EP2620561A1

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Info

Publication number: EP2620561A1
Application number: EP12153111.5A
Authority: EP
Inventors: Asko Päiviö; Nils Dahlbäck
Original assignee: Dannrup Neils
Current assignee: Dannrup Neils
Priority date: 2012-01-30
Filing date: 2012-01-30
Publication date: 2013-07-31
Anticipated expiration: 2032-01-30
Also published as: JP2015504993A; CA2863948A1; PT2620561E; CA2862321A1; JP2015510056A; US20130233806A1; CN104204371A; PL2620561T3; EP2620562A1; DK2620561T3; CN104220680A; WO2013113449A1; CA2862321C; CN104204371B; WO2013113648A1; EP2620561B1; ES2534002T3; CN104220680B; JP6073927B2; SG11201404441UA

Abstract

A device (10) for filtering stormwater inside a storm drain (11), wherein the device (10) comprises a filter unit (17) and a floating carrier (18) for carrying the filter unit (17), wherein the filter unit (17) comprises a bottom portion (21) and a top portion (22), and wherein the carrier (18) comprises an axially extending recess (28) for receiving the bottom portion (21) of the filter unit (17), so that at least a part of the bottom portion (21) of the filter unit (17) is arranged below a surface (A) of the stormwater inside the storm drain (11) when the device (10) is arranged therein, and through apertures (30) extending radially from an outer surface of the carrier (18) to the recess (28), so that stormwater at the surface (A) can pass through the apertures (30) and reach the bottom portion (21) of the filter unit (17). Also a method for filtering stormwater inside a storm drain (11) is disclosed.

Description

TECHNICAL FIELD

The invention relates to a device and a method for filtering stormwater. More specifically the present invention relates to a device and a method for filtering stormwater inside a storm drain to remove pollutants from it.

Stormwater, which also is called urban runoff, is surface runoff of rainwater, melted snow or ice, wash water or similar from different types of surfaces. Such surfaces can be parking lots, sidewalks, roofs, and similar surfaces, sometimes referred to as impervious surfaces. Water running off from such surfaces tends to become polluted by e.g. gasoline, oil, heavy metals, trash, fertilizers, pesticides and other pollutants. During rain these surfaces carry polluted stormwater to stormdrains. Stormdrains can be connected to a drainage system for discharge into receiving surface waters, such as a canal, river, lake, reservoir, sea, ocean, or other surface water, with or without treatment of the stormwater before discharge.

Stormdrains generally comprise a vertical pipe having an inlet, such as a horizontal grated inlet or a side inlet, being connected to a drainage system. Such stormdrains can comprise a catchbasin, also called sump or gully-pot, for catching small objects, such as sediment, sand, gravel, pebbles, twigs, trash and similar. Then, the catchbasin serves as a water-filled trap for trapping objects and prevent such objects from entering the subsequent drainage system. Such catchbasins also prevent gases from the drainage system from escaping. Storm water from the top of the catchbasin drains into the subsequent drainage system. The catchbasins can be emptied by means of vacuum trucks at suitable time intervals.

PRIOR ART

There are different types of devices for filtering stormwater in the prior art. Such prior art devices comprise a filter for positioning in a stormdrain. However, there is a need for an improved device for filtering stormwater inside a storm drain to remove pollutants from it.

One problem with such prior art devices for filtering stormwater is that they can be inefficient and do not remove pollutants satisfactorily.

Another problem with such prior art devices for filtering stormwater is that it can be difficult to install them inside a stormdrain and also to remove them from the stormdrain, e.g. to be replaced.

One drawback with such prior art devices for filtering stormwater is that they can impede the function of the stormdrain.

SUMMARY OF THE INVENTION

An object of the present invention is to avoid the drawbacks and problems of the prior art. The device and method according to the present invention result in a reliable and efficient filtering of stormwater as well as easy installation and replacement. In some embodiments, the present invention results in a possibility to monitor the device in an efficient manner.

The present invention relates to a device for filtering stormwater inside a storm drain, wherein the device comprises a filter unit and a floating carrier for carrying the filter unit, wherein the filter unit comprises a bottom portion and a top portion, and wherein the carrier comprises an axially extending recess for receiving the bottom portion of the filter unit, so that at least a part of the bottom portion of the filter unit is arranged below a surface of the stormwater inside the storm drain when the device is arranged therein, and through apertures extending radially from an outer surface of the carrier to the recess, so that stormwater can pass through the apertures and reach the recess. A major portion of the pollutants in stormwater is present at the surface of the stormwater inside the storm drain, also sometimes called the surface film. A part of the bottom portion of the filter unit, when the device is arranged in a storm drain, is arranged at the surface by means of the floating carrier. Further, the apertures in the floating carrier result in that stormwater at said surface can engage the bottom portion of the filter unit to remove pollutants accumulated at the surface of the stormwater. Further, the structure of the device results in easy installation of the device and easy replacement of the filter unit. For example, the filter unit is detachable from the carrier, wherein the filter unit can be replaced and the carrier can be reused.

The top portion of the filter unit can be formed with an inclined surface, e.g. by the filter unit being tapered or cone shaped, for guiding non-filterable objects to the surface of the stormwater inside the storm drain. When non-filterable objects, such as twigs, trash, sand and similar, fall through the stormdrain it will then hit the inclined surface and continue along therewith to the surface of stormwater and then continue further to a catchbasin in the stormdrain. Hence, non-filterable objects are prevented from accumulating on top of the filter unit to impede its function.

The filter unit can comprise a plurality of different filter layers. For example, the filter unit comprises one or more of an absorbing material, a heavy metal filtering peat and activated carbon. The filter unit can comprise a first filter layer including a first absorbing material, a second filter layer including heavy metal filtering peat, a third filter layer including activated carbon and a fourth filter layer including a second absorbing material, which layers can be arranged in sequence or contiguous sequence. The first filter unit can be arranged at the top and the fourth filter unit can be arranged at the bottom. The fourth filter layer can be least partially arranged in the bottom portion of the filter unit. Hence, the filter unit is arranged for efficient and reliable filtering of pollutants from stormwater.

The floating carrier can be made of a light-weight material for good floating capabilities. For example, the carrier can be made of expanded plastic, such as expanded polystyrene.

The device can comprise a sensor for monitoring the status of the device and the pollutants in the storm drain. For this purpose, the device can comprise an RFID transponder having an ID-number and a pressure sensor for monitoring the depth of the device in the stormwater and thus the weight of the device, from which the amount of collected pollutants can be calculated. Also unexpected events resulting in sudden heavy pollution of a storm drain can be detected.

The invention also relates to a method of filtering stormwater in a storm drain, including the steps of

a) providing a filter unit having a bottom portion and a top portion,
b) providing a floating carrier having an axially extending recess and through apertures extending radially from an outer surface of the carrier to the recess,
c),arranging the bottom portion of the filter unit in the recess of the carrier,
d) arranging the carrier and the filter unit in the storm drain, so that at least a part of the bottom portion of the filter unit is arranged below a surface of the storm water inside the storm drain and at least a part of the top portion is arranged above said surface,
e) providing stormwater to the bottom portion of the filter unit through the apertures of the carrier, and
f) by means of the top portion of the filter unit, receiving at least a major part of any stormwater entering the storm drain.

Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described more in detail with the aid of embodiments and with reference to the appended drawings, in which:

Fig. 1: is a schematic view of a device for filtering stormwater in accordance with one embodiment of the invention, wherein the device is installed in a stormdrain,
Fig. 2: is a schematic section view the device inFig. 1, wherein a filter unit and a floating carrier of the device have been separated from each other, and
Fig. 3: is a schematic section view of the device according to one embodiment, wherein the device is partially immersed in stormwater.

DETAILED DESCRIPTION

InFig. 1 adevice 10 for filtering stormwater according to one embodiment of the present invention is illustrated schematically. InFig. 1 thedevice 10 is arranged in astormdrain 11 having aninlet 12 for incoming stormwater, anoutlet 13 for discharging stormwater, and a catchbasin 14 for trapping objects, such as sediment, sand, gravel, pebbles, twigs, trash and similar. Hence, thedevice 10 is arranged for filtering stormwater inside thestormdrain 11 to remove pollutants from the stormwater before discharge from thestormdrain 11. Thestormdrain 11 according toFig. 1 comprises anoutlet pipe 15 forming a water trap in a conventional manner. Thestormdrain 11 is arranged in a vertical direction and extends axially, wherein theoutlet pipe 15 extends radially. A portion of theoutlet pipe 15 extends upwards, wherein the water seals theinlet 12 of the stormdrain 11 from theoutlet 13. InFig. 1, the surface of the water inside the stormdrain is indicated by the dashed line A. Alternatively, thestormdrain 11 is arranged without a water trap. Theoutlet 13 is connected to asubsequent drain system 16, such as a sewer or similar.

Thedevice 10 comprises afilter unit 17 and a floatingcarrier 18 for carrying thefilter unit 17. Thefilter unit 17 is arranged for filtering the stormwater to remove pollutants therefrom. Thefilter unit 17 is arranged on top of thecarrier 18, so that thefilter unit 17 is arranged between theinlet 12 of thestormdrain 11 and thecarrier 18. Thecarrier 18 is arranged between thefilter unit 17 and the catchbasin 14 or the bottom of thestormdrain 11.

Thedevice 10 is arranged to form agap 19 between thedevice 10 and aninterior wall 20 of thestormdrain 11. Thegap 19 is arranged so that non-filterable objects, such as sediment, sand, gravel, pebbles, twigs, trash and similar can pass by thedevice 10 to the catchbasin 14. Hence, thedevice 10 is arranged to cover less than 100% of the cross section area of the stormdrain. For example, thedevice 10 is arranged to cover 50-90% or 70-80% of the cross section area of the stormdrain to form asuitable gap 19. For example, thefilter unit 17 is arranged is arranged to cover 50-90% or 70-80% of the cross section area of the stormdrain.

With reference also toFigs. 2 and 3 thefilter unit 17 comprises abottom portion 21 and atop portion 22. Thebottom portion 21 is arranged to engage the surface A of the stormwater inside thestormdrain 11 to remove pollutants at the surface or in a surface film. For example, thebottom portion 21 is arranged to be at least partially submerged in the stormwater inside thestormdrain 11, i.e. at least a portion of thebottom portion 21 is arranged to be below the surface A of the stormwater inside thestormdrain 11. Thetop portion 22 is arranged to be above the surface A. For example, thebottom portion 21 is bevelled and more narrow in its lowermost part.

Thefilter unit 17 comprises aninclined surface 23 for guiding non-filterable objects to thegap 19. For example, thetop portion 22 of thefilter unit 17 comprises theinclined surface 23 for guiding non-filterable objects to the surface of the stormwater inside the storm drain. According to the embodiment of the drawings thetop portion 22 of thefilter unit 17 is tapered, wherein an apex is arranged upwards in a direction towards theinlet 12 of thestormdrain 11 and away from thecarrier 18, so that theinclined surface 23 extends between the apex and the widest portion of the device to guide objects along theinclined surface 23 to thegap 19. For example, thefilter unit 17 is arranged as a cone. Thebottom portion 21 of thefilter unit 17 is arranged narrower than the widest portion of thetop portion 22 thereof.

Thefilter unit 17 is arranged for filtering different types of pollutants from the stormwater. According to one embodiment the filter unit comprises a plurality of filter layers, such as afirst filter layer 24 including a first absorbing material, asecond filter layer 25 including heavy metal filtering peat, athird filter layer 26 including activated carbon and afourth filter layer 27 including a second absorbing material. Optionally, the filter unit comprises additional filtering layers. For example, said filter layers 24-27 are arranged in sequence, such as contiguous sequence, from the top to the bottom, so that thefirst filter layer 24 is arranged in thetop portion 22 of thefilter unit 17 in a direction towards theinlet 12 of thestormdrain 11 and so that thefourth filter layer 27 at least partially is arranged in thebottom portion 21 of thefilter unit 17 in a direction towards thecarrier 18. For example, the first absorbing material of thefirst filter layer 24 comprises a material having capillaries, wherein the stormwater enters said capillaries by capillary force. For example, the absorbing material of thefirst filter layer 24 is arranged to absorb 10-20 or 18 times of its own weight. According to one embodiment, the absorbing material of thefirst filter layer 24 is arranged so that the capillaries are closed when they are full. For example, the absorbing material of thefirst filter layer 24 is a synthetic fibre, such as a granular synthetic fibre. For example, the absorbing material of thefirst filter layer 24 complies with the requirements set out in table 1 below.
Thesecond filtering layer 25 comprises, for example, a heavy metal filtering peat in the form of granules. For example, thesecond filtering layer 25 is arranged for removing heavy metals, such as lead, mercury, cadmium, etc., from the stormwater.
Thethird filter layer 26 is arranged to remove pollutants remaining in the stormwater after having passed the first andsecond filter 24, 25. According to one embodiment, the activated carbon of thethird layer 26 is formed as granules. For example, the activated carbon of thethird layer 26 is formed as granules having a particle size of 1-10 mm, 2-7 mm or 3-5 mm. For example, the active carbon is a conventional active carbon for water treatment.
Thefourth filter layer 27 is arranged for removing pollutants at the surface A of the stormwater inside the stormdrain. Hence, thefourth filter layer 27 is arranged to be at the surface A, wherein a portion of thefourth filter layer 27 is submerged in the stormwater. According to one embodiment, thefourth filter layer 27 comprises an absorbing material of a similar type as thefirst filter layer 24, e.g. complying with the requirements set out in table 1 above. For example the absorbing material of the fourth filter layer is a synthetic fibre felt or fleece.
Thefilter unit 17 comprises, for example, a cover forming a stormwater permeable housing. For example, the cover is a perforated plastic cover, wherein the perforations have a diameter of 0.1-5 mm, 0.5-2 mm or about 1 mm. The cover is not disclosed in the drawings.
Thecarrier 18 is arranged for carrying thefilter unit 17, so that thetop portion 22 of thefilter unit 17 is arranged above the surface A of the stormwater inside thestormdrain 11 and at least a part of thebottom portion 21 of thefilter unit 17 is arranged below said surface A. For example, thecarrier 18 is arranged in a floating material, i.e. a material having less density than water, such as an expanded plastic material. For example, thecarrier 18 is formed in expanded polystyrene.
Thecarrier 18 comprises arecess 28 for receiving thebottom portion 21 of thefilter unit 17. Therecess 28 extends axially through thecarrier 18, so that thefilter unit 17 can be arranged on top of thecarrier 18 while thebottom portion 21 is arranged in therecess 28. When arranged in astormdrain 11 thedevice 19 is floating, wherein thefilter unit 17 is arranged to engage incoming stormwater, which is illustrated by means of the arrows B inFig. 3. For example, thetop portion 22 of thefilter unit 17 is primarily arranged to engage incoming stormwater B falling substantially in a vertical direction. When incoming stormwater come into contact with thefilter unit 17 non-filterable objects are guided by the shape of thefilter unit 17 to thegap 19 and the surface A of the stormwater in thegap 19. The filterable part of the stormwater is filtered by thefilter unit 17. For example, a main part of incoming stormwater B initially engages thefirst filter layer 24, wherein stormwater passing thefirst filter layer 24 then engages thesecond filter layer 25 and subsequently the third and fourth filter layers 26, 27.
According to the illustrated embodiment therecess 28 is optionally bevelled and wider in its top to guide thebottom portion 21 into therecess 28 and facilitate assembly of thedevice 10. For example, thecarrier 18 is provided with anoptional flange 29 forming a wider top of thecarrier 18 to support thefilter unit 17.
Thecarrier 18 comprises throughapertures 30 for conducting stormwater into therecess 28 and into contact with thebottom portion 21 of thefilter unit 17 for removal of pollutants in the stormwater at the surface A. Theapertures 30 extend radially from an outer surface of thecarrier 18 to therecess 28. Hence, when thedevice 10 is arranged in astormdrain 11 thecarrier 18 is partially submerged in the stormwater and thus positioned below the surface A, wherein at least a part of therecess 28 and at least some of theapertures 30 are located below the surface A of the stormwater inside thestormdrain 11. Then, at least a part of thebottom portion 21 of thefilter unit 17, i.e. at least a part of thefourth filter layer 27, is arranged in therecess 28 and below the surface A. Consequently, stormwater at the surface A is conducted radially through theapertures 30, which is illustrated by the arrows C. The radially conducted stormwater C is conducted into therecess 28 and into contact with thefilter unit 17 for removing pollutants in the stormwater. For example, the stormwater C is conducted to thefourth filter layer 27 in thebottom portion 21 of thefilter unit 17, so that pollutants on the surface A or close to the surface A engages thefilter unit 17 and are removed by it.
According to one embodiment of the invention thedevice 10 comprises asensor 31 for detecting the filter capacity of thefilter unit 17. For example, thesensor 31 is a pressure sensitive sensor for detecting the surrounding pressure. Thesensor 31 is arranged below the surface A of the stormwater inside thestormdrain 11. Said pressure is readily calculated to obtain the depth of thedevice 10 in the stormwater, wherein a change in the depth of thedevice 10 can be calculated. Said depth corresponds to the weight of thedevice 10, wherein the added weight, i.e. the weight of filtered material in thefilter unit 17, is calculated. Said weight is compared to the total weight capacity of thefilter unit 17, wherein the remaining filter capacity is calculated. Thesenor 31 is, for example, connected to a central monitoring unit for monitoring a plurality ofdevices 10 arranged indifferent stormdrains 11. According to one embodiment, thesensor 31 is included in an RFID transponder having an ID-number and the pressure sensor to detect the weight of the device and send a signal to the central monitoring unit when a predetermined weight has been exceeded or a sudden weight change has been detected. When a predetermined weight of thedevice 10 has been exceeded it can indicate that thefilter unit 17 is full and needs to be replaced. The detection of a sudden weight change can indicate a substantial and local discharge of pollutants, which can be related to an event, such as a traffic accident or any other event.

Claims

A device (10) for filtering stormwater inside a storm drain (11), wherein the device (10) comprises a filter unit (17) and a floating carrier (18) for carrying the filter unit (17),
wherein the filter unit (17) comprises a bottom portion (21) and a top portion (22), and wherein the carrier (18) comprises
an axially extending recess (28) for receiving the bottom portion (21) of the filter unit (17), so that at least a part of the bottom portion (21) of the filter unit (17) is arranged below a surface (A) of the stormwater inside the storm drain (11) when the device (10) is arranged therein, and
through apertures (30) extending radially from an outer surface of the carrier (18) to the recess (28), so that stormwater at the surface (A) can pass through the apertures (30) and reach the bottom portion (21) of the filter unit (17).
A device according to claim 1, wherein the top portion (22) of the filter unit (17) comprises an inclined surface (23) for guiding non-filterable objects to the surface (A) of the stormwater inside the storm drain (11).
A device according to claim 2, wherein the top portion (22) of the filter unit (17) is tapered.
A device according to any of the preceding claims, wherein the filter unit (17) comprises an absorbing material, a heavy metal filtering peat and activated carbon.
A device according to claim 4, wherein the filter unit (17) comprises a first filter layer (24) including a first absorbing material, a second filter layer (25) including heavy metal filtering peat, a third filter layer (26) including activated carbon and a fourth filter layer (27) including a second absorbing material.
A device according to claim 5, wherein the filter layers (24-27) are arranged in sequence and wherein the fourth filter layer (27) at least partially is arranged in the bottom portion (21) of the filter unit (17).
A device according to claim 5 or 6, wherein the first absorbing material of the first filter layer (24) comprises a granular synthetic fibre, the heavy metal filtering peat of the second filter layer (25) is formed as granules, the activated carbon of the third filter layer (26) is formed as granules, and the absorbing material of the fourth filter layer (27) is a synthetic fibre felt or fleece.
A device according to any of the preceding claims, wherein the floating carrier (18) is made of expanded plastic, such as expanded polystyrene.
A device according to any of the preceding claims, wherein the filter unit (17) comprises a perforated plastic cover.
A device according to any of the preceding claims, wherein the device (10) is narrower than the storm drain (11) for forming a gap (19) between the device (10) and an interior wall (20) of the storm drain (11).
A device according to any of the preceding claims, wherein the device comprises an RFID transponder having an ID-number and a pressure sensor (31) for monitoring the weight of the device.
A method of filtering stormwater in a storm drain (11), including the steps of
a) providing a filter unit (17) having a bottom portion (21) and a top portion (22),
b) providing a floating carrier (18) having an axially extending recess (28) and through apertures (30) extending radially from an outer surface of the carrier (18) to the recess (28),
c) arranging the bottom portion (21) of the filter unit (17) in the recess (28) of the carrier (18),
d) arranging the carrier (18) and the filter unit (17) in the storm drain (11), so that at least a part of the bottom portion (21) of the filter unit (17) is arranged below a surface (A) of the storm water inside the storm drain (11) and at least a part of the top portion (22) is arranged above said surface (A),
e) providing stormwater to the bottom portion (21) of the filter unit (17) through the apertures (30) of the carrier (18), and
f) by means of the top portion (22) of the filter unit (17), receiving at least a major part of any stormwater entering the storm drain (11).
A method according to claim 10, including the step of arranging the carrier (18) and the filter unit (17) in the storm drain (11), so that a gap (19) is formed between them and an interior wall of the storm drain (11).
A method according to claim 13, including the step of guiding non-filterable material to the gap (19) by means of an inclined surface (23) of the top portion (22) of the filter unit (17).
A method according to any of claims 12-14, including the steps of detecting the weight of the device by means of an RFID transponder having a pressure sensor (31), and sending a signal to a central monitoring unit when a predetermined weight has been exceeded or a predetermined weight change during a specific time period has been exceeded.