Note: Descriptions are shown in the official language in which they were submitted.
TITLE
METHOD AND APPARATUS FOR IN SITU CLEANING OF TUBE
SETTLERS IN WATER CLARIFICATION
INTRODUCTION
This invention relates to potable water
purification and, more specifically, to a method and
apparatus for cleaning tube settlers during a water
clarification process.
BACKGROUND OF THE INVENTION
In our United States Patent 6,797,166 issued
September 28, 2004, there is described and claimed a filter
underdrain apparatus and a method of utilizing such an
apparatus during water filtration. The technique utilises
certain improvements in underdrains which have worked well
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in water filtration. The present invention extends such
improvements in water clarification and relates to
improvements which take place upstream of the water
filtration.
In water clarification, tube settlers which
comprise a plurality of extended length tubes generally
molded into a composite tube settler apparatus which is
inserted into a water clarification cell. The water to be
clarified runs through the tubes of the tube settler
apparatus and deposits sediments and other solids in the
tubes. The purpose of the tube settler apparatus is to
increase the surface area exposed to the water such that the
effective settling area is increased.
A problem with such tube settlers is that because
of the solid deposition within the tubes, the tubes may
become plugged. /f the tubes become plugged, the
performance and efficiency of the settlement process is
adversely effected. In certain clarification procedures,
the tube bundles can become so fouled with heavy sludge,
collapse of the tube bundles and even the underlying support
structure for the tube bundlers can occur. This is a costly
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and time consuming problem. Thus, intermittent cleaning of
the tubes to remove the buildup of sludge over time is
required.
One existing method of cleaning the tubes is by
manually washing the tube bundles from above with a high
pressure water stream directed at the tube bundles. While
the tube bundles which are exposed to the water stream are
cleaned in a satisfactory manner using this technique, the
tube bundles that are not so exposed such as those beneath
the collection troughs and walkways are not cleaned thereby
detracting from the overall performance of the tube settler
apparatus.
Another technique is colloquially called "air
lancing" which instead of water, uses high pressure air
which plays on the tube openings in the settler. The tube
bundles are, however, sensitive to the high pressure air and
damage to the tube settler assembly can occur. Similar to
the manual washing technique, not all tube bundles can be
reached with the high pressure air. Also likewise, the
procedure is labor intensive.
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A further technique used provides a fixed air
distribution grid under the tube settler assembly. While
this technique shows promise, existing air distribution
grids do not reach a substantial potion of the tube bundle
area and no air distribution into the tubes immediately
above the support structure for the tube settler assembly is
provided. Existing air grids, therefore, do not clean the
tube settler assembly in these locations which is
disadvantageous.
SUMMARY OF THE INVENTION
According to a first aspect of the invention,
there is provided a method to dislodge sediment retained
within individual tubes of a tube settler assembly used for
water clarification, said method comprising entraining air
released below said tube settler assembly with liquid and
allowing said entrained air and liquid to move upwardly into
said tube settler assembly and to dislodge sediment within
said tubes of said tube settler assembly, said air and
liquid entrainment taking place with air released from at
least two adjacent tube laterals, said tube laterals being
supplied with by an air supply, said air supply supplying
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air to a first of said two respective tube laterals
independently of .supplying said air to a second of said two
respective tube laterals.
According to a further aspect of the invention
there is provided apparatus to remove sediment retained with.
tubes of a tube settler assembly in a water clarification
process, said apparatus comprising a tube settler assembly
having a bottom area and a plurality of tubes, a plurality
of tube laterals extending across substantially the entire
bottom area of said tube settler assembly, air holes to emit
air from said tube laterals, an air supply to provide air to
said tube laterals, at least one of said tube laterals
allowing air to exit from said air exit holes at a time
different from air exiting from said air exist holes in a
second of said tube laterals.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Specific embodiments of the invention will now be
described, by way of example only, with the use of drawings
in which:
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Figure lA is a diagrammatic side view of a raw
water treatment process which includes the clarification
step according to the invention.
Figure 1B is a diagrammatic isometric view of the
concrete clarifier cell within which the ballasted
clarification step occurs and wherein tube settlers and a
backwash flow process to clean the tube settlers takes place
according to the invention;
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Figure 2 is a diagrammatic plan view taken
generally along the plane /I-II of Figure 1B;
Figure 3 is a diagrammatic enlarged plan view of
the area III of Figure 2;
Figure 4 is a diagrammatic enlarged plan view of
the area IV of Figure 2;
Figure 5 is a partial diagrammatic side view of
the concrete clarifier cell according to Figure 1B but
particularly illustrating the tube settler assembly and the
air supply ducts beneath the tube settler assembly which are
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used to supply cleaning air for the tube settler assembly;
Figures 6A and 63, respectively, are enlarged
diagrammatic views of the areas VIA and VIB of Figure 5;
Figure 7 is a partial sectional diagrammatic view
of the section VII-VII of Figure 2;
Figure 8 is an enlarged view of the area VIII of
Figure 7;
Figure 9 is a diagrammatic isometric view of a
typical tube settler assembly used in accordance with the
invention;
Figure 10A is a diagrammatic partial sectional
side view of the tube laterals extending across and beneath
the tube settler assembly;
Figure 103 is a diagrammatic enlarged partial side
view of the tube laterals connected to the air pipes in the
area XB of Figure 10A;
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Figure 11 is a diagrammatic bottom enlarged view
of the tube laterals and air pipes beneath the tube settler
assembly;
Figure 12 is an isometric enlarged view of the
overflow water troughs positioned above the tube settler
assembly and showing sediment deposition in various of the
tubes of the tube settler assembly;
Figure 13 is an enlarged isometric partial plan
view of the tube settler assembly illustrating sediment
deposition within various tubes of the tube settler
assembly; and
Figure 14 is an isometric partially sectional view
of a filter underdrain system located downstream from the
concrete clarifier cell of Figure 1B.
DESCRIPTION OF SPECIFIC EMBODIMENT
Referring now to the drawings and, more
particularly, to Figure 1A, the water tree ent process
particularly in a high rate clarification pplication
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includes a clarification step according to the invention and
is illustrated generally at 200. Three(3) basins, namely
the coagulation basin 201, the injection basin 202 and the
maturation basin 203 are illustrated in Figure 1A. The
lamella clarifier basin or concrete clarifier cell 204,
which may be used in both high speed and conventional
clarification procedures, is positioned downstream from the
initial three basins 201, 202, 203. Its operation will be
explained in greater detail hereafter.
Raw water to be clarified and filtered enters the
coagulation basin 201 from raw water trough or flume 210. A
coagulant is introduced into coagulation basin 201 and with
the mixer diagrammatically illustrated, the suspended solids
are destabilised. The coagulated water then passes to the
injection basin 202 where a polymer and microsand are
typically added to the coagulated water. This water is
passed to the maturation or flocculation basin 203 where it
acquires a weight and volume. The flocculated water passes
to the lamella clarifier basin 204 where the ballasted floc
settles. The clarified water overflows to the filter
assembly 100 in the concrete filtration basin 101 through
troughs 112 (Figure 14).
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The lamella clarifier basin of concrete clarifier
cell 204 (Figures LA and 12). It uses the flocculated
water which passes from troughs 112 extending from the
maturation basin 203 (Figure 1A). The flocculated water is
introduced beneath the tube settler assembly generally
illustrated at 121 (Figure 12) and passes upwardly through
the tube settlers generally illustrated at 122 where the
ballasted floc within the water settles over time as more
clearly seen in Figures 12 and 13. The clarified water
passing through the tube settlers overflows from the tube
settler assembly 121 into troughs 112 which pass the
clarified water to the filter assembly generally
illustrated at 100 in the concrete filter basin 101 (Figure
14). The subsequent use of the filter assembly 100 where
the clarified water from the tube settlement basin 120
flows into the filter assembly from troughs 112 from the
lamella clarifier basin forms no part of the present
invention and is disclosed for the purposes of a full
explanation of the process. The filter assembly 100 is
described more fully in our United States Patent 6,797,166.
Referring to Figure IB, the tube settlement basin
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204 carries the tube settler assembly generally illustrated
at 121 (shown more clearly in Figures 12 and 13). The air
supply assembly used to carry air and distribute the air to
the tube settler assembly 121 is generally illustrated at
122.
The air supply assembly 122 includes a first and
second air pipe 123, 124, respectively, as seen in Figure
18. Each of the air pipes 123, 124 extends the length of
the tube settler assembly 121 and each terminates with a
closed end to prevent the exit of air under pressure from
the ends of the air pipes 123, 124. A plurality of tube
laterals generally illustrated at 130, are connected to the
first and second air pipe 123, 124. Each of the plurality
of tube laterals 130 extend normal or perpendicular to the
first and second air pipes 123, 124 and across substantially
the entire area of the tube settler assembly 121. The
plurality of tube laterals 130 emit air under pressure below
the tube settler assembly 122 through the air discharge
holes 211 (Figure 103) which are positioned so as to emit
air upwardly or outwardly from the tube laterals 130 as
required and are positioned such that the emitted air enters
the bottom of the tube settler assembly 122 with some force
=
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which force of the emitted air and entrained liquid is
intended to dislodge sediment within the tube settler
assembly 122.
Each of the tube laterals 130 is connected to a
bar 132 (Figure 3) which is connected to the concrete of the
concrete clarifier cell 120. The bar 132 provides support
for each of the tube laterals 130. An air deflector 135 is
positioned over the tube laterals 130 as also seen in Figure
6A. The air deflector assembly 135 may conveniently be
perforated with a predetermined number of perforations (not
illustrated). The air deflector 135, also seen in Figure
6A, traps air beneath it and redistributes the air to the
tubes within the tube settler assembly 122 which are located
above the support structure or I-beams 144 which tubes of
the tube settler assembly 135 would otherwise not be
reachable by the emitted air leaving the tube laterals 130.
The tube settler assembly 122 is supported by a
plurality of steel /-sections 144 (Figure 5 and 6A) which
extend laterally across the bottom of the tube settler
assembly 122 on the top of each I-section 144 and which are
connected to support rails 134 (Figure 6A) which extend
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normal to the tube laterals 130. Attachment clips 140
secure the I-sections 144 to the support rails 134.
Reference is made to Figures 10A and 10B wherein
the first and second air pipes 123, 124 are illustrated as
being connected to the tube laterals 130. Only one tube
lateral 130 is shown but it will be appreciated that there
is a series of tube laterals 130 located immediately behind
tube lateral 130 extending the extent of the area of the
tube settler assembly 121. Second air pipe 124 is connected
through a manifold 141 which is also connected to tube
laterals (not illustrated) directly behind tube lateral 130.
First air pipe 123 is connected through a manifold 142
directly to tube laterals 130. Thus, the plurality of tube
laterals 130 are connected alternatively to the air pipes
123, 124 across the bottom of the tube settler assembly 121
as is illustrated in Figure 1B; that is, a first one of the
air pipes 123, 124 is connected to a first one of the tube
laterals 130 with the tube laterals 130 on either side of
the first one of the tube laterals 130 being connected to
the other of the air pipes 123, 124 as seen more clearly in
Figure 11. By using air generated by each of the air pipes
123, 124, air may be supplied only to one set of the tube
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laterals 130. Thereafter, air supplied by the other of the
air pipes 123,124 is supplied to the second set of tube
laterals 130 as also seen in Figure 11. By the use of
appropriate controls such as solenoids and interruption
switches (not illustrated) which stop and release the supply
of air from each of the air pipes 123, 124, independently
and alternatively, air can be supplied to each of the tube
laterals 130 which sets up a rhythmic air supply bearing on
the bottom of the tube settler assembly 121 which is found
to be beneficial for the dislodgement of sediment and debris
within the tubes 125 of the tube settler assembly 121 as
will be explained in greater detail.
The tube settler assembly 121 with the above
located water troughs 112, generally made from a fiberglass
composition, is shown in Figure 12. As the water proceeds to
move upwardly within the tubes 125 of the tube settler
assembly 121, the individual tubes 125 will also act as a
depository of sediment and other debris over time as seen in
Figures 12 and 13. This sediment will, over time, settle
within the tubes 125 of the tube settler assembly 121 and
will degrade the water clarification process so it is
desirable to remove this sediment in accordance with the
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invention described. Following the sediment removal within
the tubes 125 of the tube settler assembly 121, the water
will then pass to a filtration station generally
illustrated 100 in Figure 14 and will also pass to an ozone
or chlorination treatment (not illustrated) before being
considered satisfactory for potable uses.
The water filtration step 100 takes place in a
concrete open top tank or basin generally illustrated at
100 which basin is defined by a bottom slab 102, side walls
103 and end walls 104. A partition 110, parallel to side
wall 103, define an overflow trough or gullet 111 for
receiving backwash water from semicylindrical metal,
concrete or fibreglass troughs 112 (see also Figure 12)
which extend transversely of the basin 101 above the bed or
basin 113 and carry the water leaving the tube settler
assembly 121. The troughs 112 distribute the incoming
water into the basin 113 for filtration according to the
teachings of our United States Patent 6,797,166.
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OPERATION
With reference initially to Figure 1A, raw water
is admitted to the coagulation basin 201 through flume 210.
A coagulant is added to destabilise the suspended solids and
the water passes to the injection basin 202. Polymer and
micro-sand are added in the injection basin 202 to the
incoming water. The floc is fixed to the micro-sand with
the polymer in a flocculation or maturation basin 203 where
it acquires weight and volume. The flocculated water then
passes from the maturation basin 203 to the lamella
clarifier 204 as is illustrated in Figure 1A.
As the flocculated water moves upwardly through
the tube settler assembly 121 as viewed in Figure 13, sludge
and sediment settles within and without the individual tubes
125 as seen in Figure 9, 12 and 13, of the tube settler
assembly 121. The sludge and sediment settles into the
bottom of the lamella clarifier 204 and is removed by way of
a sludge pump 205 and a hydro cyclone 206 as in Figure 1A,
particularly in a high rate of clarification application
although other techniques, including manual removal, may be
used with a conventional clarifier.
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The tube settler assembly 121 provides an
increased effective settling area for the settleable solids
in the flocculated water. In addition to settling on the
bottom of the lamella clarifier 204 as seen in Figure 1A,
the sediment will also be deposited in the individual tubes
125. In due course, the tubes 125 will become blocked or
partially blocked with sediment which will degrade the
sediment settling process significantly. When that occurs,
the air and water dislodgement technique according to the
invention is utilized to clean the tubes 125 of the tube
settler assembly 121.
With reference to Figure 1, air under pressure is
provided to each of the air pipes 123, 124, the air in each
of the air pipes 123, 124 being under individual control.
Each of the air pipes 123, 124 (Figures 10B and 11). The
tube laterals 130 extend beneath substantially the entire
area of the tube settler assembly 121 and have air discharge
holes 211 (Figure 10B) which allows the discharged air to be
directed outwardly and upwardly into the tubes 125 of tube
settler assembly 121. The air emitted by the holes 211
mixes with the water in the clarifier cell and will act to
assist in the dislodgement of the sediment settled within
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the tubes of the tube settler assembly 121.
Two air pipes 123, 124 are referred to although
more may be conveniently used if desired. First air pipe
123 provides air to the first set of tube laterals 130 and
second air pipe 124 provides air to the second set of tube
laterals 130. Thus and since the operation of each air pipe
123, 124 is independent of the other, the tube laterals 130
may be operated in a way best deemed necessary to dislodge
the sediment and other debris and offers significant
advantages in the cleaning operation of the tube settler
assembly 121.
Air from one of the air pipes 124, 125 may be
emitted from its connected tube laterals 130 at a pressure
different from that of the other one of the air pipes 124,
125. Likewise, it may be desired to emit air from one set
of the tube laterals 130 at a time different from the time
of emission of the remaining set of the tube laterals 130.
Or, if desired, the air can be emitted for a predetermined
period from one set of tube laterals 130 and then shut off.
The remaining set of tube laterals 130 can then emit air for
a second predetermined period while the first set of tube
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laterals 130 is not emitting air.
Thus, the sediment dislodged from the tubes 125 in
the tube settler assembly 121 may allow the dislodged
sediment to move downwardly and through the adjacent tubes
within the tube settler assembly 120 to the bottom of the
lamella clarifier basin 120 where it can be removed as has
been described with the settled sludge using the sludge pump
205 or manually as noted. In any event, the use of
independent air supplies for the air pipes 123, 124 allows
significant cleaning advantages over the prior art and
allows more efficient water clarification within the lamella
clarifier basin 120 without the necessity of extended
downtime and the requirement for using significant manual
labor for cleaning the tube settler assembly 121.
Following the clarifier step within the clarifier
204, the water passes through troughs 112 to the filtration
step generally illustrated at 100 in Figure 14. A concrete
open tank or basin 101 is defined by bottom slab 102, side
walls 103 and end walls 104, A partition 110, parallel to
side wall 103, defines an overflow trough or gullet 111 for
receiving backwash water from semicylindrical metal,
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concrete or fiber glass troughs 112 (see also Figure 12)
which extend transversely of the basin 101 above the bed 113
and carry the water leaving the clarifier phase 204 (Figure
1A). The troughs 112 distribute the incoming water into the
basin 113 for filtration.
Reference is now made to Figure 6A where the air
deflector or collector assembly 135 beneath the tube settler
assembly 121 is illustrated as being attached to the support
components or I-sections 144 supporting the tube settler
assembly 121.. The use of the air deflector or collector
assembly 135 may be conveniently used if desired. The use
of the air deflector or collector assembly 135 can create a
turbulence condition between the released air and the water
to assist the entrainment process of air mixed with the
water and may assist in settlement dislodgement within the
tubes 125 of the tube settler assembly 121. The air
deflector 135 is perforated with openings made of a
predetermined size. The deflector 135 is intended to relase
and/or direct air upwardly into those tubes of the tube
settler assembly 121 which may usually be blocked or
otherwise not readily accessible to the air released by the
tube lateral's 130 due to the position of the I-sections 144
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and other support structure for the tube settler assembly
121.
Many modifications may readily be contemplated by
those skilled in the art to which the invention relates.
For example, while only two air pipes 123, 124 have been
described, increasing the number of independent air pipes
123, 124 and their respectively associated tube laterals 130
may provide additional tube settler cleaning efficiencies.
And allowing the air pressure in one of the air pipes 123,
124 to be greater than the air pressure in the remaining one
of the air pipes 123, 124 may similarly allow cleaning
efficiencies the tubes 125 of the tube settler assembly 121
to take, place. Similarly, the use of a rotatingtube
lateral, assembly 121 is contemplated to have additional
advantages in cleaning the tubes of the tube settler
assembly 121 and in this event, appropriate support
structure would be designed to allow the tube laterals 130
to rotate beneath the tube settler assembly 121.
Many further modifications may readily be
contemplated. The description set out above is particularly
applicable to high rate clarification applications. However,
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in conventional clarification where the upstream or
downstream processes herein described are not used, the
teachings according to the invention may have considerable
merit and are also applicable. The specific embodiments
described, therefore, should be taken as illustrative of the
invention only and not as limiting its scope as defined in
accordance with the accompanying claims.
