimed in claims 1-5, wherein the filter tank is provided with an inlet for fresh water which is separated from the dirty water inlet by means of a flexible membrane.
7. Filter unit as claimed in claim 6, wherein the flexible membrane is provided with non-return valves operating on the dirty water side.
8. Filter unit as claimed in claims 1-7, wherein aerating means are arranged above the layer of filter material .
9. Filter unit as claimed in claim 8, wherein the aerating means are arranged between the layer of filter material and the flexible membrane.
10. Filter unit as claimed in claim 4 or 5, wherein the sealing material comprises a carrier material and a swelling agent.
11. Method for biological cleaning of water, wherein water is guided through a filter comprising a filter unit as claimed in claims 1-10.
12. Method for biological cleaning of water, wherein the water has been in contact with plants and organisms.
13. Method for biological cleaning of water, wherein the water comes from a recirculation system for the horticultural sector.
14. Method for the substrate culture of plants, wherein water optionally containing nutrients is recircu¬ lated and the recirculated water is purified with a filter unit as claimed in claims 1-10.
*****
PCT/NL1996/000214 1995-05-31 1996-05-31 Method for biological cleaning of water, for the substrate culture of plants, and a filter and a filter unit therefor WO1996038387A1 (en)

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NL1000463A NL1000463C2 (en) 1995-05-31 1995-05-31 Method for the biological cleaning of water, for the substrate cultivation of plants, and a filter and a filter unit therefor.

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EP0852222A1 (en) * 1997-01-06 1998-07-08 Cultilene BV Processes and devices for disinfecting and recycling an aqueous effluent
WO2003064005A2 (en) * 2002-01-29 2003-08-07 Walter Hauer Filter material
WO2005124236A3 (en) * 2004-06-18 2006-04-27 Ultra Violet Star Holding B V Method and apparatus for clearing water from micro-organisms, and water supply system and shower unit provided with such apparatus
DE102012011816A1 (en) 2011-06-28 2013-01-03 Roland Graf Filters for aquariums, fish ponds, swimming pools, swimming ponds or the like
AT516276A4 (en) * 2015-03-19 2016-04-15 Egon Gruber filtering device
WO2016167831A1 (en) * 2015-04-16 2016-10-20 Dow Global Technologies Llc Filtration assembly including spiral wound bioreactors and membrane modules positioned in separate pressure vessels
WO2016167832A1 (en) * 2015-04-16 2016-10-20 Dow Global Technologies Llc Filtration assembly including spiral wound bioreactors and hyperfiltration membrane modules
US9725344B1 (en) 2014-09-24 2017-08-08 Dow Global Technologies Llc Spiral wound filtration assembly including integral bioreactor
WO2017165091A1 (en) 2016-03-23 2017-09-28 Dow Global Technologies Llc Bioreactor assembly
JP2018143902A (en) * 2017-03-01 2018-09-20 鹿島建設株式会社 Microorganism carrier for biological treatment and fixed bed production method
WO2020174082A1 (en) 2019-02-28 2020-09-03 Rockwool International A/S Method of filtering slurry

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FR2758135A1 (en) * 1997-01-06 1998-07-10 Saint Gobain Isover METHODS AND DEVICES FOR THE DISINFECTION AND RECYCLING OF AQUEOUS EFFLUENT
EP0852222A1 (en) * 1997-01-06 1998-07-08 Cultilene BV Processes and devices for disinfecting and recycling an aqueous effluent
WO2003064005A2 (en) * 2002-01-29 2003-08-07 Walter Hauer Filter material
WO2003064005A3 (en) * 2002-01-29 2003-12-18 Walter Hauer Filter material
WO2005124236A3 (en) * 2004-06-18 2006-04-27 Ultra Violet Star Holding B V Method and apparatus for clearing water from micro-organisms, and water supply system and shower unit provided with such apparatus
EP2282132A3 (en) * 2004-06-18 2013-01-02 Ultra Violet Star Holding B.V. Vase comprising means for clearing water from micro organism, method for clearing water from micro organism in a vase.
DE102012011816A1 (en) 2011-06-28 2013-01-03 Roland Graf Filters for aquariums, fish ponds, swimming pools, swimming ponds or the like
US10358366B2 (en) 2014-09-24 2019-07-23 Dow Global Technologies Llc Spiral wound filtration assembly including integral bioreactor
US9725344B1 (en) 2014-09-24 2017-08-08 Dow Global Technologies Llc Spiral wound filtration assembly including integral bioreactor
AT516276A4 (en) * 2015-03-19 2016-04-15 Egon Gruber filtering device
AT516276B1 (en) * 2015-03-19 2016-04-15 Egon Gruber filtering device
US11945734B2 (en) 2015-03-19 2024-04-02 Gruber Egon Filter device
WO2016167832A1 (en) * 2015-04-16 2016-10-20 Dow Global Technologies Llc Filtration assembly including spiral wound bioreactors and hyperfiltration membrane modules
CN107530631A (en) * 2015-04-16 2018-01-02 陶氏环球技术有限责任公司 Filtering assembly comprising the screw winding bioreactor being positioned in independent pressure vessel and film module
US10286361B2 (en) 2015-04-16 2019-05-14 Dow Global Technologies Llc Filtration assembly including spiral wound bioreactors and hyperfiltration membrane modules
US10335737B2 (en) 2015-04-16 2019-07-02 Dow Global Technologies Llc Filtration assembly including spiral wound bioreactors and membrane modules positioned in separate pressure vessels
CN107531526B (en) * 2015-04-16 2021-04-06 陶氏环球技术有限责任公司 Filtration assembly comprising a spiral wound bioreactor and an ultrafiltration membrane module
WO2016167831A1 (en) * 2015-04-16 2016-10-20 Dow Global Technologies Llc Filtration assembly including spiral wound bioreactors and membrane modules positioned in separate pressure vessels
WO2017165091A1 (en) 2016-03-23 2017-09-28 Dow Global Technologies Llc Bioreactor assembly
JP2018143902A (en) * 2017-03-01 2018-09-20 鹿島建設株式会社 Microorganism carrier for biological treatment and fixed bed production method
WO2020174082A1 (en) 2019-02-28 2020-09-03 Rockwool International A/S Method of filtering slurry

Also Published As

Publication number Publication date
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