WO2020031567A1

WO2020031567A1 - Flocculation and sedimentation device, and startup method thereof

Info

Publication number: WO2020031567A1
Application number: PCT/JP2019/026497
Authority: WO
Inventors: 田中　一平
Original assignee: 栗田工業株式会社
Priority date: 2018-08-10
Filing date: 2019-07-03
Publication date: 2020-02-13
Also published as: JP7139771B2; JP2020025921A; KR20210035801A

Abstract

A flocculation and sedimentation device and startup method thereof are provided with which is it possible to prevent discharge of low-concentration sludge when, at start-up of a portable-type flocculation and sedimentation device or a flocculation and sedimentation device with the flocculation tanks filled with water, water to be treated flows into the flocculation and sedimentation device. The flocculation and sedimentation device 1 is provided with a first flocculation tank 2 which subjects raw water to flocculation treatment with a first flocculant, a second flocculation tank 3 which subjects the first flocculated water to flocculation treatment with a second flocculant and a sedimentation promoter, and a sedimentation tank 4 which settles and separates the second flocculated water into treated water and a slurry, and a cyclone 20 which separates the slurry extracted from the sedimentation tank 4 into a separated sludge and the sedimentation promoter, and which returns the separated sedimentation promoter into the second flocculation tank 3; the flocculation and sedimentation device 1 is characterized by being provided with a controller 30 which returns the separated sludge from the cyclone to the first flocculation tank 2 at start-up of the flocculation and sedimentation device 1, and, after completing start-up, controls a switching means to perform switching such that at least part of the separated sludge from the cyclone 20 is discharged to outside of the system.

Description

Coagulation sedimentation apparatus and start-up method thereof

(4) The present invention relates to a coagulation sedimentation apparatus for adding a sedimentation promoting agent and a coagulant to raw water containing a suspended substance to cause coagulation and sedimentation to separate sludge and treated water, and a control method therefor. The present invention particularly relates to a coagulation and sedimentation apparatus configured to separate a slurry extracted from a sedimentation tank into sludge and a sedimentation promoting material by a cyclone, and to return the sedimentation promoting material to the coagulation tank, and a method of starting the same.

A coagulation sedimentation device that separates and removes suspended substances (hereinafter sometimes referred to as SS [Suspended {Solid]}) from raw water by coagulation and sedimentation. A flocculation tank for forming flocculated floc by adding a sedimentation promoting material and a flocculant; a sedimentation tank for sedimenting and separating flocculated floc flowing out of the flocculation tank; and a cyclone for separating the slurry drawn out from the sedimentation tank into particulate matter and sludge. There are known devices that are configured to return granular materials to a coagulation tank and discharge sludge (Patent Documents 1 to 3).

In the coagulation and sedimentation apparatuses of Patent Documents 1 to 3, the inorganic coagulant is added to the raw water introduced into the coagulation tank, the mixture is stirred with a stirrer, then the polymer coagulant is added, and the mixture is stirred with a stirrer to obtain a granular material. (Agglomerated flocs are formed together with (sand etc.). The coagulated water is introduced into a sedimentation tank to separate it by sedimentation, and the treated water flows out from the upper part of the sedimentation tank. Further, the slurry is extracted from the lower part of the settling tank by a pump and sent to a cyclone. In the cyclone, the slurry is centrifuged into sludge and particulate matter, and the separated sludge is discharged out of the coagulation settling apparatus. The particulate matter separated by the cyclone is returned to the flocculation tank and reused for sedimentation.

In Patent Document 3, a flow control valve is provided in a sludge return line for returning at least a part of the sludge discharged from the cyclone to the flocculation tank, and when the SS concentration of the raw water is low, the sludge return amount is increased, and the SS concentration is increased. It is described that control is performed so as to reduce the sludge return amount when the value is high (paragraph 0072).

JP 2000-317220 A JP-A-2002-355507 JP 2014-237122 A

In the case of coagulation sedimentation equipment installed in a facility that treats rainwater drainage in large yards, such as steelworks and cement factories, the tanks of the industrial sedimentation equipment should be used when the equipment is started or when the equipment is restarted after maintenance. Is not filled with water. When the coagulated sedimentation layer is portable, drain water from each tank and extract the sedimentation promoting material during non-rainfall. At the time of rainfall, first, water is poured into each tank of the coagulation sedimentation apparatus, and then operation is resumed by receiving drainage from the yard (hereinafter referred to as yard drainage).

Since the water in each tank (water in the tank) has a remarkably low SS concentration, if the yard wastewater flows into the coagulation sedimentation device at the beginning of rainfall, the yard wastewater is diluted with the water in the tank. The SS concentration in the tank is low. In addition, even if yard wastewater directly flows in without filling, SS concentration is not sufficient because it is not concentrated. Therefore, the concentration of sludge discharged from the coagulation sedimentation device becomes low.
In addition, in the conventional sedimentation tank, the extraction from the sedimentation tank may be intermittently operated in order to promote the concentration of SS. However, when the sedimentation promoting material is contained in the sludge as in the present invention, the sedimentation promoting material accumulates in the bottom pit of the sedimentation tank or in the drawing line, and there is a concern that the sedimentation promoting material is fixed. is there.

The present invention prevents the discharge of low-concentration sludge at the time of startup of a portable coagulation sedimentation device or a coagulation sedimentation device in which water to be treated flows into a coagulation sedimentation device in a state where water is filled in each coagulation tank. It is an object of the present invention to provide a coagulating sedimentation apparatus capable of shortening the start-up time by increasing the SS concentration and a method for starting the same.

The coagulation and sedimentation apparatus of the present invention has a first coagulation tank into which raw water is introduced and performs coagulation treatment with a first coagulation agent, and a first coagulation treatment water discharged from the first coagulation tank, and a second coagulation agent. A second coagulation tank for coagulation treatment with a sedimentation promoting material, a second coagulation treatment water discharged from the second coagulation tank, introduced thereinto, and a sedimentation tank for sedimentation and separation into treated water and slurry, and withdrawn from the sedimentation tank A cyclone for separating the slurry into separated sludge and a sedimentation promoting material and returning the separated sedimentation promoting material to the second flocculation tank, wherein a separated sludge line from a sludge outlet of the cyclone is a sludge discharge line and a sludge circulation line. And the sludge circulation line is connected to the first coagulation tank, and the coagulation and sedimentation device has switching means for switching between the sludge circulation line and the sludge discharge line. The dirt Connected to a circulation line, the separated sludge from the cyclone is returned to the first coagulation tank through the sludge circulation line, and after the start of the coagulation settling apparatus, the separated sludge line is discharged continuously or intermittently. A control means for controlling the switching means so as to be connected to a line or branched to the sludge discharge line and the sludge circulation line to discharge at least part of the separated sludge from the cyclone continuously or intermittently out of the system. It is characterized by having.

In one aspect of the present invention, as the control means, an SS meter provided 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 meter rises to a predetermined concentration. A controller for controlling the switching means so as to return to the first coagulation tank.

In one aspect of the present invention, the amount of the first coagulant added to the first coagulation tank and the amount of the first coagulant added to the second coagulation tank are at least part of the time until the SS concentration detected by the SS meter rises to a predetermined concentration. A coagulant addition amount control unit for increasing the addition amount of the second coagulant is provided.

In one aspect of the present invention, as the control unit, the switching unit is controlled to return 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. It has a timer.

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

In the method for controlling the coagulation sedimentation apparatus of the present invention, a raw water is introduced, a first coagulation tank for coagulation treatment with a first coagulant, and a first coagulation treatment water discharged from the first coagulation tank are introduced. A second coagulation tank for coagulating with a coagulant and a sedimentation promoting material, a sedimentation tank into which second coagulation treatment water discharged from the second coagulation tank is introduced, and sedimented and separated into treated water and slurry; And a cyclone for returning the separated sedimentation promoting material to the second flocculation tank, wherein the separated sludge line from the cyclone sludge outlet is a sludge discharge line and a sludge discharge line. A method for activating a coagulation sedimentation device which is branched into a circulation line and the sludge circulation line is connected to the first coagulation tank. When the coagulation / sedimentation device is started, the separated sludge from the cyclone is passed through the sludge circulation line. No. It returned to flocculation tank, after start end of the aggregated precipitate device and switches to continuously or intermittently out of the system discharging at least a portion of the separated sludge from the cyclone.

In one aspect of the present invention, the amount of the first coagulant added to the first coagulation tank and the amount of the second coagulant added to the second coagulation tank are increased when the coagulation settling apparatus is started.

In one embodiment of the present invention, the raw water is yard drainage.

According to the present invention, the separated sludge discharged from the cyclone is returned to the first flocculation tank when the flocculation and settling apparatus is started, so that the low-concentration sludge is prevented from being discharged. As a result, the SS concentration in the system increases at an early stage, and the start-up time is shortened.

の一 In one embodiment of the present invention, the coagulation action is enhanced by increasing the amount of the first coagulant added when the coagulation and sedimentation apparatus is started, and the discharge of low-concentration sludge is prevented. Further, by increasing the amount of the second coagulant to be added to the first coagulant, insufficient coagulation can be prevented.

It is a block diagram of the coagulation sedimentation apparatus which concerns on embodiment. It is a block diagram of the coagulation sedimentation apparatus which concerns on embodiment. It is a block diagram of the coagulation sedimentation apparatus which concerns on embodiment. It is a block diagram of the coagulation sedimentation apparatus which concerns on embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a coagulation-sedimentation apparatus 1 according to a first embodiment. This coagulation-sedimentation apparatus 1 includes a first coagulation tank 2, a second coagulation tank 3, and a sedimentation tank 4 disposed adjacent to the first coagulation tank 2.

Raw water is introduced into the first flocculation tank 2 through a raw water introduction line 5, an inorganic flocculant (PAC in FIG. 1) is added as a first flocculant by a first chemical injection device 6, and stirred by a stirrer 7. Is done. In the first flocculation tank 2, the inorganic flocculant flocculates the suspended substance to generate fine flocs.

Although not shown, the first coagulation tank 2 is provided with a pH meter and a pH adjuster (caustic soda, sulfuric acid, hydrochloric acid, etc.), and maintains the pH in the first coagulation tank 2 within a predetermined range. It is configured to be able to.

The first coagulation treatment water from the first coagulation tank 2 is introduced into the second coagulation tank 3 through the advection port 8, and a polymer coagulant (polymer) is added as a second coagulant by the second chemical infusion device 9. You. A sedimentation promoting material such as sand is added to the second flocculation tank 3, and fine floc is taken into the sedimentation promoting material via the polymer flocculant by stirring by the stirrer 10, and the flocculation floc having a large specific gravity is added. To grow.

砂 In addition to sand, crushed slag can be used as a sedimentation promoting material. The average particle size of the sedimentation promoting material is preferably about 0.01 to 0.5 mm, and the true specific gravity is preferably 2 or more, particularly 2.5 or more and 4 or less, but is not limited thereto.

{Circle around (2)} The second flocculated water containing the flocculated floc that has grown flows over the overflow weir 12 and is introduced into the sedimentation tank 4. The second flocculated water descends along the weir plate of the overflow weir 12, then rises, passes through the separator, and flows into the outflow chamber 15. In the sedimentation tank 4, flocculated flocs in the second flocculated water are precipitated.

(4) A separator composed of a plurality of inclined plates 13 is provided at the upper part in the sedimentation tank 4 to promote sedimentation and separation of flocculated flocs. The treated water that has passed through the separator is taken out of the outflow pipe 16 through the outflow chamber 15. A rake 14 is provided in the settling tank 4.

(4) A drawing line 17 for extracting a slurry containing precipitated flocculated flocs is connected to the bottom of the settling tank 4. In the drawing line 17, a drawing pump 18 is provided to the cyclone 20 for drawing the slurry. The cyclone 20 is installed such that the axial direction is a vertical direction.

In the cyclone 20, the sent slurry is separated by centrifugation into sludge collected at the axis of the cyclone and sedimentation promoting material collected at the peripheral surface on the cyclone side. The separated sedimentation promoting material is returned from the bottom of the cyclone 20 to the second flocculation tank 3 again by the pipe 19 and is used for circulation.

分離 The separated sludge collected on the axis side in the cyclone 20 flows out to a pipe 21 (separated sludge line) connected to a sludge outlet at the center of the upper surface of the cyclone 20. The pipe 21 branches into

pipes

22 and 25.

Pipe 22 is connected to pipe 24 via valve 23. A sludge discharge line is constituted by the

pipes

22, 24 and the valve 23.

The pipe 25 can return the separated sludge to the first flocculation tank 2 via the valve 26 and the pipe 27. A sludge circulation line is constituted by the

pipes

25 and 27 and the valve 26. The

valves

23 and 26 constitute switching means.

ＳＳ An SS meter 28 such as an optical turbidity meter is installed in the pipe 27, and the detection signal is input to the controller 30. The

valves

23 and 26 are controlled by the controller 30 to switch ON / OFF or adjust the flow rate.

When the coagulating sedimentation apparatus 1 is started to operate, first, fresh water having relatively high clarity such as clean water, well water, river water, rain water, and purified water is filled in each of the

tanks

2, 3, and 4 to a specified water level. . This is to check whether the tanks 2 to 4 and the members are damaged.

(4) When raw water such as yard wastewater starts flowing into this coagulation sedimentation apparatus, an inorganic coagulant is added to the first coagulation tank 2 and a polymer coagulant (polymer) is added to the second coagulation tank 3. Further, a predetermined amount of a sedimentation promoting material is added to the second coagulation tank 3.

The raw water mixes with the fresh water in the first flocculation tank 2, is diluted and subjected to flocculation treatment, flows into the sedimentation tank 4 via the second flocculation tank 3, sedimentation and separation of flocculated floc, and the treated water (clear water) ) Is discharged from the pipe 16.

As described above, when the coagulation and sedimentation apparatus 1 is started, since the raw water is diluted with the fresh water in each of the

coagulation tanks

2 and 3, the SS concentration in each of the

coagulation tanks

2 and 3 is low. The SS concentration of the precipitated slurry is also low. Therefore, the SS concentration of the separated sludge separated by the cyclone 20 is low, and it is not appropriate to discharge the sludge as it is.

Therefore, in this embodiment, the valve 23 is closed and the valve 26 is opened when the coagulation and sedimentation apparatus 1 is started, and the entire amount of the separated sludge from the cyclone 20 is returned from the pipe 27 to the first coagulation tank 2.

(4) The SS concentration of the separated sludge flowing in the pipe 27 is measured by the SS meter 28, and the detection signal is input to the controller 30. The controller 30 controls the valve 23 until the SS concentration detected by the SS meter 28 reaches a preset predetermined concentration (in the case of the coagulation sedimentation apparatus for treating yard wastewater, about 10 to 50 g / L, particularly about 15 to 30 g / L). Is closed and the valve 26 is opened to return the entire amount of the separated sludge to the first flocculation tank 2.

すると When this state is maintained, the SS concentration in the first and

second coagulation tanks

2 and 3 gradually increases, and the SS concentration detected by the SS meter 28 also gradually increases. When the SS concentration detected by the SS meter 28 rises to the above-mentioned predetermined concentration, the controller 30 opens the valve 23 and closes the valve 26, and discharges the entire amount of the separated sludge from the cyclone 20 from the pipe 24.

Thus, when the flocculation and settling apparatus 1 is started, sludge having a low SS concentration is prevented from being discharged from the pipe 24.

In the above description, after the detected SS concentration of the SS meter 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 discharged from the pipe 27 to the first pipe 27. It may be returned to the coagulation tank 2. Further, the separation sludge may be discharged intermittently instead of continuously.

In the first embodiment, the amount of the coagulant added by the first and second

chemical infusion devices

6 and 9 is fixed (quantitative addition method). However, the SS concentration of the raw water may be detected, and the added amount of the flocculant may be controlled according to the detection result.

FIG. 2 shows an aggregating and settling apparatus 1A according to a second embodiment. In the coagulation and sedimentation apparatus 1A, the controller 30 is configured to control the first and second

chemical injection devices

6 and 9 as described later. Other configurations of the coagulation and sedimentation apparatus 1A are the same as those of the coagulation and sedimentation apparatus 1, and the same reference numerals indicate the same parts.

The controller 30 controls opening and closing of the

valves

23 and 26 according to the same starting method as in the first embodiment until the detected concentration of the SS meter 28 rises to a predetermined value when the coagulating sedimentation apparatus 1A is started. . In this embodiment, the controller 30 further controls the inorganic coagulant and the polymer by the first and

second dispensing devices

6 and 9 until the concentration detected by the SS meter 28 increases to a predetermined value. The addition amount of the flocculant is larger than the standard addition amount during the steady operation (for example, 1.5 to 5 times the standard addition amount, particularly 2 to 5 times the standard addition amount). Thereby, the aggregation effect in the first and

second aggregation tanks

2 and 3 is increased, and the SS concentration of the slurry precipitated in the precipitation tank 4 is increased. As a result, the concentration of sludge separated by the cyclone 20 quickly increases to a predetermined value.

FIG. 3 shows a coagulation-sedimentation apparatus 1B according to a third embodiment.

In this embodiment, a timer 31 is provided instead of the controller 30 to control the opening and closing of the

valves

23 and 26. Also, the SS meter 28 is omitted. Other configurations are the same as those of the coagulation and sedimentation apparatus 1 of FIG. 1, and the same reference numerals indicate the same parts.

In this embodiment, the valve 26 is opened and the valve 23 is closed until a predetermined time has elapsed from the start of the flow of raw water into the coagulation and sedimentation device 1B when the coagulation and sedimentation device 1B is started. The entire amount of the separated sludge is returned to the first flocculation tank 2. After a lapse of a predetermined time, 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 returned to the first flocculation tank 2 from the pipe 27, or may be intermittent treatment instead of continuous treatment. The predetermined time is preferably about 0.5 to 4 times the HRT of the coagulation sedimentation apparatus 1B.

も Also in this embodiment, the SS concentration of the slurry precipitated in the precipitation tank 4 increases early. As a result, the concentration of sludge separated by the cyclone 20 increases early.

FIG. 4 shows a coagulating sedimentation apparatus 1C according to a fourth embodiment. The coagulation and sedimentation device 1C includes a timer 31 as in the coagulation and sedimentation device 1B of FIG. 3, and further includes a controller 32 that controls the amount of coagulant added by the first and second

chemical injection devices

6, 9. I have.

The timer 31 opens the valve 26 and closes the valve 23 until a predetermined time elapses from the start of inflow of raw water into the coagulation and sedimentation apparatus 1C (start of operation of the raw water pump), similarly to the coagulation and sedimentation apparatus 1B of FIG. The entire amount of the separated sludge from the cyclone 20 is returned to the first flocculation tank 2. After a lapse of a predetermined time, 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 returned to the first flocculation tank 2 from the pipe 27, or may be intermittent treatment instead of continuous treatment.

The controller 32 controls the inorganic coagulant and the polymer by the first and second

chemical injection devices

6 and 9 until a predetermined time elapses from the start of the coagulation and sedimentation device 1C (start of the timer 31 (start of operation of the raw water pump)). The addition amount of the flocculant is made larger than the standard addition amount in the steady operation (for example, 1.5 to 5 times the standard addition amount, respectively). Thereby, the aggregation effect in the

aggregation tanks

2 and 3 increases, and the SS concentration of the slurry precipitated in the precipitation tank 4 increases. As a result, the concentration of sludge separated by the cyclone 20 increases to a predetermined value at an early stage.

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

凝集 The coagulation sedimentation apparatus and its activation method according to the present invention are suitable for treating yard wastewater, but can also be applied to other various wastewater treatments.

「“ Starting up ”of the coagulation sedimentation apparatus in the present invention includes not only the start of operation of the newly installed apparatus but also the first start of operation after draining water from each tank, such as for maintenance and transportation.

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

The above embodiment is an example of the present invention, and the present invention may be applied to other modes. For example, in the embodiments of FIGS. 1 and 2, the SS meter is provided on the pipe 27, but may be provided on the

pipe

21 or 25. In addition, in the embodiments of FIGS. 2 and 4, the period in which the amount of addition of various coagulants is increased may be a part of the period in which the valve 26 is open.

Although the 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 spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2018-151718 filed on August 10, 2018, which is incorporated by reference in its entirety.

1, 1A, 1B, 1C Coagulation and sedimentation apparatus 2 First coagulation tank 3 Second coagulation tank 4 Sedimentation tank 6 First chemical injection device 9 Second chemical injection device 20

Cyclone

23, 26 Valve 28 SS meter 30, 32 Controller 31 timer

Claims

A first coagulation tank into which raw water is introduced and coagulation treatment is performed with a first coagulant;
A second coagulation tank into which the first coagulation treatment water discharged from the first coagulation tank is introduced and coagulated by a second coagulant and a sedimentation promoting material;
A second coagulation treatment water discharged from the second coagulation tank is introduced, and the sedimentation tank sediments and separates into treated water and slurry;
A cyclone for separating the slurry extracted from the sedimentation tank into separated sludge and a sedimentation promoting material, and returning the separated sedimentation promoting material to the second flocculation tank;
A separated sludge line from the sludge outlet of the cyclone is branched into a sludge discharge line and a sludge circulation line,
The sludge circulation line is connected to the first flocculation tank,
In the coagulation sedimentation apparatus having switching means for the sludge circulation line and the sludge discharge line,
When the coagulation settling apparatus is started, the separated sludge line is connected to the sludge circulation line, and the separated sludge from the cyclone is returned to the first coagulation tank through the sludge circulation line,
After the start of the coagulation sedimentation apparatus, the separated sludge line is connected to the sludge discharge line continuously or intermittently or branched into the sludge discharge line and the sludge circulation line to separate at least one of the separated sludge from the cyclone. A coagulating sedimentation apparatus comprising: a control unit that controls the switching unit so that the unit is continuously or intermittently discharged from the system.
As the control means, an SS meter provided in the separated sludge line or the sludge circulation line, and the separated sludge from the cyclone is returned to the first flocculation tank until the detected SS concentration of the SS meter rises to a predetermined concentration. The coagulating sedimentation apparatus according to claim 1, further comprising: a controller that controls the switching unit so as to perform the switching.
The amount of the first flocculant added to the first flocculating tank and the amount of the second flocculant added to the second flocculating tank during at least a part of the period until the SS concentration detected by the SS meter rises to the predetermined concentration. The coagulation sedimentation apparatus according to claim 2, further comprising a coagulant addition amount control unit for increasing the amount of coagulant.
A timer for controlling the switching means so that the separated sludge from the cyclone is returned to the first flocculation tank for a predetermined time after starting supply of raw water to the first flocculation tank, as the control means. 2. The coagulation sedimentation apparatus according to 1.
In at least a part of a 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 to the second coagulation tank The coagulation sedimentation apparatus according to claim 4, further comprising a coagulant addition amount control unit for increasing the addition amount of the agent.
A first coagulation tank into which raw water is introduced and coagulation treatment is performed with a first coagulant;
A second coagulation tank into which the first coagulation treatment water discharged from the first coagulation tank is introduced and coagulated by a second coagulant and a sedimentation promoting material;
A second coagulation treatment water discharged from the second coagulation tank is introduced, and the sedimentation tank sediments and separates into treated water and slurry;
A cyclone for separating the slurry extracted from the sedimentation tank into separated sludge and a sedimentation promoting material, and returning the separated sedimentation promoting material to the second flocculation tank;
A separated sludge line from the sludge outlet of the cyclone is branched into a sludge discharge line and a sludge circulation line,
In the method for starting a coagulation settling apparatus in which the sludge circulation line is connected to the first coagulation tank,
When the coagulation settling apparatus is started, the separated sludge from the cyclone is returned to the first coagulation tank through the sludge circulation line,
A method for activating a coagulation sedimentation device, comprising switching at least part of the separated sludge from the cyclone to be continuously or intermittently discharged from the system after the start of the coagulation sedimentation device.
The start-up of the coagulation-sedimentation apparatus according to claim 6, wherein when the coagulation-sedimentation apparatus is started, the amount of the first coagulant added to the first coagulation tank and the amount of the second coagulant added to the second coagulation tank are increased. Method.
The method according to claim 6 or 7, wherein the raw water is yard drainage.