JP2021007913A - Control device and solid-liquid separation system - Google Patents

Abstract

To provide a control device and a solid-liquid separation system capable of achieving high solid-liquid separation performance regardless of a quality of water used for dilution.SOLUTION: A control device for a solid-liquid separation system includes a reforming device, a dissolution tank, a flocculation tank, and a solid-liquid separation device, and has a measurement unit and a control unit. The reforming device modifies the dilution water. The dissolution tank mixes the dilution water modified by the reforming device with a polymer flocculant to prepare a polymer solution. The flocculation tank injects the polymer solution into the treated water to coagulate the solids in the treated water. The solid-liquid separation device separates the treated water in which the solids have been flocculated into solids and water. The measurement unit is located between the reforming device and the dissolution tank, and measures any one or more of the amount of calcium, magnesium, or hardness of the diluted water after reforming. The control unit stops the supply of dilution water from the reforming device to the dissolution tank when the measurement result of the dilution water by the measurement unit exceeds a threshold value.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to control devices and solid-liquid separation systems.

Solid-liquid separation is one of the treatment methods for wastewater and sludge. Solid-liquid separation in wastewater treatment is performed as a pretreatment for wastewater treatment. By separating the solid matter in the wastewater by solid-liquid separation and then treating the solid matter and the wastewater by a method suitable for each, the wastewater can be treated easily at low cost. Further, in the case of wastewater treatment, the solid-liquid separated wastewater may be discharged as treated water to the sewer or the like.

The solid-liquid separation in the case of sludge is a treatment for reducing the water content in the sludge, and specifically, the sludge is dehydrated. By reducing the water content in the sludge by the dehydration treatment, the volume of the sludge can be reduced to the dehydrated sludge, and the transportation cost and the disposal cost of the dehydrated sludge can be reduced.

In solid-liquid separation, a polymer flocculant may be used to enhance solid-liquid separation performance. By adding the polymer flocculant to the wastewater or sludge, the solid matter in the wastewater or sludge is aggregated to form coarse flocs. This improves solid-liquid separability.

More specifically, for example, a granular polymer flocculant is added to water as a solvent (hereinafter referred to as dilution water) and dissolved by stirring to obtain a polymer flocculant solution (hereinafter referred to as a polymer solution). .. By injecting this polymer solution into wastewater or sludge and stirring it, solid matter in the wastewater or sludge is agglomerated. Next, the wastewater or sludge in which the solid matter is aggregated is separated into solid and liquid, and the treated water from which the solid matter has been removed and the solid content in which the solid matter is concentrated are separated.

The polymer flocculant acts on solid matter contained in wastewater and sludge. Therefore, in the solid-liquid separation treatment, it is necessary to adjust the injection rate of the polymer solution with respect to the solid matter concentration of wastewater or sludge to the optimum injection rate at which the solid-liquid separation performance is good. If the injection rate of the polymer solution is less than the optimum injection rate, the solid-liquid separation performance deteriorates and the treated water and solid content having desirable properties cannot be obtained. On the other hand, when the injection rate is higher than the optimum injection rate, the solid-liquid separation performance is also lowered, and the amount of the polymer flocculant used is increased, resulting in an excessive treatment cost. In addition, there is a concern that the residual polymer flocculant remains in the water, the water quality of the water deteriorates, and the environment of the water discharge destination also deteriorates. Therefore, in the conventional solid-liquid separation process, it is common to perform a test to simulate solid-liquid separation in advance, select the optimum injection rate that improves the solid-liquid separation performance, and manually set the injection rate of the polymer solution. It is done in the same way.

However, when preparing a polymer solution, if dilution water having deteriorated water quality is used, the agglutination performance of the polymer solution may be deteriorated. In general solid-liquid separation treatment, a polymer solution prepared in advance is stored in a coagulant tank, and each time solid-liquid separation is performed, the polymer solution is extracted from the coagulant tank and added to wastewater or the like. There is. Therefore, the polymer solution may be stored for a long period of time after preparation. At this time, the cohesive performance of the polymer solution prepared from the water for dilution whose water quality has deteriorated may deteriorate over time.

In this way, when the solid-liquid separation treatment is performed using a polymer solution with reduced aggregation performance or a polymer solution with deteriorated aggregation performance over time, sufficient solid-liquid liquid is injected even though the injection rate is optimal. Separation performance may not be obtained in some cases.

Gehr, Ronald & Kalluri, Ramesh. (1983). EFFECTS OF SHORT-TERM STORAGE AND ELEVATED TEMPERATURES ON THE FLOCCULATION ACTIVITY OF AQUEOUS POLYMER SOLUTIONS .. Water pollution research journal of Canada. 18. 23-43.

An object to be solved by the present invention is to provide a control device and a solid-liquid separation system that exhibit high solid-liquid separation performance regardless of the water quality of the water for dilution.
Is an issue.

The control device of the embodiment is a control device of a solid-liquid separation system including a reformer, a dissolution tank, a coagulation tank, and a solid-liquid separation device, and has a measurement unit and a control unit.
The reformer reforms the water for dilution. The dissolution tank prepares a polymer solution by mixing the dilution water modified by the reformer and the polymer flocculant. In the coagulation tank, the polymer solution is injected into the water to be treated to coagulate the solid matter in the water to be treated. The solid-liquid separation device separates the water to be treated, in which solids are aggregated, into solids and water.
The measuring unit is located between the reformer and the dissolution tank, and measures one or more of the amount of calcium, the amount of magnesium, and the hardness of the diluted water after reforming. The control unit stops the supply of the dilution water from the reformer to the dissolution tank when the measurement result of the dilution water by the measurement unit exceeds the threshold value.

The figure which shows the structural example of the conventional solid-liquid separation system. The figure which shows the structural example of the solid-liquid separation system of 1st Embodiment. The figure which shows the specific example of the functional structure of the control device in 1st Embodiment. The figure which shows the result of an Example. The figure which shows the result of an Example. The figure which shows the result of an Example.

Hereinafter, the control device and the solid-liquid separation system of the embodiment will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a conventional solid-liquid separation system. The solid-liquid separation system 90 shown in FIG. 1 includes a dissolution tank 91, a first stirrer 92, a polymer solution injection pump 93, a coagulation tank 94, a second stirrer 95, and a solid-liquid separation device 96. The dissolution tank 91 dissolves a granular polymer flocculant in water as a solvent (hereinafter referred to as "dilution water") to prepare an aqueous solution of the polymer flocculant (hereinafter referred to as "polymer solution"). It is a water tank of. The first stirrer 92 is a device that stirs the polymer flocculant and the water for dilution charged into the dissolution tank 91. The polymer solution injection pump 93 is a device for injecting the polymer solution prepared in the dissolution tank 91 into the coagulation tank 94. The coagulation tank 94 is a water tank for mixing the polymer solution and the water to be treated to coagulate the solid matter in the water to be treated. The second stirrer 95 is a device that stirs the polymer solution and the water to be treated in order to mix them. The solid-liquid separation device 96 is a device that separates the water to be treated, in which solids are aggregated, into solids and water.

Here, the polymer solution injection pump 93 is configured to operate at an injection rate (hereinafter referred to as “set injection rate”) determined based on the result of a mock test of solid-liquid separation conducted in the laboratory L. Will be done. Basically, the set injection rate is an injection rate determined based on the test results in which good solid-liquid separation performance is obtained, and is also called an optimum injection rate.

However, when preparing a polymer solution, if dilution water having deteriorated water quality is used, the agglutination performance of the polymer solution may be deteriorated. In general solid-liquid separation treatment, a polymer solution prepared in advance is stored in a coagulant tank, and each time solid-liquid separation is performed, the polymer solution is extracted from the coagulant tank and added to wastewater or the like. There is. Therefore, the polymer solution may be stored for a long period of time after preparation. At this time, the cohesive performance of the polymer solution prepared from the water for dilution whose water quality has deteriorated may deteriorate over time.

In this way, when the solid-liquid separation treatment is performed using a polymer solution with reduced aggregation performance or a polymer solution with deteriorated aggregation performance over time, sufficient solid-liquid liquid is injected even though the injection rate is optimal. Separation performance may not be obtained in some cases.

FIG. 2 is a diagram showing a configuration example of the solid-liquid separation system of the present embodiment. The solid-liquid separation system 100 of the present embodiment includes a reformer 10, a dissolution tank 1, a polymer solution injection pump 2, a coagulation tank 3, a solid-liquid separation device 4, and a control device 5. The control device 5 includes a measurement unit 12 and a control unit 15.

The reformer 10 is a device that reforms the water for dilution. The diluting water is water used as a solvent for dissolving the polymer flocculant in the dissolution tank 1. The reformer 10 is provided with a cation exchange resin. As the dilution water, for example, well water or industrial water is used. By bringing the diluting water into contact with the cation exchange resin, calcium and magnesium contained in the diluting water are removed. Further, although not shown, the reformer 10 is communicably connected to the control device 5. The operation of the reformer 10 is controlled based on the control signal notified from the control device 5.

A dilution water supply pump 13 is provided between the reformer 10 and the dissolution tank 1. The dilution water supply pump 13 is communicably connected to the control device 5. The dilution water supply pump 13 supplies the dilution water to the dissolution tank 1 based on the control signal notified from the control device 5.

The dissolution tank 1 is for dissolving a granular polymer flocculant in water for dilution modified by the reformer 10 to prepare an aqueous solution of the polymer flocculant (hereinafter referred to as "polymer solution"). It is a water tank. The dissolution tank 1 is provided with a first stirrer 11 for stirring the polymer solution.

The polymer solution injection pump 2 is a device for injecting the polymer solution prepared in the dissolution tank 1 into the coagulation tank 3. The polymer solution injection pump 2 is communicably connected to the control device 5. The polymer solution injection pump 2 performs a polymer solution injection operation based on a command from the control device 5.

The coagulation tank 3 is a water tank for mixing the polymer solution injected by the polymer solution injection pump 2 with the water to be treated to coagulate the solid matter in the water to be treated. The coagulation tank 3 is provided with a second stirrer 31 that stirs the mixed water of the polymer solution and the water to be treated.

The solid-liquid separation device 4 is a device that separates the water to be treated (mixed water) in which solids are aggregated by injecting a polymer solution into solids and water.

The control device 5 monitors the water quality of the dilution water reformed by the reformer 10, and if the water quality of the dilution water deteriorates, the supply of the dilution water from the reformer 10 to the dissolution tank 1 is stopped.

The control device 5 includes a measurement unit 12 and a control unit 15.
The measuring unit 12 is located between the reforming device 10 and the dissolution tank 1 and is a measuring device that measures one or more of the amount of calcium, the amount of magnesium, and the hardness of the diluted water after reforming. More specifically, the measuring unit 12 includes any one of a calcium concentration meter for measuring the amount of calcium in the water for dilution, a magnesium concentration meter for measuring the amount of magnesium in the water for dilution, and a hardness meter for measuring the hardness of the water for dilution. Or two or more types are provided. In particular, the measuring unit 12 is a calcium ion densitometer for measuring the divalent calcium ion amount of the diluting water, a magnesium ion densitometer for measuring the divalent magnesium ion amount of the diluting water, and a hardness meter for measuring the hardness of the diluting water. It is preferable that any one or two or more of them are provided.

The control unit 15 stops the supply of the dilution water from the reforming device 10 to the dissolution tank 1 when the measurement result of the dilution water by the measurement unit 12 exceeds the threshold value.

FIG. 3 is a diagram showing a specific example of the functional configuration of the control unit 15 in the present embodiment. The control unit 15 in the present embodiment includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, and the like connected by a bus, and executes a program. The control unit 15 functions as a device including a communication unit 51, a storage unit 52, a measurement data acquisition unit 53, and a modification control unit 54 by executing a program. All or part of each function of the control unit 15 may be realized by using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a flexible disk, a magneto-optical disk, a portable medium such as a ROM or a CD-ROM, or a storage device such as a hard disk built in a computer system. The program may be transmitted over a telecommunication line.

The communication unit 51 is a communication interface. The communication unit 51 may be a wired communication interface or a wireless communication interface. The communication unit 51 is communicably connected to the reformer 10, the measurement unit 12, the dilution water supply pump 13, and the polymer solution injection pump 2.

The storage unit 52 is configured by using a storage device such as a magnetic hard disk device or a semiconductor storage device. The storage unit 52 stores the measurement data of the measurement unit 12. Further, the storage unit 52 stores in advance the calcium amount, magnesium amount, and hardness thresholds of the water for dilution.

The measurement data acquisition unit 53 acquires measurement data from the measurement unit 12 via the communication unit 51. The measurement data acquisition unit 53 stores the acquired measurement data in the storage unit 52.

The reforming control unit 54 has a function of controlling the reforming device 10 or the water supply pump 13 for dilution. Specifically, when the measurement result of the water for dilution by the measuring unit 12 exceeds the threshold value, the reforming control unit 54 stops the function of the reforming device 10 or dilutes via the communication unit 51. The water supply pump 13 is stopped. As a result, the supply of dilution water to the dissolution tank 1 is stopped.

Next, the operations of the solid-liquid separation system 100 and the control device 5 of the present embodiment will be described.

First, the water for dilution is supplied to the reformer 10 to reform the water for dilution. Here, reforming the diluting water means reducing the amount of calcium and magnesium in the diluting water. Modification of the water for dilution also includes reducing the hardness of the water for dilution. Specifically, as the dilution water, well water, industrial water, or the like is used. Further, the reformer 10 is provided with a cation exchange resin. The diluting water supplied to the reformer 10 is brought into contact with the cation exchange resin. At this time, calcium and magnesium in the dilution water are adsorbed on the cation exchange resin, the amount of calcium and magnesium in the dilution water is reduced, and the hardness is also reduced.

Next, the modified water for dilution is sent to the dissolution tank 1 by the water supply pump 13 for dilution. Further, the water quality of the dilution water is measured by the measuring unit 12 while being supplied from the reformer 10 to the dissolution tank 1. The measurement item is any one or more of calcium amount, magnesium amount and hardness in the water for dilution. The measurement result of the water for dilution is sent to the control unit 15 of the control device 5.

The polymer flocculant also supplied to the dissolution tank 1 is added to the reformed water for dilution supplied to the dissolution tank 1, and the water for dilution and the polymer flocculant are stirred and mixed by the first stirrer 11. Will be done. The polymer flocculant gradually dissolves in water for dilution to form a polymer solution.

The prepared polymer solution is supplied to the coagulation tank 3 by the polymer solution injection pump 2.
In the coagulation tank 3, the polymer solution is injected into the water to be treated, and the solid matter in the water to be treated is agglomerated into a lump by the agglutination action of the polymer solution. Then, the water to be treated in which the solid matter is aggregated is sent to the solid-liquid separation device 4.

In the solid-liquid separation device 4, the water to be treated having the agglomerated solid matter is separated into water and solid content.

When the reforming treatment in the reformer 10 is functioning well, the calcium concentration, magnesium concentration, and hardness of the diluting water are maintained at low values. By reforming the diluting water in the reformer 10, the amount of calcium, the amount of magnesium, or the hardness of the diluting water is reduced. As a result, diluting water whose calcium concentration, magnesium concentration, and hardness are lower than the threshold value is used for dissolving the polymer flocculant. A polymer solution in which a polymer flocculant is dissolved in water for dilution after modification has improved cohesive performance and less deterioration of coagulation performance over time. The agglutination performance of the polymer solution refers to the agglutination ability of solids in the water to be treated. Compared to polymer solutions with low aggregation performance, polymer solutions with excellent aggregation performance can sufficiently aggregate solids by adding a small amount to the water to be treated, and solids in water after solid-liquid separation. The component concentration decreases.

On the other hand, the water for dilution, which has been reformed by the reformer 10 but whose water quality has deteriorated until the measurement result by the measuring unit 12 exceeds the threshold value, lowers the aggregation performance of the polymer solution and of the polymer solution. The deterioration of the aggregation performance over time becomes large. It is considered that this is because calcium or magnesium contained in the water for dilution adversely affects the agglutination performance of the polymer solution.

When the dilution water having deteriorated water quality is continuously supplied to the dissolution tank 1, a polymer solution in which the agglomeration performance is deteriorated and the agglomeration performance is deteriorated with time is prepared. When such a polymer solution is subjected to a solid-liquid separation treatment, the solid content concentration in the water flowing out from the solid-liquid separation device 4 increases and the water quality deteriorates. In such a case, the control unit 15 acquires the measurement result of the dilution water transmitted from the measurement unit 12 by the communication unit 51. The acquired measurement result is sent to the storage unit 52 via the measurement data acquisition unit 53. Then, the reforming control unit 54 determines whether or not the measurement result of the dilution water by the measuring unit 12 exceeds the threshold value. When the measurement result of the dilution water exceeds the threshold value, the reforming control unit 54 stops the operation of the reforming device 10 or the dilution water supply pump 13 via the communication unit 51. As a result, the preparation of the polymer solution is interrupted, and the deterioration of the aggregation performance of the polymer solution and the deterioration of the aggregation performance with time are prevented.

It is considered that the main cause of the deterioration of the water quality of the dilution water is the decrease in the ion exchange capacity due to the breakage of the cation exchange resin provided in the reformer 10, so in such a case, the cation exchange resin is used. Just play it.

According to the solid-liquid separation system 100 and the control device 5 of the present embodiment, deterioration of the agglutination performance of the polymer solution can be prevented, and deterioration of the agglutination performance over time can be prevented, so that the solid-liquid separation performance of the water to be treated can be prevented. The decrease can be suppressed.

According to at least one embodiment described above, a reformer for reforming the water for dilution, a measuring unit for measuring one or more of the amount of calcium, the amount of magnesium, and the hardness of the water for dilution after reforming. High solid-liquid separation regardless of the quality of the water for dilution by having a control unit that stops the supply of water for dilution from the reformer to the dissolution tank when the measurement result of the water for dilution by the measuring unit exceeds the threshold value. It is possible to provide a control device and a solid-liquid separation system that exhibit high performance.

The effects of calcium concentration, magnesium concentration, and hardness on the agglutination performance of the polymer solution were evaluated as the water quality of the water for dilution. The dilution water used is shown in FIG. Groundwater having a hardness of 281 as hard water containing a high concentration of calcium and magnesium and having a high hardness, and ion-exchanged water obtained by treating the groundwater with an ion-exchange resin were targeted.

A polymer flocculant (strongly cationic, molecular weight 8.5 million) was dissolved in these two types of water for dilution to prepare a polymer solution having a concentration of 0.2%. The agglutination test was carried out by the following procedure using the polymer solution immediately after preparation. Then, assuming storage at room temperature, storage at 28 ° C. for 1 week was followed by an agglutination test. After further storing at 28 ° C. for 1 week (2 weeks in total), an agglutination test was performed.

In the coagulation test, the polymer solution was stirred at 120 rpm for 1 minute at an injection rate of 1 to 4% with respect to the digested sludge (concentration 1.50%) collected from the sewage treatment plant, and then at 1500 G with a centrifuge. The concentration of suspended substances in the separation solution obtained by centrifugation for 2 minutes was measured.

The injection rate at which the concentration of the floating substance was the lowest was compared and evaluated as the optimum injection rate of the polymer solution. The results are shown in FIG. The optimum injection rate of ion-exchanged water did not change at 2.0% regardless of the storage time, but the optimum injection rate of groundwater was 2.5% and 0.5% even immediately after the preparation of the polymer solution (storage time 0 weeks). It became high, and an injection rate of 3.0% was required for a storage time of 1 week or more.

From this, in groundwater, the cohesiveness of the polymer solution deteriorates and more polymer coagulant is required. By modifying the groundwater to remove calcium ions, magnesium ions, and hardness, It was suggested that it could be prevented. That is, it was suggested that the polymer injection rate could be reduced by up to 1.0% by modifying the groundwater.

The simulator was used to evaluate whether the reforming cost of the dilution water was commensurate with the reduction cost of the polymer injection rate. The modification cost by the ion exchange method was estimated using WAVE (Water Appliation Value) manufactured by DOWN WATER & PROCESS SOLUTION. The conditions and results are shown in FIG. In the ion exchange method, it was 1530 yen / day, which was less than 1/10 of the polymer usage reduction effect of 20400 yen / day. It was found that the modification of the water for dilution can reduce the polymer injection rate at low cost.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... dissolution tank, 3 ... coagulation tank, 4 ... solid-liquid separation device, 5 ... control device, 10 ... reformer, 12 ... measurement unit, 15 ... control unit, 100 ... solid-liquid separation system.

Claims (6)

A reforming device for reforming water for dilution, a dissolution tank for preparing a polymer solution by mixing the water for dilution modified by the reformer and a polymer flocculant, and the polymer solution to be treated Solid-liquid separation including a coagulation tank that is injected into water to aggregate the solid matter in the water to be treated, and a solid-liquid separation device that separates the solid matter to be treated, in which the solid matter is aggregated, into the solid matter and water. It is the control device of the system
A measuring unit that measures any one or more of the amount of calcium, magnesium, or hardness of the diluted water after modification, and
It is provided with a control unit for stopping the supply of the dilution water from the reformer to the dissolution tank when the measurement result of the dilution water by the measurement unit exceeds the threshold value.
Control device. When the measurement result of the dilution water exceeds the threshold value, the control unit suppresses the operation of the reformer to reform the dilution water or the operation of supplying the reformed dilution water to the dissolution tank.
The control device according to claim 1. The control device according to claim 1 or 2, wherein the reformer of the solid-liquid separation system is provided with a cation exchange resin that removes calcium or magnesium in the dilution water. A reformer that reforms the water for dilution and
A dissolution tank that prepares a polymer solution by mixing the dilution water modified by the reformer and a polymer flocculant.
A coagulation tank in which the polymer solution is injected into water to be treated to agglomerate solid substances in the water to be treated,
A solid-liquid separator that separates the water to be treated, in which the solid matter is aggregated, into the solid matter and water.
A measuring unit that measures one or more of the amount of calcium, magnesium, or hardness of the diluted water after modification.
When the measurement result of the diluting water by the measuring unit exceeds the threshold value, the control unit for stopping the supply of the diluting water from the reformer to the dissolution tank.
A solid-liquid separation system. When the measurement result of the dilution water exceeds the threshold value, the control unit suppresses the operation of the reformer to reform the dilution water or the operation of supplying the reformed dilution water to the dissolution tank.
The solid-liquid separation system according to claim 4. The solid-liquid separation system according to claim 4 or 5, wherein the reformer of the solid-liquid separation system is provided with a cation exchange resin that removes calcium or magnesium in the dilution water.

Images