WO2017068825A1

WO2017068825A1 - Flocculant injection assistance device and control method

Info

Publication number: WO2017068825A1
Application number: PCT/JP2016/071208
Authority: WO
Inventors: 清一村山; 美意早見; 法光阿部; 卓毛受; 太黒川; 服部　大; 哲平山本; 一将大高
Original assignee: 株式会社東芝
Priority date: 2015-10-20
Filing date: 2016-07-20
Publication date: 2017-04-27
Also published as: JP6633342B2; JP2017077525A

Abstract

A flocculant injection assistance device of an embodiment of the present invention includes an acquisition unit and a control unit, and is used in a water treatment process in which water that has been separated from sludge in a wastewater treatment step is returned as return water to a flocculant settling step, in order to control the amount of flocculant injected during the flocculant settling step. The acquisition unit acquires water quality information relating to the water quality of the treated water in the flocculant settling step. The control unit controls the injected amount of the flocculant on the basis of the water quality information acquired by the acquisition unit.

Description

Flocculant injection support device and control method

Embodiments of the present invention relate to a flocculant injection support device and a control method.

Generally, a water treatment process performed at a water purification plant or the like includes a coagulation sedimentation step and a wastewater treatment step, and the outline of each step is as follows. In the coagulation sedimentation process, a solid-liquid separation process is performed to remove unnecessary substances such as suspended substances contained in water to be purified (hereinafter referred to as “water to be treated”). In the solid-liquid separation treatment, first, unnecessary substances are aggregated into flocs by injecting a flocculant into the water to be treated. Flocked aggregates are separated from the water to be treated by precipitation treatment and removed. In addition, after the precipitation treatment, a filtration treatment such as sand filtration may be further performed. Sludge containing agglomerates separated from the water to be treated by precipitation or filtration is sent to a wastewater treatment process.

In the wastewater treatment process, the sludge separated in the coagulation sedimentation process is concentrated and separated. Concentration separation processing is processing which makes the sludge containing a lot of water sent from a coagulation sedimentation process into a state with much less moisture. The water separated from the sludge by the concentration and separation treatment is added to the water to be treated before the flocculant is injected as return water, and is sent again to the coagulation sedimentation step. Therefore, the quality of the water to be treated before the flocculant is injected fluctuates due to the influence of the fluctuation of the return water inflow in addition to the influence of the fluctuation of the quality of the raw water itself sent to the water treatment process. Therefore, the amount of the flocculant to be injected should be appropriately adjusted according to the change in the quality of the water to be treated which varies under the influence of raw water and return water.

Generally, the amount of flocculant injected is often determined by conducting a beaker-scale agglomeration test (hereinafter referred to as “beaker test”) on the collected raw water and using the test results as a guide. In order to keep the amount of flocculant injected appropriately, the frequency of the beaker test needs to be increased, but it is not realistic considering the work load. Therefore, in many cases, the flocculant is excessively injected so as not to cause insufficient injection. However, if the amount of flocculant injected increases, the amount of sludge generated also increases, increasing the load of wastewater treatment. In addition, since the load of the filtration process is increased, the frequency of performing the washing process (back pressure washing or the like) of the filtration equipment is increased. Therefore, it is desirable to control the injection amount of the flocculant to an appropriate amount so as not to over-inject.

For such a problem, for example, a method for improving the coagulation effect by returning sludge separated and removed by coagulation sedimentation has been proposed. While such a method can be expected to improve the coagulation effect, it may lead to deterioration of the quality of the water to be treated and may increase the treatment load as a whole. Especially in water treatment plants, deterioration of water quality in the water treatment process is fatal. The same applies to the return water returned from the wastewater treatment process to the coagulation sedimentation process, and deterioration of the quality of the treated water due to the return water must be avoided. In fact, problems such as the generation of off-flavors and increased manganese concentration have arisen due to the deterioration of water quality due to the return water, and there are some entities that need countermeasures.

Japanese Patent Laid-Open No. 2003-340208 JP 2009-226285 A JP 2012-45494 A

The problem to be solved by the present invention is to provide a coagulant injection support device and a control method that can more appropriately control the injection amount of the coagulant according to the inflow of return water.

The flocculant injection support device of the embodiment is a device that controls the injection amount of the flocculant in the coagulation sedimentation step in a water treatment process in which water separated from sludge in the wastewater treatment step is returned to the coagulation sedimentation step as return water. It has an acquisition unit and a control unit. An acquisition part acquires the water quality information regarding the quality of the to-be-processed water in the said coagulation sedimentation process. The control unit controls the injection amount of the flocculant based on the water quality information acquired by the acquisition unit.

The figure which shows the specific example of a water treatment process provided with the coagulant | flocculant injection assistance apparatus of 1st Embodiment. The functional block diagram which shows the function structure of the injection | pouring control system 200 in 1st Embodiment. The figure which shows an example of the injection | pouring rate of a coagulant | flocculant and the turbidity of to-be-processed water. The figure which shows an example of the injection | pouring rate of a coagulant | flocculant, and SC relationship. The figure which shows an example of the change of the turbidity of to-be-processed water before injection | pouring, the SC value of to-be-processed water after injection | pouring, and electrical conductivity in the case of operating the water treatment process 1 by injection | pouring rate fixed control. The figure which shows an example of the relationship between pH of a to-be-processed post-injection water, and SC value in the case of operating the water treatment process 1 by injection rate fixed control. The figure which shows an example of the relationship between electrical conductivity and SC value. The figure which shows an example of the result of the feedback control of the water treatment process 1 by the injection | pouring assistance apparatus 220 of 1st Embodiment.

Hereinafter, the flocculant injection support device and the control method of the embodiment will be described with reference to the drawings.

(First embodiment)
[Outline]
In the water treatment process, water to be treated may be returned from the wastewater treatment process to the coagulation sedimentation process. And the to-be-processed water (henceforth "returned water") returned to a coagulation sedimentation process from a wastewater treatment process may contain the residual component of a coagulant | flocculant. Therefore, if the flocculant contained in the return water can be used effectively, the amount of flocculant injected can be reduced.

Specifically, the turbidity in the water to be treated usually has a negative surface charge, repels each other, and is difficult to settle. By injecting the flocculant, the surface charge approaches zero and the repulsive action between the particles is weakened. The cross-linking action of the flocculant is also added to facilitate the formation of floc, and the flocculent particles are separated by precipitation. The purpose of injecting the flocculant in this way is to neutralize the turbid surface charge. Therefore, by controlling the injection amount of the flocculant according to the state of the surface charge of the turbidity in the water to be treated, an appropriate flocculant that takes into account the residual components of the flocculant contained in the return water It is thought that injection can be realized.

For example, the surface charge of suspended particles in the water to be treated is the flow current value (SC value: Streaming Current) of the mixed water (specifically, the water to be treated immediately after the flocculant is injected and rapidly stirred in the mixing pond). It can be grasped by measuring.

The SC value is an index correlated with the “zeta potential” indicating the charged state of the suspended particle surface. An electric double layer is formed at the interface between suspended particles in water and water. By flowing water in this state, the electric charge distributed to the water side flows together with the water, and flow electrification occurs. The current generated in the water by this flow electrification is called a flow current (SC). While the SC value changes depending on the aggregation state, it changes under the influence of pH, conductivity, and water temperature. Therefore, when the SC value is used to determine the charged state of the turbid surface, correction for removing these effects is necessary.

[Details]
FIG. 1 is a diagram illustrating a specific example of a water treatment process including the flocculant injection support device according to the first embodiment. In addition, the water treatment process 1 demonstrated here may be applied to what kind of equipment which performs the solid-liquid separation process using a flocculant. For example, the water treatment process 1 can be applied to facilities such as water purification plants and paper mills. FIG. 1 shows an example in which the water treatment process 1 is applied to a water purification plant.

The water treatment process 1 includes adjustment of the intake well 10, the landing well 20, the mixing basin 30, the flock formation basin 40, the sedimentation basin 50, the wastewater treatment step 60, the sand filtration ridge 70, and the distribution reservoir 80. Unit 90, flocculant 100, injection control system 200, pH meter 300, and conductivity meter 400. The intake well 10 temporarily stores raw water. The raw water here is water before purification treatment is performed, for example, water drawn from a dam or river, groundwater, and the like. Raw water is sent from the intake well 10 to the receiving well 20, and return water is sent from the wastewater treatment process 60. Hereinafter, water in which raw water and return water are mixed in the landing well 20 is referred to as treated water. In the landing well 20, unnecessary substances such as plants and earth and sand that can be easily separated by gravity settling are separated from the water to be treated.

The treated water of the supernatant of the landing well 20 is sent to the mixing basin 30 (rapid stirring pond). In the mixing basin 30, the coagulant 100 is poured into the water to be treated by the adjustment unit 90. Note that the operator may manually inject the flocculant in the mixing basin 30. A mixing device 31 is attached to the mixing basin 30. The mixing device 31 mixes the water sent from the landing well 20 and the flocculant 100. The mixing device 31 is, for example, a rapid stirring device (flash mixer), a stirring device having a driving unit such as a motor, or a stirring device (static mixer) having no driving unit. In the mixing basin 30, the charge state of the suspended matter (Suspended Solids) is neutralized by the flocculant 100. Due to the neutralization of the charged state, the suspended material aggregates. The suspended material is, for example, a colloidal component. In the mixing basin 30, minute flocs (hereinafter referred to as “fine flocs”) are formed in the water by stirring by the mixing device 31.

Water containing fine floc is fed from the mixing basin 30 to the flock formation pond 40. The floc formation pond 40 grows flocs by colliding fine flocs contained in water with each other.

The sedimentation basin 50 sediments flocs grown in water. The sedimented flock accumulates as mud at the bottom of the sedimentation basin, is periodically withdrawn, and is sent to the waste water treatment step 60.

In the wastewater treatment process 60, the sludge sent from other processes is concentrated and separated into sludge and water. Of the water separated from the sludge, the supernatant water is returned to the landing well 20. The return is often performed intermittently rather than continuously. In addition, not only the sludge extracted from the sedimentation basin 50 but the sludge and waste water which generate | occur | produced at the various other processes included in the water treatment process 1 are sent to the waste water treatment process 60.

The supernatant water of the sedimentation basin 50 is sent to the sand filtration building 70. The sand filtration building 70 filters the water sent from the sedimentation basin 50. Sand as a filter medium becomes clogged as the filtration duration time elapses, and the differential pressure increases. Therefore, the counter pressure cleaning is periodically performed, and the cleaning waste water is sent to the waste water treatment step 60.

The filtered water is sent from the sand filtration building 70 to the distribution reservoir 80. In the distributing reservoir 80, chlorine is injected into the water. The water sterilized by chlorine is distributed from the distribution reservoir 80 to houses and the like.

The adjustment unit 90 may have any mechanism as long as it can adjust the injection amount of the flocculant 100. The adjustment unit 90 is, for example, a pump (hereinafter referred to as “medicine injection pump”). The adjustment unit 90 injects the injection amount of the flocculant 100 determined by the injection control system 200 including an information processing apparatus or the like into the mixing basin 30. The adjusting unit 90 may inject the flocculant 100 into the mixing basin 30 at the injection rate determined by the injection control system 200. The injection rate of the flocculant 100 is the ratio of the injection amount of the flocculant 100 to the total amount of water (flow rate per hour) at the location where the flocculant 100 is injected. For example, the adjustment unit 90 may change the injection amount or injection rate of the flocculant 100 using an inverter or a solenoid valve.

The flocculant 100 is a drug charged to a positive charge. In addition, suspended substances in water have a negative charge on the surface. For this reason, the flocculant 100 is injected into the water to be treated to neutralize the charged state of the suspended matter, and agglomerates particles such as the suspended matter contained in the water to be treated. The aggregating agent 100 is an inorganic aggregating agent such as polyaluminum chloride (PAC), sulfate band, ferric chloride, ferrous sulfate, polysilica iron, and the like.

The flocculant 100 may be used in combination with a polymer flocculant. Examples of the polymer flocculant include a cationic polymer, an anionic polymer, and an amphoteric polymer. Further, the flocculant 100 may be used in combination with a pH adjuster. The pH adjuster can adjust the pH value of water to a pH range that is appropriate for aggregation. The pH adjusting agent may be an acidic adjusting agent or an alkaline adjusting agent. Examples of the acidic regulator include sulfuric acid and hydrochloric acid. Examples of the alkaline adjusting agent include caustic soda and calcium hydroxide.

The injection control system 200 is a system that controls the injection amount of the flocculant 100 by the adjusting unit 90. The injection control system 200 controls the injection amount of the flocculant 100 based on the water quality information related to the quality of the water to be treated. The water quality information is various quantities relating to the quality of the water to be treated, and is information indicating quantities such as a flowing current value, pH, and conductivity.

The pH meter 300 is a measuring device that measures the pH of the mixed water. The pH meter 300 transmits information indicating the measured value of the pH of the admixed water to the injection control system 200.

The conductivity meter 400 is a measuring device that measures the pH of the mixed water. The conductivity meter 400 transmits information indicating the measured value of the conductivity of the admixed water to the injection control system 200.

FIG. 2 is a functional block diagram showing a functional configuration of the injection control system 200 in the first embodiment. The injection control system 200 includes a flow ammeter 210, an injection support device 220, and a presentation device 230. Hereinafter, the flowing ammeter 210 is referred to as an SC (Streaming Current) meter 210. Similarly, in the following, the flowing current value is described as the SC value.

The SC value of the water to be treated in the mixing basin 30 increases or decreases according to the amount of the flocculant 100 injected. The SC meter 210 may be a flow potentiometer that continuously detects the charged state of suspended substances in the water to be treated. Further, the SC meter 210 may be a zeta electrometer that intermittently detects the charged state of suspended substances in the water to be treated. The SC meter 210 continuously measures the SC value of the water to be treated in the mixing basin 30. The measurement interval is preferably about 1 minute, but if it is within 10 minutes, the performance of the injection control in this embodiment is not greatly affected. The SC meter 210 outputs the SC value of the water to be treated in the mixing basin 30 to the injection support device 220.

The injection support apparatus 220 includes a CPU (Central Processing Unit) connected via a bus, a memory, an auxiliary storage device, and the like, and executes an injection support program. The injection support device 220 functions as a device including the acquisition unit 221, the storage unit 222, and the control unit 223 by executing the injection support program. All or some of the functions of the injection support apparatus 220 may be realized using hardware such as ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), and FPGA (Field Programmable Gate Array). . The injection support program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built in the computer system. The injection support program may be transmitted via a telecommunication line.

The acquisition unit 221 acquires the SC value of the water to be treated in the mixing basin 30 from the SC meter 210. The acquisition unit 221 outputs the SC value measured by the SC meter 210 to the control unit 223.

The storage unit 222 includes, for example, a non-volatile storage medium (non-temporary recording medium) such as a ROM (Read Only Memory), a flash memory, and an HDD (Hard Disk Drive). The storage unit 222 may include a volatile storage medium such as a RAM (Random Access Memory) or a register, for example. For example, the storage unit 222 may store a computer program for causing the device itself to function as the injection support device 220.

The control unit 223 controls the amount of the flocculant injected into the water to be treated in the mixing basin 30. Specifically, the control unit 223 determines the injection amount of the flocculant 100 so that the SC value of the water to be treated approaches a predetermined target value. The control unit 223 generates a control signal for operating the adjustment unit 90 (drug injection pump) so as to inject the coagulant 100 with the determined injection amount. The control unit 223 controls the amount of the flocculant 100 injected into the water to be treated by transmitting the generated control signal to the adjustment unit 90.

Note that the injection support device 220 may be configured as a single device or may be configured as a plurality of devices. When the injection support apparatus 220 is configured by a plurality of apparatuses, the injection support apparatus 220 may operate using cloud computing technology. The injection support apparatus 220 may perform operations on various types of data in the key value store format using cloud computing technology.

In addition, in the injection support apparatus 220, a web browser may operate. In addition, the entity that performs the operation and monitoring of the injection support apparatus 220, the failure response, and the like may be one entity or a plurality of entities. For example, an entity different from the entity that operates the water treatment process 1 (for example, ASP: Application Service Provider) may act on behalf of the injection support apparatus 220 for operation, monitoring, and failure handling. Further, some or all of the operation and monitoring of the injection support apparatus 220 and the failure handling may be performed by a plurality of subjects.

The presentation device 230 is configured using a display device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, or an organic EL (Electro-Luminescence) display. Or the presentation apparatus 230 may be comprised as an interface which connects these display apparatuses to an own apparatus. The presentation device 230 displays the injection support information generated by the injection support device 220. The injection support information is various information that supports the injection of the flocculant 100. For example, the target value of the injection amount of the flocculant 100, the determination result of whether the flocculant 100 is excessive or insufficient, and the like. It is information to show. The injection support information may be displayed in the form of a graph or may be displayed in another form. The presentation device 230 may display the injection support information according to control by the control unit 223.

Further, the presentation device 230 may be a voice processing device including a speaker (presentation unit). The presentation device 230 may present the injection support information to the operator by voice. The presentation device 230 may include an operation device such as a keyboard or a touch panel. The operation device may output a value designated by the operator to the control unit 223 in accordance with an operation by the operator. The value output to the control unit 223 is, for example, a value that represents a target value for the injection amount of the flocculant 100. The value output to the control unit 223 may be a SC value target value, for example. The control unit 223 may control the injection amount and injection rate of the flocculant 100 based on the value output from the operation device to the control unit 223.

FIG. 3 is a diagram showing an example of the relationship between the injection rate of the flocculant and the turbidity of the water to be treated. In FIG. 3, the horizontal axis represents the injection rate of the flocculant, and the vertical axis represents the turbidity of the water to be treated. In the case of the example in FIG. 3, the turbidity of the water to be treated changes from decreasing to increasing at the injection rate in the vicinity of 20 [mg / L] as the injection rate increases. That is, in the situation as in the example of FIG. 3, it is considered that the vicinity of 20 mg / L is an appropriate value for the injection rate. Thus, the injection rate of the flocculant 100 may not be too much or too little.

The tendency of the turbidity of the treated water to change from decreasing to increasing as the coagulant injection rate increases varies depending on the type and nature of the treated water. For example, in some water to be treated, the turbidity does not start to increase unless the flocculant injection rate is increased to some extent. Further, for example, depending on the water to be treated, the gradient of increase in turbidity varies. In any case, the amount of the flocculant injected should be controlled to an appropriate value as shown in the example of FIG. 3 in accordance with the type and properties of the water to be treated at that time.

FIG. 4 is a diagram showing an example of the relationship between the flocculant injection rate and the SC value. Specifically, FIG. 4 shows the relationship between the flocculant injection rate and the SC value for the same treated water as in FIG. In FIG. 4, the vertical axis represents the SC value, and the horizontal axis represents the injection rate of the flocculant. FIG. 4 shows that the SC value increases as the flocculant injection rate increases. That is, FIG. 4 shows that there is a positive correlation between the SC value and the injection rate of the flocculant.

Further, from FIG. 4, the SC value takes a value near the charge neutralization point (near +2) with respect to an appropriate value (near 20 [mg / L]) of the coagulant injection amount in the example of FIG. I understand. From these facts, it can be understood that the surface charge of the suspended substance in the water to be treated is neutralized by the injection of the flocculant by grasping the SC value.

FIG. 5 shows the turbidity of the water to be treated before the flocculant injection (hereinafter referred to as “water to be treated before injection”) and the flocculant injection when the water treatment process 1 is operated at a constant injection rate control. It is a figure which shows an example of the SC value of a post-processed water (henceforth "the post-injection treated water" or "mixed water"), and an electrical conductivity change. From FIG. 5, it can be seen that during the period in which the return water is returned from the waste water treatment process 60, the turbidity of the pre-injection treated water increases in accordance with the inflow of the return water. Moreover, in FIG. 5, it turns out that the SC value of the to-be-processed water after injection | pouring is rising with the raise of the turbidity of the to-be-processed water before injection | pouring. And that SC value of to-be-processed water is rising after injection | pouring by mixing of return water has shown that the charged state of the underwater particle surface is fluctuating to the positive side. In addition, since the conductivity increases at the timing when the return water flows, the return water can be captured from the change in the conductivity.

As described above, when the injection rate of the flocculant is constant, the SC value of the water to be treated increases at the timing of returning water, so that the water treatment process reduces the injection rate at the timing of returning water. By controlling 1, the increase of the SC value can be suppressed. That is, the controller 223 of the injection support device 220 controls the injection rate of the flocculant so that the SC value of the post-injection treated water becomes constant, thereby charging the surface charge of the suspended matter in the post-injection treated water. It can be kept in a neutral state.

FIG. 6 is a diagram showing an example of the relationship between pH and SC value of post-injection treated water when the water treatment process 1 is operated with constant injection rate control. In FIG. 6, the horizontal axis represents pH and the vertical axis represents SC value. FIG. 6 shows that the SC value decreases with increasing pH. That is, FIG. 6 shows that there is a negative correlation between pH and SC value. Based on this correlation, the SC value when the pH fluctuates with a certain value as a reference can be expressed as the following equation (1). Here, a reference value for changing the pH is referred to as a reference value.

In the equation (1), “SC value (pH standard)” represents an SC value that is normalized according to the amount of variation from the standard value of pH. “SC value (actually measured value)” represents the measured value of the SC value. K _pH is a coefficient for converting the fluctuation amount of the pH into the fluctuation amount of the SC value. For example, K _pH = −13.8. pH ₀ is a reference value of pH, for example, pH ₀ = 7.0.

FIG. 7 is a diagram showing an example of the relationship between conductivity and SC value. FIG. 7 shows the change in SC value when the conductivity of the water to be treated is changed by injection of sodium chloride. In FIG. 7, the horizontal axis represents the logarithm of conductivity (EC), and the vertical axis represents the SC value. In addition, since the pH of to-be-processed water also changes with addition of sodium chloride, FIG. 7 shows the SC value calculated by the above formula (1), not the SC value (actual value), as the relationship between the SC value and the conductivity. It is expressed in relation to (pH standard). FIG. 7 shows that the SC value increases as the conductivity increases. That is, FIG. 7 shows that there is a positive correlation between the conductivity and the SC value. Based on this correlation, the SC value when the conductivity varies with a certain value as a reference can be expressed as the following equation (2).

In the equation (2), “SC value (pH reference, conductivity reference)” represents an SC value normalized according to the amount of variation from the reference value of pH and conductivity. K _EC-pH is a coefficient for converting the variation amount of the conductivity into the variation amount of the SC value. For example, K _EC-pH = 8.2. EC ₀ is a reference value of conductivity, for example, EC ₀ = 4.5. Note that equation (2) is an approximate equation when the reference value of conductivity (hereinafter referred to as “reference conductivity”) is, for example, 5 [mS / m].

In addition, the reference value of pH in the above-described formula (1) and the reference value of conductivity in the formula (2) may be expressed by an average value of values that can be taken in the environment. If the change in conductivity is not large, the normalization of the SC value in the equation (2) may be omitted, and the SC value may be normalized only by the equation (1).

FIG. 8 is a diagram illustrating an example of a result of feedback control of the water treatment process 1 performed by the injection support apparatus 220 according to the first embodiment. FIG. 8 shows an example in which the SC value is approximated only by the equation (1), and the water treatment process 1 is feedback controlled with the target value of the pH-based SC value being zero.

In the control result of the example of FIG. 8, the flocculant injection rate changes in a cycle with the injection rate of about 15 mg / L as the upper limit. The upper limit of the injection rate is a set value of the injection rate at the time of constant injection rate operation. On the other hand, as described above, the SC value increases when the return water flows. On the other hand, since the control here sets the target value of the SC value to zero, the control unit 223 performs feedback control on the water treatment process 1 in a direction in which the SC value decreases. That is, the control unit 223 performs control to reduce the injection rate of the flocculant with respect to the water treatment process 1.

Also, it can be seen from the control results in the example of FIG. 8 that the turbidity of the water to be treated is kept good. This means that the water treatment process 1 can effectively use the flocculant remaining in the return water, and the turbidity of the water to be treated is kept good even when the flocculant injection rate is reduced. It shows that. That is, in this case, the injection support apparatus 220 can reduce the coagulant for the areas of the reduction regions 500-1, 500-2, and 500-3 shown in FIG. In the case of the example of FIG. 8, the average of the injection rate is 12.8 mg / L, and the amount of the flocculant to be injected can be reduced by about 15% compared to the operation at a constant injection rate.

The injection support apparatus 220 of the first embodiment configured as described above controls the amount of the flocculant injected into the water to be treated based on the SC value of the water to be treated after the flocculant is injected, Appropriate injection of the flocculant using the residual component of the flocculant contained in the return water can be realized.

(Second Embodiment)
The injection support apparatus 220 according to the second embodiment is different from the injection support apparatus 220 according to the first embodiment in that the injection amount of the flocculant 100 is based on the quality of the water to be treated (for example, flowing current value) after the flocculant injection. However, the feed rate of the flocculant injection rate is controlled based on the quality of the water to be treated before the flocculant injection. Hereinafter, the injection support device 220 of the second embodiment is referred to as an injection support device 220a in order to distinguish it from the injection support device 220 of the first embodiment.

In this case, the injection support device 220a captures the return water inflow state based on one or both of the conductivity and pH of the pre-injection treated water, and increases or decreases the injection amount of the flocculant according to the return water inflow state. . In addition, since the inflow situation of return water appears more strongly in terms of conductivity than pH, it is desirable to monitor the conductivity of return water for grasping the inflow situation.

In this case, an appropriate injection amount of the flocculant according to the inflow state (hereinafter referred to as “appropriate injection amount”) is determined by correspondence information set in advance based on the result of the beaker test, for example. In general, it is known that the appropriate injection amount of the flocculant changes in proportion to the conductivity. Therefore, by clarifying the details of such a relationship in advance by a beaker test, it is possible to generate correspondence information indicating the relationship between the conductivity and the appropriate injection amount of the flocculant.

For example, the injection support device 220a determines the presence or absence of inflow of the return water by monitoring the conductivity of the pre-injection treated water for the water treatment process 1 in which the coagulant injection rate is constant. When an inflow of return water is detected, the injection support device 220 determines an appropriate injection amount of the flocculant according to the inflow state at that time based on the correspondence information. The injection assisting device 220a performs feedforward control of the adjustment unit 90 (drug injection pump) so that the appropriate amount of the flocculant determined as described above is injected.

The correspondence information can also be expressed as a relationship between the inflow rate of the return water and the appropriate injection amount, but the water quality of the treated water greatly affects the appropriate injection amount of the flocculant. Therefore, it is desirable that the correspondence information be expressed using the conductivity of the water to be treated that reflects the change in water quality due to the return water, rather than the simple inflow rate of the return water. The following formula (3) is a formula showing a specific example of a method for determining an appropriate injection rate of the flocculant when the conductivity of the water to be treated is used.

In the formula (3), A is an appropriate injection rate [mg / L] of the coagulant to be determined. A ₀ is the flocculant injection rate [mg / L] (constant value) when there is no return water. EC _{treated water} has a conductivity [mS / m] before being injected, and EC ₀ is a reference conductivity. The reference conductivity is a standard conductivity value in various environments to which the control of this embodiment is applied. The reference conductivity may be expressed by an average value of values that can be taken by the conductivity in the environment to be controlled. K _A is a coefficient for converting conductivity into injection rate.

In the water treatment process 1 in which the water separated from the sludge in the wastewater treatment process is returned to the coagulation sedimentation process as the return water, the injection support apparatus 220a of the second embodiment configured as described above is an injection rate of the flocculant. Is determined based on the conductivity of the water to be treated before injection. By determining the injection rate of the flocculant in this way, water treatment is performed with an appropriate injection amount of the flocculant considering the residual components of the flocculant contained in the return water, even when the water quality fluctuation is small. Process 1 can be operated.

Hereinafter, modified examples of the flocculant injection support device of the embodiment will be described.

The method by which the control unit 223 normalizes the SC value and the coagulant injection amount is not limited to the examples shown in the equations (1) to (3). For example, the control unit 223 may perform normalization using an expression that includes the temperature of the water to be treated as a parameter.

When the coagulant and the pH adjuster are used together in the coagulation sedimentation step of the water treatment process 1, the control unit 223 functions to control the injection amount of the pH adjuster in addition to the function of controlling the injection amount of the coagulant. May be provided. In this case, the control unit 223 determines that the pH of the water to be treated is suitable for agglomeration of unnecessary substances by the flocculant based on the water quality information (for example, the pH of the water to be treated before or after injection measured by the pH meter 300). The injection amount of the pH adjusting agent is controlled so as to be within the predetermined range. When the control unit 223 has such a pH adjustment function, it is possible to enhance the aggregation effect of unnecessary substances due to the injection of the flocculant. Note that the functional unit that controls the injection amount of the pH adjusting agent may be configured as a second control unit different from the control unit 223.

According to at least one embodiment described above, an acquisition unit that acquires water quality information regarding the quality of the water to be treated in the coagulation sedimentation step, and the injection amount of the flocculant is controlled based on the water quality information acquired by the acquisition unit. By having the control unit, it is possible to control the injection amount of the flocculant according to the quality of the water to be treated which varies depending on the inflow of the return water. For example, the flow quality value of the water to be treated may be used as the water quality information, or the pH of the water to be treated may be used. Moreover, the electrical conductivity of to-be-processed water may be used for water quality information, and the flow volume of return water may be used.

Specifically, the flocculant injection support device of the above embodiment is a water treatment process having a coagulation sedimentation step and a wastewater treatment step typified by a water treatment process, and the water separated from sludge in the wastewater treatment step. In the water treatment process returned to the coagulation sedimentation process, the quality of the water to be treated (for example, the surface charge of suspended particles) is determined by measuring the quality of the water to be treated before or after the flocculant is injected. The injection amount of the flocculant is controlled according to the water quality. By performing such control, in the water treatment process described above, it is possible to realize an appropriate injection of the flocculant in consideration of the residual component of the flocculant contained in the return water.

Although several 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 spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

Claims

A flocculating agent step for injecting a flocculating agent to agglomerate and precipitate unnecessary substances in the water to be treated; and a waste water treatment step for concentrating the sludge precipitated in the flocculating precipitation step and separating water from the sludge, In the water treatment process in which the water separated from the sludge in the wastewater treatment process is returned to the coagulation sedimentation process as return water, and the return water is added to the raw water sent to the coagulation sedimentation process to form the treated water. , An apparatus for controlling the amount of the flocculant injected in the coagulation sedimentation step,
An acquisition unit for acquiring water quality information on the quality of the water to be treated in the coagulation sedimentation step;
A control unit for controlling the amount of the flocculant injected based on the water quality information acquired by the acquisition unit;
A flocculant injection support device.
The acquisition unit acquires a flow current value of the treated water as the water quality information,
The control unit controls the injection amount of the flocculant according to the flowing current value indicated by the water quality information.
The flocculant injection support device according to claim 1.
The acquisition unit acquires the pH or conductivity of the treated water as part of the water quality information,
The control unit controls the injection amount of the flocculant based on the flow current value normalized using the pH or conductivity of the water to be treated.
The flocculant injection support device according to claim 2.
The acquisition unit acquires the water quality information about the water to be treated after the flocculant is injected,
The control unit controls the injection amount of the flocculant so that the water quality of the treated water approaches a predetermined target value according to a change in the quality of the treated water indicated by the water quality information.
The flocculant injection support device according to any one of claims 1 to 3.
The acquisition unit acquires the water quality information about the water to be treated before the flocculant is injected,
The control unit detects whether or not the return water is returned based on the water quality information, and the aggregation is performed according to the quality of the treated water indicated by the water quality information while the return water is being returned. To control the injection amount of the agent,
The flocculant injection support device according to any one of claims 1 to 3.
The acquisition unit acquires the conductivity of the treated water as the water quality information,
The control unit detects the presence or absence of the return water based on a change in conductivity of the water to be treated.
The flocculant injection support device according to claim 5.
The acquisition unit acquires the pH of the treated water as the water quality information,
The control unit detects the presence or absence of the return water based on a change in pH of the water to be treated.
The flocculant injection support device according to claim 5 or 6.
The acquisition unit acquires the flow rate of the return water as the water quality information,
The control unit detects the presence or absence of the return water based on a change in the flow rate of the return water.
The flocculant injection support device according to any one of claims 5 to 7.
In the coagulation sedimentation step, in addition to the coagulant, an acid agent or an alkaline agent pH adjuster is injected into the water to be treated.
The control unit controls the injection amount of the pH adjusting agent based on the water quality information so that the pH of the water to be treated is within a predetermined range.
The flocculant injection support device according to any one of claims 1 to 8.
A flocculating agent step for injecting a flocculating agent to agglomerate and precipitate unnecessary substances in the water to be treated; and a waste water treatment step for concentrating the sludge precipitated in the flocculating precipitation step and separating water from the sludge, In the water treatment process in which the water separated from the sludge in the wastewater treatment process is returned to the coagulation sedimentation process as return water, and the return water is added to the raw water sent to the coagulation sedimentation process to form the treated water. A control method for controlling the amount of the flocculant injected in the coagulation sedimentation step,
An acquisition step of acquiring water quality information relating to the quality of water to be treated in the coagulation sedimentation step;
A control step of controlling the injection amount of the flocculant based on the water quality information acquired in the acquisition step;
A control method.