U.S. patent application number 13/877199 was filed with the patent office on 2013-09-05 for filter for polluted water.
This patent application is currently assigned to GROSS POLLUTANT TRAPS PTY LTD. The applicant listed for this patent is Leo Crasti. Invention is credited to Leo Crasti.
Application Number | 20130228527 13/877199 |
Document ID | / |
Family ID | 45927132 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130228527 |
Kind Code |
A1 |
Crasti; Leo |
September 5, 2013 |
FILTER FOR POLLUTED WATER
Abstract
An apparatus for filtering polluted water in drainage systems.
The apparatus comprising a collection chamber for collecting the
water, having a first end, a second end opposite the first end, and
two sides between the ends. An inlet is disposed at or near the
first end for the water to enter the collection chamber and a
filter screen is disposed in the sides through which the water
exits the collection chamber. A deflector is disposed at or near
the second end of the collection chamber to deflect downwardly the
water flowing towards it.
Inventors: |
Crasti; Leo; (Kirribilli,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Crasti; Leo |
Kirribilli |
|
AU |
|
|
Assignee: |
GROSS POLLUTANT TRAPS PTY
LTD
Riverstone, NSW
AU
|
Family ID: |
45927132 |
Appl. No.: |
13/877199 |
Filed: |
October 5, 2011 |
PCT Filed: |
October 5, 2011 |
PCT NO: |
PCT/AU11/01277 |
371 Date: |
April 24, 2013 |
Current U.S.
Class: |
210/747.2 ;
210/170.03 |
Current CPC
Class: |
E03F 5/16 20130101; C02F
1/40 20130101; C02F 2103/001 20130101; Y02A 20/152 20180101; C02F
1/28 20130101; E03F 5/14 20130101; C02F 2301/022 20130101; Y02A
20/156 20180101; C02F 1/004 20130101 |
Class at
Publication: |
210/747.2 ;
210/170.03 |
International
Class: |
E03F 5/16 20060101
E03F005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2010 |
AU |
2010904450 |
Claims
1. An apparatus for filtering polluted water in drainage systems,
comprising a collection chamber for collecting the water, having a
first end, a second end opposite the first end, and two sides
between the ends; an inlet at or near the first end for the water
to enter the collection chamber; and at least one filter screen
disposed in at least one of the sides through which the water exits
the collection chamber; characterised in that a deflector is
disposed at or near the second end of the collection chamber, the
deflector being arranged to deflect downwardly the water flowing
towards it, so that as the water flows through the collection
chamber at least a portion of it tumbles about a substantially
horizontal axis such that at the centre of the collection chamber
the water near the surface flows substantially towards the second
end, and the water near the bottom of the collection chamber flows
substantially towards the first end.
2. An apparatus for filtering polluted water as claimed in claim 1,
wherein the deflector establishes a laminar flow state in the water
in the vicinity of the deflector.
3. An apparatus for filtering polluted water as claimed in claim 1,
wherein the collection chamber is elongate such that the distance
between the ends of the collection chamber is greater than the
distance between the sides of the collection chamber.
4. An apparatus for filtering polluted water as claimed in claim 1,
wherein the deflector is at least partially submerged when the
water is flowing though the apparatus.
5. An apparatus for filtering polluted water as claimed in claim 1,
wherein at least a portion of the deflector is shaped such that the
distance between the front of the portion and the first end of the
collection chamber increases as the portion extends towards the
bottom of the collection chamber.
6. An apparatus for filtering polluted water as claimed in claim 1,
wherein the deflector comprises an array of spaced apart elements,
disposed parallel to the flow of the water past the deflector.
7. An apparatus for filtering polluted water as claimed in claim 1,
further comprising an oil separator for removing oil from the
water, the oil separator being attached to or integral with the
deflector.
8. An apparatus for filtering polluted water as claimed in claim 7,
wherein the deflector comprises the oil separator, and the
deflector comprises an array of spaced apart elements disposed
parallel to the flow of the water past the deflector, and each
element comprises an oil absorption material.
9. An apparatus for filtering polluted water as claimed in claim 6,
wherein each element has a smooth front edge that faces the flow of
the water towards the deflector.
10. An apparatus for filtering polluted water as claimed in claim
1, wherein the inlet is a pipe, and the distance between the first
and second ends of the collection chamber is at least four times
the diameter of the pipe.
11. An apparatus for filtering polluted water as claimed in claim
1, further comprising a discharge chamber and an outlet, wherein
the water passing through the filter screen flows into the
discharge chamber, and then out of the apparatus through the
outlet.
12. An apparatus for filtering polluted water as claimed in claim
1, wherein the filter screen is replaceable.
13. An apparatus for filtering polluted water as claimed 1, wherein
the filter screen comprises at least two modular panels.
14. An apparatus for filtering polluted water as claimed in claim
1, wherein the filter screen is made from at least one plastic
material.
15. An apparatus for filtering polluted water as claimed in claim
7, wherein the apparatus comprises a winch system for lowering and
raising the oil separator into the collection chamber.
16. (canceled)
17. (canceled)
18. (canceled)
19. A stormwater contaminant separator and collector device for
installation with stormwater pipes, said device comprising a
collection chamber for collecting water, having a first end, a
second end opposite the first end, and two sides between the ends;
a stormwater inlet at or near said first end for said water to
enter the collection chamber; and at least one filter screen
disposed in at least one of said sides through which said water
exits said collection chamber, characterised in that a deflector
structure is disposed at or near said second end of said collection
chamber, at least a portion of said deflector structure being
arranged to deflect downwardly water flowing towards it, and as
said water flows through said collection chamber at least a portion
thereof tumbles about a substantially horizontal axis such that at
the centre of said collection chamber said water near the surface
flows substantially towards said second end, and said water near
the bottom of said collection chamber flows substantially towards
said first end.
20. A stormwater contaminant separator and collector device as
claimed in claim 19, wherein solid pollutants are substantially
deposited in an area below said inlet at or near said first end,
and buoyant pollutants are collected in an upper central zone of
said collection chamber between said first and second ends.
21. A stormwater contaminant separator and collector device as
claimed in claim 19, wherein an oil and scum collection zone is
disposed at or near said deflector structure at said second
end.
22. A method of separating stormwater contaminants by passing
polluted stormwater through a collection chamber, said method
comprising imparting a tumbling motion about a substantially
horizontal axis to a portion of the flow entering said collection
chamber through an inlet, such that said portion of flow is
directed downwardly and back towards said inlet.
23. A stormwater contaminant separator and collector device as
claimed in claim 20, wherein an oil and scum collection zone is
disposed at or near said deflector structure at said second end.
Description
TECHNICAL FIELD
[0001] The present invention relates to filters for water drainage
systems, and in particular to filters for stormwater drainage
systems.
BACKGROUND
[0002] For environmental reasons, it is becoming increasingly
necessary to filter or trap pollutants from water collected by
drainage systems to prevent these pollutants from being discharged
into bays, rivers, creeks, or other environmentally sensitive
areas. This is particularly the case for stormwater drainage
systems, in which water run-off from streets, roof areas, pathways,
etc. collects trash, debris, and other waste with it before it runs
into a water way. In recent times the filtration and trapping of
pollutants has become important, as "stormwater harvesting" has
become a viable way of sustaining water resources. In some areas,
government regulations now mandate that in new developments
stormwater filtration must be provided. There is also often a need
to filter pollution from water in industrial systems.
[0003] Pollutants in stormwater fall into a number of categories.
There are larger solid pollutants, known as gross pollutants, fine
solid pollutants, and liquid pollutants. Solid pollutants can be
further categorised by their relative density to water. Solid
pollutants having a relative density of less than 1, such as twigs,
closed containers, etc., are buoyant pollutants that float on the
water. Solid pollutants with a relative density of between 1 and
1.5 are considered to be low density pollutants, and this includes
most plastics. Solid pollutants with a relative density higher than
1.5 are considered to be high density pollutants, and this includes
dense sediment. Whilst dense sediments such as clay particles are
part of the environment, they are contributors to pollution. It has
recently become understood that chemicals become attached to clay
particles, which then cause aggregation and storage of chemicals in
sediment beds. High density pollutants tend to sink faster than low
density pollutants. Liquid pollutants include floating liquids
having a relative density of less than 1, such as oils. Scum is
also a pollutant that floats on the water and may include mixtures
of liquid and fine particles.
[0004] Various stormwater filters are known and are in use. They
are often referred to as "gross pollutant traps" or "solid
pollutant filters". They are typically installed in-ground with
their top exposed for access, and are connected in-line with a
stormwater pipe. Prior art stormwater filters employ various
methods of trapping pollutants. One method is to use filter screens
to trap solid pollutants. In typical prior art systems employing
filter screens, the water flows directly at the screens, which
reduces the efficiency of the filter screen because when the screen
becomes partially blocked it creates a high resistance to water
flowing directly at it.
[0005] Typically, prior art filters employing filter screens also
include a means for water to bypass the screens if they become
blocked or the flow through the filter is excessive (such as in
heavy storms). An example of a prior art stormwater filter with
filter screens and a bypass system is disclosed in WO 98/17875
(Ecosol Pty Ltd). The bypass system in this filter is a barrier
that normally directs polluted water through the filter, but allows
overflow to bypass it. Another prior art arrangement uses a bypass
system comprising a floating or otherwise movable boom. Bypass
systems are typically necessary where filter screens are employed,
but it is desirable for a stormwater filter to minimise the amount
of water that bypasses the filter screens because the bypass water
carries pollutants with it.
[0006] An alternative type of stormwater filter utilizes cyclonic
motion about a vertical axis. One example is the Rocla CDS.TM. unit
by Rocla Pty Ltd which utilises the energy of the inflow to create
a a vortex flow regime within the screening chamber. Another
example of this type of filter is sold by Humes Water Solutions
under the brand Humeceptor.TM.. A disadvantage of this latter
stormwater filter is that a deep, costly excavation is required to
install it and collected pollutants are deposited deep in the
filter, which can be difficult to remove. Also, the capture volume
of such a filter is limited.
[0007] Another disadvantage of typical prior art gross pollutant
traps is that they do not efficiently capture oil or scum in the
polluted water. Also, access to clean or replace the filter
screens, or to remove collected solid waste, is often difficult in
prior art filters due to the nature of their design. Also, the
design of some prior art filters is such that collected pollutants
build up and block filter access. Furthermore, some prior art
filters have many components constructed from steel, which results
in a relatively short service life unless they are constructed from
expensive corrosion resistant steels.
[0008] The present invention seeks to ameliorate at least one of
the disadvantages of the prior art.
SUMMARY OF INVENTION
[0009] In a first aspect, the present invention consists of an
apparatus for filtering polluted water in drainage systems,
comprising
[0010] a collection chamber for collecting the water, having a
first end, a second end opposite the first end, and two sides
between the ends;
[0011] an inlet at or near the first end for the water to enter the
collection chamber; and
[0012] at least one filter screen disposed in at least one of the
sides through which the water exits the collection chamber,
characterised in that
[0013] a deflector is disposed at or near the second end of the
collection chamber, the deflector being arranged to deflect
downwardly the water flowing towards it.
[0014] Preferably, as the water flows through the collection
chamber at least a portion of it tumbles about a substantially
horizontal axis such that at the centre of the collection chamber
the water near the surface flows substantially towards the second
end, and the water near the bottom of the collection chamber flows
substantially towards the first end.
[0015] Preferably, the deflector establishes a laminar flow state
in the water in the vicinity of the deflector. Preferably, the
collection chamber is elongate such that the distance between the
ends of the collection chamber is greater than the distance between
the sides of the collection chamber. Preferably, the deflector is
at least partially submerged when the water is flowing though the
apparatus.
[0016] Preferably, at least a portion of the deflector is shaped
such that the distance between the front of the portion and the
first end of the collection chamber increases as the portion
extends towards the bottom of the collection chamber. Preferably,
the deflector comprises an array of spaced apart elements, disposed
parallel to the flow of the water past the deflector.
[0017] Preferably, the filter further comprises an oil separator
for removing oil from the water, the oil separator being attached
to or integral with the deflector. Preferably, the deflector
comprises the oil separator, and the deflector comprises an array
of spaced apart elements disposed parallel to the flow of the water
past the deflector, and each element comprises an oil absorption
material.
[0018] Preferably, each element has a smooth front edge that faces
the flow of the water towards the deflector.
[0019] Preferably, the inlet is a pipe, and the distance between
the first and second ends of the collection chamber is at least
four times the diameter of the pipe.
[0020] Preferably, the filter screen is replaceable. In one
preferred embodiment, the filter screen comprises at least two
modular panels.
[0021] Preferably the filter screen is made from at least one
plastic material.
[0022] Preferably in one embodiment the apparatus comprises a winch
system for lowering and raising the oil separator into the
collection chamber.
[0023] In a second aspect, the present invention consists of an
apparatus for filtering polluted water in drainage systems,
comprising a collection chamber for collecting the water, having a
first end, a second end opposite the first end, and an inlet at or
near the first end for the water to enter the collection chamber,
characterised in that an oil separator is disposed at or near the
second end of the collection chamber for removing oil from the
water.
[0024] Preferably, the oil separator comprises an array of spaced
apart elements disposed parallel to the flow of the water past the
oil separator, and each element comprises an oil absorption
material. Preferably, the oil separator deflects downwardly the
water flowing towards it.
[0025] In a third aspect, the present invention consists of a
stormwater contaminant separator and collector device for
installation with stormwater pipes, said device comprising
[0026] a collection chamber for collecting water, having a first
end, a second end opposite the first end, and two sides between the
ends;
[0027] a stormwater inlet at or near said first end for said water
to enter the collection chamber; and
[0028] at least one filter screen disposed in at least one of said
sides through which said water exits said collection chamber,
characterised in that
[0029] a deflector structure is disposed at or near said second end
of said collection chamber, at least a portion of said deflector
structure being arranged to deflect downwardly water flowing
towards it, and as said water flows through said collection chamber
at least a portion thereof tumbles about a substantially horizontal
axis such that at the centre of said collection chamber said water
near the surface flows substantially towards said second end, and
said water near the bottom of said collection chamber flows
substantially towards said first end.
[0030] Preferably, solid pollutants are substantially deposited in
an area below said inlet at or near said first end, and buoyant
pollutants are collected in an upper central zone of said
collection chamber between said first and second ends. Preferably,
an oil and scum collection zone is disposed at or near said
deflector structure at said second end.
[0031] In a fourth aspect, the present invention consists of a
method of separating stormwater contaminants by passing polluted
stormwater through a collection chamber, said method comprising
imparting a tumbling motion about a substantially horizontal axis
to a portion of the flow entering said collection chamber through
an inlet, such that said portion of flow is directed downwardly and
back towards said inlet.
BRIEF DESCRIPTION OF DRAWINGS
[0032] FIG. 1 is a perspective view of a first preferred embodiment
of a stormwater pollutant filter in accordance with the present
invention with its lid not shown, and the top portion of its
enclosure cut-away.
[0033] FIGS. 2, 3 and 4 are various partial cut-away perspective
views of the pollutant filter of FIG. 1.
[0034] FIG. 5 is a longitudinal sectional view through the
pollutant filter of FIG. 1 showing various trapped pollutants.
[0035] FIG. 6 is an enlarged front perspective view of the oil
separator assembly of the pollutant filter of FIG. 1.
[0036] FIGS. 7, 8, 9 and 10 show the normal flow through the filter
of FIG. 1 without bypass flow, with FIGS. 7 and 8 being partial cut
away views, FIG. 9 being a longitudinal sectional view, and FIG. 10
being a plan view.
[0037] FIG. 11 is a partial sectional view through the filter of
FIG. 1, showing flow that includes bypass flow.
[0038] FIG. 12 is a partial sectional view through the Filter of
FIG. 1, showing total bypass flow.
[0039] FIG. 13 is a perspective view of a second preferred
embodiment of a stormwater pollutant filter in accordance with the
present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0040] FIGS. 1 to 12 show a first preferred embodiment of a
stormwater pollutant filter 1 in accordance with the present
invention. Filter 1 is adapted to be installed in-line with a
stormwater drain to separate and collect pollutants (contaminants)
from stormwater passing through it. Referring to FIG. 1, filter 1
comprises a water tight, open, box shaped enclosure (a main pit) 2
that is divided into chambers and houses the operating components
of filter 1. In use, a lid (not shown) covers enclosure 2. In FIG.
1, the "top portion" of enclosure 2 and inlet and outlet pipes 4, 5
are cut-away, to more clearly show the location of a collection
chamber 7 disposed within enclosure 2.
[0041] Referring to FIG. 5, polluted stormwater 19 enters filter 1
through inlet pipe 4 at one end of enclosure 2, and filtered water
20 exits through an outlet pipe 5 at the opposite end of enclosure
2. Filter 1 is usually installed in the ground, with its lid (not
shown) at or near ground level and exposed for access. Inlet and
outlet pipes 4, 5 are typically below ground level. Inlet pipe 4
and outlet pipe 5 are at about the same height, near the top of
enclosure 2. When filter 1 is installed and there is no flow
through it, there is still residual water held in enclosure 2 at a
residual water level 21 at the height of the bottom (i.e. the
invert) of outlet pipe 5, which in this embodiment is the same
height as the bottom of inlet pipe 4.
[0042] Polluted water flowing into filter 1, through inlet pipe 4,
is collected in collection chamber 7, having a first end 8 and a
second end 9 opposite thereto. Inlet pipe 4 is at first end 8 of
collection chamber 7, and opens through the wall of end 8 of
collection chamber 7. At the opposite end 9 of collection chamber 7
there is a "deflector", namely oil separator 10. The construction
and function of oil separator 10 is described below. There are no
openings in the wall of end 9 for water to flow through. Collection
chamber 7 has two sides (side frames) 11, between ends 8 and 9. A
plurality of vertical filter screens 12 is disposed in each side 11
of collection chamber 7. The filter screens 12 are disposed below
the residual water level 21 and extend to the bottom 22 of
collection chamber 7, and are disposed towards end 9 of collection
chamber 7.
[0043] Filter screens 12 have a large area, preferably greater than
twenty times the area of inlet pipe 4. This creates a relatively
slow flow velocity through screens 12, which assists in preventing
blockage and reduces the stress in screens 12. This allows screen
materials of a fine micron to be used to increase particle capture
efficiency and reduce the size of particles that can be captured.
Filter screens 12 may be constructed from various materials
including stainless steel and/or plastics, depending on the water
conditions, and they may have a single layer of filter material or
multiple layers. In this preferred embodiment the side frames 11
are made from high density polyethylene (HDPE) and the filter
screens from a suitable polyethylene.
[0044] Filter screens 12 are removable for cleaning, servicing, or
to replace with a different type of filter material as conditions
change or filter material technology improves. Also, different
filter screens 12 may be used depending on the specific
environmental needs of a particular installation, which may vary
with vegetation constraints, etc. For example, in stormwater
harvesting systems requiring a higher degree of filtration, finer
screens 12 can be used. This ability to change screens 12 of a
particular installation is an advantage over the prior art.
[0045] Collection chamber 7 is elongate such that its length, the
distance between its ends 8 and 9, is greater than its width, the
distance between its sides 11. Referring to FIG. 5, the distance 28
between the ends 8, 9 of collection chamber 7 is preferably greater
than four times the diameter 29 of inlet pipe 4, for reasons
discussed below.
[0046] A centre weir 13 is positioned between ends 8 and 9 of
collection chamber 7, across the width of collection chamber 7. Two
elevated spaced apart weir walls 38 extend from inlet 4 to weir 13
in the upper zone of enclosure 2. In as best seen in FIG. 10,
centre weir 13 has a pointed tip 23 facing inlet pipe 4. Referring
to FIG. 5, centre weir 13 extends above residual water level 21.
Below centre weir 13, an opening 26 extends the width of collection
chamber 7. Centre weir 13 is closer to end 8 than end 9 of
collection chamber 7, and filter screens 12 extend approximately
from centre weir 13 to end 9.
[0047] Centre weir 13 divides collection chamber 7 length-wise into
two zones. A settling zone 30 is between end 8 and centre weir 13,
and an exit zone 31 is between centre weir 13 and end 9. Opening 26
below centre weir 13 allows free fluid flow between zones 30 and 31
in the lower half of collection chamber 7. The bottom of settling
zone 30 extends the width of enclosure 2, whilst the width of exit
zone 31 is the distance between sides (side frames) 11.
[0048] Oil separator 10 is constructed as an array of spaced apart
elements 15, each comprising a frame 17 surrounding and supporting
a sheet of oil absorption material 16. Frames 17 are preferably
made of HDPE, however they may be made of any suitable plastic or
stainless steel. Oil absorption material 16 may for instance be
OilSorb.TM. filtration media or some other suitable filtration
media.
[0049] Frames 17 may be individually removable for servicing.
Elements 15 are vertical and are aligned parallel to the sides 11
of collection chamber 7 such that they are also aligned parallel to
the direction of flow of water past them. As shown in FIG. 6, a
pivotal retainer 40 may be used hold frames 17 and elements 15 in
place. Retainer 40 may be lockable using a movable cam lock (not
shown) or the like.
[0050] Oil separator 10 is positioned at a height such that it is
partially submerged when water is flowing through filter 1, and
when water is at residual water level 21. Front 18 of oil separator
10 includes the front edges 56 of elements 15 and it faces inlet
pipe 4. Preferably front edges 56 of elements 15 are smooth and
rounded. Front 18 of oil separator 10 is sloped (angled) from a
vertical plane such that the distance between front 18 and end 8 of
collection chamber 7 increases as front 18 extends towards the
bottom 22 of collection chamber 7. In this embodiment, each element
15 and frame 17 has a profile which is substantially
"frusto-triangular", meaning it is triangular but its tip has been
truncated by a plane parallel to its triangle base. The
frusto-triangular profile each element has a "right angle" disposed
near the top of end 9 of collection chamber 7, and its long edge
(front edge 56) facing towards the bottom of end 8.
[0051] A discharge chamber 34 is formed in enclosure 2 between end
9 of collection chamber 7 and the end wall of enclosure 2 that
outlet pipe 5 opens into. Two bypass channels 37 are each disposed
between a side 11 of collection chamber 7 and a respective internal
sidewall of enclosure 2.
[0052] When the lid (not shown) of enclosure 2 is removed, it
allows for collected waste to be readily removed from collection
chamber 7, and to allow oil separator 10 or its components to be
easily replaced or serviced. A shut off gate (not shown) can be
used to block inlet pipe 4 for servicing filter 1.
[0053] Enclosure 2 may be constructed from concrete based
materials, preferably having a design service life exceeding 100
years. As previously indicated the components making up collection
chamber 7 such as side frames 11, screens 12 may be made of
suitable plastic material or stainless steel.
[0054] The operation of filter 1 will now be described. FIGS. 7, 8,
9 and 10 show the normal flow through filter 1. Normal flow is
defined as the flow condition when all of the water passing through
filter 1 passes through filter screens 12. This type of flow occurs
during normal rainfall rates (i.e. not heavy storms) and when
filter screens 12 are not blocked.
[0055] Referring to FIG. 9 in particular, polluted water 19
entering collection chamber 7 through inlet pipe 4 flows along its
surface, through opening 26 below centre weir 13, towards end 9 of
collection chamber 7. As the flow approaches end 9, oil separator
10 deflects the flow downwards towards bottom 22 of collection
chamber 7. As water 19 nears bottom 22 it then flows back towards
end 8. As it approaches end 8, water 19 flows up again and merges
with the incoming flow from inlet pipe 4. In this manner, water 19
tumbles (swirls) about an approximately horizontal axis 42, as
indicated by flow arrows 57. As this tumbling flow occurs, water 19
is drawn off from the tumbling flow and exits collection chamber 7
through filter screens 12 at the same rate as the inflow through
inlet pipe 4. Filtered water 20 that has passed through filter
screens 12 then flows into discharge chamber 34, as indicated by
flow arrows 58 and 59 in FIGS. 7, 8 and 10.
[0056] Referring to FIG. 5, as polluted water 19 enters collection
chamber 7 through inlet pipe 4, the dissipation of energy causes
high density pollutants 44 to immediately drop out and settle in
settling zone 30 of collection chamber 7, near end 8, below inlet
pipe 4. The remaining pollutants are initially carried with water
19 as it goes through its tumbling motion. The centrifugal action
of the tumbling motion also deposits low density pollutants 45 in
settling zone 30 and at the bottom 22 of collection chamber 7. In
this manner, the tumbling motion deposits various pollutants to
designated capture areas.
[0057] The shape and construction of oil separator 10, with
assistance from the elongate construction of collection chamber 7,
establishes this beneficial tumbling flow. Sloping front 18 of oil
separator 10, and its construction as an array of spaced apart
elements 15, smoothly deflects the flow downwards to establish the
tumbling flow with a minimum of turbulence (i.e. substantially
laminar flow). Distance 28 between ends 8 and 9 of collection
chamber 7 being greater than four times diameter 29 of inlet pipe 4
is beneficial in establishing the tumbling flow. Whilst front 18 of
oil separator 10 is "substantially flat", in other not shown
embodiments it may have various other shapes to deflect the flow.
For example the front 18 may have a concave shape.
[0058] The smooth front edges 56 of elements 15 of oil separator 10
and its spaced apart construction establishes a laminar flow state
in the vicinity of oil separator 10, by dissipating the energy of
the flow in a controlled manner, such that water 19 in the spaces
between elements 15 is largely stagnant at its surface. This causes
oil and scum type pollutants in water 19 to coalesce in the gaps
between elements 15. The oil and scum is then attracted to and
absorbed by oil absorption material 16, which retains these
pollutants until absorption material 16 is replaced, by replacing
individual elements 15 or the whole of oil separator 10. As with
filter screens 12, elements 15 can be changed to use different
types of absorption materials 16. The area in the vicinity of oil
separator 10 where oil and scum collects is an oil and scum
collection zone 49, as shown in FIG. 5.
[0059] Due to the tumbling flow, state in collection chamber 7, the
polluted water is largely flowing across the surface of filter
screens 12, with a portion of this flow being drawn off out of the
tumbling flow to exit through filter screens 12. This improves the
efficiency of filter screens 12 compared with prior art
arrangements in which the water flows directly at screens, because
the flow through filter screens 12 is relatively slow and smooth
(less turbulence), and larger particles are deflected off screens
12, so they do not clog screens 12, to eventually be deposited in
settling zone 30. Filter screens 12 may be sized, as an example, to
trap particles down to sizes of 25 microns. Another reason that
water flowing across the surface of screens 12 improves efficiency,
is that particles sizes less than the aperture size of screens 12
can still be captured. The water flowing across the surface of
filter screens 12, due to the tumbling flow, also washes pollutants
off filter screens 12 such that the screens 12 are
self-cleaning.
[0060] Some fine particles of pollutant will pass through filter
screens 12. However, a proportion of these pollutants will settle
to bottom 22 outside of collection chamber 7 due to the slow flow
velocity through screens 12, Pollutants collected in the bottom 22
can be removed when filter 1 is serviced.
[0061] Referring to FIG. 5, centre weir 13 collects buoyant
pollutants 46 that float on the surface of water 19 in an upper
central zone 48 between centre weir 13 and oil separator 10. These
buoyant pollutants 46 are washed through opening 26 in centre weir
13 and then become trapped.
[0062] FIG. 11 shows the flow through filter 1 when the flow rate
through inlet pipe 4 is near its maximum, such as during a heavy
storm. In this case some of the flow bypasses filter screens 12. In
this condition, the water level in collection chamber 7 rises such
that some of the water passes over weir walls 38, indicated by flow
arrows 60, directly into bypass channels 37, before exiting filter
1 through discharge chamber 34 and outlet pipe 5. Even though some
flow bypasses filter screens 12 under these conditions, the design
of filter 1 minimises this bypass flow, which minimises the amount
of polluted water 19 that is not filtered. In particular, the
relatively slow, smooth flow through filter screens 12 continues
such that they still operate efficiently in these conditions.
[0063] FIG. 12 shows the flow through filter 1 when filter screens
12 are completely blocked. In this condition, all flow is over weir
walls 38, through bypass channel 37 and into discharge chamber 34,
as indicated by flow arrows 60, 61. The design of filter 1 is such
that pollutants collected in collection chamber 7 do not escape
during this flow condition. The location of weir walls 38, centre
weir 13, and inlet pipe 4 creates a substantially laminar flow
condition between inlet pipe 4 and bypass weirs 38 during total
bypass flow such that the water below the bottom of inlet pipe 4 is
substantially stagnant, which does not stir up pollutants 44, 45
deposited in collection chamber 7.
[0064] In the abovementioned embodiment, oil separator 10 is
integral with the "deflector", such that oil separator 10 is also
the deflector of filter 1. However, in other not shown embodiments
of the invention, oil separator 10 can be replaced with a dedicated
"deflector structure" to establish the tumble flow without
necessarily collecting oil. In this case, the deflector may have a
similar construction to oil separator 10 except with plates
replacing absorption material 16 in elements 15. Furthermore, a
dedicated deflector may be constructed as other than spaced apart
elements. For example, it may be a full surface facing the incoming
flow to deflect it downwards. Also, the front of a dedicated
deflector may have various shapes. For example, it may have a flat
sloping face like front 18 of oil separator 10, or it may have a
concaved surface facing the flow towards it. Also, in other not
shown embodiments of the invention, the oil separator may be a
separate component that is attached to a deflector, or otherwise
positioned nearby.
[0065] In other not shown embodiments of the invention, various
sensors may be added to filter 1 to indicate that servicing is, or
may soon be, required. For example, a sensor may be added to oil
separator 10 to monitor the volume of oil captured to signal that
oil absorption material 16 needs to be changed. Such a sensor may
detect the oil concentration in the oil absorption material 16.
Other sensors may be added to, for example, detect the level of
sediments captured or the amount of buoyant pollutants captured.
Also, blockage of filter screens 12 may be detected by monitoring
pressure differential across screens 12. The information collected
by these sensors may be transmitted wirelessly for remote
monitoring, and they may be powered by a solar panel with battery
storage.
[0066] FIG. 13 shows a second embodiment of a stormwater pollutant
filter 1a in accordance with the present invention. Filter 1a is
similar to filter 1 described above, except that is has a deeper
enclosure (i.e. a deeper main pit) 2a, and therefore a deeper
collection chamber 7a and discharge chamber 34a. In this
embodiment, each side 11, is made of two modular frame panels 11a
abutted end to end. Each panel 11a has plurality of filter screens
12 similar to filter 1 of the first embodiment. Like the first
embodiment it has a centre weir 13 and weir walls 38 and an oil
separator. In this second embodiment as enclosure 2a is quite deep,
a winch mechanism 70 is used to lower and raise oil separator 10
for the purposes of servicing and replacement. In use oil separator
10 is disposed at location 71. In use, a similar tumbling action
and flow arrangement occurs through collection chamber 7a of filter
1a of this second embodiment as does in collection chamber 7 of
filter 1. The shape and construction of oil separator 10, with
assistance from the elongate construction of collection chamber 7a,
establishes this beneficial tumbling flow.
[0067] Whilst the above described embodiments depict filters 1 and
1a having enclosures 2 and 2a that are substantially rectangular in
shape, it should be understood that in other embodiments the shape
of the enclosure may vary. For example, the shape of the enclosure
may be substantially cylindrical, similar to that of the
Humeceptor.TM. prior art filter or any other shape that can be
readily made as pre-cast concrete component, including cubic or
elliptical.
[0068] Whilst the above described embodiments are directed to
stormwater systems, the invention is also applicable to other
drainage applications. Also, filters in accordance with the present
invention may be constructed from other than concrete, or be
adapted to be above ground rather than placed in the ground.
[0069] The terms "comprising" and "including" (and their
grammatical variations) as used herein are used in an inclusive
sense and not in the exclusive sense of "consisting only of".
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