COAGULATION/FLOCCULATION APPARATUS FOR THE TREATMENT OF
A HYDRAULIC FLOW, AND IMPLEMENTATION PROCESS
The invention relates to an apparatus that makes it
5 possible to carry out a coagulation/flocculation that
precedes a phase of physical separation by flotation or
by filtration or through membranes with a view to water
clarification (removal of particles or colloids in
suspension) .
10
The invention is more especially adapted to
clarification via flotation which does not require
flocks (aggregates of particles) to be produced that
are as dense and as large as those required by
15 settling.
The field of application is that of the clarification
of surface waters, subterranean waters, seawaters,
waste waters and industrial waters, rainwaters and
20 generally all types of water or liquid suspensions
suitable for flotation, or even for filtration or
separation through membranes which require the same
type of flocks as flotation.
25 Apparatuses of this type are known, in particular from
French patent FR 2835247 or patent EP 1 483 210 B1
filed in the name of the company DEGREMONT.
In order to clarify water, it is necessary to form a
30 flock or agglomerate of neutralized colloids or
particles. This flock will then be able to be separated
from the liquid phase either by settling by virtue of
its settling velocity, or by flotation, following the
binding thereto of microbubbles, by virtue of its
35 upflow velocity. For a person skilled in the art,
flotation is reserved for lightly polluted waters
generally having pollution loadings of less than 30 NTU
or 30 g/m3 of suspended matter.
In order to form a flock, it is necessary to carry out
a coagulation and then a flocculation. Coagulation
consists of an addition of reactant, the coagulant (in
5 general trivalent cations), in particular iron or
aluminum salts, enabling the destabilization of the
colloidal particles present in the water and the
neutralization of all the electronegative charges on
these particles. During this step, the neutralized
10 particles begin to agglomerate in order to form
microflocks. These microflocks are too small to settle
and even too small to hook microbubbles.
Flocculation, which follows coagulation, is a step
15 intended to enlarge the flocks. During this step, a
flocculation aid (polymer, generally synthetic polymer)
is often injected in order to make the flocks larger
and denser. This injection of polymer is quasisystematic
for settling tanks and, under a few
20 particular conditions, for flotation units.
In order to be physically separated from the water by
settling, a flock must be dense and preferably of large
size. Curiversely, in order to be separated by
25 flotation, it is sufficient for said flock to be well
formed: it must be light and may be of small or large
size.
The coagulation/flocculation phases are carried out for
30 almost all cases in reactors of the same type for
settling and flotation.
For settling, use is generally made of:
- a coagulator having a residence time of around 1
35 minute with a high energy per unit volume (50 to
200 w/m3),
- a 1- or 2-stage (sometimes 3-stage) flocculator,
these stages being stirred by impellers with a high
axial component and at relatively slow speed for
overall residence times of between 15 and 30 minutes.
Some more sophisticated flocculators are stirred by
impellers that are jacketed and/or equipped with a
5 recirculation of natural ballast (sludge) or added
ballast (ballast or sand). In the last case, the
residence times may be shorter: 6 to 12 minutes. In
order to obtain flocks having a high settling velocity
that make it possible to reduce the cross section of
10 the settling zone, polymer is injected at the top of
the flocculator.
Flocculation referred to as static flocculation, that
is to say without a stirring member (tank with
15 deflectors or baffles) has been used in the past ahead
of very slow velocity settling tanks before the
appearance of synthetic polymers.
The actual settling tank may be static or equipped with
20 a plate in order to reduce the settling cross section.
The settled sludges are discharged via the bottom with
or without the use of a scraper or a hopper when the
clarified water is discharged at the surface.
25 For the flotation, in most cases the same
coagulators/flocculators are found:
- a coagulator having a residence time generally of
less than or equal to 1 minute with a high energy per
unit volume (50 to 200 w/m3)
30 - a 1- or 2-stage flocculator, these stages being
stirred by impellers with a high axial component and at
relatively slow speed, or even very slow speed for
overall residence times between 15 and 30 minutes. Some
more sophisticated flocculators comprise, as in the
35 case of settling tanks, jacketed impellers. In the last
case, the residence times are sometimes reduced and
become: 15 to 20 minutes. The injection of polymer is
not necessary in flotation except in cases of highly
loaded or very cold waters.
- An actual flotation unit at the head of which the
flocculated water is mixed with an emulsion of microbubbles
of gas, generally of air, which attach to the
5 flocks and make them rise to the surface where they are
collected and discharged whilst the clarified water is
discharged through the bottom of the flotation
apparatus.
10 It is therefore seen that the coagulation/flocculation
phases are carried out in almost all cases in reactors
of the same type and practically of the same volume
irrespective of the separation, settling or flotation
technology. However, the quality desired for the flocks
15 is not the same.
The objective of the invention is above all to propose
a coagulation/flocculation apparatus suitable for a
type of physical separation other than settling, in
20 particular separation by flotation or by filtration or
through membranes, which makes it possible to reduce
the overall coagulation/flocculation residence time, to
improve the performances and to increase in particular
the field of appiication of separation by flotation.
25
According to the invention, a coagulation/flocculation
apparatus for the treatment of a hydraulic flow of any
type of liquid, upstream of a physical separation
element, in particular upstream of a flotation unit, or
30 of a filtration unit, in particular a membrane
filtration unit, which apparatus comprises at least one
coagulator with injection of coagulant, followed by a
flocculator, which are successively passed through by
the hydraulic flow, is characterized in that:
35 - the coagulator comprises a reactor for injection
of coagulation under high energy, followed by a lowenergy
coagulation reactor,
- a high-energy intermediate element is positioned
between the coagulation reactor and the flocculator,
- and the flocculator is a static flocculator of
plug-f low type.
5 The static flocculator of plug-flow type may be the
same width as the physical separation element located
downstream.
Advantageously, the static flocculator of plug-flow
10 type is a baffle flocculator.
The high-energy coagulant injection reactor may be
separated from the coagulation reactor. The coagulant
injection reactor may be at an energy between 40 and
15 10 000 w/m3. The coagulant injection reactor may be an
in-line mixer with an energy per unit volume of between
200 and 10 000 w/m3. As a variant, the coagulant
injection reactor may consist of at least one stirred
tank reactor having an energy per unit volume of
20 between 40 and 250 w/m3, or preferably two stirred tank
reactors in series, having an energy per unit volume of
between 40 and 250 w/m3.
--.C.- ~ . - , L ~ - rreLerduly, ihe coagulation reactor has an energy per
25 unit volume of less than 10 w/m3.
Advantageously, the high-energy intermediate element
induces an energy per unit volume of greater than
20 w/m3 in the upper zone of the plug-flow flocculator,
30 in particular an energy between 20 and 100 w/m3. The
high-energy intermediate element may consist of a weir
having a fall head of at least 5 cm. Generally, the
weir has a fall head of less than or equal to 25 cm.
35 In practice, the plug-flow flocculator is at an energy
per unit volume of less than 1 w/m3, preferably less
than 0.3 w/m3.
The invention also relates to a process for
implementing a coagulation/fl.occulation apparatus as
defined previously, for the treatment of a hydraulic
flow of any type of liquid, characterized in that the
5 residence time in the low-energy coagulation reactor is
less than 1 minute. The residence time in the plug-flow
type flocculation reactor is preferably between 2 and 8
minutes. The residence time in the coagulant injection
reactor, in the case of a stirred tank reactor, is
10 between 2 and 6 minutes, depending on the type of water
to be treated.
Thus, in order to produce a coagulation/flocculation
apparatus that is compact and performs well in
15 flotation, the invention proposes to combine the
following reactors or pieces of equipment:
- a high-energy coagulant injection reactor,
- a low-energy coagulation reactor (not stirred),
- a high-energy component (weir) over the entire
20 width of the flocculator,
- a static flocculator of plug-flow type having the
same width as the separator or the flotation unit from
which the clarified water and the sludges originate.
25 The results obtained owing to this combination of
components are surprising. The overall residence time
of the flocculation (3 to 8 minutes), and the overall
time of the coagulation/flocculation (4 to 12 minutes)
are very significantly reduced with respect to the
30 times of conventional coagulation/flocculation (16 to
31 minutes). Furthermore, the use of plug-flow
flocculation compared t o stirred (impeller)
flocculation has surprisingly made it possible to treat
polluted waters up to 200 or 300NTU whereas
35 conventionally the limit is around 30 NTU.
The invention consists, apart from the provisions as
set out above, of a certain number of other provisions
of which mention will be made more explicitly below
with regard to examples described with reference to the
appended drawings, but which are in no way limiting. In
these drawings:
5
Fig. 1 is a vertical schematic cross section of a
coagulation/flocculation apparatus according to the
invention, followed by a flotation unit.
10 Fig. 2 is a schematic top view of the assembly from
Fig. 1.
Fig. 3 is a vertical schematic cross section of a
variant of the coagulation/f1occulation apparatus, with
15 a variant for the flotation unit.
Fig. 4 is a schematic top view of the assembly from
Fig. 3, and
20 Fig. 5 is a graph comparing the performances of
various flocculators for the removal of phosphorus.
The coagulation/flocculation apparatus of the invention
dpplies Lo driy iype oi iloLdiiori ur~ii, cor~veriiioridi or
25 rapid. It is preferably compatible with flotation units
of rectangular cross section.
As illustrated in Fig. 1 and 2, the raw water arrives,
via a channel or a pipe, in a coagulant injection
30 reactor 1. Depending on the applications, the coagulant
a is injected either inline via a static mixer (not
represented), or into the high-energy coagulant
injection reactor 1, in any case greater than 40 w/m3,
In the latter case, specific amongst others to surface
35 waters and seawaters, the residence time in this
reactor is at least equal to 2 minutes. This is a
desired time for the invention (a condition for a
floated water of quality), whereas the times generally
observed in this phase are less than or around 1
minute.
Preferably, the coagulant injection reactor 1 is at an
5 energy of greater than 40 w/rn3, in particular between
40 w/m3 and 250 w/m3 for a stirred tank reactor and
between 200 w/m3 and 10 000 w/m3 in the case of in-line
mixers. On leaving this reactor, most of the colloids
are neutralized and microflocks appear. The energy or
10 power per unit volume corresponds to that dissipated by
stirring means, such as impellers, installed in the
reactor or in-line mixers.
The water undergoing coagulation arrives in a low-
15 energy coagulation reactor 2, preferably having an
energy of less than 10 w/rn3, where the microflocks
continue to appear and agglomerate. The objective is to
have microflocks which begin to be visible to the naked
eye. The residence time in this reactor 2 is less than
20 1 min. The coagulation reactor 2 is separate from the
coagulant injection reactor 1, these reactors in
particular being made in the form of separate basins or
tanks. The coagulation reactor 2 constitutes a transfer
zor~e betwee11 Li~e cudguldnt injection reactor 1 and a
25 plug-flow flocculator 4.
At the top of the reactor 2, a weir 3 with a fall of
water having a head advantageously between 5 and 25 cm,
is positioned over the entire width of the plug-flow
30 flocculator 4. A high-energy zone, created by the weir
3, which follows the low-energy zone of the reactor 2,
is surprising for a person skilled in the art who
normally positions reactors with decreasing energies
after the maximum energy coagulation reactor so as not
35 to destroy the flocks already formed.
Unexpectedly, the weir 3 downstream of the low-energy
reactor 2 allows hydraulic and process advances
relative to the plug-flow flocculator that follows it.
As a variant, a perforated tube could be installed
instead of the weir 3.
5 The energy generated by the weir 3 (greater than
20 w/m3) will advantageously be used to ensure the
mixing of the polymer should it prove necessary. If the
flock is broken, it will be reformed under the action
of the polymer. However, surprisingly, it has been
10 possible to observe that even without polymer the weir
3 did not cause degradation but on the contrary it
improved the quality of the treated water (see example
2 provided below). Two explanations are proposed. The
first is that the microflocks are not yet large enough
15 to be destroyed but are small enough to benefit from
this energy which will increase their probability of
meeting in this zone and therefore their chance of
agglomerating and getting bigger. The second is
revealed by measurement of dissolved oxygen. It has
20 been possible to observe that this weir increased the
amount of air dissolved in the water. Surface waters
are often not saturated in oxygen, and therefore the
microbubbles of air injected in order to make the
Clocks ilodi dre pdrily CVIISUI[L~b~y iiie u~isdtu~dted
25 water. This fall of water just before the flotation
therefore promotes the clarification by effective
increase of the active microbubbles.
The weir 3 also makes it possible to distribute the
30 hydraulic flow over the entire width of the plug-flow
flocculator 4. A good distribution over the entire
width of the flocculator is a condition favorable to
plug flow in the flocculator.
35 In conclusion, the weir 3 makes it possible to
distribute the hydraulic flow over the entire width of
the plug-flow flocculator 4, to inject, if necessary,
polymer without Adding a specific reactor, to dissolve
air thus leaving more active microbubbles and finally
preceded by a lov-energy reactor 2, the weir 3 promotes
the formation of microflocks.
5 The coagulated water now feeds in the top part, under
perfect conditions, the plug-flow flocculator 4.
It will be recalled that the object of flocculation, in
view of a physical separation in particular by
10 flotation, is to enlarge the flocks a minimum amount
without however densifying them as is sought to do in
settling. According to the invention, the plug-flow
flocculator 4, which constitutes a low-energy reactor,
is provided at an energy of less than 1 w/m3, generally
15 of less than 0.3 w/m3, with a distribution that is as
consistent as possible in order to avoid short circuits
and enable all the incoming flocks to have the same
residence time in order to thus have a uniform size on
leaving the flocculator. It is in this way that
20 installing the static flocculator 4 of plug-flow type
makes it possible to obtain very good performances with
very short residence times (3 to 8 minutes) depending
on the applications and the temperatures of the
effluent to be treated.
25
The static flocculator 4 of plug-flow type is
preferably a baffle reactor consisting of alternate
vertical plates 4a and 4b, which are parallel to the
weir 3 and to the low feed zone of the actual flotation
30 unit 5. The plates extend over the entire width of the
reactor. The plates 4a have their upper edge located
above the level of the water, whilst their lower edge
is at a distance from the floor so as to leave the
liquid only a lower passage. The plates 4b extend down
35 to the floor and stop below, at a distance from, the
level of the water so as to only allow the liquid an
upper passage. These plates restrict the flow to
successively carry out descending and ascending
movements in each of the cells 4c formed by the plates
4a and 4b.
The spaces between plates 4a and 4b and between the
5 high plates 4a and the floor, are such that the
hydraulic velocities are greater than the settling
velocities of the heaviest particles and thus the washout
velocities of the sludge formed by the flocks
settled on the floors of each cell 4c. The self-
10 cleaning thus limits deposits on the floors. The curved
profile 4d, concave towards the top, of the floors of
the cells further reduces the deposits and slightly
promotes plug flow.
15 On leaving the plug-flow flocculator 4, in the bottom
part, the velocities of approach of the flotation unit
5 are very low and perfectly homogenous. This is
without doubt what explains the astonishing results
obtained on the treatment of polluted waters. Indeed,
20 as will be apparent in the examples given below (see
example 3), the plug-flow flocculator makes it possible
to treat loaded effluents whilst the results are
greatly deteriorated when stirred flocculators (high
vel"u"cl cles and rutaiiv~~a~i~ t~vve~~a[r~ee ~u~siedj. It
25 should be specified that with polluted waters (above
all that are polluted with mineral materials) the
floated sludges are very delicate and therefore
sensitive to the turbulences which may make them fall.
30 In conclusion the baffle plug-flow static flocculator
4, fed homogeneously with homogeneous microflocks,
allows a very compact flocculation and a flotation unit
approach velocity that is consistent and very low.
35 The plug-flow static flocculator may have plates spaced
further and further apart in order to reduce the
flotation unit approach velocities.
The actual flotation unit 5 may be a conventional
flotation unit with velocities of between 6 and 15 m/h
in the flotation zone or a rapid flotation unit with
velocities of 20 to 60 m/h. The qualities and the
5 compactness of the coagulation/flocculation apparatus
of the invention further increase the current
competitiveness and attractiveness of rapid flotation
units. Water is supplied to the flotation unit, from
the flocculator 4, by a passage located in the bottom
10 part and that extends over the entire width.
The clarified water exits at 6 (Figs. 1 and 2),
generally in the bottom part. The sludges, recovered at
the surface of the flotation unit, are discharged at 7
15 (Figs. 1 and 2).
Figs. 3 and 4 show an embodiment variant of the
apparatus. The coagulant injection reactor consists of
two reactors in series (1.1 and 1.2, each at high
20 energy, with stirring impellers hl, h2. Advantageously,
each coagulant injection reactor 1.1 and 1.2 is at an
energy between 40 and 250 w/m3.
The coagulation reactor 2 2nd the plug-flow Elocculator
25 4 are similar to those from Figs. 1 and 2. The
flocculated raw water is conveyed through a feed
passage in a low zone 8 of the flotation unit 5a. ' ~ n
upflow is created with microbubbles produced by a
pressurization-expansion system comprising a pump 9
30 that recycles a fraction of the clarified water to a
pressurization vessel 10. The pressurized water is
injected and expanded by a nozzle 11 in the bottom
part. The mixing zone 8 is separated from the actual
flotation zone by an inclined weir 12 that starts from
35 the floor, leaning towards downstream and that stops at
a distance below the upper level of the water. The
suspended matter entrained by the ~nicrobubbles *
accumulates at the surface and is discharged downstream
by a transverse channel constituting the outlet 7 of
the sludges. The clarified water is discharged from a
downstream cell connected to the outlet 6 and to the
pump suction inlet 9.
5
Examples
Several series of tests were carried out on various
types of water (tertiary treatment of residual waters,
10 treatment of seawater and treatment of polluted river
water) .
Depending on the case, the tests were carried out on
one or two mini industrial units (or pilot units)
15 placed in parallel.
The pilot units have a capacity of 24 m3/h and make it
possible to carry out the steps of coagulation,
flocculation and clarification by flotation (cross
20 section of the flotation unit 0.8 m2). These steps, or
the components of the pilot unit, are adjustable and
make it possible to change the treatment steps, to
install different types of reactors and to vary the
volumes of the reactors. The microbubbles are generated
25 by a pressure-expansion system comprising a
pressurization vessel at 5 bar connected to an
expansion system that ensures the formation of
microbubbles having a diameter of around 40 pm (40
micrometers). The recirculation ratio in the
30 pressurization is around 10%.
First series of tests
A first series of tests was carried out on a residual
35 water leaving a biological treatment in order to carry
out a final phosphorus removal .treatment (tertiary
treatment). The objective is to test various
flocculation reactors on a water having a relatively
constant turbidity and where the kinetics for the
removal of phosphorus are well controlled.
This water coagulates easily. The base version proved
5 effective: the coagulant is injected by a high-energy
in-line mixer, having an energy of at least 1000 W/m3,
the water to be treated then passes through the nonstirred
reactor equipped at its outlet with a weir,
then finally through the actual flocculation reactor
10 followed by the same flotation unit.
The flocculation reactors tested with their residence
time were:
a static reactor with deflectors, residence time 8
15 minutes,
stirred reactor, residence time 8 minutes (2 tanks in
series with impeller mixers),
static plug-flow reactor with baffles, residence times
successively 3, 4.5 and 7.5 minutes.
20
The characteristics of the raw water are:
turbidity of the raw water RW = 5 to 10 NTU
suspended matter in the raw water RW = 7 to 15 g/m3
total phosphorus raw water RW: between 0.5 and 7 y/m3
25 throughput treated: 24 m3/h
reactants: coagulant (FeC13) 50 9/m3, polymer = 0
The results were shown on the graph on Fig. 5. They
express the phosphorus in the floated water (ppm or
30 9/m3) shown on the ordinate, as a function of the
phosphorus of the raw water (ppm or g/m3), shown on the
abscissa, for the various types of reactors mentioned.
The best results, illustrated by the curve C1, are
35 obtained with the static plug-flow flocculation reactor
with baffles, according to the invention, whatever the
residence time greater than 3 minutes.
The stirred flocculator (8 minutes) gives results that
are quite close, illustrated by curve C2, but that are
more dispersed for a longer residence time.
5 The other static reactor with deflectors, therefore
that is not plug flow, gives worse results, illustrated
by the curve C3 (in this type of reactor the short
circuits are very significant). Furthermore, the bottom
sludges appear very quickly due to the absence of
10 bottom sweeping.
In conclusion, in this application the plug-flow
flocculator is used. It is believed that this plug-flow
flocculator reduces, or eliminates, the short circuits,
15 which favors the phosphorus removal reactions.
Second series of tests
A second series of tests xias carried out on seawater
20 and with the same pilot unit.
Seawater is more difficult to coagulate. The coagulant
is injected at the inlet of a coagulant injection
reactor, with a residence time of 3 minutes, folloried
25 by a zone without stirring of less than 1 minute that
forms the coagulation reactor, followed or not by a
weir (10 cm fall of water) and by the flocculation
reactor which is the one defined in the preceding
example with a flocculation time of 6 minutes.
30 The characteristics of the raw water are:
turbidity of the raw water RW = 1 to 15 NTU
throughput treated: 24 m3/h
reactants: coagulant (FeC13) 10 9/m3, polymer = 0
35 The configuration is satisfactory, but the test which
is of interest here is the impact or otherwise of the
weir on the quality of the floated water wherein no
polymer is injected into the weir.
The results are the following:
The test shows that the positive effect of the weir is
5 marked and unexpectedly assumes the turbidity as the
seawater incr'eases, here beyond around 3 NTU.
Under difficult flocculation conditions, the weir 3 has
a favorable effect on the clarification by flotation.
Seawater (NTU)
1.6
2
2.9
5
10 Third series of t e s t s
A third series of tests was carried out on river water
and on the same pilot unit. Applied to the treatment of
surface waters (river or subterranean waters) the
15 configuration has proved very efficient. The limitation
of the applications of flotation with respect to
settling stem from the fact that the flotation cannot
normally treat waters for which the turbidities are
greater than 30 NTU or even 50 NTU. The tests reported
20 here have the objective of confirming the best
flocculator for treating polluted waters (50 to
300 NTU). For these tests, the two pilot lines are
placed parallel.
Floated water (NTU)
25 The two technologies compared were:
- a stirred flocculation reactor: two flocculation
reactors in series (two tanks in series with impeller
stirrers) with 12 minutes of residence time,
without weir
0.7
0.9
1.5
2.
with weir
0.7
0.95
1.2
1.5
- a static plug-flow flocculation reactor with
baffles having a residence time of 5 minutes.
For the two configurations, the coagulant is injected
5 by an in-line mixer at the inlet of a coagulant
injection reactor having a residence time of 3 minutes
followed by a zone without stirring (constituting the
coagulation reactor 2) of less than 1 minute, by a weir
and by one of the two flocculation reactors. The
10 flotation unit is still the same and the throughput
applied to each of the two pilot lines is between 16
and 24 m3/h.
The characteristics of the tests are the following:
15 turbidity of the raw water RW = 10 to 250 NTU
(temperature 5 to 7°C)
throughput treated: 24 m3/h and reduced to 16 m3/h for
turbidities of greater than 100 NTU
reactants: coagulant (FeC13) 30 to 40 g/m3, polymer =
20 0.2 to 0.4 g/m3 depending on the turbidity of the raw
water (less than or greater than 50 NTU).
flocculator flocculator
Up to 50 NTU, the 2 types of flocculator have quite
similar performances. Beyond that, the turbidity of the
floated water is around 2 to 10 times greater than that
of the plug-flow flocculator. In conclusion, in order
5 to treat high turbidities by flotation, the energy-free
static plug-flow flocculator gives far superior
results. In addition the static plug-flow flocculator
is relatively less bulky, and it consumes less energy.
10 Other applications
- For.more delicate treatments (seawater, etc.) or
for polluted waters or for generally providing more
flexibility and effectiveness, it is possible to carry
15 out the coagulant injection step in two stirred
reactors 1.1 and 1.2 in series (Figs. 3 and 4) . This
makes it possible, for example, to shift the injection
of polymer into the second reactor instead of injecting
it into the weir 3. Furthermore, this configuration
20 makes it possible to carry out the double injection of
coagulant described in French patent No. 2 909 993 (06
10866 filed on 13/12/2006). A first injection of
coagulant into the coagulant injection reactor, the
25 reactor and the second injection of coagulant into the
weir 3.
- The coagulation/flocculation apparatus of the
invention could be used in front of a filter or
30 membranes where it is desired, as in front of a
flotation unit, to filter flocks formed that are light
and non-clogging (in particular without polymer).
- The coagulation/flocculation apparatus of the
35 invention could optionally be used before a settling
tank, on condition that the flocculation times are
adapted (longer), there is an objective to reduce the
energy consumed and finally it is accepted to work on
the settling tank at slower speeds (larger apparatus)
CLAIMS
1. A coagulation/flocculation apparatus for the
treatment of a hydraulic flow of any type of liquid,
5 upstream of a physical separation element, in
particular upstream of a flotation unit, or of a
filtration unit, in particular a membrane filtration
unit, which apparatus comprises at least one coagulator
with injection of coagulant, followed by a flocculator,
10 which are successively passed through by the hydraulic
flow, characterized in that:
- 'the coagulator comprises a high-energy coagulant
injection reactor (I), followed by a low-energy
coagulation reactor (2),
15 - a high-energy intermediate element (3) is
positioned between the coagulation reactor (2) and the
flocculator (4) ,
- and the flocculator is a static flocculator of
plug-flow type (4).
20
2. The apparatus as claimed in claim 1, characterized
in that the static flocculator of plug-flow type (4)
has the same width as the physical separation element
(5) located downstream.
2 5
3. The apparatus .as claimed in claim 1 or 2,
characterized in that the static flocculator of plugflow
type (4) is a baffle flocculator (4a, 4b).
30 4. The apparatus as claimed in one of claims 1 to 3,
characterized in that the high-energy coagulant
injection reactor (1) is separated from the coagulation
reactor (2) .
35 5. The apparatus as claimed in any one of the
preceding claims, characterized in that the coagulant
injection reactor (1) is at an energy between 40 and
10 000 w/m3.
6 . The apparatus as claimed in claim 5, characterized
in that the coagulant injection reactor (1) is an inline
mixer with an energy per unit volume of between
5 200 and 10 000 w/m3.
7. The apparatus as claimed in claim 5, characterized
in that the coagulant injection reactor (1) consists of
at least one stirred tank reactor having an energy per
10 unit volume of between 40 and 250 w/m3.
8. The apparatus as claimed in claim 7, characterized
in that the coagulant injection reactor (1) consists of
two stirred tank reactors in series (1.1 1.2) having
15 an energy per unit volume of between 40 and 250 w/m3.
9. The apparatus as claimed in any one of the
preceding claims, characterized in that the coagulation
reactor (2) has an energy per unit volume of less than
20 10 w/m3.
10. The apparatus as claimed in any one of the
preceding claims, characterized in that the high-energy
intermediate element (3) induces an energy per uiiit
25 volume of greater than 20 w/m3 in the upper zone of the
plug-flow flocculator ( 4 ) , in particular an energy
between 20 and 100 w/m3.
11. The apparatus as claimed in any one of the
30 preceding claims, characterized in that the high-energy
intermediate element consists of a weir (3) having a
fall head of at least 5 cm.
12. The apparatus as claimed in claim 11,
35 characterized in that the weir (3) has a fall head of
less than or equal to 25 cm.
13. The apparatus as claimed in any one of the
preceding claims, characterized in that the plug-flow
flocculator (4) is at an energy per unit volume of less
than 1 w/m3, preferably less than 0.3 w/m3.
5 14. A process for implementing a coagulation/floccul-
ation apparatus as claimed in any one of the
preceding claims, for the treatment of a hydraulic flow
of any type of liquid, characterized in that the
residence time in the low-energy coagulation reactor
10 (2) is less than 1 minute.
15. The process as claimed in claim 14, characterized
in that the residence time in the plug-flow type
floccu1.ation reactor (4) is between 2 and 8 minutes.
15
16. A process for implementing a coagulation/flocculation
apparatus as claimed in claim 6 or 7,
characterized in that the residence time in the
coagulant injection reactor (I), in the case of a
20 stirred tank reactor, is between 2 and 6 minutes,
depending on the type of water to be treated.
Dated this July 02, 2014
[RANJNA h4EHTA-DUTT]
01' REMFRY & SAGAR
ATTORNEY FOR THE API'J,ICAN'T[S]