KR20210035801A - Coagulation and precipitation device and its starting method - Google Patents

Abstract

A flocculation and sedimentation device capable of preventing the discharge of low-concentration sludge at the time of starting the flocculation and sedimentation device in which water to be treated flows into the portable flocculation and sedimentation device or the flocculation and sedimentation device in a state filled with water Is provided. A first coagulation tank 2 for coagulating raw water with a first coagulant, a second coagulation tank 3 for coagulating the first coagulation treated water with a second coagulant and a settling accelerator, and a second coagulation treatment The sedimentation tank 4 for sedimentation and separation of water into treated water and slurry, and the slurry extracted from the settling tank 4 are separated into separating sludge and a settling accelerator, and the separated sedimentation accelerator is returned to the second coagulation tank 3. In the flocculation and sedimentation apparatus 1 having a rotating cyclone 20, when the flocculation and sedimentation apparatus 1 is started, the separated sludge from the cyclone 20 is returned to the first flocculation tank 2, and after the start-up is completed, the cyclone (20) A coagulation and precipitation apparatus (1) comprising a controller (30) for controlling the switching means to divert at least a part of the separated sludge from the system to be discharged out of the system.

Description

Coagulation and precipitation device and its starting method

The present invention relates to an agglomeration and precipitation apparatus for separating into sludge and treated water by adding a sedimentation accelerator and a coagulant to raw water containing a suspended substance and separating it into sludge and treated water, and a method for starting the same. The present invention particularly relates to an agglomeration and sedimentation apparatus configured to separate a slurry extracted from a sedimentation tank into sludge and a sedimentation accelerator by a cyclone, and to convey the sedimentation accelerator to the coagulation tank, and to a method for starting the same.

This is a coagulation and precipitation device that separates and removes suspended substances (hereinafter sometimes referred to as SS [Suspended Solid]) from raw water by coagulation and precipitation. Sedimentation consisting of granular substances (sand, etc.) having a particle diameter of 10 to 200 µm in raw water. A coagulation tank for forming agglomerated flocs by adding an accelerator and a coagulant, a settling tank for sedimenting and separating agglomerated flocs flowing out of the coagulation tank, and a cyclone for separating the slurry drawn from the settling tank into granular material and sludge, and granular material An apparatus configured to be conveyed to a coagulation tank and to discharge sludge is known (Patent Documents 1 to 3).

In the agglomeration and precipitation apparatus of Patent Documents 1 to 3, an inorganic coagulant is added to the raw water introduced into the coagulation tank, stirred with a stirrer, then a polymer coagulant is added and stirred with a stirrer to form agglomerated flocs together with particulate matter (sand, etc.). To form. This coagulation-treated water is introduced into a settling tank, sedimentation is separated, and the treated water is discharged from the top of the settling tank. Further, the slurry is extracted by a pump from the lower part of the settling tank and transferred to a cyclone. In the cyclone, the slurry is centrifuged into sludge and granular material, and the separated sludge is discharged out of the agglomeration and precipitation device. The granular material separated by the cyclone is returned to the coagulation tank and is used for sedimentation again.

In Patent Document 3, a flow control valve is formed on the sludge conveying line that returns at least a part of the sludge discharged from the cyclone to the coagulation tank, and when the SS concentration of raw water is low, the amount of sludge conveyed is increased, and the SS concentration is high. Describes how to control to reduce the amount of sludge conveyed (paragraph 072).

Japanese Patent Laid-Open Publication No. 2000-317220 Japanese Unexamined Patent Publication No. 2002-355507 Japanese Unexamined Patent Publication No. 2014-237122

In the case of a coagulation settling device installed in a facility that treats rainfall drainage in a yard with a large site area, such as a steel mill or a cement factory, when the device is started up or when the device is restarted after maintenance, each tank of the flocculating settling device is not filled with water. In addition, in the case of carrying out the coagulation and sedimentation layer, during non-rainfall, the water in each tank is removed and the precipitation accelerating material is extracted. During rainfall, water is first filled in each tank of the coagulation and sedimentation device, and then, drainage from the yard (hereinafter referred to as yard drainage) is received and operation is resumed.

Since the water (water in the tank) filled in each tank has a remarkably low SS concentration, when the yard drainage flows into the coagulation sedimentation device at the beginning of rainfall, the yard drainage is diluted with the tank water, so the SS concentration in each tank is low. . In addition, even if the yard drainage is directly introduced without filling with water, since it is not concentrated, the SS concentration is not sufficient. Therefore, the concentration of sludge discharged from the coagulation and precipitation device is low.

In addition, in a conventional sedimentation tank, in order to accelerate the concentration of SS, the drawing from the sedimentation tank may be operated intermittently. However, when the sludge contains a sedimentation accelerator as in the present invention, the sedimentation accelerator may accumulate in the pit at the bottom of the sedimentation tank or in the drawing line and may be fixed. Therefore, in principle, the drawing is normally operated continuously.

The present invention prevents the discharge of low-concentration sludge at the time of startup of a portable type flocculation and sedimentation device or a flocculation and sedimentation device in which water to be treated flows into the flocculation and sedimentation device in a state where water is filled in each flocculation tank. It is an object of the present invention to provide an agglomeration and precipitation apparatus capable of shortening the starting time by increasing the starting time and a starting method thereof.

In the coagulation and precipitation apparatus of the present invention, raw water is introduced, a first coagulation tank for coagulation treatment with a first coagulant, and the first coagulation treated water discharged from the first coagulant are introduced, and the second coagulant and a sedimentation accelerator are The second agglomeration tank to be coagulated by means of the second coagulation tank, the second coagulation treated water discharged from the second coagulation tank is introduced, and the settling tank for sedimentation and separation into treated water and slurry, and the slurry extracted from the settling tank are separated into sludge and sedimentation accelerator. A cyclone for separating and returning the separated sedimentation accelerator to the second coagulation tank is provided, and the separated sludge line from the sludge outlet of the cyclone is branched into a sludge discharge line and a sludge circulation line, and the sludge circulation line is 1 In a flocculation and sedimentation device connected to a flocculation tank and having a means for switching between the sludge circulation line and the sludge discharge line, when the flocculation and sedimentation device is started, the separated sludge line is connected to the sludge circulation line and The separated sludge is conveyed to the first flocculation tank through the sludge circulation line, and after the start of the flocculation and sedimentation device is terminated, the separated sludge line is continuously or intermittently connected to the sludge discharge line, or the sludge discharge line and And a control means for controlling the switching means to branch to a sludge circulation line and to continuously or intermittently discharge at least a part of the separated sludge from the cyclone out of the system.

In one aspect of the present invention, as the control means, the SS system formed in the separated sludge line or the sludge circulation line, and the separated sludge from the cyclone until the detected SS concentration of the SS system rises to a predetermined concentration. And a controller for controlling the switching means so as to be conveyed to the first coagulation tank.

In one aspect of the present invention, in at least a part of the period until the detected SS concentration of the SS system rises to a predetermined concentration, the amount of the first flocculant added to the first flocculating tank and the second flocculating agent for the second flocculating tank A coagulant addition amount control unit is provided to increase the addition amount of.

In one aspect of the present invention, as the control means, a timer for controlling the switching means to return the separated sludge from the cyclone to the first agglomeration tank for a predetermined time after starting raw water supply to the first coagulation tank is provided. .

In one aspect of the present invention, in at least a part of the period from the start of supply of raw water to the first coagulation tank until a predetermined time elapses, the amount of the first coagulant added to the first coagulation tank and the second coagulation tank A coagulant addition amount control unit is provided to increase the addition amount of the second coagulant.

In the control method of the coagulation and precipitation apparatus of the present invention, raw water is introduced, a first coagulation tank for coagulation treatment with a first coagulant, and a first coagulation treated water discharged from the first coagulant are introduced, and a second coagulant and sedimentation A second flocculation tank for coagulation treatment by an accelerator, a second flocculation treatment water discharged from the second flocculation tank is introduced, and a settling tank for sedimentation and separation into treated water and a slurry, and a slurry extracted from the settling tank are separated and sludge and sedimentation A cyclone for separating into an accelerator and returning the separated sedimentation accelerator to the second coagulation tank is provided, and the separated sludge line from the sludge outlet of the cyclone diverges into a sludge discharge line and a sludge circulation line, and the sludge circulation line In this method of starting the flocculation and precipitation device connected to the first flocculation tank, when the flocculation and precipitation device is started, the separated sludge from the cyclone is returned to the first flocculation tank through the sludge circulation line, and the flocculation and precipitation. It is characterized in that after the start-up of the device is terminated, at least a portion of the separated sludge from the cyclone is switched to continuously or intermittently discharge out of the system.

In one aspect of the present invention, when the agglomeration and precipitation device is started, the amount of the first flocculant added to the first flocculating tank and the second flocculant added to the second flocculating tank are increased.

In one aspect of the present invention, the enemy is a yard water multiple.

In the flocculation and sedimentation apparatus and its starting method of the present invention, when the flocculation and sedimentation apparatus is started, the separated sludge discharged from the cyclone is conveyed to the first flocculation tank, so that the discharge of low-concentration sludge is prevented. Thereby, the SS concentration in the system increases early, and the start-up time is shortened.

In one aspect of the present invention, by increasing the amount of the first flocculant added at the time of starting the flocculation and precipitation device, the flocculation action is strengthened, and the discharge of low-concentration sludge is prevented. Further, by increasing the amount of the second coagulant to be added so as not to be insufficient with respect to the first coagulant, a cohesive failure is prevented.

1 is a configuration diagram of a coagulation and precipitation apparatus according to an embodiment.
2 is a configuration diagram of an agglomeration and precipitation device according to an embodiment.
3 is a configuration diagram of a coagulation and precipitation apparatus according to an embodiment.
4 is a configuration diagram of an agglomeration and precipitation apparatus according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 shows an agglomeration and precipitation apparatus 1 according to a first embodiment. This coagulation and precipitation device 1 is equipped with a 1st coagulation tank 2, a 2nd coagulation tank 3, and the settling tank 4 arrange|positioned adjacent thereto.

Raw water is introduced into the first coagulation tank 2 through the raw water introduction line 5, and an inorganic coagulant (PAC in Fig. 1) as a first coagulant is added by the first chemical injection device 6, and the stirrer 7 ). In the first coagulation tank 2, the inorganic coagulant agglomerates the suspended material to form a fine floc.

Although not shown, a device for adding a pH meter and a pH adjuster (caustic soda, sulfuric acid, hydrochloric acid, etc.) is formed in the first coagulation tank 2, and the pH in the first coagulation tank 2 is maintained in a predetermined range. It is structured to be able to.

The first coagulation-treated water from the first coagulation tank 2 is introduced into the second coagulation tank 3 through the air flow port 8, and a polymer coagulant (polymer) is used as the second coagulant. It is added by the device 9. In the second agglomeration tank 3, a sedimentation accelerator such as sand is added, and by stirring by the stirrer 10, the fine flocs flow into the sedimentation accelerator through the polymer flocculant to form a large specific gravity floc. Grow.

As the sedimentation accelerating material, in addition to sand, crushed products of various slags can also be used. The average particle diameter of the sedimentation accelerator is preferably about 0.01 to 0.5 mm, and the true specific gravity is 2 or more, particularly 2.5 or more, and 4 or less is preferable, but is not limited thereto.

The 2nd coagulation-treated water containing the grown coagulated floc overflows the overflow bank 12 and is introduced into the settling tank 4. The second coagulation treated water descends along the checkerboard of the overflow dam 12, rises, passes through the separator, and flows into the outflow chamber 15. In the sedimentation tank 4, agglomerated flocs in the second coagulation-treated water are precipitated.

A separator made of a plurality of swash plates 13 is provided on the upper part of the settling tank 4, and sedimentation and separation of agglomerated flocs is promoted. The treated water passing through the separator is taken out from the outflow pipe 16 via the outflow chamber 15. A lake 14 is formed in the settling tank 4.

To the bottom of the settling tank 4, a drawing line 17 for discharging the slurry containing the precipitated floc is connected. In the drawing line 17, a drawing pump 18 is provided in the cyclone 20 for the extracted slurry. The cyclone 20 is provided with the axial center direction as a vertical direction.

In the cyclone 20, the conveyed slurry is separated by centrifugal separation into sludge collected in the axial center of the cyclone and a sedimentation accelerating material collected on the circumferential surface of the cyclone side. The separated sedimentation accelerator is returned from the bottom of the cyclone 20 to the second coagulation tank 3 again by a pipe 19 and used for circulation.

The separated sludge collected on the axial center side of the cyclone 20 flows out to the pipe 21 (separated sludge line) connected to the sludge outlet at the center of the upper surface of the cyclone 20. The pipe 21 is branched into pipes 22 and 25.

The pipe 22 is connected to the pipe 24 via a valve 23. The sludge discharge line is constituted by the pipes 22 and 24 and the valve 23.

The pipe 25 is capable of conveying the separated sludge to the first coagulation tank 2 via the valve 26 and the pipe 27. The pipes 25 and 27 and the valve 26 constitute a sludge circulation line. The switching means is constituted by the valves 23 and 26.

An SS system 28 made of an optical turbidimeter or the like is provided in the pipe 27, and a detection signal thereof is input to the controller 30. The valves 23 and 26 are controlled by the controller 30, and ON/OFF switching or flow rate adjustment is performed.

When starting the operation of this coagulation and sedimentation device 1, first, fresh water with relatively high clarity, such as fresh water, well water, river water, rainwater, and purified water, is filled to the prescribed water level in each tank 2, 3, 4. This is to confirm that there is no damage to each tank (2 to 4) or member.

When raw water such as yard drainage starts to flow into this coagulation and precipitation device, an inorganic coagulant is added to the first coagulation tank 2 and a polymer coagulant (polymer) is added to the second coagulation tank 3. In addition, a predetermined amount of a settling accelerator is added to the second agglomeration tank 3.

The raw water is mixed with the fresh water in the first coagulation tank 2, diluted and coagulated, flows into the settling tank 4 through the second coagulation tank 3, sedimentation and separation of coagulation flocs is performed, and treated water (Clarification water) is discharged from the pipe (16).

As described above, when the coagulation and precipitation device 1 is started, the raw water is diluted with fresh water in the coagulation tanks 2 and 3, so that the SS concentration in the coagulation tanks 2 and 3 is low, and in the settling tank 4 The SS concentration of the slurry precipitated in is also small. Therefore, the SS concentration of the separated sludge separated by the cyclone 20 is low, and it is not appropriate to discharge as it is.

Therefore, in this embodiment, when the coagulation precipitation device 1 is started, the valve 23 is closed and the valve 26 is opened, so that the total amount of separated sludge from the cyclone 20 is reduced to the piping 27 ) From the first coagulation tank (2).

The SS concentration of the separating sludge flowing in the pipe 27 is measured by the SS meter 28, and the detection signal is input to the controller 30. In the controller 30, the detected SS concentration of the SS system 28 is a preset predetermined concentration (in the case of an agglomeration and precipitation apparatus that treats yard drainage, 10 to 50 g/L, particularly about 15 to 30 g/L). The valve 23 is closed and the valve 26 is opened until it becomes, and the entire amount of the separated sludge is conveyed to the first coagulation tank 2.

If this state is maintained, the SS concentration in the first and second agglomeration tanks 2 and 3 gradually increases, and the detected SS concentration in the SS system 28 also gradually increases. When the detection SS concentration of the SS system 28 rises to the predetermined concentration, the controller 30 opens the valve 23 and closes the valve 26, so that the total amount of separated sludge from the cyclone 20 Is discharged from the pipe (24).

In this way, sludge having a low SS concentration is prevented from being discharged from the pipe 24 when the coagulation and precipitation device 1 is started.

In the above description, after the detection SS concentration of the SS system 28 has risen to a predetermined value, the entire amount of sludge is discharged from the pipe 24, but a part of the separated sludge from the cyclone 20 is connected to the pipe ( You may convey it to the 1st coagulation tank 2 from 27). Further, the separated sludge may be discharged intermittently rather than continuously.

In this first embodiment, the amount of the coagulant added by the first and second chemical injection devices 6 and 9 is constant (a fixed amount addition method). However, the SS concentration of raw water may be detected, and the amount of the coagulant added may be controlled according to the detection result.

Fig. 2 shows a coagulation and precipitation apparatus 1A according to a second embodiment. In this coagulation and precipitation device 1A, the controller 30 is configured to also control the first and second chemical injection devices 6 and 9 as described later. Other configurations of the flocculation and precipitation device 1A are the same as those of the flocculation and precipitation device 1, and the same reference numerals denote the same parts.

The controller 30 operates the valves 23 and 26 according to the same starting method as in the first embodiment until the detection concentration of the SS system 28 rises to a predetermined value at the start of the coagulation and precipitation device 1A. Control the opening and closing of the door. In this embodiment, the controller 30 further comprises an inorganic coagulant by the first and second chemical injection devices 6 and 9 until the detection concentration of the SS system 28 rises to a predetermined value. The addition amount of the polymer coagulant is made larger than the standard addition amount during normal operation (for example, 1.5 to 5 times the amount of each standard addition, especially 2 to 5 times). Thereby, the flocculation effect in the first and second flocculation tanks 2 and 3 is increased, and the SS concentration of the slurry precipitated in the settling tank 4 is increased. Thereby, the concentration of sludge separated by the cyclone 20 rises to a predetermined value early.

3 shows a coagulation and precipitation apparatus 1B according to the third embodiment.

In this embodiment, the timer 31 is provided instead of the controller 30 in order to control the opening and closing of the valves 23 and 26. In addition, the SS system 28 is omitted. Other configurations are the same as those of the coagulation and precipitation apparatus 1 in Fig. 1, and the same reference numerals denote the same parts.

In this embodiment, at the time of starting the coagulation and precipitation device 1B, the valve 26 is opened and the valve 23 is closed until a predetermined time elapses from the start of inflow of raw water to the coagulation and precipitation device 1B. As a result, the entire amount of the separated sludge from the cyclone 20 is conveyed to the first flocculation tank 2. Then, after the predetermined time has elapsed, the valve 26 is closed and the valve 23 is opened, and the entire amount of the separated sludge from the cyclone 20 is discharged from the pipe 24. Also in this case, a part of the separated sludge from the cyclone 20 may be conveyed from the piping 27 to the first coagulation tank 2, or an intermittent treatment may be used instead of a continuous treatment. The predetermined time is preferably about 0.5 to 4 times the HRT of the agglomeration and precipitation device 1B.

Also in this embodiment, the SS concentration of the slurry precipitated in the settling tank 4 rises early. Thereby, the concentration of sludge separated by the cyclone 20 rises early.

4 shows a coagulation and precipitation apparatus 1C according to a fourth embodiment. This coagulation and precipitation device 1C is provided with a timer 31 similarly to the coagulation and precipitation device 1B of FIG. 3, and additionally, the amount of coagulant added by the first and second chemical injection devices 6 and 9 It is provided with a controller (32) for controlling.

Like the coagulation and precipitation device 1B of FIG. 3, the timer 31 is the valve 26 until a predetermined time has elapsed from the start of inflow of raw water to the coagulation and precipitation device 1C (start of operation of the raw water pump). Is opened and the valve 23 is closed, and the entire amount of the separated sludge from the cyclone 20 is conveyed to the first coagulation tank 2. Then, after the predetermined time has elapsed, the valve 26 is closed and the valve 23 is opened, and the entire amount of the separated sludge from the cyclone 20 is discharged from the pipe 24. Also in this case, a part of the separated sludge from the cyclone 20 may be conveyed from the piping 27 to the first coagulation tank 2, or an intermittent treatment may be used instead of a continuous treatment.

The controller 32 is in the first and second chemical injection devices 6 and 9 until a predetermined time elapses from the start of the coagulation and precipitation device 1C (start of the timer 31 (start of operation of the raw water pump)). The amount of the inorganic coagulant and the polymer coagulant added is greater than the standard addition amount during normal operation (for example, 1.5 to 5 times the standard addition amount, respectively). Thereby, the flocculation effect in the flocculation tanks 2 and 3 increases, and the SS concentration of the slurry precipitated in the settling tank 4 rises. Thereby, the concentration of sludge separated by the cyclone 20 rises to a predetermined value early.

The control by the timer as in the third and fourth embodiments is particularly effective when the SS concentration in raw water is stable (the fluctuation width is relatively small).

The flocculation and sedimentation apparatus according to the present invention and the starting method thereof are suitable for treatment of yard water, but are applicable to treatment of various other types of water.

The term "starting" of the coagulation and precipitation device in the present invention includes not only at the start of operation of the newly installed device, but also the first attempt to start the operation after the water of each tank such as maintenance or conveyance is once drained.

The type of the inorganic coagulant or polymer coagulant used in the present invention is not particularly limited, and examples of the inorganic coagulant include polyaluminum chloride (PAC), ferric chloride, ferric sulfate, and iron polysulfate. I can. As the polymer coagulant, for example, a nonionic, cationic, anionic or amphoteric polymer coagulant can be used.

The above embodiment is an example of the present invention, and the present invention may be an aspect other than the above. For example, in the embodiment of FIGS. 1 and 2, the SS system is formed in the pipe 27, but may be formed in the pipe 21 or 25. In addition, in the aspect of FIG. 2 and FIG. 4, the period in which the addition amount of various flocculants is increased may be a part of the period in which the valve 26 is opened.

Although the present invention has been described in detail using a specific aspect, it is clear to those skilled in the art that various changes can be made without departing from the intention and scope of the present invention.

This application is based on Japanese Patent Application No. 2018-151718 for which it applied on August 10, 2018, The whole is used by reference.

1, 1A, 1B, 1C: flocculation and precipitation device
2: first flocculation tank
3: second flocculation tank
4: sedimentation tank
6: first medicine injection device
9: second medicine injection device
20: cyclone
23, 26: valve
28: SS series
30, 32: controller
31: timer

Claims (8)

A first coagulation tank in which raw water is introduced and coagulated with a first coagulant,
A second agglomeration tank in which the first coagulation treated water discharged from the first coagulation tank is introduced and coagulated with a second coagulant and a settling accelerator,
A sedimentation tank in which the second coagulation treated water discharged from the second coagulation tank is introduced, and sedimentation and separation into treated water and slurry,
A cyclone for separating the slurry extracted from the sedimentation tank into separating sludge and a sedimentation accelerator, and returning the separated sedimentation accelerator to the second coagulation tank,
The separated sludge line from the sludge outlet of the cyclone diverges into the sludge discharge line and the sludge circulation line,
The sludge circulation line is connected to the first coagulation tank,
In the coagulation and precipitation apparatus having a switching means for the sludge circulation line and the sludge discharge line,
When the flocculation and sedimentation device is started, the separated sludge line is connected to the sludge circulation line, and the separated sludge from the cyclone is conveyed to the first flocculation tank through the sludge circulation line,
After the start-up of the coagulation and sedimentation device is completed, the separated sludge line is connected to the sludge discharge line continuously or intermittently, or branched to the sludge discharge line and the sludge circulation line to continuously or intermittently separate at least a part of the separated sludge from the cyclone. Or intermittently to discharge out of the system
And a control means for controlling said switching means. The method of claim 1,
As the control means, the SS system formed in the separated sludge line or the sludge circulation line, and the separated sludge from the cyclone are conveyed to the first coagulation tank until the detected SS concentration of the SS system rises to a predetermined concentration. A coagulation and precipitation apparatus provided with a controller for controlling the switching means. The method of claim 2,
In at least a part of the period until the detected SS concentration of the SS system rises to a predetermined concentration, the amount of coagulant added to increase the amount of the first coagulant added to the first coagulation tank and the second coagulant added to the second coagulation tank A coagulation precipitation device in which a control unit is provided. The method of claim 1,
As the control means, a timer for controlling the switching means to convey the separated sludge from the cyclone to the first coagulation tank for a predetermined time after starting supply of raw water to the first coagulation tank. The method of claim 4,
In at least a part of the period from the start of supply of raw water to the first coagulation tank until a predetermined time elapses, the addition amount of the first coagulant to the first coagulation tank and the addition amount of the second coagulant to the second coagulation tank are increased. An agglomeration and precipitation device in which a coagulant addition amount control unit to be made is provided. A first coagulation tank in which raw water is introduced and coagulated with a first coagulant,
A second agglomeration tank in which the first coagulation treated water discharged from the first coagulation tank is introduced and coagulated with a second coagulant and a settling accelerator,
A sedimentation tank in which the second coagulation treated water discharged from the second coagulation tank is introduced, and sedimentation and separation into treated water and slurry,
A cyclone for separating the slurry extracted from the sedimentation tank into separating sludge and a sedimentation accelerator, and returning the separated sedimentation accelerator to the second coagulation tank,
The separated sludge line from the sludge outlet of the cyclone diverges into the sludge discharge line and the sludge circulation line,
In the starting method of the flocculation and precipitation device in which the sludge circulation line is connected to the first flocculation tank,
When the flocculation and sedimentation device is started, the separated sludge from the cyclone is returned to the first flocculation tank through the sludge circulation line,
A method of starting a flocculation and sedimentation device, characterized in that after the start-up of the flocculation and sedimentation device is completed, at least a part of the separated sludge from the cyclone is continuously or intermittently discharged out of the system. The method of claim 6,
The starting method of the agglomeration and precipitation device, wherein the amount of the first flocculant added to the first flocculating tank and the second flocculant added to the second flocculating tank are increased when the flocculation and precipitation device is started. The method of claim 6 or 7,
The starting method of the coagulation precipitation device, wherein the raw water is yard drainage.

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