WO2021020125A1 - Flocculation processing device - Google Patents

Abstract

According to the present invention, an inorganic flocculant is added to a first flocculation tank 3 by a first chemical injection device 4, and an organic flocculant is added to a second flocculation tank 5 by a second chemical injection device 6. A detection signal from a flocculation state monitoring sensor 10 is input to a controller 8, and the chemical injection devices 4, 6 are controlled. The flocculation state monitoring sensor 10 includes: a light emitting unit which irradiates a flocculation treated liquid with laser light; and a light receiving unit which has a light receiving optical axis orthogonal to a light emission optical axis of the light emitting unit, wherein the particle diameter distribution of particles in the second flocculation tank 5 is obtained from a temporal change of a scattered light intensity signal.

Description

Coagulation processing equipment

The present invention relates to a coagulation treatment apparatus used for coagulation treatment of various industrial wastewaters, industrial water, sludge, etc., and in particular, a coagulation treatment in which an inorganic coagulant is added to raw water or sludge and then a polymer coagulant is added. The present invention relates to a suitable coagulation treatment apparatus.

When performing agglomeration treatment to remove turbid substances and organic substances from various wastewaters and irrigation water, an inorganic flocculant such as iron chloride or polyaluminum chloride may be used in combination with a polymer flocculant. By using these two types of chemicals, the coagulation flocs become coarse and the solid-liquid separation operation in the subsequent stage becomes easy, and the amount of sludge generated can be reduced by suppressing the addition amount of the inorganic coagulant.

In addition, when dewatering sludge generated by biological treatment of wastewater, an inorganic coagulant such as iron chloride or polyaluminum chloride and an organic polymer coagulant may be used in combination to coagulate the sludge prior to the dehydration treatment. .. By using the inorganic flocculant and the polymer flocculant together in this way, the sludge is efficiently charge-neutralized and the floc strength is improved, so that the water content of the sludge (dehydrated cake) after the dehydration treatment can be increased. It can be greatly reduced.

It is necessary to add an appropriate amount of coagulant according to the quality of the water to be treated and the properties of the sludge to be treated. In the coagulation treatment of wastewater and irrigation water, if the amount of chemicals added (injection amount) is insufficient, the removal of turbid substances and organic substances contained in the water to be treated becomes insufficient, and the quality of the treated water deteriorates. On the other hand, if the amount of chemicals added is excessive, the chemicals may leak to the subsequent stage, causing an increase in load and contamination in the subsequent stage treatment.

Further, in sludge treatment, if the amount of chemicals added is insufficient, the charge neutralization of the sludge becomes insufficient, the floc strength decreases, the water content of the dehydrated cake increases, and the sludge leaks into the dehydrated separation liquid. There were times when it happened. On the other hand, even when the amount of the chemical added is excessive, the floc strength is lowered, so that the water content of the dehydrated cake may be increased or sludge may leak into the dehydrated separation liquid.

In order to determine the optimum amount of chemicals added, it is basic to perform desktop tests such as jar test, aggregation, filtration, and squeezing test (Nuche test). However, it takes time and effort, and it is not possible to immediately respond to fluctuations in actual water treatment and sludge treatment by conducting a desktop test every time the water quality of the water to be treated or the properties of the sludge to be treated changes. Not the target.

In Patent Document 1, it is possible to control the addition of a coagulant by using a coagulation state monitoring sensor that irradiates laser light into water and receives scattered light scattered by flocs in the water to measure the coagulation state. Has been described.

JP-A-2017-26438

When the agglutinating agent injection amount is controlled by using the agglutinating state monitoring sensor, the agglutinating state is monitored by the monitoring sensor after the organic agglutinating agent is injected, and the injection amount of the inorganic agglutinating agent is controlled based on the result. It has been.

In chemical injection control based on such an agglutination state monitoring sensor, it is possible to determine whether the change in the output signal of the agglutination state monitoring sensor is greatly affected by the injection amount of the inorganic coagulant or the organic coagulant. is important.

An object of the present invention is to provide a coagulation treatment apparatus capable of accurately controlling the amount of an inorganic coagulant and an organic coagulant added.

The coagulation treatment device of the present invention includes a first pipe or a first coagulation tank, an inorganic coagulant addition device for adding an inorganic coagulant to the first pipe or the first coagulation tank, and a liquid to which the inorganic coagulant is added. , A second pipe or a second coagulation tank introduced from the first pipe or the first coagulation tank, an organic coagulant adding device for adding an organic coagulant to the second pipe or the second coagulation tank, and the second. Control to control the inorganic coagulant addition device and the organic coagulant addition device based on the coagulation state monitoring sensor provided so as to be in contact with the coagulation liquid in the pipe or the second coagulation tank and the detection value of the coagulation state monitoring sensor. The agglomeration state monitoring sensor has an irradiation unit that irradiates laser light into water and a light receiving unit that receives scattered light, and the controller has a device that receives temporal changes in the scattered light intensity signal. It is a coagulation processing device that determines the floc formation state in the second pipe or the second coagulation tank, and the controller occupies the number of particles in the measurement region of the coagulation state monitoring sensor from the detection signal of the coagulation state monitoring sensor. Control is performed based on the proportion of small-diameter particles smaller than the first set particle size and the proportion of large-diameter particles larger than the second set particle size.

In one aspect of the present invention, the controller reduces the amount of the organic flocculant added when the proportion of the small diameter particles is less than the first predetermined value and the proportion of the large diameter particles is greater than the second predetermined value. Let me.

In one aspect of the present invention, in the controller, the proportion of the small-diameter particles is larger than the first predetermined value, and the proportion of the large-diameter particles is a third predetermined value (however, the third predetermined value is the second predetermined value). When it is less than the value, the amount of the organic flocculant added is increased.

In one aspect of the present invention, a pH meter is provided in the second pipe or the second coagulation tank, and the controller has a proportion of the small-diameter particles larger than the first predetermined value and the large-diameter particles. When the ratio of is larger than the third predetermined value, the amount of the inorganic flocculant added is controlled based on the pH of the pH meter.

In one aspect of the present invention, when the pH of the pH meter is higher than the first set pH, the controller has a second set pH (however, the second set pH is lower than the first set pH). The amount of the inorganic flocculant added is increased until

In one aspect of the present invention, when the pH of the second coagulant tank is lower than the first set pH, the controller reduces the amount of the inorganic flocculant added until the pH becomes higher than the first set pH. ..

In the coagulation treatment apparatus of the present invention, the coagulation state in the liquid to which the organic coagulant is added is monitored by the coagulation state monitoring sensor, and the inorganic coagulant and the inorganic coagulant are injected according to the ratio of the small-diameter particles and the large-diameter particles. The amount can be controlled accurately.

It is a block diagram of the coagulation processing apparatus which concerns on embodiment. It is a block diagram of the agglutination state monitoring sensor. It is a schematic diagram of the measurement area of the agglutination state monitoring sensor. 4a and 4b are detection waveform diagrams of the agglutination state monitoring sensor. It is a flowchart which shows the control method.

Hereinafter, the coagulant injection control device according to the embodiment will be described with reference to the drawings.

As shown in FIG. 1, in this coagulant injection control device, the raw sludge to be treated is introduced into the first coagulation tank 3 via the inflow pipe 1 having the flow meter 2, and is inorganic by the first chemical injection device 4. A flocculant is added. A stirrer 3a is installed in the first coagulation tank 3.

The liquid (first coagulation treatment liquid) coagulated in the first coagulation tank 3 is introduced into the second coagulation tank 5 via the advection port (or advection pipe), and is an organic polymer by the second chemical injection device 6. A flocculant is added. In addition to the stirrer 5a, the second agglutination tank 5 is equipped with a pH meter 7 and an agglutination state monitoring sensor 10, and the detection signal thereof is input to the controller 8. The controller 8 controls the first and second drug injection devices 4 and 6 based on this detection signal.

The sludge that has been agglomerated in the second coagulation tank 8 is sent to the solid-liquid separation step.

Examples of the inorganic flocculant include ferric chloride, ferric sulfate, polyferric chloride, polyferric sulfate and other iron-based inorganic flocculants, aluminum chloride, polyaluminum chloride, sulfate band, aluminum hydroxide and aluminum oxide. Examples thereof include aluminum-based inorganic flocculants.

As the organic polymer flocculant (polymer flocculant), a cationic or amphoteric polymer flocculant, particularly a cationic polymer flocculant is preferable. Examples of the cationic polymer flocculant include homopolymers of cationic monomers such as dimethylaminoethyl acrylate or a quaternized product thereof, dimethylaminoethyl methacrylate or a quaternized product thereof, a copolymer with acrylamide, and polyvinylamidine. Examples thereof include poly (diallyldimethylammonium chloride), polyethyleneimine, polyallylamine, polyvinylamine, poly (2-vinyl-1-methylpyrinidium), dialkylamine-epichlorohydrin polycondensate, polylysine, chitosan, diethylaminoethyldextran and the like. ..

Examples of the amphoteric polymer flocculant include cationic monomers such as dimethylaminoethyl acrylate or its quaternized product, dimethylaminoethyl methacrylate or its quaternized product, nonionic monomer such as acrylamide, and acrylic acid or its quaternized product. A copolymer with a salt or the like can be used.

In the present invention, as the organic polymer flocculant, one having an intrinsic viscosity of about 0.1 to 20 dL / g in a 1N NaCO ₃ aqueous solution at 30 ° C. can be preferably used.

Further, the organic polymer flocculant is preferably crosslinked when it is used for dehydration treatment of sludge.

As the agglutination state monitoring sensor 10, the one described in Patent Document 1 is preferably used. FIG. 2 shows the configuration of the probe portion of this agglutination state monitoring sensor. This probe includes a block 11 having orthogonal surfaces 11a and 11b and an apex 11c where they intersect, a light emitting unit 12 provided along the surface 11a that irradiates a laser beam toward the coagulation treatment liquid, and a surface 11b. It has a light receiving unit 13 having a light receiving optical axis oriented along the light emitting unit 12 in a direction orthogonal to the light emitting optical axis of the light emitting unit 12. Further, the agglutination state monitoring sensor 10 includes a light emitting circuit, a detection circuit, and a measurement circuit (not shown) in order to perform the light emitting operation of the light emitting unit 12 and the analysis of the light receiving signal of the light receiving unit 13. The measurement circuit includes a timing circuit, an A / D conversion unit, a calculation unit, and the like.

Similar to Patent Document 1, the laser light emitted from the light emitting unit 12 to the measurement area A near the top 11c is scattered by the particles in the measurement area A, and the scattered light is received by the light receiving unit 13, and the light receiving intensity thereof is received. The state of aggregation is measured based on the change over time. The block 11 is made of an opaque material.

The light emitting circuit sends an electric signal having a constant modulation frequency to the light emitting part according to the signal from the timing circuit to cause laser light emission. The light emitting unit emits laser light by a signal from the light emitting circuit. The light receiving unit receives the scattered light generated by the laser light hitting the suspension in water and converts it into an electric signal. The detection circuit removes the modulation component from the electric signal from the light receiving unit and outputs the light receiving voltage according to the scattered light intensity.

The measurement circuit transmits a signal for light emission (specific frequency modulated wave) to the light emitting circuit, converts the signal from the detection circuit into a digital signal, performs a logical operation, and outputs information on aggregation.

As the agglutination state monitoring sensor, the monitoring device of Patent Document 1, in particular, the monitoring device described in Japanese Patent No. 6281534, which is patented thereto, can be preferably used, but is not limited thereto.

The agglutination monitoring device of Japanese Patent No. 6281534 is available.
"A coagulation monitoring device that monitors the treatment status of the water to be coagulated.
A measurement light irradiation unit that irradiates the measurement area of the water to be treated with measurement light,
A scattered light receiving unit that receives scattered light by the particles of the water to be treated in the measurement area,
The subject includes an amplitude measuring means for measuring the amplitude of a received signal obtained by the scattered light receiving unit, monitors and aggregates the appearance of the measured amplitude, calculates the occurrence rate or occurrence frequency of a specific amplitude, and obtains the subject. A measurement value calculation unit that calculates an index related to the aggregation of the water to be treated, which represents the particle size of the flocs in the treated water.
With
The amplitude measuring means detects a first inflection point in which the received light signal changes from rising to falling and a second inflection point in which the received signal changes from falling to rising, and the first inflection point and the second inflection point. An aggregation monitoring device characterized in that the amplitude is measured from the level difference of an inflection point. "
Is.

FIG. 3 is a schematic view showing a cross section perpendicular to the optical axis of the laser beam L in the measurement region A of FIG. As shown in FIG. 3, at a certain point in time, five particles are present in the measurement region A. At this point, the laser light irradiated to the measurement region A is scattered by each particle, and the scattered light S is incident on the light receiving unit 13. When a predetermined time Δt (preferably a time selected from the range of 0.1 to 10 mSec, for example, about 1 mSec) elapses from this point, the number of particles existing in the measurement region A fluctuates (theoretically, the particles). Although the number may not change, the number of particles usually fluctuates because the particles move in Brownian motion and the sludge liquid in the coagulation tank 5 is agitated.)

When the number of particles fluctuates, the scattered light intensity fluctuates in conjunction with it, and the light receiving intensity of the light receiving unit 13 fluctuates.

The larger the particle size of the particles, the larger the fluctuation range of the light receiving intensity when one particle enters or exits the measurement region A. Therefore, it is possible to detect the size of the particle size of the particles entering and exiting the measurement region A from the fluctuation range of the light receiving intensity. That is, the difference between the light receiving intensity at an arbitrary time t _{k and} the light receiving intensity at the time t _{k + 1} after the elapse of Δt is a value proportional to the surface area of the particles entering and exiting the measurement region A during the Δt.

FIG. 4a shows an example of the time-dependent change of the agglutination state monitoring sensor output signal obtained by signal processing the received signal of the agglutination state monitoring sensor. The output signal in FIG. 4a is a value proportional to the light receiving intensity of the light receiving unit 13, and the unit is, for example, mV.

Figure 4a is a graph plotting the measured signal strength at each time of the time _{t 1, t 2 ... t z} , interval between the time Delta] t (i.e. _{t k -t k-1)} is as defined above, preferably Is 0.1 to 10 mSec, for example 1 mSec.

In FIG. 4b, the minimum points P ₁ , P ₂ ... And the maximum points Q ₁ , Q ₂ ... Are entered in FIG. 4a, and the difference between the minimum points and the maximum points (hereinafter, may be referred to as a peak difference). It is explanatory drawing which filled in h ₁ , h ₂ ....

As mentioned above, any difference h _k of the signal intensity at time t _k-1 of the signal strength and the time t _k is the time t _{k-1 ~} t _k value proportional to the surface area of the measurement region A out particles between Is.

All peak differences h ₁ , h ₂ ... h _n at Δt · z seconds (z is, for example, 200, and Δt · z is 0.2 seconds when Δt = 1 mSec) from time t ₁ to t _z . Therefore, the particle size distribution of the particles existing in the vicinity of the measurement region A during this time t ₁ to t _z is detected.

This detection principle will be described with reference to FIG. 4b. In FIG. 4b, h ₁ <h _n <h ₃ <h ₂ . The peak difference h ₁ indicates that particles having a small diameter were detected, the peak difference h ₂ indicates that particles having a large diameter were detected, and the peak difference h ₃ indicates that particles having a particle size between them were detected. Represents that. The peak difference h _n indicates that particles slightly larger than the particles of h ₁ were detected.

Therefore, aggregation state monitoring sensor output signal of intensity reference value difference _{h a,} is determined in advance and _{h b (h a <h b} ), within the scope of the following _{h a} of the n peak difference _h 1 ~ _{h n} the number _{N a} of peak difference, _{h a} super _h and the number _{N b} of peak difference belonging to the range of less than _b, and counts the number _{N c} of peak difference falling within the scope of the above _{h b,} the total number N (= N _a + _N b + _{N c)} accounts _{N a,} the ratio of N b, the ratio _N a _/ N of _{N c, N} b / _N, by calculating the _N c / N, small particles occupying the entire number of the particles, middle size The ratio of particles and the ratio of large-diameter particles are obtained.

It should be noted that the usage time of the light emitting element can be extended by repeating light emission and non-light emission at predetermined time intervals. For example, when the light emission time is 0.2 seconds / time and the light emission interval is 2 seconds, the usage time (life) of the light emitting element can be extended 10 times as compared with the case where continuous light emission is performed. In this way, when repeating light emission and non-light emission, the proportion of particles is not determined within a continuous light emission time (0.2 seconds in the above example), but for example, light emission and non-light emission are repeated 10 The ratio of small particles and large particles to the number of detected particles can be obtained within the measurement time of one minute.

In general, if the amount of the coagulant injected is insufficient, coagulation will be poor and the proportion of small-diameter particles in the total number of particles will increase. If the amount of the organic flocculant injected is excessive, the proportion of large-diameter particles becomes excessively high.

In consideration of such agglutination characteristics, the amount of the inorganic coagulant and the organic coagulant to be injected is controlled according to the detection signal of the agglutination state monitoring sensor 10 installed in the second coagulation tank 5. An example of this control flowchart is shown in FIG.

In this example, the reference values ha and hb of the output signal intensity difference (signal intensity difference) are 350 mV and 2000 mV, respectively, and the particles belonging to the range of the signal intensity difference of 350 mV or less are small diameter particles (hereinafter, small particles), and are 2000 mV or more. Particles belonging to the range of are defined as large-diameter particles (hereinafter referred to as large particles). The signal strength difference of 10 mV or less was excluded from the measurement target because the difference from the disturbance is unknown.

In general, as the amount of the above-mentioned iron salt-based or aluminum salt-based inorganic flocculant added increases, the pH in the liquid decreases (when the amount of the inorganic flocculant added is an appropriate amount, the pH of the coagulation treatment liquid becomes Generally, it is 4.0 to 4.5 or less.) Therefore, in the flow of FIG. 5, the amount of the inorganic flocculant injected is controlled with reference to the detected pH of the pH meter 7.

After the start, in step 1, it is determined whether the proportion of small particles is small (for example, 35% or less). If the proportion of small particles is small, the process proceeds to step 2 to determine whether the proportion of large particles is very large (for example, 20% or more). If the proportion of large particles is less than 20%, it is determined that the addition amount of both the inorganic flocculant and the organic flocculant is appropriate, and the process returns to step 1.

In step 2, when the proportion of large particles is 20% or more, it is considered that the amount of the organic flocculant added is excessive. Therefore, the process proceeds to step 3 and the amount of the organic flocculant (polymer flocculant) added is reduced by a predetermined amount. Then, it is left as it is for a predetermined time, and after the predetermined time elapses, it is determined whether the proportion of large particles is within an appropriate range of less than 20% (and 10% or more) (step 4). Then, the amount of the organic flocculant added is reduced until the proportion of the large particles is within the appropriate range, and after the proportion of the large particles is within the appropriate range, the process returns to step 1.

When the proportion of small particles exceeds 35% in step 1, it is considered that poor aggregation has occurred due to insufficient addition of one or both of the inorganic flocculant and the organic flocculant. Therefore, the process proceeds from step 1 to step 5 to determine whether the proportion of large particles is large (10% or more). When the proportion of large particles is large (for example, 10% or more), the amount of the organic flocculant added is appropriate, but it is considered that poor aggregation occurs due to the excessive or insufficient amount of the inorganic flocculant added. Therefore, the process proceeds from step 5 to step 6 to determine whether the detected pH of the pH meter 7 is higher than 4.5.

When pH> 4.5 in step 6, it is considered that the amount of the inorganic flocculant added is insufficient. Therefore, the process proceeds to step 7, the amount of the inorganic flocculant added is increased by a predetermined amount, and the mixture is waited for a predetermined time to be predetermined. The pH is detected again after a lapse of time (step 8). The amount of the inorganic flocculant added is increased until pH ≦ 4.0, and after pH ≦ 4.0, the process returns to step 1.

In step 5, when the proportion of large particles is less than 10%, it is considered that the amount of the organic coagulant added is insufficient. Therefore, the process proceeds from step 5 to step 9, and the amount of the organic coagulant added is increased by a predetermined amount. , Wait for a predetermined time. After a lapse of a predetermined time, it is determined whether the proportion of large particles is within an appropriate range of 10% or more (and less than 20%) (step 10). Then, after increasing the amount of the organic flocculant added until the proportion of the large particles reaches the appropriate range, the process returns to step 1.

In step 6, when the pH is ≦ 4.5, it is considered that the amount of the inorganic flocculant added is excessive. Therefore, the process proceeds to step 11, the amount of the inorganic flocculant added is reduced by a predetermined amount, and then the patient waits for a predetermined time. .. After the lapse of a predetermined time, the pH is detected again (step 12), and if the pH is still 4.5 or less, the amount of the inorganic flocculant added is further reduced, and after the pH becomes 4.5 or more, the step Return to 1.

In this way, the aggregation state monitoring sensor 10 and the pH meter 7 can be used to control the addition amounts of the inorganic flocculant and the organic flocculant so as to be appropriate.

In the explanation of FIG. 5, the reference values ha and hb of the intensity difference of the output signal for distinguishing the size of the particles are set to 350 mV and 2000 mV, respectively, but the present invention is not limited to this. That is, the reference values ha and hb are the specifications of the agglutination state monitoring sensor 10 (laser light intensity from the light emitting unit 12, processing method of the light receiving signal from the light receiving unit 13, etc.), measurement target (water, wastewater, sludge), inorganic. It depends on the type of coagulant and organic coagulant, and the coagulation treatment device and solid-liquid separation device (dehydration treatment device). Therefore, the reference values ha and hb are appropriately set by performing a test in which the amount of the treatment agent added varies in advance using the treatment target, the treatment apparatus, and the treatment agent to be actually applied.

Further, in the explanation of FIG. 5, the ratios of small particles and large particles are set to 35%, 20%, and 10% as an example in steps 1, 2, and 5, but these values are also set to the reference values ha and hb. Similarly, it differs depending on the measurement target (water, wastewater, sludge), the type of inorganic coagulant or organic coagulant, and the coagulation treatment device and solid-liquid separation device (dehydration treatment device). Therefore, these ratios are also appropriately set by conducting a test in which the amount of the treatment agent added varies in advance.

By sampling the agglutinated sludge, visually measuring the agglutinated floc particle size, and comparing it with the agglutinated state monitoring sensor output signal at that time, the agglutinated state monitoring sensor output signal and the agglutinated particle particle size can be directly measured. It may be associated with.

In FIG. 4b, the difference between the maximum point and the minimum point immediately before it is obtained, but the difference between the maximum point and the minimum point immediately after that may be obtained. Further, the minimum points immediately before and after one maximum point may be connected by a straight line, and the distance from the maximum point to the straight line below the maximum point may be obtained and used as the above difference.

Although the coagulation tanks 3 and 5 are installed in FIG. 1, an inorganic coagulant may be added in the pipe 1 and the coagulation tank 3 may be omitted.

Further, in FIG. 1, the organic coagulant is added to the second coagulation tank 5, but a second pipe is installed instead of the second coagulation tank 5, and the organic coagulant is added to the second pipe. May be good.

The agglutination state monitoring sensor 10 may be installed in the agglutination liquid outflow pipe from the second agglutination tank 5. Further, a measuring tank into which the liquid in the second coagulation tank 5 is introduced may be provided, and the coagulation state monitoring sensor 10 may be installed in the measuring tank.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the intent and scope of the invention.
This application is based on Japanese Patent Application No. 2019-138402 filed on July 26, 2019, which is incorporated by reference in its entirety.

3,5 Coagulation tank 4,6 Chemical injection device 8 Controller 10 Coagulation status monitoring sensor

Claims (6)

1. With the first pipe or the first coagulation tank,
   An inorganic coagulant addition device that adds an inorganic coagulant to the first pipe or the first coagulation tank,
   The liquid to which the inorganic coagulant is added is introduced from the first pipe or the first coagulation tank into the second pipe or the second coagulation tank.
   An organic coagulant addition device that adds an organic coagulant to the second pipe or the second coagulation tank,
   An agglutination state monitoring sensor provided so as to be in contact with the agglutinating liquid of the second pipe or the second agglutination tank,
   It has a controller for controlling the inorganic coagulant addition device and the organic coagulant addition device based on the detection value of the agglutination state monitoring sensor.
   The agglutination state monitoring sensor has an irradiation unit that irradiates laser light into water and a light receiving unit that receives scattered light.
   The controller is a coagulation processing device that determines the flock formation state in the second pipe or the second coagulation tank from the temporal change of the scattered light intensity signal.
   From the detection signal of the agglomeration state monitoring sensor, the controller has a ratio of small-diameter particles smaller than the first set particle size to the number of particles in the measurement region of the agglomeration state monitoring sensor, and a large particle size larger than the second set particle size. A coagulation processing device that controls based on the proportion of particle size particles.
2. The controller is characterized in that the amount of the organic flocculant added is reduced when the proportion of the small-diameter particles is less than the first predetermined value and the proportion of the large-diameter particles is more than the second predetermined value. The coagulation processing apparatus according to claim 1.
3. In the controller, the proportion of the small-diameter particles is larger than the first predetermined value, and the proportion of the large-diameter particles is larger than the third predetermined value (however, the third predetermined value is smaller than the second predetermined value). The coagulation treatment apparatus according to claim 2, wherein the amount of the organic coagulant added is increased when the amount is too small.
4. A pH meter is provided in the second pipe or the second coagulation tank.
   When the proportion of the small-diameter particles is higher than the first predetermined value and the proportion of the large-diameter particles is higher than the third predetermined value, the controller of the inorganic flocculant is based on the pH of the pH meter. The coagulation treatment apparatus according to claim 2 or 3, wherein the addition amount is controlled.
5. In the controller, when the pH of the pH meter is higher than the first set pH, the inorganic flocculant is used until the pH reaches the second set pH (however, the second set pH is lower than the first set pH). The coagulation treatment apparatus according to claim 4, wherein the addition amount is increased.
6. The controller is characterized in that when the pH of the second coagulation tank is lower than the first set pH, the amount of the inorganic coagulant added is reduced until the pH becomes higher than the first set pH. 4 or 5 coagulation treatment device.

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