JP2019063764A - Coagulator and operational method therefor - Google Patents

Abstract

To provide a method and device capable of cleaning a polluted pipeline without needing a large amount of labor nor using a cleaned water.SOLUTION: There is provided the operational method for a coagulator separating a water to be treated into a sludge and a treated water. The coagulator has a sludge blanket type settling tank from which the sludge and the treated water are discharged, and includes a process of extracting a sludge blanket-forming fluid from the settling tank to clean at least a part of a polluted pipeline through which the sludge flows. The coagulator is suitably used for the above cleaning method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coagulation sedimentation apparatus.

  Coagulation and settling equipment, which is one of water treatment apparatuses, is widely used for wastewater treatment and the like. In the coagulation / sedimentation apparatus, suspended matter contained in the treated water (raw water) supplied to the coagulation / sedimentation apparatus is coagulated to form flocculated flocs, and the flocculated floccs are precipitated in the sedimentation tank, whereby the raw water is converted to sludge. Separate with treated water. The flocculation of the suspended matter can be carried out, for example, in a reaction vessel or flocculation vessel provided upstream of the settling vessel.

  The sludge discharged from the settling tank is sent to a sludge treatment facility (for example, including a sludge dehydrator and a sludge concentration tank) provided downstream of the coagulation settling apparatus. In addition, it is known that in the coagulation settling apparatus, part of the sludge discharged from the settling tank is returned to the reaction tank.

  Patent Document 1 discloses a coagulation / sedimentation apparatus provided with a reaction tank, a sedimentation tank, a sludge discharge pit at the bottom of the sedimentation tank, and a return pipe that returns part of the sedimented sludge to the reaction tank. The apparatus is provided with a supernatant water outlet pipe whose upper end opens above the sludge settling interface of the sedimentation tank and whose lower end communicates with the sludge discharge pit or return pipe. The supernatant water from the supernatant water extraction pipe is mixed with the sedimented sludge from the return pipe, and then returned to the reaction tank to completely prevent the sludge from being clogged in the return pipe, while the sludge in the sedimentation tank is Increase sedimentation and efficiently carry out sedimentation.

  This document discloses that when the sedimented sludge is transported to the reaction tank without mixing the supernatant water, the concentration of the sludge proceeds but, on the other hand, the clogging of the sludge occurs in the return pipe. Also, it is disclosed that the clogging of the sludge in the return pipe does not occur during continuous operation but occurs when the inflow of the raw water to the reaction tank is stopped. Furthermore, when clogging occurs, it is necessary to clean the return pipe with high-pressure water, or to physically clean by hand to remove the clogged sludge, and it is disclosed that much effort is required for recovery. Ru.

  In addition, Patent Document 2 discloses a coagulation sedimentation system including a reaction tank and a coagulation sedimentation tank. The coagulation sedimentation tank comprises a sludge blanket portion having a floc growth zone and a separation zone formed above the growth zone. It is said that the increase in linear velocity (LV) of the upflow in the sludge blanket can be suppressed by extracting the sludge from below the separation zone and returning the extracted sludge to the coagulation reaction tank for circulation.

JP-A-8-299705 JP, 2015-181975, A

  Patent Document 1 describes that clogging of sludge in the return pipe does not occur during continuous operation. However, according to the study of the present inventors, the piping of the coagulation sedimentation apparatus through which the sludge discharged from the settling tank flows (hereinafter sometimes referred to as "sludge piping") may be clogged even during continuous operation. is there.

  Patent Document 1 mentions high-pressure water washing and physical washing by manpower as a method for solving the clogging of sludge. However, as described also in Patent Document 1, these methods require much effort.

  Furthermore, clear water such as industrial water is used for high pressure water washing. Therefore, when the sludge piping is washed with high pressure water, the sludge piping is filled with the clear water when the operation of the coagulation sedimentation apparatus is restarted after the clogging is eliminated. Therefore, when the operation is resumed, the clear water flows into the sludge treatment facility, and also flows into the reaction tank and the coagulation tank which exist upstream of the settling tank. The fact that the clear water flows into the sludge treatment facility means that the load on the sludge treatment facility (for example, a sludge dewatering machine, a sludge concentration tank) is increased. In addition, when clear water flows into the reaction tank or the coagulation tank, the concentration of SS (suspended substance) in these tanks changes rapidly, so the amount of chemicals such as coagulant is out of the proper range As a result, there is a possibility that the quality of treated water obtained from the coagulating settling apparatus may be reduced after resuming operation.

  Even if it is considered to wash the sludge piping using the supernatant water as described in Patent Document 1, the supernatant water is clear water since it is water present on the upper side of the sludge sedimentation interface. Therefore, the load increase of the above-mentioned sludge treatment equipment and the water quality fall of treated water may occur.

  An object of the present invention is to provide a method and an apparatus capable of cleaning a sludge pipe without much labor and without using clear water.

According to one aspect of the invention,
An operation method of a coagulation sedimentation apparatus for separating water to be treated into sludge and treated water,
The coagulating settling apparatus has a sludge blanket type settling tank to which the sludge and the treated water are discharged,
a) removing the fluid forming the sludge blanket from the settling tank and using the removed fluid as washing water to wash at least a part of the sludge piping, which is a piping through which the sludge flows;
There is provided a method of operating a flocculating and settling apparatus comprising:

According to another aspect of the invention,
A coagulation sedimentation apparatus for separating water to be treated into sludge and treated water,
A sludge blanket type settling tank from which the sludge and the treated water are discharged;
Sludge piping, which is a piping through which sludge discharged from the settling tank flows;
A pipe for extracting a fluid forming a sludge blanket from the settling tank, the pipe being connected to the sludge pipe;
A first valve provided in the extraction pipe;
A coagulation / sedimentation apparatus is provided, which is provided in the sludge pipe, and includes a second valve located between the sludge pipe and a portion where the extraction pipe is connected and the sedimentation tank.

  ADVANTAGE OF THE INVENTION According to this invention, the method and apparatus which can wash | clean a sludge piping without using a lot of labor and using clear water are provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of one form of the coagulating sedimentation apparatus suitable for implementing this invention.

  The present invention relates to a method of operating a coagulation / sedimentation apparatus for separating water to be treated (raw water) supplied to the coagulation / sedimentation apparatus into sludge and treated water. This coagulating settling apparatus has a sludge blanket type settling tank in which sludge and treated water are discharged. And this operation method includes the process a.

  There is no restriction | limiting in particular about raw water, Raw water known in the field | area of a coagulation sedimentation apparatus can be used suitably.

[Sludge blanket type sedimentation tank]
The sludge blanket type sedimentation tank discharges sludge and treated water while forming a sludge blanket which is a floating layer of flocculated floc in treated water. As this settling tank, a sludge blanket type settling tank known in the field of coagulating settling apparatuses can be adopted appropriately.

  The sludge blanket is a floating layer of flocculated floc. A flocculated floc can be formed by flocculating suspended matter in the raw water. This aggregation can be performed upstream of the sludge blanket type sedimentation tank, for example, in a reaction tank provided upstream of the sedimentation tank. In the case where a coagulation tank is provided upstream of the settling tank and downstream of the reaction tank, coagulation can be promoted in the coagulation tank.

  In the sludge blanket, the treated water containing flocculated floc flows upward, the settling speed of the flocculated floc and the rising speed of the treated water are balanced, and the flocculated floccs are densely floated.

  A layer of clear water is formed on the sludge blanket. Treated water can be drained from the layer of clear water. The interface between the sludge blanket and the clear water layer can be detected by an ultrasonic interface meter or the like.

  The sludge blanket type sedimentation tank is provided with a sludge concentration unit that precipitates flocculated floc in the fluid flowing out from the sludge blanket and condenses flocculated floc to obtain sludge.

  In the sludge blanket type sedimentation tank, for example, the sludge blanket can be stirred and granulated in the sedimentation tank to increase the particle size of the flocculated floc contained in the sludge blanket to form so-called pellets. Alternatively, a sludge blanket type settling tank which does not perform such stirring and granulation can also be used.

[Return of sludge]
In the coagulation / sedimentation apparatus, the sludge discharged from the sludge blanket type sedimentation tank can be returned upstream from the sedimentation tank, for example, to a reaction tank or a coagulation tank provided upstream from the sedimentation tank.

[Step a]
In step a, the fluid forming the sludge blanket (hereinafter sometimes referred to as "sludge blanket forming fluid") is extracted from the sedimentation tank, and the extracted fluid is used as cleaning water, and piping through which the sludge flows (i.e. sludge) Clean at least part of the piping). The sludge piping may include piping (hereinafter, also referred to as “sludge transfer piping”) for transferring at least a part of the sludge discharged from the sludge blanket type sedimentation tank to the sludge treatment facility downstream of the coagulation sedimentation apparatus. it can. In addition, the sludge piping can include piping (hereinafter, may be referred to as “sludge return piping”) that returns a part of the sludge discharged from the settling tank upstream of the settling tank in the coagulation sedimentation apparatus.

  Cohesive floc floats in the sludge blanket. On the other hand, in the case of sludge, flocculated floc which constitutes the sludge blanket is concentrated by sedimentation and the like. Thus, the flocculated floc concentration of the fluid withdrawn from the sludge blanket is lower than that of the sludge. Also, the flocculated floc concentration of this fluid is higher than that of clear water. By washing the sludge piping using such a fluid instead of the clear water, it is possible to stably send high concentration sludge to the sludge treatment facility without filling the sludge piping with the clear water, the sludge treatment facility Without increasing the load on In addition, when sludge is returned to the upstream side of the settling tank, the concentration of the returned sludge is not changed rapidly, so the SS concentration in the reaction tank or the aggregation tank does not need to be changed rapidly, and the water quality of the treated water is lowered. You can prevent. In addition, a great deal of effort is not required for cleaning.

  The above cleaning can be performed by flowing the fluid extracted from the sludge blanket to at least a part of the sludge piping. Which part of the sludge piping is to be cleaned can be determined as appropriate. There are parts in the sludge piping where it is difficult for the fluid extracted from the sludge blanket to flow, such as in the vicinity of the sludge discharge port of the sludge blanket type sedimentation tank (for example, for convenience of trimming by valves etc.) In that case, the fluid may not flow in that portion. The fluid after being used for cleaning can be returned upstream (for example, a reaction tank or a coagulation tank) than the sedimentation tank, or can be discharged from the coagulation sedimentation apparatus (in particular, sent to a sludge treatment facility). It is also possible to do both return and discharge.

  In the coagulating settling apparatus, separation of the sludge from the raw water and the treated water is usually performed continuously. At this time, sludge is continuously discharged from the sludge blanket type settling tank. If sludge piping is blocked while sludge is being discharged from the sludge blanket type sedimentation tank, such as during continuous operation of the coagulation sedimentation apparatus, problems such as pump shut-off occur, and piping and pumps are damaged. there's a possibility that.

  In order to avoid such a situation, step a is performed. Preferably, step b described later is performed.

  Step a can be performed while the operation of the coagulation sedimentation apparatus is continued. At the time of normal treatment, that is, when raw water is supplied to the coagulating and settling apparatus and the treated water and the sludge are discharged from the settling tank, the sludge extracted from the settling tank is flowed to the sludge piping. When step a is performed, that is, at the time of washing, discharge of sludge from the settling tank is stopped, and instead, the sludge blanket forming fluid can be extracted from the settling tank and allowed to flow into the sludge piping. Also when performing the process a, supply of the raw water to a coagulation-sedimentation apparatus can be continued, and treated water can be obtained from a sedimentation tank.

  The flow rate of the sludge blanket forming fluid extracted from the sedimentation tank as washing water in step a is the specification of equipment such as the degree of contamination of the sludge piping and the pump for transporting the sludge blanket forming fluid (pump P in FIG. 1). Depends on If a pump with an inverter control function is used as the pump, a greater cleaning effect can be obtained by increasing the inverter output in step a.

  Also, step a can be performed to such an extent that washing can be sufficiently performed. For example, the washing by the step a can be performed until the flow rate of the washing water flowing through the sludge piping becomes approximately the same as the sludge discharge flow rate from the settling tank at the time of normal treatment.

[Step b]
In step b, while the sludge is being discharged from the sludge blanket type settling tank, the blockage of the sludge pipe is detected or predicted based on the measurement value of the flow meter that detects the flow rate of the sludge in the sludge pipe. Then, when the blockage is detected or predicted, the discharge of the sludge from the sludge blanket type settling tank is stopped, and the process proceeds to step a. Steps a and b can be performed automatically using an appropriate measurement control device.

  When the measured value of the flowmeter which detects the flow rate of the sludge becomes zero, it can be judged that the blockage of the sludge piping has been detected. In addition, when the measured value of the flowmeter decreases, for example, when the measured value of the flowmeter decreases while operating the coagulation sedimentation apparatus under the condition that the flow rate of sludge in the sludge pipe becomes constant, the sludge pipe It can be determined that the occlusion of the patient is predicted. For example, when operating the coagulation sedimentation apparatus under the condition that the flow rate of sludge in the sludge pipe becomes constant at a certain value F, when the measured value of the flowmeter falls below a predetermined ratio of the flow rate F It can be judged that the clogging of the sludge piping was predicted. This predetermined ratio can be appropriately set by a preliminary test or the like, and for example, 80% can be adopted.

  As a flow meter, there is no internal structure that obstructs the flow of sludge, and there is substantially no pressure loss compared to a float type or impeller type flow meter so that there is no sludge blockage in the flow meter. Preferred are flow meters such as electromagnetic flow meters and ultrasonic flow meters.

  Moreover, as a flow meter, what can carry out analog output of a 4-20 mA output etc. of the signal according to a measured value is preferable. Alternatively, a switch-type flow meter that can output a signal when the measured flow value becomes equal to or less than a predetermined value, and can open / close control the valve by this signal is also preferable.

  If an analog output flowmeter is used, it can be known that the flow rate has decreased with the passage of time, so it is easy to predict the clogging of the sludge piping. Therefore, the sludge piping can be cleaned relatively early. Furthermore, depending on the degree of flow rate reduction, it is possible to use different types of washing water having different flocculated floc concentrations. In addition, in the case where the flow rate decreases frequently, it may be combined with a timer to control the cleaning time and the cleaning frequency.

  Even when using a flow meter whose output is a switch type, switches (signals) at multiple points are prepared, and it is possible to selectively use washing water with different flocculated floc concentrations depending on the decreased flow rate, and The frequency can be controlled in combination with the timer.

  The piping for discharging the sludge from the sludge blanket type sedimentation tank is branched, one branch piping is connected to the sludge treatment facility downstream of the coagulation sedimentation device, and the other branch piping is sedimented in the coagulation sedimentation device. It can be returned upstream from the tank. In this case, it is preferable to install the flowmeter on a pipe (sometimes referred to as a "header pipe") upstream of the branch point and discharging the sludge from the sludge blanket type settling tank. This is because sludge blockage can be detected or predicted regardless of which branch piping is used.

[Control by timer]
Aside from the step b or in addition to the step b, the step a can be performed periodically by stopping the discharge of the sludge from the settling tank. Such periodic operation is particularly effective, for example, when sludge clogging frequently occurs, and can be implemented using a timer. For example, when it is assumed that the flow rate reduction occurs about once in one hour, the periodic operation (stoppage of sludge discharge and step a) is automatically performed about once in 50 minutes, Control can be performed by the timer. The periodic operation is preferably performed in addition to step b, from the viewpoint of more reliably preventing clogging.

[Extraction from multiple places]
Among the sludge blanket zones, flocculated flocs with low settling velocity flow on top. Therefore, the flocculated floc concentration in the sludge blanket is different depending on the position in the height direction. Therefore, by providing a plurality of extraction pipes for extracting the sludge blanket forming fluid from different positions in the height direction of the sludge blanket, it is possible to extract cleaning water having different flocculated floc concentrations.

  One of a plurality of such extraction pipes can be selected, and the fluid extracted from the selected extraction pipe can be used as cleaning water. For example, when it is desired to obtain a higher cleaning effect, for example, when the degree of blockage is large, selecting a pipe with a higher extraction position from the sludge blanket, that is, extracting a fluid with a lower concentration of flocculated floc from the sludge blanket. Is preferred. However, from the viewpoint of making the change of the flocculated floc concentration smaller and stabilizing the quality of the treated water, it is better to select a drain pipe with a lower location from the sludge blanket, that is, a fluid with a higher flocculated floc concentration from the sludge blanket. It is preferable to withdraw.

  Also, in some cases, the clear water above the sludge blanket can be withdrawn and used as wash water to wash at least a portion of the sludge piping. To that end, in addition to one or more withdrawal pipes, a pipe may be provided to withdraw the clear water above the sludge blanket.

  The height of the upper surface of the blanket (the position of the interface with the clear water layer) when the water to be treated continues to flow into the sludge blanket type sedimentation tank can be roughly estimated from the specifications and dimensions of the coagulating sedimentation apparatus. Therefore, it is possible to determine the connection position of the piping for drawing out the sludge blanket forming fluid, and in some cases, to determine the connection position of the piping for drawing the clear water.

[Flocculated floc concentration]
Although depending on the specification and operation conditions of the coagulation / sedimentation apparatus, the concentration of the sludge discharged from the sludge blanket type sedimentation tank (aggregation floc concentration) is, for example, about 3 to 20% by mass. Typical sludge concentration is about 3 to 6% by mass with a general sludge blanket, and among the sludge blanket types, pellets are gently stirred in the sedimentation tank and coagulated / granulated / concentrated in the sedimentation tank In the case of a blanket type coagulating sedimentation apparatus, it is about 8 to 20% by mass.

  On the other hand, the flocculated floc concentration in the sludge blanket forming fluid is, for example, about 0.2 to 12% by mass. However, when the same flocculation settling apparatus is operated at the same operating conditions, the flocculated floc concentration in the sludge blanket forming fluid is lower than the concentration of sludge discharged from the sludge blanket type settling tank.

  The clear water layer formed above the sludge blanket has, for example, an SS concentration of 20 mg / L or less and is in a very clean state.

[Configuration of flocculating and settling apparatus]
Hereinafter, the present invention will be described with reference to the drawings, but the present invention is not limited thereby. FIG. 1 is a view showing a schematic configuration of one embodiment of a coagulation sedimentation apparatus suitable for practicing the present invention.

  The coagulating and settling apparatus shown in FIG. 1 has a reaction vessel 10 and a settling vessel 20.

Raw water is supplied to the reaction tank 10 from the reaction vessel line L1. In the water to be treated contained in the reaction tank 10, a flocculant for aggregating suspended matter in the water to form aggregation flocs, and a pH adjuster for adjusting the pH of the water to be treated Is added.

  As a structure of the reaction tank 10, a well-known structure can be suitably employ | adopted in the field | area of a coagulation precipitation apparatus. The reaction vessel 10 can have a stirrer 11. The stirrer 11 rapidly stirs the treated water to which the coagulant is added to form a flocculated floc.

  As the flocculant and the pH adjuster, those known in the field of coagulating and settling apparatuses can be appropriately adopted. As the coagulant, for example, PAC (polyaluminum chloride) which is an inorganic coagulant, and a cationic polymer which is a polymer coagulant are used. The pH adjuster is, for example, caustic soda (sodium hydroxide).

  Furthermore, a part of the sludge discharged from the settling tank 20 can be returned to the reaction tank 10 through the pipe L6.

[Settling tank]
The to-be-processed water containing an aggregation floc flows in into the sludge blanket type sedimentation tank 20 through the piping L2. The settling tank 20 has a region in which a sludge blanket is formed, that is, a sludge blanket portion Z1 and a region in which a layer of clear water is formed thereon, that is, a clear water portion Z2. Treated water is discharged from the layer of clear water, particularly from the upper end thereof, through the pipe L3.

  Before the water to be treated sent from the reaction tank 10 reaches the sludge blanket, a promoter that promotes the grain growth or coarsening of the flocculated floc can be added to the water to be treated. For example, when using the settling tank 20 which has the distributor 21 as shown in FIG. 1, a promoter can be added to to-be-processed water in the distributor 21. As shown in FIG. Alternatively, an accelerator may be added in the middle of the pipe L2. As the promoter, promoters known in the field of coagulating and settling apparatuses can be appropriately adopted. The promoter is, for example, an anionic polymer.

  The distributor 21 has an inlet to which the water to be treated from the pipe L2 is supplied, and an outlet of the water to be treated opened at the bottom of the sludge blanket zone Z1. Moreover, the stirring blade 22 is fixed to the distributor 21, and by rotating the distributor 21, the sludge blanket can be stirred to promote aggregation to perform granulation (pellet formation). In this case, the pellets form a sludge blanket.

  The sludge blanket type sedimentation tank 20 has a double cylinder structure. The outer cylinder of the double cylinder structure is used as the sludge blanket portion Z1, that is, the sludge blanket is formed on the outer cylinder. The sludge concentration part Z3 is provided in the inner cylinder of a double cylinder structure. The sludge blanket portion Z1 and the sludge concentration portion Z3 are partitioned by a cylindrical body 23 extending in the vertical direction. The upper end of the cylinder state is open, and the pellets constituting the sludge blanket portion Z1 flow out in a form overflowing the opening and are introduced into the sludge concentration portion Z3. Therefore, in the vertical direction, the position of the upper end of the sludge concentration section Z3 is the same as the position of the upper end of the sludge blanket section Z1.

  In the sludge concentration section Z3, flocculated floc in the fluid flowing out of the sludge blanket is precipitated and concentrated to form concentrated sludge. The distributor 21 has a support member 24 provided with a stirring blade different from the stirring blade 22 (a stirring blade for stirring the sludge deposited in the sludge concentration section Z3 to suppress the sticking thereof). The support member 24 extends into the sludge concentration section Z3. The support member 24 is rotated by the motor M, and as a result, the distributor 21 is rotated.

  Concentrated sludge is discharged from the sludge concentration unit Z3 through the pipe L4. The pipe L4 is provided with a valve V4, a pump P, and a flow meter FI. The pipe L4 is branched into a sludge transfer pipe L5 for transferring sludge to a sludge treatment facility located downstream of the coagulating sedimentation apparatus, and a sludge return pipe L6 for returning sludge to the reaction tank. The pipes L5 and L6 are provided with valves V5 and V6, respectively. The pipe L4 corresponds to the aforementioned header pipe.

  While the concentrated sludge is being discharged from the sedimentation tank 20, that is, when the concentrated sludge is discharged, the blockage of the sludge pipe is detected or predicted based on the measurement value of the flowmeter which detects the flow rate of the sludge in the sludge pipe When the blockage of the sludge is detected or predicted, the discharge of the concentrated sludge from the settling tank is stopped and the step a is performed (step b).

  When sludge is discharged, sludge may be returned upstream or may not be returned. When the sludge is not returned, the sludge flows through the pipes L4 and L5 but not through the pipe L6 (valves V4 and V5 are open and V6 is closed). In this case, the pipes L4 and L5 correspond to sludge pipes. When the sludge is returned upstream, the sludge flows through the pipes L4, L5 and L6 (all the valves V4, V5 and V6 are open). In this case, the pipes L4, L5 and L6 correspond to sludge pipes. In addition, when return of sludge is unnecessary, piping L6 and valve V6 are unnecessary.

  The detection or prediction of the clogging of the sludge pipe can be performed as described above using the flow meter FI.

  The sludge blanket type sedimentation tank 20 is provided with a plurality of extraction pipes for extracting the sludge blanket forming fluid from the sedimentation tank from different positions in the height direction of the sludge blanket (pipes L11, L12 and L13). Valves V1, V2 and V3 are respectively provided to the plurality of extraction pipes. The drawn pipes L11, L12 and L13 are all connected to the sludge pipe (in particular, the pipe L4). However, the extraction pipes L11, L12 and L13 share a part with each other.

  The valves (valves V1, V2 and V3) provided in the extraction pipe (pipes L11, L12 and L13) may be referred to as "first valve". On the other hand, a valve (valve V4) provided in the sludge pipe (pipe L4) and located between the connection point between the sludge pipe and the withdrawal pipe and the sludge blanket type sedimentation tank 20 is a “second valve” It may be called.

  In step a, one of the plurality of drawn pipes L11, L12 and L13 can be selected, and the fluid drawn from the selected pipe can be used as cleaning water. The method of selecting one pipe is as described above.

  An output signal of the flow meter FI is sent to a controller (not shown). This controller is based on the measured value of the flowmeter FI while the second valve V4 of the sludge line is open and all the first valves V1, V2 and V3 of the withdrawal line are closed, ie when the sludge is discharged. To detect or predict the blockage of sludge piping. And when the obstruction of sludge piping is detected or predicted, the control device closes the second valve V4 of the sludge piping, and is provided for only one of the plurality of extraction piping. It has a function of opening the valve (a function of opening one of the first valves V1, V2 and V3 and closing the other two). As a control device, a programmable control device known in the field of coagulation sedimentation devices, such as a computer, can be suitably used. The controller is suitably programmed to perform the above functions. In addition, the control device appropriately performs input / output of signals, for example, input of signals from the flow meter FI, and output of signals for operating the respective valves.

  In addition, as the valves V1 to V6, a closing valve or a flow control valve can be appropriately selected and used. In addition to the devices described thus far, known devices in the field of the flocculating and settling apparatus can be used as appropriate. For example, in the middle of sludge return piping, the reproduction tank which reproduces aluminum by addition of an acid or alkali can be provided.

Example 1
Raw water was separated into sludge and treated water using a coagulation sedimentation apparatus having the configuration shown in FIG. The main equipment specifications are as follows.
The diameter of the sludge blanket type settling tank 20: 1.1 m.
The diameter of the sludge concentration section Z3: 0.25 m.
Sludge concentration part Z3 height: 0.9 m.

  As raw water, kaolin simulated drainage (SS concentration: about 500 mg / L) in which kaolin was suspended in filtered water obtained by filtering ground water was used.

Raw water was first introduced into the reaction tank 10, where PAC and cationic polymer were added such that the concentration in the water to be treated had the value indicated below. In addition, sodium hydroxide for pH adjustment was also added (pH adjusted to 7).
PAC (inorganic flocculant): 150 mg / L.
Cationic polymer (polymer flocculant): 2.0 mg / L.

In the reaction vessel 10, fibrous clumps of floc were formed. An anionic polymer was added to the treated water containing flocculated floc near the inlet of the distributor 21 so that the concentration in the treated water had the value shown below.
Anionic polymer (aggregation promoter): 3.0 mg / L in treated water.

  In the sludge blanket portion Z1, stirring was gently performed by a stirring blade, and the mechanical dewatering action of the flocculated floc and the rolling motion of the floc formed spherical pellets having a high settling speed.

In the sludge blanket type sedimentation tank 20, the flow rate of the water to be treated was 18 m ³ / h (linear velocity LV: 19 m / h).

Concentrated sludge sediment-concentrated in the sludge concentration section Z3 is withdrawn from the sedimentation tank 20 to the pipe L4 by the pump P, and is returned to the upstream reaction tank 10 through the pipe L6 (valves V4 and V6 open, valve V5 is Closed). The sludge flow rate measured by the flow meter FI was 2 m ³ / h.

  As described above, the steady and continuous operation of the coagulating and settling apparatus was continued, and the separation of raw water into sludge and treated water was continuously continued. However, when the concentrated sludge was accumulated in the sludge concentration section Z3, the concentrated sludge was temporarily discharged to the sludge treatment facility via the pipes L4 and L5 (valves V4 and V5 are open and valve V6 is closed).

During continuous operation, when the sludge blockage is detected or predicted by the flow meter FI that measures the sludge flow rate, the sludge withdrawal valve (second valve) V4 is closed, and one of the first valves V1 to V3 is closed. Was cleaned to confirm that the sludge flow rate recovered to 2 m ³ / h.

Specifically, when the measured value of the flow meter FI becomes 80% or less (1.6 m ³ / h or less) of the above steady-state value 2 m ³ / h, the valve V4 is closed and the valve V1 is opened. Washing was continued until the measured value of the total FI reached 1.9 m ³ / h or more. Then, after the flow rate recovered to 1.9 m ³ / h or more, washing was continued for another 10 seconds from that point on just in case, and valve V1 was closed and V4 was opened. By this operation, it was confirmed that the sludge circulation amount recovered to 2 m ³ / h. The same test was conducted by operating the valve V2 or V3 instead of the valve V1.

  In addition, the height of the interface between the sludge blanket and the clear water layer may temporarily decrease at the time of washing, but since the washing can be performed while the operation of the coagulation sedimentation apparatus is continued, the height of this interface is , Can be returned to the height before the start of cleaning.

  The results are shown in Table 1. The properties of the sludge discharged from the pipe L4 during continuous operation are also shown in Table 1.

  As a result of the experiment, the sludge concentration was different depending on the withdrawal position (height) of the sludge blanket, and the sludge concentration was higher closer to the bottom of the settling tank. The washing water withdrawal site 3 (the position where the sludge blanket was withdrawn by the pipe L13) was at the interface position of the sludge blanket with the clear water layer. Therefore, in the washing water extraction place 3, a mixture of the fluid forming the sludge blanket and the clear water on the upper part was extracted, and the sludge concentration was 0.8 mass%.

When the sludge (sludge concentration 8 to 12% by mass) was discharged from the sedimentation tank 20, the flow rate measurement value of the flowmeter FI dropped irregularly. The detection of the decrease in the flow rate corresponds to the detection or prediction of the clogging of the sludge pipe. As soon as a drop in flow rate is detected, as shown in Table 1, one of the valves V1 to V3 is opened, and the fluid withdrawn from the sludge blanket is used to clean the sludge piping whose clogging has been detected or predicted. The sludge discharge amount (flow rate in the pipe L4) could be recovered to the specified flow rate (2 m ³ / h).

10 Reaction tank 20 Sludge blanket type sedimentation tank Z1 Sludge blanket part Z2 Clearing water part Z3 Sludge concentration part L1 Piping (for raw water supply)
L2 piping (for supply of treated water to settling tank)
L3 piping (for treated water discharge)
L4 Sludge piping header pipe L5 Sludge transfer piping L6 Sludge return piping L11 to L13 Extraction piping P Pump FI Flow meter V1 to V3 Valve provided on the extraction piping (first valve)
Valve (second valve) provided on the header pipe of V4 sludge piping
V5 Valve provided on sludge transfer piping V6 Valve provided on sludge return piping

Claims (9)

An operation method of a coagulation sedimentation apparatus for separating water to be treated into sludge and treated water,
The coagulating settling apparatus has a sludge blanket type settling tank to which the sludge and the treated water are discharged,
a) removing the fluid forming the sludge blanket from the settling tank and using the removed fluid as washing water to wash at least a part of the sludge piping, which is a piping through which the sludge flows;
The method of operation of the coagulation sedimentation device, including: b) while discharging the sludge from the settling tank, detect or predict the blockage of the sludge pipe based on the measurement value of a flow meter that detects the flow rate of the sludge in the sludge pipe, and
Stopping the discharge of the sludge from the settling tank and moving to the step a when the clogging of the sludge pipe is detected or predicted;
The operating method according to claim 1, comprising A plurality of extraction pipes are connected to the sedimentation tank for extracting the fluid forming the sludge blanket from different positions in the height direction of the sludge blanket,
The operating method according to claim 1 or 2, wherein in the step a, one of the plurality of drawn pipes is selected, and a fluid extracted from the selected pipe is used as the cleaning water. The settling tank has a double cylinder structure,
The sludge blanket is formed on the outer cylinder of the double cylinder structure,
The operation method according to any one of claims 1 to 3, wherein the inner cylinder of the double cylinder structure is provided with a sludge concentration unit that condenses flocculated floc of the fluid flowing out from the sludge blanket to form the sludge. A coagulation sedimentation apparatus for separating water to be treated into sludge and treated water,
A sludge blanket type settling tank from which the sludge and the treated water are discharged;
Sludge piping, which is a piping through which sludge discharged from the settling tank flows;
A pipe for extracting a fluid forming a sludge blanket from the settling tank, the pipe being connected to the sludge pipe;
A first valve provided in the extraction pipe;
A coagulation / sedimentation apparatus comprising: a second valve provided in the sludge pipe and located between the sludge pipe and a point where the extraction pipe is connected and the settling tank. The sludge pipe is provided with a flow meter for detecting the flow rate of the sludge, and
The second valve of the sludge pipe is opened so that the sludge is discharged from the settling tank, and the first valve of the extraction pipe is closed, based on the measurement value of the flow meter. It has a function of detecting or predicting the blockage of the sludge pipe, and closing the second valve of the sludge pipe and opening the first valve of the extraction pipe when the blockage of the sludge pipe is detected or predicted. , Including control unit,
The coagulating sedimentation apparatus according to claim 5. A plurality of the extraction pipes are connected to the sedimentation tank, and the plurality of extraction pipes are connected to different positions in the height direction of the sludge blanket,
The coagulating settling apparatus according to claim 5 or 6. While the second valve of the sludge pipe is open so that the sludge is discharged from the sedimentation tank, the control device closes all the first valves provided to the plurality of extraction pipes. The second valve of the sludge pipe is closed and the first valve provided in only one of the plurality of extraction pipes is selected when the blockage of the sludge pipe is detected or predicted The coagulating and settling apparatus according to claim 7 having an opening function. The settling tank has a double cylinder structure,
The sludge blanket is formed on the outer cylinder of the double cylinder structure,
The sludge concentration part which concentrates the flocculated floc of the fluid which flowed out of the sludge blanket, and forms the said sludge is provided in the inner cylinder of the said double cylinder structure, The aggregation as described in any one of Claims 5-8 Precipitation equipment.