Note: Descriptions are shown in the official language in which they were submitted.
CA 02780861 2012-05-14
1
Method for producing potable water and/or purifying water comprising the
elimination of a target compound and a filtration within a filter drum
1. Field of the invention
The field of the invention is that of methods for treating water with a view
to
purifying it and/or making it potable or drinkable.
The invention concerns especially the purification of any kind of water (urban
wastewater, industrial wastewater) and/or the potabilizing of any type of
water
(surface freshwater or ground freshwater, treated urban wastewater, industrial
wastewater, sea water, etc.) containing any type of pollutant (organic malter
of
natural origin, organic micropollutants such as for example pesticides,
micropollutants such as for example bromates, chemical pollutants etc.).
2. Prior art and drawbacks of the prior art
Water treatment methods are commonly used especially in order to produce
potable water.
These methods, also called potabilization methods, generally comprises a step
of elimination in which the water to be treated is put into contact with an
active
particulate material in a stirred tank. This step of elimination is
necessarily followed
by a step of separation during which the active particulate material is
separated from
the mixture of water and active particulate material, and treated water is
collected.
The active particulate material is then rerouted into the stirred tank. The
collected
treated water is, as the case may be, conveyed towards filtering units placed
downstream in order to reduce its residual turbidity.
There is a known technique for producing drinking water wherein the
elimination step implements PAC (powder activated carbon). In this case, the
separation of the PAC and of the treated water is obtained by decantation.
This
presupposes the prior injection of a polymer into the mixture of PAC and water
so as
to ballast or weigh down the PAC and facilitate its decantation.
CA 02780861 2012-05-14
2
There is another known technique for potabilizing that is described in the
international patent application WO-A1-96/07615, in which the elimination step
implements magnetic ion-exchange resins ballasted or settled by metal oxides.
In this
case, In this case, the separation of the resins, of a part of the fines
resulting from the
attrition of the resins and of the treated water is obtained by decantation.
The
remainder of the fines that has not been separated by decantation is
subsequently
recovered by magnetization.
The decantation implemented in these techniques is influenced by numerous
parameters (temperature, flow-rate variations, etc) even further complicating
the
control of this separation step. In addition, this separation technique has
the
drawback of not permitting a separation as absolute and speedy as that of a
physical
barrier, such as is formed by a screen. Consequently, the decantation may
possibly
give rise to a loss of active particulate material and of the initially added
reagents.
These possible losses of active particulate matter and, as the case may be, of
polymer play a part, inter alia, in augmenting the rapidity of clogging of the
filtering
units placed downstream.
The international patent application WO-A1-96/07615 teaches the possibility
of implementing a screen so as to separate the ion-exchange resins from the
mixture
of treated water and resins. It is true that this technique makes it possible
to limit the
losses of active particulate material in the treated waters. However, it
entails
particular constraints in being implemented. It presupposes indeed that the
screen,
which gets rapidly clogged, will be regularly cleaned. These cleaning
operations
dictate the stopping of the production of treated water, and this reduces
productivity
and increases operating costs.
The Japanese patent applicant JP-A-55157333 describes a technique that
prevents the leakage of active particulate material in the treated water. This
technique
consists in introducing water for treatment into a tank. A lower part of a
porous
rotating cylinder containing ion-exchange resins effects a paddling action in
this tank.
CA 02780861 2012-05-14
3
The water to be treated enters the cylinder, cornes into contact with the ion-
exchange
ions which that are housed therein, then cornes out of the cylinder and is
collected,
while the ion-exchange resins remain inside the cylinder. The ion-exchange
ions are
extracted continuously from the cylinder in order to be regenerated and then
again
introduced continuously into the cylinder.
This technique has the advantage of preventing the leakage of ion-exchange
resins into the treated water and cancels out the drawbacks resulting
therefrom (such
as clogging of downstream filtering units, excess operating costs related to
the use of
fresh or regenerated active particulate material to compensate for the losses,
etc.).
This technique however has the drawback of limiting the efficiency of the
contact between the water to be treated and the ion-exchange resins because of
an
unsatisfactory stirring of the active, particulate material within the
cylinder. This
induces relatively lengthy treatment times. Increasing the speed of rotation
of the
cylinder could enable improvement of the contact between the water to be
treated and
the ion-exchange resins. The ion-exchange resins are however subject to the
attrition
phenomenon. In other words, these resins tend to get gradually used up when
they
are subjected to friction. Increasing the speed of rotation of the cylinder
would
therefore prompt a speedy deterioration of the resins.
3. Goals of the invention
The invention is aimed especially at mitigating these drawbacks of the prior
art.
More specifically, it is a goal of the invention to provide a technique for
potabilizing that includes at least one step for putting the water to be
treated in
contact with an active particulate material and a step for separating the
active
particulate material from a mixture of active particulate material and water,
which
makes it possible to both maximize the contact between the active particulate
material
and the water to be treated and prevent the losses of active particulate
material in the
treated water.
CA 02780861 2012-05-14
4
In particular, it is a goal of the present invention to procure, in at least
one
embodiment, a technique of this kind that enables the total separation of the
active
particulate material from the water treated.
It is another goal of the invention to implement, in at least one embodiment,
a
technique of this kind that makes it possible to ensure high stability of the
water
treatment process. In particular, the invention pursues the goal of
maintaining,
throughout the water treatment process, an appreciably constant concentration
of
active particulate material.
It is yet another goal of the invention to provide, in at least one embodiment
of
the invention, a technique of this kind that makes it possible to increase
productivity.
In particular, the invention aims to reduce idle times during which the
production of
the treated water is stopped.
The invention is also aimed at providing, in at least one embodiment, a
technique of this kind that makes it possible to lirait the degradation of the
active
particulate material, for example as beads or grains.
It is also a goal of the invention, in at least one embodiment, to procure a
technique of this kind that seeks to reduce the operating costs inherent in
potabilizing
or making water drinkable, especially by the absence of the use of coagulant
and/or
flocculent reagents.
It is yet another goal of the invention, in at least one embodiment, to
provide a
technique of this kind that is reliable and efficient, and bas a relatively
small impact
on the environment, especially because of the absence of the use of coagulant
and/or
flocculent reagents.
4. Summary of the invention
These goals, as well as others that shall appear here below, are attained
according to the invention by means of a method for treating water charged
with
pollutant matter with a view to potabilizing it and/or purifying it, said
method
comprising:
CA 02780861 2012-05-14
a step for eliminating consisting in putting said water charged with pollutant
matter into contact, within a stirred contact tank, with an active particulate
material according to a predetermined concentration of active particulate
material in said water;
5 - a step for extracting consisting in continuously extracting, from said
contact
tank, a mixture constituted by water and active particulate material;
a step for separating consisting in continuously separating said active
particulate material.
Said step for continuously separating consists in:
- introducing said mixture into a rotating filter drum,
- filtering said mixture through said rotating filter drum so as to trap said
active
particulate material inside said drum,
- recovering filtered water outside said drum, in its lower part, and, and
- discharging laid filtered water.
Said method also comprises steps for washing said rotating filter drum, said
steps for washing consisting in:
counter-current injecting of a constant given volume of filtered water under
pressure, forming wash water, on the external surface of an upper part of said
filter drum to detach the residues accumulated inside it, and,
- recovering said wash water and said residues inside said filter drum without
putting them into contact with said mixture introduced inside said filter
drum;
said steps for washing being implemented according to a predetermined cycle.
Said wash water and said residues recovered during said steps for washing are
stored momentarily in a recirculation tank, stirred and then sent back
essentially in
their totality into said contact tank so as to keep said predetermined
concentration in
active particulate material essentially constant in said contact tank.
Thus the invention relies on an original approach which, in a technique for
potabilizing or making water drinkable, including a putting of water to be
treated in
CA 02780861 2012-05-14
6
contact with an active particulate material, consists in separating the active
particulate
material from the treated water by means of a rotating filter drum.
As understood in the invention, a filter drum is a hollow element of a
generally cylindrical shape, the walls of which, demarcating its external
surface, are
at least partly porous. Stating that such a filtering drum has a generally
cylindrical
shape signifies that it is cylindrical or capable of being inscribed within a
cylinder.
The use of a stirred tank in which the water to be treated is put into contact
directly with active particulate material makes it possible to increase the
contact
between these two elements and improve the efficiency of the treatment while
at the
same time limiting its duration.
The fact of introducing the mixture of water to be treated and active
particulate material into said filtering drum makes it possible, when it is
put into
rotation, to integrally separate the active particulate material, which
remains trapped
inside the drum, from the treated water which flows outside the drum through
the
pores that pass through it.
The treated water collected at the outlet of the filtering drum is thus
totally
free of active particulate material. This contributes to preventing the
clogging of
filtering units which could be placed downstream so as to eliminate the
residual
turbidity of the treated water produced.
This technique therefore makes it possible both to improve the contact
between the water to be treated and the active particulate material and
prevent losses
of this material.
The washing of the drum makes it possible to recover the totality of the
active
particulate material whi le at the same time continuing the filtering of the
water
through the drum. This implementation therefore makes it possible to avoid
idle times
and increase productivity.
The mixture of wash water and active particulate material is recirculated
essentially in its totality in the stirred contact tank so that the
concentration in active
CA 02780861 2012-05-14
7
particulate material inside this tank is kept constant. This guarantees the
stability of
the treatment of the water and reduces the costs inherent in the consumption
of active
particulate material.
Furthermore, the cleaning of the drum with water under pressure does not
necessitate the use of cleaning solution. This limits the impact of the
potabilizing of
water on the environnent.
The washing of the drum is implemented according to a predetermined cycle.
The steps for washing can for example be implemented according to a
predetermined
frequency, or else whenever the maximum level of water in the daim is reached
or
again whenever the maximum threshold of clogging of the daim is reached or
again
in taking account of two or three of these items of information.
Said active particulate material preferably has a grain size of 20 micrometers
to 500 micrometers and advantageously a coefficient of uniformity of 1.0 to
1.5.
Preferably, the coefficient of uniformity will range from 1 to 1.2.
Preferably, said active particulate material has a grain size equal to 350
micrometers.
The coefficient of uniformity is equal to the ratio between the mesh aperture
size of a screen enabling the passage of 60% of particles of a given size and
the mesh
aperture size of a screen enabling the passage of 10% of said particles. The
Gloser the
coefficient of uniformity of an active particulate material is to 1, the
greater the extent
to which this material is monodispersed, i.e. the lower is the dispersion of
the size of
the particles that constitute it. Inversely, the greater the distance of the
coefficient of
uniformity of active particulate material from 1, the greater the extent to
which this
material is heterodispersed, i.e. the greater is the dispersion of the size of
the particles
that constitute it.
The fact, according to the invention, of using an active particulate material,
the coefficient of uniformity of which is from 1 to 1.5 and preferably from 1
to 1.2
makes it possible to ensure that the size of the particles that compose it
varies very
CA 02780861 2012-05-14
8
little. It is thus possible to use a filter drum with a higher cut-off
threshold. This
limits the clogging of the filter drum and reduces the frequency of the steps
for
cleaning it.
The fact of using an active particulate material, for which the size of the
particles is greater than or equal to 20 micrometers make it possible to
ensure a
gravitational filtering of the mixture of water and active particulate
material through
the filter drum. This makes it possible to avert the use of a pump to force
this mixture
to go through the pores of the filter drum.
According to an advantageous characteristic, a method according to the
invention comprises purges of saturated active particulate material from said
recirculation tank in order to eliminate them or regenerate them and inputs of
supplements of fresh and/or regenerated active particulate material in said
contact
tank, the quantities of said purges being essentially identical to the
quantities of fresh
and/or regenerated active particulate material.
When the active particulate material is saturated, it is no longer efficacious
so
that it has to be replaced by a fresh and/or regenerated active particulate
material. The
saturated active particulate material is then extracted from the recirculated
tank, and
then an equal quantity of fresh and/or regenerated active particulate material
is
injected into the stirred contact tank. This makes it possible to preserve a
constant
concentration in active particulate material inside the stirred contact tank
and thus
ensure the stability of the treatment.
Fresh active particulate material is material that has never been used.
Regenerated active particulate material is material that has already been used
to treat
water and, after that, has been reactivated so as to recover, in great part,
its original
active properties.
Preferably, the purges of active particulate material consist in continuously
extracting a small quantity of saturated or non-saturated active particulate
material
from the recirculation tank. At the same time, an identical quantity of fresh
and/or
CA 02780861 2012-05-14
9
regenerated material is introduced into the contact tank. The quantities
brought into
play depend on the operating conditions.
According to a preferred characteristic, a method according to the invention
comprises a step of in-situ regeneration of said saturated active particulate
material.
Certain saturated active particulate materials can be regenerated directly
within the installation used to implement the method. They are for example ion-
exchange resins. The method then comprises a corresponding step for
regenerating.
The différent types of regeneration implemented are proper to each
regenerable active particulate material and are well known to those skilled in
the art.
If the active particulate material is an ion-exchange resin, the regeneration
could for
example consist of a co-current regeneration, or a counter-current
regeneration.
Certain regeneration techniques are fairly complex so that they cannot be
implemented directly within the method according to the invention.
If the active particulate material is active carbon, the regeneration could be
implemented off site.
Other active particulate materials as well as other regeneration techniques
can
of course be implemented.
In this case, said fresh and/or regenerated active particulate material input
into
said contact tank during said input step cornes from said step of in-situ
regeneration
of said saturated active particulate material.
Preferably, said discharged filtered water then undergoes a final filtering
step
aimed at reducing its residual turbidity.
Said final filtering is advantageously a classic filtering on a granular
filtering
medium such as sand.
Its implementation significantly reduces turbidity and possible fines
resulting
from the attrition of the beads or grains of active particulate material.
Said final filtering is advantageously a membrane filtration
In this case, said membrane filtration is an ultrafiltration.
CA 02780861 2012-05-14
Its implementation significantly or even totally reduces turbidity, viruses,
bacteria and possible fines resulting from the attrition of the grains or
beads of active
particulate material.
5. List of figures
5 Other features and advantages of the invention shall appear more clearly
from
the following description of preferred embodiments, given by way of simple
illustratory and non-restrictive examples and from the appended drawings, of
which:
- Figure 1 illustrates an installation for implementing a method according to
the
invention implementing an active particulate material regenerable in situ;
10 - Figure 2 illustrates an installation for implementing a method according
to the
invention implementing an active particulate material non-regenerable in situ
;
Figures 3 and 4 illustrate a variant of a filter drum implementing one of the
filtering disks.
6. Description of one embodiment of the invention
6.1 Reminder of the principle of the invention
The general principle of the invention consists, in a potabilization and/or
purification technique in which water to be treated is put into contact with
an active
particulate material, in separating the active particulate material from the
water
treated by means of a rotary filter drum.
The fact of putting the water to be treated into direct contact with active
particulate material in a stirred tank makes it possible to improve the
efficiency of the
treatment while at the same time limiting its duration.
The implementing of a filter drum enables the total separation of the active
particulate material, which remains trapped inside the drum, from the treated
water
which flows outside the drum through the pores that pass through it.
This prevents the loss of active particulate material in the treated water and
the
clogging of the filtering units which can be placed downstream.
CA 02780861 2012-05-14
11
The washings of the drum consists of the counter-current injection of filtered
water under pressure, forming wash-water, on the external surface of an upper
part of
said filter drum to detach the residues that have collected inside it, and to
recover said
wash-water and said residues inside said filtering daim without placing them
in
contact with said mixture introduced into the interior of said filter drum.
These
washings there do not require the stopping of production, and this averts idle
times
and increases productivity.
Furthermore, these washing operations enable the recovery of the totality of
the active particulate material. The mixture of wash water and active
particulate
material is then recirculated essentially in its totality, i.e. almost
totally, in the stirred
contact tank so that the concentration in active particulate material inside
this tank is
kept constant. This ensures the stability of the treatment of the water and
reduces the
costs inherent in the consumption of active particulate material.
In addition, the cleaning of the drum with water under pressure does not
necessitate the use of cleansing solution. This limits the impact on the
environment of
the potabilizing of the water.
6.2 Example of an installation according to the invention
6.2.1 Case of an active particulate material regenerable in situ
Referring to figure 1, we present an embodiment of a water treatment
installation according to the invention.
Such an installation comprises a piping 1 for the intake of water to be
treated.
This piping opens into a contact tank 2, housing a stirring means 3, for
example a
stirrer within which the water to be treated is put into contact with an
active
particulate material 19 regenerable in situ.
The contact tank 2 has an outlet connected to a piping 20 which opens into a
filter drum 4.
The filter drum 4 has the shape of a hollow cylinder, the external surface of
which is porous. In this embodiment, the external surface of the filter drum
is
CA 02780861 2012-05-14
12
constituted by a screen. The diameter of the pores of the screen are chosen so
that
they make it possible to retain the active particulate material with which the
water to
be treated is put into contact.
The filter drum 4 is mounted rotationally inside a chamber 5. A motor 6 is
capable of driving the filter drum 4 in rotation.
A chute 9 is housed inside the filter drum 4 in an upper part of it.
A water injection bar 7 comprising nozzles is housed outside the filter drum 4
in proximity to its external surface. It approximately faces the chute 9.
The injection bar 7 is connected to the bottom of the chamber 5 containing
treated water 21 by a piping on which there is mounted a pump 8. Control means
(not
shown) make it possible to activate the pump 8 according to an adjustable
predetermined frequency. In this case, a wash cycle of the drum could be
implemented according to a predetermined frequency.
In one variant, an installation according to the invention could include an
"all-
or-nothing sensor" comprising two electrodes placed at the entry to the drum.
The
resistance between these two electrodes could be measured in order to
determine
whether the maximum of water in the drum, defined by the height of the sensor,
has
been reached. A wash cycle of the drum could, in this case, be triggered each
time
that the maximum level of water in the drum is reached.
According to yet another variant, an installation according to the invention
could comprise a piezoelectric type analog sensor to determine the level of
clogging
of the drum. A wash cycle of the drum could in this case be triggered each
time that a
maximum threshold of clogging of the drum is reached.
The chute 9 is connected by means of a piping 9 to a recirculation tank 10
housing a stirring means 11, for example a stirrer.
A recirculation piping 12 connects the recirculation tank 10 to the contact
tank
2.
CA 02780861 2012-05-14
13
A piping for extracting saturated active particulate material 13 connects the
recirculation tank 10 to a regeneration unit 15.
The regeneration unit 15 is connected to the contact tank 2 by means of a
piping for regenerated active particulate material 14.
The bottom of the chamber 5 has an outlet for discharging treated water which
is connected via a piping 17 to a filtering unit 16.
The filtering unit 16 has an outlet connected to a piping for discharging
treated and filtered water 18.
6.2.2 Case of an active particulate material non-regenerable in situ
Figure 2 illustrates a variant of a treatment installation according to the
invention that is to be implemented when the active particulate material
injected
inside the contact tank 2 is not regenerable in situ.
In this case, no regeneration unit is implemented in situ. The piping 13 for
extracting saturated active particulate material 13 then opens into a zone for
elimination or treatment ex-situ. The plant then comprises a piping 14' of
fresh or
regenerated active particulate material which opens into the contact tank 2.
6.2.3 Variant
Figures 3 and 4 illustrate a variant of a filter drum according to the
invention.
According to this variant the filter drum comprises a tube 31, the surface of
which is traversed by perforations 32 distributed so that they form rings that
are
distant from one another around the periphery of the tube 31.
Disk portions 35 are attached all around certain of the rings to form filter
disks
36 which are fixedly joined to the tube 31. Each of the disk portions 35
constitutes a
frame that houses filtering elements 37. In this way, water introduced into
the tube 31
flows through the perforations 32 up to the disk portions 35 and exits
therefrom while
the impurities that it contained remain trapped in the filtering elements 37
that they
bear.
CA 02780861 2012-05-14
14
Water injection bars 38 are placed in proximity to the external surface of the
disks 35, in an upper part of the filter drum.
In this embodiment, the filter disks 36 show a polygonal type external
outline.
The injection bars are mounted so as to be rotationally mobile along an axis
parallel
to the axis of rotation of the drum. They can thus be driven by a to-and-fro
motion
synchronized with the rotation of the disks 36 in order to cover the total
surface area
of the disk portion 35.
A chute 9 is housed inside the filter drum beneath the injection bars 38.
6.3 Example of a method according to the invention
6.3.1 Case of an active particulate material regenerable in situ
A method of treatment according to the invention is now described with
reference to figure 1.
A given volume of water to be treated in order to be potabilized,
preliminarily
decanted, is introduced continuously into the contact tank 2 by means of the
piping 1.
The water is mixed therein by means of stirring means 3 with an active
particulate
material regenerable in situ according to a given concentration. The fact that
the
concentration in active particulate material in the contact tank 2 is
essentially constant
provides for better stability and a better control over the treatment of the
water. The
water to be treated then undergoes a step for eliminating in which the target
pollutant
or pollutants are eliminated.
In this embodiment, the active particulate material is constituted by ion-
exchange resins 19 having a grain size equal to 350 micrometers and a
coefficient of
uniformity equal to 1.2.
The mixture of water and ion-exchange resins contained in the contact tank 2
is introduced into the filter drum 4, essentially beneath its axis of
rotation, by means
of the piping 20.
The size of the pores of the screen of the filter drum 4 is chosen so that it
makes it possible to retain the totality of active particulate material. The
filter drum 4,
CA 02780861 2012-05-14
driven by a rotational motion by means of the motor 6, therefore makes it
possible to
filter this mixture and separate the water and the ion-exchange resins.
The ion-exchange resins are trapped by the screen of the filtering drum 4 and
remain inside it, white the treated water 21, free of active particulate
material, flows
5 through the pores of the screen into the bottom of the chamber 5.
The treated water 21 is conveyed via the piping 17 into a filtering unit 16 so
as
to reduce its residual turbidity. The treated and filtered water is then
discharged via
the piping 18.
The filtering unit 16 is a membrane filtering unit, for example of the
10 ultrafiltration type. Its use enables the significant and even the total
reduction of the
turbidity, the viruses, the bacteria and possible fines resulting from the
attrition of the
ion-exchange resins.
In one variant, the filtering unit could be a unit for filtering on media,
such as
for example sand. Its use enables the significant reduction of the turbidity
and
15 possible fines resulting from the attrition of the ion-exchange resins.
As and when the mixture of water and ion-exchange resins is filtered into the
filtering drum 4, this drum is clogged by the ion-exchange resins. At the end
of each
treatment cycle, a washing step is implemented. As understood in the
invention, a
treatment cycle starts as soon a given volume of water to be treated is
introduced into
the contact tank 2, and finishes as soon as the given volume of water to be
treated has
undergone an elimination in the contact tank 2; and then a filtering in the
filter drum
4. In this embodiment, the steps for washing are activated according to a
predetermined frequency corresponding approximately to the duration of a
cycle. In
one variant, they could be activated each time that the maximum level of water
that
could be present in the filtering drum is reached or as soon as a
predetermined
threshold of maximum clogging of the drum is reached.
Such a step of washing consists in injecting, under pressure, a constant
volume of treated water 21 in a counter current to the externat surface of the
filter
CA 02780861 2012-05-14
16
drum 4. To this end, the pump 8 is implemented so as to draw treated water 21
from
the bottom of the chamber 5 and infect it via bar the 7 on to the external
surface of the
filter drum 4. The ion-exchange resins that have collected on the inner
surface of the
filter drum 4 gets detached from it. A mixture of wash water and ion-exchange
resins
gets shed into the chute 9. It is therefore not put into contact with the
mixture of water
and active particulate material introduced into the filter drum 4 via the
piping 20.
At the end of the washing step, the totality of the ion-exchange resins which
had collected inside the filter drum 4 during the treatment cycle have got
detached
from it.
The mixture of wash water and ion-exchange resins gets shed from the chute 9
into the recirculation tank 10.
The concentration in ion-exchange resins in the contact tank 2 is constant. A
new washing step is triggered after each treatment cycle, i.e.; after a
constant given
volume of water has been treated. The quantity of water used during each
washing
step is constant. A washing enables the recovery of the totality of the ion-
exchange
resins trapped in the filter drum 4 during a treatment cycle. The
concentration of ion-
exchange resins in the recirculation tank 10 is therefore constant.
The mixture of wash water and ion-exchange resins contained in the
recirculation tank 10 at the end of the washing is essentially, in its
totality, reinjected
into the contact tank 2 throughout the following treatment cycle.
It must be noted that a new treatment cycle is implemented at the beginning of
each washing step. Indeed, the mixture of water and ion-exchange resins is
filtered at
the bottom of the filter drum 4 while its washing is done at its top part. In
other
words, the production of water is not stopped during the steps for washing.
Besides,
the fact that the drum is essentially cylindrical and rotary improves the
efficiency of
the washing and therefore reduces its duration and the quantity of water
needed to
implement it. The washing therefore gives rise to no addition or any loss of
water.
CA 02780861 2012-05-14
17
The saturated ion-exchange resins contained in the recirculation tank 10 are
extracted therefrom by the implementation of purges by means of the piping 13.
These saturated ion-exchange resins conveyed into the regeneration unit 15 in
order
to be regenerated.
The ion-exchange resins can for example be regenerated within the
regeneration unit 15 in the following way.
The regeneration unit 15 comprises a accumulation tank (not shown) in which
the saturated ion-exchange resins are conveyed from the recirculation tank 10.
The
accumulation tank comprises, at its base, a filtering screen. The ion-exchange
resins
therein are stored, concentrated and collected in the course of time
(filtering of the
interstitial water through the filtering screen to concentrate the exchanging
resins).
After a duration predetermined by the operator, corresponding to the
accumulation of a known quantity of ion-exchange resins, the mixture of water
and
resins, which is concentrated, is oriented towards a reaction tank; also
equipped with
a filtering screen in its lower part.
The regeneration of the ion-exchange resins proper is then initiated.
At an initial stage, the volume (or bed) of accumulated ion-exchange resins is
measured.
At a second stage, a regeneration solution is introduced into the reaction
tank.
The inj ected volume of regeneration solution is generally a function of the
volume of
ion-exchange resins to be regenerated. The regeneration solution is prepared
prior to
the regeneration step within a preparation tank (preparation done to the
desired
concentration using water from the mains supply and a concentrated
regeneration
solution).
A percolation of the regeneration solution through the bed of ion-exchange
resins then takes place at a fixed flow rate.
Used brine is then drawn from the reaction tank and discharged towards the
drains or kept in order to be re-utilized.
CA 02780861 2012-05-14
18
The ion-exchange resins are then rinsed with water from the mains supply
with this water being percolated through the bed of resins at a fixed flow
rate.
The rinsing water is drawn off and discharged towards a subsequent
appropriate treatment.
The regenerated ion-exchange resins are then recovered. The are mixed with
water from the mains supply so as to form a slurry. A certain quantity of
fresh ion-
exchange resins can be integrated into the barbotine.
The regenerated ion-exchange resins in barbotine form coming from the
regeneration unit 15 are injected into the contact tank 2 through the piping
14. The
quantity of saturated ion-exchange resins extracted from the recirculation
tank 10 is
appreciably equal to the quantity of regenerated ion-exchange resins
introduced into
the contact tank 2 via the piping 14. Thus, the concentration of ion-exchange
resins
within the contact tank 2 is kept constant.
The washing of the drum is obtained efficiently without addition of any
chemical washing product. Besides, the treatment of the water does not
necessitate
the use of coagulant. Furthermore, the fact of implementing a filtering drum
averts
the implementation of a decantation step which most often makes it necessary
to
inject polymer into the mixture of water and active particulate material in
order to
facilitate its decantation. The technique according to the invention therefore
has a
limited impact on the environment.
The prior art separation techniques most often require that the active
particulate material be concentrated in the collecting tank after it has been
separated
from the treated water and then reinjected into the contact tank. According to
the
invention, the implementation of the filtering drum makes it possible to
directly
obtain a mixture of wash water and active particulate material that is highly
concentrated in active particulate material (approximately between 200ml and
500 ml
of active particulate material per liter of mixture). The invention therefore
forestalls
CA 02780861 2012-05-14
19
the implementing of a step of concentration, thus making it possible to reduce
the
duration of treatment and increase productivity.
6.3.2 Case of an active particulate material non-regenerable in situ
A method of treatment according to the invention is now described with
reference to figure 2.
Only the différences between the method described with reference to figure 1
and the method described with reference to figure 2 are described here below.
In this embodiment, the active particulate material implemented is not
regenerable in situ. It is constituted by granular activated carbon (GAC).
In this case the saturated GAC contained in the recirculation tank 10 is
extracted from it by the implementing of the purges by means of the piping 13.
This
saturated CAG is conveyed towards an ex-situ treatment zone, i.e. situated
outside the
plant used to implement the method. Fresh GAC is injected into the contact
tank 2
via the piping 14. The quantity of saturated GAC extracted from the
recirculation
tank 10 is appreciably equal to the quantity of fresh GAC introduced into the
contact
tank 2 via the piping 14. Thus, the concentration in GAC inside the contact
tank 2 is
kept constant.
6.3.3 Variant
Différent types of adsorbent particulate materials, regenerable or non-
regenerable in situ, can be implemented such as, for example, ion-exchange
resins,
CAG, PAC (powdered activated carbon), composite particles etc.
The methods described with reference to figures 1 and 2 can be implemented
within an installation in which the filter drum comprising a screen could be
replaced
by a filter drum such as the one described here above with reference to
figures 3 and
4.
In this case, the washing of the drum consists in injecting treated water in a
counter current against the external surface of the disks 36 by means of the
bars 38.
CA 02780861 2012-05-14
The mixture of wash water and active particulate material is then collected in
the
chute 9.
The techniques according to the invention which have been described can be
implemented to treat water to potabilize it and/or to purify it.
