JPH0561963B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Purpose of the Invention [Field of Industrial Application] The present invention involves applying a flocculant to raw water in order to flocculate suspended solids from the raw water, remove the precipitate, and discharge it as treated water. Regarding the flocculant injection control method of controlling the injection amount of flocculant according to the properties of raw water during injection, in particular, the set value of the flowing current is selected according to at least one of the hydrogen ion concentration index and the temperature of the raw water. This invention relates to a flocculant injection control method in which the amount of flocculant to be injected is determined so that the measured value of the flowing current approaches the target value of the flowing current obtained by the method.

[Prior Art] Conventionally, this type of flocculant injection control method includes:
A device that measures in advance the flowing current (referred to as "optimum flowing current") when a desired flocculating state is achieved by injecting a flocculant (inorganic flocculant or organic flocculant) into raw water and sets it as the set value of the flowing current. The set value of the flowing current (that is, the optimum flowing current) is selected according to the measurement result of the treated water turbidity, and the measured value of the flowing current is brought close to the determined flowing current target value. A system has been proposed in which a control device determines the amount of flocculant to be injected so as to maintain the turbidity at a desired level.

[Problems to be Solved] However, in the conventional flocculant injection control method, the amount of flocculant to be injected was determined while determining the target value of the flowing current based on the measurement results of the turbidity of the treated water. i) Even if the amount of flocculant injection is changed immediately when the turbidity of the treated water fluctuates, there is a drawback that the flocculant injection control will be delayed by the residence time in the rapid stirring pond, slow stirring pond, and sedimentation pond. Furthermore, (ii) there is a drawback that it is not possible to sufficiently suppress fluctuations in treated water turbidity due to changes in raw water properties, and as a result (iii) it is difficult to maintain the desired treated water turbidity regardless of changes in raw water properties. In order to maintain this level, the amount of coagulant injected must always be set large.

Therefore, in order to eliminate these drawbacks, the present invention sets the flowing current to the target value of the flowing current obtained by selecting the set value of the flowing current according to at least one of the hydrogen ion concentration index and the temperature of the raw water. It is an object of the present invention to provide a flocculant injection control method that determines the flocculant injection amount so that the measured values are close to each other.

(2) Structure of the Invention [Means for Solving the Problems] The first means for solving the problems provided by the present invention is as follows. In a flocculant injection control method, the flocculant injection amount is controlled according to the properties of the raw water when the flocculant is injected into the raw water, the method comprising: (a) a first step of measuring a hydrogen ion concentration index of the raw water; (b) a second step of measuring the flowing current of the raw water into which the flocculant has been injected, and (c) selecting a set value of the flowing current according to the hydrogen ion concentration index of the raw water measured in the first step. (d) a third step of comparing the target value of the flowing current determined in the third step with the measured value of the flowing current measured in the second step; and (e) a fifth step of determining the amount of coagulant to be injected according to the results compared in the fourth step. .

The second solution to the problem provided by the present invention is that ``When a flocculant is injected into raw water in order to flocculate suspended solids from the raw water, remove the precipitate, and discharge it as treated water, the properties of the raw water are changed. In a flocculant injection control method that controls the amount of flocculant injected according to a second step; (c) a third step of selecting a set value of the flowing current according to the temperature of the raw water measured in the first step and determining it as a target value of the flowing current; (e) a fourth step of comparing the target value of the flowing current determined in step 3 with the measured value of the flowing current measured in the second step; and a fifth step of determining the amount of coagulant to be injected.

A third solution to the problem provided by the present invention is that ``When a flocculant is injected into raw water in order to flocculate suspended solids from raw water, remove precipitates, and discharge as treated water, the properties of the raw water are In the flocculant injection control method, which controls the injection amount of flocculant according to (c) a third step of measuring the flowing current of the raw water into which the flocculant has been injected, and (d) the hydrogen ion concentration index of the raw water measured in the first step and the hydrogen ion concentration index measured in the second step. a fourth step of selecting a set value of the flowing current according to the temperature of the raw water and determining it as the target value of the flowing current; (e) the target value of the flowing current determined in the fourth step and the third step; (f) a sixth step of determining the amount of coagulant to be injected according to the results of the comparison in the fifth step; ``A coagulant injection control method'' characterized by:

[Function] The first flocculant injection control method according to the present invention includes:
When injecting a flocculant into raw water in order to flocculate suspended water from raw water, remove precipitates, and discharge it as treated water, the amount of flocculant injected is controlled according to the properties of the raw water. As clearly stated as the first solution in the previous section, (a) ~
Since it includes the first to fifth steps listed in paragraph (e), (i) it acts to determine the amount of coagulant to be injected in immediate response to changes in the hydrogen ion concentration index of raw water, and (ii) ) It has the effect of suppressing fluctuations in the turbidity of the treated water, and also has the effect of (iii) reducing the amount of flocculant to be injected.

The second flocculant injection control method according to the present invention is characterized in that when a flocculant is injected into raw water in order to flocculate suspended water from raw water, remove precipitates, and discharge it as treated water, the flocculant is injected into the raw water according to the properties of the raw water. In particular, as specified as the second solution in the middle section of [Means for solving the problem], the amount of injection is controlled, and in particular, the injection amount of
(iv) The amount of coagulant to be injected is determined immediately in response to changes in the raw water temperature, and as a result, as in the first coagulant injection control method described above, (ii) ( iii).

The third flocculant injection control method according to the present invention is characterized in that when a flocculant is injected into raw water in order to flocculate suspended solids from raw water, remove precipitates, and discharge as treated water, the flocculant is flocculated according to the properties of the raw water. The injection amount of the agent is controlled, and in particular, as specified as the third solution in the latter part of [Means for solving the problem], the first to sixth methods listed in items (a) to (f) are
(v) It acts to determine the amount of coagulant to be injected in immediate response to changes in the hydrogen ion concentration index of raw water and changes in raw water temperature, and as a result, the above-mentioned first and second flocculation The effects of (ii) and (iii) above are achieved more favorably than the drug injection control method.

[Example] Next, the flocculant injection control method according to the present invention will be specifically explained by giving preferred examples thereof and referring to the attached drawings.

However, the examples described below are described to facilitate or accelerate understanding of the present invention, and are not described to limit the present invention.

In other words, each element disclosed in the embodiments described below includes all design changes and equivalent substitutions that fall within the spirit and technical scope of the present invention.

(Explanation of the attached drawings) FIG. 1 is a conceptual diagram showing a coagulation-sedimentation processing apparatus in which flocculant injection control is executed according to the first embodiment of the flocculant injection control method according to the present invention. It is.

FIG. 2 is an enlarged cross-sectional view showing an example of a flowing ammeter provided in the coagulation-sedimentation treatment apparatus shown in FIGS. 2 and 1. FIG.

3a to 3c are operation explanatory diagrams for explaining the embodiment shown in FIG. 1, in which the optimum flowing current, the optimum injection amount of flocculant, and the turbidity of the treated water are respectively plotted against the raw water PH. .

FIGS. 4a to 4d are operation explanatory diagrams for explaining a specific example of the embodiment in FIG. The amount and treated water turbidity are plotted.

FIG. 5 is a conceptual diagram showing a coagulation-sedimentation processing apparatus in which flocculant injection control is executed according to the second embodiment of the flocculant injection control method according to the present invention.

6a to 6c are operation explanatory diagrams for explaining the embodiment in FIG. 5, in which the optimum flowing current, the optimum injection amount of flocculant, and the turbidity of the treated water are plotted against the temperature of the raw water, respectively. There is.

FIGS. 7a to 7d are operation explanatory diagrams for explaining specific examples of the embodiment shown in FIG. The amount and treated water turbidity are plotted.

FIG. 8 is a conceptual diagram showing a coagulation-sedimentation processing apparatus in which flocculant injection control is executed according to the third embodiment of the flocculant injection control method according to the present invention.

9a to 9c are operation explanatory diagrams for explaining the embodiment in FIG. 8, in which the optimum flowing current, the optimum injection amount of flocculant, and the turbidity of the treated water are plotted for the raw water PH, respectively. .

10a to 10c are other operation explanatory diagrams for explaining the embodiment in FIG. 8, in which the optimum flowing current, the optimum injection amount of flocculant, and the turbidity of the treated water are plotted, respectively, for the temperature of the raw water. has been done.

11a to 11e are operation explanatory diagrams for explaining the specific example of the embodiment in FIG. 8, and show the raw water PH, raw water temperature,
The target value of the flowing current, the amount of coagulant injected, and the turbidity of the treated water are plotted.

(Structure of the first embodiment) First, with reference to FIG. 1, the first embodiment of the flocculant injection control method according to the present invention will be described. The configuration will be explained in detail while explaining the configuration of the precipitation processing apparatus.

Reference numeral 10 denotes a coagulation-sedimentation treatment apparatus in which injection control of a coagulant is executed by a coagulant injection control method according to the present invention, in which suspended water (hereinafter referred to as "suspended water" such as tap water, sewage, human waste, or factory wastewater) is used as raw water. “Josei”
2) is supplied from a raw water supply source (not shown) through a raw water supply pipe 11A as shown by arrow A, and large foreign substances contained in the raw water (i.e., suspended water) are precipitated. Raw water (that is, suspended water) is supplied from the receiving well 12 for removal through the raw water supply pipe 11B, and the flocculant injected by rapid stirring is mixed with the raw water (that is, suspended water). A rapid stirring pond 13 is used to flocculate suspended solids to form aggregates (i.e., flocs), and raw water (hereinafter referred to as raw water) in which a flocculant is injected from the rapid stirring basin 13 and is rapidly stirred to form flocs. A slow stirring pond 14 is provided with water (referred to as "rapid stirring pond effluent") and is used to slowly agitate the rapid stirring pond effluent to enlarge the aggregates, and suspension water given from the slow stirring pond 14. (hereinafter referred to as "slow stirring pond effluent") is used to settle flocculants (inorganic flocculants or organic A flocculant injection device 16 for injecting a flocculant) is provided. In the rapid stirring pond 13,
A stirring member 13B is provided which is rapidly rotated (that is, rotated at a relatively high speed) by a drive source (for example, an electric motor) 13A. The slow stirring pond 14 is provided with a stirring member 14B that is slowly rotated (that is, rotated at a relatively low speed) by a drive source (for example, an electric motor) 14A. A discharge pipe (not shown) is provided at the bottom of the settling tank 15 to remove the settled aggregates as sludge. The flocculant injection device 16 includes a flocculant storage tank 16A for holding the flocculant.
and a metering pump 16B for metering and supplying the flocculant from the flocculant storage tank 16A to the rapid stirring pond 13.

The coagulation and sedimentation treatment device 10 also includes a raw water supply pipe 1
A hydrogen ion concentration index meter (hereinafter also referred to as "raw water PH meter") 18 for measuring the hydrogen ion concentration index (hereinafter also referred to as "raw water PH") of raw water and a rapid stirring pond 13 arranged for 1B. A flow current meter 19 for measuring the flow current of the raw water (i.e., suspended water) into which a flocculant has been injected is disposed for a flow current meter 19 for measuring the flow current of the raw water (that is, suspended water) into which a flocculant is injected, and a treatment for discharging the treated water from the settling tank 15 as shown by arrow B. A treated water turbidity meter 20 for measuring the turbidity of treated water (hereinafter also referred to as "treated water turbidity") is provided with respect to the water discharge pipe 11C.
By the way, the flowing ammeter 19 is the rapid stirring pond 13B.
Water sampling pipe 19a and water sampling pump 19a ⁺
The raw water injected with the flocculant collected through the pipe is temporarily held as a sample and subjected to measurement of flowing current, and then the sample (i.e., the raw water injected with the flocculant) is transferred to the rapid stirring pond through the drain pipe 19b. 1
3B, two electrodes 19B and 19C spaced apart from each other on the inner peripheral surface of the cylindrical container 19A, and a cylindrical container 19A disposed inside the cylindrical container 19A. A piston 19E is reciprocated by a power source 19D located outside the container 19A and is connected to the electrodes 19B and 19C via connecting wires 19c and 19d to move the sample (that is, the raw water injected with a flocculant). The current generated between the electrodes 19B and 19C due to the movement of the sample (i.e., the raw water injected with the flocculant) due to the reciprocating movement of the piston 19E is measured, appropriately amplified, and sent to the comparison circuit 22 as a flowing current. It includes an ammeter 19F that outputs the output. Flowing ammeter 1
The measured value of flowing current according to No. 9 will decrease if the amount of coagulant injected is not increased when the raw water flow rate or raw water turbidity increases, and if the amount of coagulant injected is decreased when the raw water flow rate or raw water turbidity decreases. If it is not decreased, it will increase, so in the present invention, this is set by the setting device 2.
By controlling the amount of coagulant injected so as to match the set value of the flowing current output from 1,
Eliminates the need to pay attention to raw water flow rate and raw water turbidity. Since the treated water turbidity meter 20 is provided only for evaluating the flocculant injection control method according to the present invention, it may be removed if desired.

The coagulation-sedimentation treatment device 10 further maintains a correlation between the raw water PH measured in an appropriate manner and an optimum flowing current, and uses the raw water PH given from the raw water PH meter 18 based on the correlation. Connected to the setting device 21 for appropriately selecting the optimum flowing current (i.e., the set value of the flowing current) according to the measured value of PH and outputting it as the target value of the flowing current, the flowing ammeter 19, and the setting device 21. and a comparison circuit 22 for comparing the measured value of the flowing current given from the flowing ammeter 19 and the target value of the flowing current (that is, the optimum flowing current) given from the setting device 21; The injection amount of the flocculant is determined according to the comparison result of the comparison circuit 22 (i.e., the difference between the target value of the flowing current and its measured value), and the flocculant is injected as a flocculant injection control signal. and a control device 23 for providing information to the device 16.

(Description of the first embodiment) Further, with reference to FIGS. 1 to 3 a to 3c, the first embodiment of the flocculant injection control method according to the present invention will be described. The operation will be explained in detail while explaining the operation of the coagulation and sedimentation processing apparatus under which control is executed.

Coagulation and sedimentation operation Suspended water supplied from a raw water supply source (not shown) as raw water through the raw water supply pipe 11A as shown by arrow A is the raw water in which large foreign matter is precipitated and removed in the water landing well 12. It is supplied to the rapid stirring pond 13 via the supply pipe 11B.

Suspended water (that is, raw water) supplied to the rapid stirring pond 13 is mixed with an appropriate amount of flocculant injected from the flocculant injection device 16 by rapid stirring, and the suspended matter is flocculated. In suspended water, aggregates (ie, flocs) are formed as suspended solids aggregate. The raw water in which aggregates have been formed in the rapid stirring pond 13 is supplied to the slow stirring pond 14 as rapid stirring pond effluent.

In the slow stirring pond 14, the aggregates are enlarged by slowly stirring the water flowing out of the rapid stirring pond. The rapid stirring pond outflow water that has been slowly stirred in the slow stirring pond 14 is supplied to the sedimentation basin 15 as slow stirring pond outflow water.

In the sedimentation tank 15, aggregates are precipitated by allowing the water flowing out of the slow stirring tank to stand still. The aggregates precipitated in the settling tank 15 are removed as sludge through a discharge pipe (not shown) formed at the bottom of the settling tank 15. On the other hand, the water flowing out of the slow stirring pond from which the aggregates have been precipitated and removed in the settling tank 15 is discharged as treated water as shown by arrow B through the treated water discharge pipe 11C, and is then sent to a subsequent treatment device (not shown). supplied to

Coagulant injection control setting operation Prior to the start of operation of the coagulation sedimentation processing device 10 ,
In an appropriate manner, the relationship between the raw water PH and the optimal flowing current (ie, "the flowing current that corresponds to when the desired flocculation state is achieved") is grasped. The relationship between raw water PH and optimal flowing current is
This may be achieved by preliminary operation or by creating a scaled-down model of the coagulation-sedimentation treatment apparatus 10 , but in this case, a PH meter, a jar test device, and a flow ammeter attached to the jar test device are used. This will be explained as something that can be achieved using this method.

Measure raw water PH by feeding the collected raw water to a PH meter.

The optimum flowing current is measured by repeating a jear test using a jear test device while measuring the flow current using a flow ammeter. That is, the flowing current corresponding to the optimum injection amount of the flocculant determined by the Jar test (i.e., the injection amount of the flocculant that can achieve the desired flocculation state; see FIGS. 3 b and c) is defined as the optimal flowing current ( Figure 3 a).

The measurement of raw water PH and optimum flowing current is repeated, and the optimum flowing current corresponding to various raw water PHs is measured (see Fig. 3a).

After that, the raw water PH and the corresponding optimal flowing current are set as one set in the setting device 21 in sequence, and the correlation between the raw water PH and the optimal flowing current (see FIG. 3 a) is set in the setting device 21. hold it. The optimum flowing current set in the setting device 21 is also referred to as a set value of the DC current.

Injection control operation When the operation of the coagulation sedimentation treatment device 10 is started, the rapid stirring pond 13 is fed as raw water from the landing well 12.
The raw water PH meter 18 starts measuring the raw water PH of the suspended water given to the raw water. The measured value of the raw water PH is given to the establishment device 21.

In the setting device 21, each time a measured value of raw water PH is given from the raw water PH meter 18, a correlation is set in advance corresponding to the measured value (see Fig. 3 a).
The optimum flowing current (that is, the set value of the flowing current) is determined as appropriate from the above, and is outputted to the comparison circuit 22 as the target value of the flowing current.

In the comparison circuit 22, the difference between the target value of the flowing current (that is, the optimum flowing current) given from the setting device 21 and the measured value of the flowing current given from the flowing ammeter 19 is determined, and control is performed as a result of the comparison. It is output towards the device 23.

In the control device 23, the injection amount of the flocculant is determined according to the comparison result given from the comparison circuit 22 (i.e., the difference between the target value of the flowing current and its measured value), and is determined as the flocculant injection control signal. It is output toward the flocculant injection device 16. Incidentally, the control circuit 23 determines the injection amount of the flocculant so that the comparison result given from the comparison circuit 22 is zero. Further, the initial value of the injection amount of the flocculant is determined by experience or a jar test performed separately.

In the flocculant injection device 16, the metering pump 16B is operated according to the flocculant injection control signal given from the control device 23, and the flocculant storage tank 1 is operated.
A flocculant is injected from 6A toward the rapid stirring pond 13.

As described above, according to the present invention, it is possible to immediately change the amount of coagulant injected in the rapid stirring pond 13 according to fluctuations in the raw water PH, thereby reducing the turbidity of the treated water while avoiding an unnecessary increase in the amount of coagulant injected. Fluctuations can be suppressed reliably.

Specific Example 1 In addition, with reference to FIG. 1 and FIGS. 4 a to 4 d, specific numerical values will be given in order to further deepen the understanding of the first embodiment of the flocculant injection control method according to the present invention. This will be explained in detail.

Here, dam stored water is used as raw water, and a first coagulation and sedimentation treatment device in which coagulant injection control is executed by the coagulant injection control method according to the present invention, and a coagulant injection method disclosed as a prior art. The second control method executes coagulant injection control according to the control method.
was supplied to the coagulation and sedimentation processing equipment.

The first and second coagulation and sedimentation treatment devices are both equipped with a rapid stirring basin, a slow stirring basin, and a settling basin of the same structure, and the residence time of the rapid stirring basin, slow stirring basin, and settling basin is 3. minutes, 27 minutes and 2 hours
The treatment time was 30 minutes, the raw water (ie suspended water) throughput was 100 m ³ /h, and polyaluminum chloride (so-called "PAC") was used as the flocculant.

Raw water PH changes over time from the start of operation.
It changed between 7.5 and 6.5 as shown in Figure 4a. Incidentally, the raw water turbidity and raw water temperature were almost constant at 20°C and 25°C, respectively. Furthermore, the turbidity of the treated water was targeted at 2 degrees.

Example 1 First stage (i.e. period from 0:00 to 1:00)
In this case, the raw water PH given to the setting device as measured by the raw water PH meter was constant at 7.5 (Figure 4 a).
Therefore, the target value (in this case, the optimum flowing current) of the flowing current outputted from the setting device and given to the comparator circuit was -3 (see FIG. 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (that is, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 10 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 4c). By the way, 10mg/ is
This was determined by a separate jar test.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the coagulant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the slow stirring basin effluent was allowed to stand still in order to settle and remove aggregates. however,
Since the residence time in the sedimentation tank was 2 hours and 30 minutes, the raw water given to the rapid stirring tank at the start of operation was
The treated water had not yet been discharged from the settling pond. Therefore, the measurement results of the treated water turbidity meter are not plotted (see Figure 4d).

Second phase (i.e. period from 1:00 to 5:00)
Now, since the raw water PH measured by the raw water PH meter and given to the setting device gradually decreased from 7.5 to 6.5 (see Figure 4 a), the flowing current output from the setting device and given to the comparison circuit is The target value (optimal flowing current here) is -3 during the period from 1 o'clock to 4 o'clock.
It gradually increased from -1 to -1, and was maintained at -1 during the period from 4 o'clock to 5 o'clock (see Fig. 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison results showed that the target value of flowing current gradually increased as the raw water PH decreased.

In the control device, as the comparison results gradually increased, the flocculant injection amount was gradually increased from 10 mg/ to 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (Fig. 4c). reference).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was left standing to settle and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and the turbidity was 3, which corresponds to the first stage.
2 degrees in the period from 4:00 to 4:00, and increased from 2 to 3 degrees in the period from 4:00 to 5:00, which corresponds to the beginning of the second stage, and then decreased again to 2 degrees (Fig. 4d). reference).

Third stage (i.e. period from 5:00 to 13:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device is 6.5 (see Figure 4 a).
Therefore, the target value of the flowing current that is output from the setting device and given to the comparison circuit (here, the optimal flowing current)
was maintained at -1 (see Figure 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 4c).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond increased from 1.5 degrees to 3 degrees during the period from 5 o'clock to 8 o'clock, which corresponds to the middle to late stage of the second stage, as measured by a treated water turbidity meter. Afterwards, it decreased again to nearly 1.5 degrees and remained at 2 degrees during the period from 08:00 to 13:00, which corresponds to the early to middle stage of the third stage (see Figure 4 d).

Stage 4 (i.e. period from 13:00 to 17:00)
Now, since the raw water PH measured by the raw water PH meter and given to the setting device gradually increased from 6.5 to 7.5 (see Figure 4 a), the flowing current output from the setting device and given to the comparison circuit The target value of (optimal flowing current here) gradually decreased from -1 to -3 during the period from 13:00 to 16:00, and was maintained at -3 during the period from 16:00 to 17:00 (the (See Figure 4 b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison results showed that the target value of flowing current decreased gradually as the raw water PH increased.

In the control device, as the comparison result gradually decreased, the flocculant injection amount was gradually increased from 15 mg/ to 10 mg/, and was given to the flocculant injection device as a flocculant injection control signal (Fig. 4c). reference).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the sedimentation basin, the water flowing out of the slow stirring basin was allowed to stand still in order to settle and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling basin was measured using a treated water turbidity meter, and it was found that the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, was also the same from 16:00, which corresponds to the early stage of the fourth stage. to 17:00, the temperature remained at 2 degrees (see Figure 4d).

Stage 5 (i.e. period from 17:00 to 24:00)
In this case, the raw water PH given to the setting device as measured by the raw water PH meter was 7.5 (see Figure 4 a).
Therefore, the target value of the flowing current that is output from the setting device and given to the comparison circuit (here, the optimal flowing current)
was maintained at -3 (see Figure 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 10 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 4c).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling basin, measured by treated water turbidity, fluctuated around 2 degrees during the period from 17:00 to 20:00, which corresponds to the middle to late stage of the 4th stage. It was maintained at 2 degrees during the period from 20:00 to 24:00, which corresponds to the early to middle stages of the 5th stage (see Figure 4 d).

Comparative Example 1 First stage, i.e. (period from 0:00 to 1:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device is 7.5 (see Figure 4 a), and the elapsed time from the start of operation is the stagnation in the rapid stirring tank, slow stirring tank, and settling tank. time (i.e. 3 hours)
Since the turbidity of the treated water had not yet been measured as described below, the target value of the flowing current output from the setting device and given to the comparison circuit was maintained at -3 (see Figure 4b). .

In the comparison circuit, the measured value of the flow current by the flow ammeter was compared with the target value of the flow current, and the comparison result was given to the control device.

In the control device, the injection rate of flocculant was determined to be maintained at 10 mg/cm according to the comparison results (see Figure 4c). The injection amount of the flocculant is given to the flocculant injection device as a flocculant injection control signal,
Incidentally, 10 mg/ was determined by a jar test conducted separately.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond according to the flocculant injection control signal.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly stirred and then fed to the settling pond as slow stirring pond effluent.

In the settling basin, the slow stirring basin effluent was allowed to stand still in order to settle and remove aggregates. however,
Since the residence time in the sedimentation tank was 2 hours and 30 minutes, the raw water given to the rapid stirring tank at the start of operation was
The treated water had not yet been discharged from the settling pond. Therefore, the measurement results of the treated water turbidity meter were not plotted and were not used to determine the target value of the flowing current (see Figure 4d).

Second phase (i.e. period from 1:00 to 5:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device gradually decreased from 7.5 to 6.5 (see Figure 4 a), but the flowing current output from the setting device and given to the comparison circuit gradually decreased from 7.5 to 6.5. The target value was determined because (i) the elapsed time from the start of operation was less than the residence time (i.e., 3 hours) in the rapid stirring pond, slow stirring pond, and sedimentation pond, and the turbidity of the treated water had not yet been measured as described below. , was maintained at -3 during the period from 1:00 to 3:00, and (ii) the turbidity of the treated water was constant during the period from 3:00 to 4:00, corresponding to the first stage, so it was maintained at -3. , (iii) The turbidity of the treated water started to increase at 4 o'clock, corresponding to the beginning of the second stage, so it was set to -2 and then maintained until 5 o'clock (see Figure 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant injected gradually decreased from 10 mg/ to 5 mg/ during the period from 1 o'clock to 4 o'clock, and increased to 7.5 mg/ at 4 o'clock and maintained until 5 o'clock, depending on the comparison result. (See Figure 4c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and the raw water from the first stage had not yet been discharged as treated water between 1:00 and 3:00. Not done, first
2 degrees in the period from 3 o'clock to 4 o'clock, corresponding to the second phase, and increased from 2 degrees to 4 degrees in the period from 4 o'clock to 5 o'clock, corresponding to the beginning of the second phase (Fig. 4d).
reference).

Third stage (i.e. period from 5:00 to 13:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device was 6.5 (see Figure 4 a),
As the turbidity of the treated water was fluctuating as described below due to the influence of the second stage, the target value of the flowing current output from the setting device and given to the comparison circuit was set to -1 at 5 o'clock and maintained until 6 o'clock. After being set to 0 at 6 o'clock, it was maintained until 11 o'clock, and after being set to -1 at 11 o'clock,
It was maintained until 13:00 (see Figure 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the injection amount of flocculant increases from 7.5 mg/ to 10 mg/ in the period from 5 o'clock to 6 o'clock and from 10 mg/ to 17.5 mg in the period from 6 o'clock to 7 o'clock, depending on the comparison result. /, then maintained until 11 o'clock, decreased to 15 mg / at 11 o'clock, then 13
(See Figure 4c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond increased from 4 degrees to 9 degrees during the period from 5 o'clock to 8 o'clock, corresponding to the middle to late stage of the second stage, as measured by a treated water turbidity meter. Later, it decreased again to nearly 6 degrees, and gradually decreased from 4 degrees to less than 2 degrees during the period from 08:00 to 13:00, which corresponds to the early to middle stage of the third stage (see Figure 4 d).

Stage 4 (i.e. period from 13:00 to 17:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device gradually increased from 6.5 to 7.5 (see Figure 4 a), but due to the influence of the late stage 3 or early stage 4, As described below, since the turbidity of the treated water was maintained at less than 2 degrees, the target value of the flowing current output from the setting device and given to the comparison circuit was 13
It was maintained at -1 for the period from
reference).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the injection amount of flocculant is maintained at 15 mg/during the period from 13:00 to 14:00 and from 15 mg/deg/during the period from 14:00 to 16:00, depending on the comparison results.
It was determined that the amount increased monotonically up to 25 mg/h and rapidly decreased from 25 mg/l to 12.5 mg/l during the period from 16:00 to 17:00 (see Figure 4c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly stirred and then fed to the settling pond as slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the sedimentation basin was measured using a treated water turbidity meter, and it was found that the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, was also the same from 16:00, which corresponds to the early stage of the fourth stage. During the period from 17:00 to 17:00, the temperature remained below 2 degrees, with almost no change (see Figure 4 d).

Stage 5 (i.e. period from 17:00 to 24:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device is 7.5 (see Figure 4 a), and the
As explained below, the turbidity of the treated water was maintained at less than 2 degrees due to the influence of the stage, so the target value of the flowing current output from the setting device and given to the comparison circuit was set to -2.5 at 17:00 and then at 19:00. It was maintained at -3 at 19:00 and maintained until 24:00 (see Figure 4b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant injected gradually decreases from 12.5 mg/ to 10 mg/in the period from 17:00 to 20:00, and to 10 mg/in the period from 20:00 to 24:00, depending on the comparison results. It was decided that this should be maintained (see Figure 4c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, after the aggregates of the rapid stirring pond effluent were slowly stirred, they were fed to the settling pond as slow stirring pond effluent.

In the settling basin, the water flowing out from the slow stirring basin was left standing to settle and be removed, and then was discharged as treated water.

As measured by a treated water turbidity meter, the turbidity of the treated water discharged from the settling pond gradually decreased from 2 degrees to 1 degree during the period from 17:00 to 19:00, which corresponds to the middle to late stage of the 4th stage. It gradually increases from 1 to 2 degrees during the period from 19:00 to 22:00, corresponding to the late stage 4 to early stage 5, and from 22:00 to 24:00, corresponding to the middle of stage 5. It was maintained at 2 degrees during the period up to (see Figure 4 d).

Comparison of Example 1 and Comparative Example 1 As is clear from the above, in Example 1, compared to Comparative Example 1, the target value of the flowing current given to the comparison circuit can suitably follow fluctuations in the raw water PH, and as a result, There was no apparent excess or deficiency in the amount of coagulant injected, and as a result, fluctuations in the turbidity of the treated water could be reliably suppressed.

(Structure and operation of second embodiment) Also, with reference to FIGS. The structure and operation of the coagulation and sedimentation processing apparatus will be explained in detail while explaining the coagulation and sedimentation processing apparatus in which injection control is performed.

As is clear from a comparison between FIG. 1 and FIG. 5, in the second embodiment, a raw water thermometer 18A is provided in place of the raw water PH meter 18, and the aggregation is performed based on the measured values of the raw water temperature and flowing current. Except for determining the injection volume of the agent,
This embodiment has substantially the same configuration and operation as the first embodiment.

That is, in the second embodiment, the raw water thermometer 18
The temperature of the raw water measured by A functions as an index equivalent to the raw water PH in the first embodiment (see FIGS. 6a to 6c).

Therefore, in order to simplify the explanation, the same reference numerals as in the first embodiment are given to the same members as in the first embodiment, so that the same reference numerals as in the first embodiment are used to refer to the same members. Detailed explanation will be omitted.

Specific Example 2 In addition, with reference to FIGS. 5 to 7 a to 7 d, specific numerical values will be given in order to further deepen the understanding of the second embodiment of the flocculant injection control method according to the present invention. This will be explained in detail.

Here, dam stored water is used as raw water, and a first coagulation and sedimentation treatment device in which coagulant injection control is executed by the coagulant injection control method according to the present invention, and a coagulant injection method disclosed as a prior art. The second control method executes coagulant injection control according to the control method.
was supplied to the coagulation and sedimentation processing equipment.

The first and second coagulation and sedimentation treatment devices have a rapid stirring tank, a slow stirring tank, and a settling tank with residence times of 3 minutes, 27 minutes, and 2 hours and 30 minutes, respectively, and have a processing capacity of 100 cm of suspended water. ³ /hour and polyaluminum chloride (so-called "PAC") was used as the flocculant.

The temperature of the raw water varied between 25°C and 15°C as time elapsed from the start of operation, as shown in Figure 7a. Incidentally, the raw water turbidity and raw water PH were almost constant at 20 degrees and 7.5, respectively. Furthermore, the turbidity of the treated water was targeted at 2 degrees.

Example 2 First stage (i.e. period from 0:00 to 1:00)
Now, since the temperature of the raw water measured by the raw water thermometer and given to the setting device was 25°C (see Figure 7a), the target value of the flowing current output from the setting device and given to the comparison circuit is (here the optimum flowing current) was -3 (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (that is, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 7c). By the way, 15mg/ is
Determined by a separately performed jar test.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the coagulant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the slow stirring basin effluent was allowed to stand still in order to settle and remove aggregates. however,
Since the residence time in the sedimentation tank was 2 hours and 30 minutes, the raw water given to the rapid stirring tank at the start of operation was
The treated water had not yet been discharged from the settling pond. Therefore, the measurement results of the treated water turbidity meter are not plotted (see Figure 7d).

Second phase (i.e. period from 1:00 to 5:00)
Now, since the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually decreased from 25°C to 15°C (see Figure 7a), it is output from the setting device and given to the comparison circuit. The target value of the flowing current (optimal flowing current here) gradually increases from -3 to -2 during the period from 1:00 to 4:00, and from 4:00 to 5:00.
-2 during the period up to (Fig. 7b)
reference).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison results showed that the target value of the flowing current gradually increased as the temperature of the raw water decreased.

In the control device, as the comparison results gradually increased, the flocculant injection amount was gradually increased from 15 mg/ to 20 mg/, and was given to the flocculant injection device as a flocculant injection control signal. (See Figure 7c).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and the turbidity was 3, which corresponds to the first stage.
2 degrees in the period from 4:00 to 4:00, and increased from 2 to 2.5 degrees in the period from 4:00 to 5:00, corresponding to the beginning of the second stage (see Figure 7d).

Third stage (i.e. period from 5:00 to 13:00)
Now, since the temperature of the raw water measured by the raw water thermometer and given to the setting device was 15°C (see Figure 7a), the target value of the flowing current output from the setting device and given to the comparison circuit is (here optimal flowing current) was maintained at -2 (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 20 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 7c).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond decreased from 2.5 degrees to nearly 1.5 degrees during the period from 5 o'clock to 8 o'clock, which corresponds to the middle to late stage of the second stage, as measured by a treated water turbidity meter. It then increased again to nearly 2 degrees, and was expected to reach 2 degrees in the period from 08:00 to 13:00, corresponding to the early to middle stage of the third stage (see Figure 7d).

Stage 4 (i.e. period from 13:00 to 17:00)
Now, as the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually increased from 15°C to 25°C (see Figure 7a), the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually increased from 15°C to 25°C (see Figure 7a). The target value of the flowing current (optimal flowing current here) gradually decreases from -2 to -3 during the period from 13:00 to 16:00, and from 16:00 to 17:00.
-3 during the period up to (Fig. 7b)
reference).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison results showed that the target value of flowing current gradually decreased as the raw water temperature increased.

In the control device, since the comparison result gradually decreased, the injection amount of flocculant was gradually decreased from 20 mg/ to 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (Fig. 7c). reference).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling basin was measured using a treated water turbidity meter, and it was found that the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, was also the same from 16:00, which corresponds to the early stage of the fourth stage. to 17:00, the temperature remained at 2°C (see Figure 7d).

Stage 5 (i.e. period from 17:00 to 24:00)
Now, since the temperature of the raw water measured by the raw water thermometer and given to the setting device was 25°C (see Figure 7a), the target value of the flowing current output from the setting device and given to the comparison circuit is (here optimal flowing current) was maintained at -3 (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 7c).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the sedimentation basin was measured with a treated water turbidity meter, and it fluctuated around 2 degrees during the period from 17:00 to 20:00, which corresponds to the middle to late stage of the 4th stage. It was maintained at 2 degrees during the period from 20:00 to 24:00, which corresponds to the early to middle stage of the fifth stage (see Figure 7d).

Comparative Example 2 First stage (i.e. period from 0:00 to 1:00)
In this case, the temperature of the raw water measured by the raw water thermometer and given to the setting device is 25°C (see Figure 7 a), and the elapsed time from the start of operation is the rapid stirring tank, slow stirring tank, and settling tank. Since the turbidity of the treated water has not yet been measured as described below, the target value of the flowing current output from the setting device and given to the comparison circuit is as follows:
-3 (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current, and the comparison result was provided to the control device.

In the control device, the injection rate of flocculant was determined to be maintained at 15 mg/cm according to the comparison results (see Figure 7c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.
Incidentally, 15 mg/ was determined by a jar test conducted separately.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond according to the flocculant injection control signal.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the slow stirring basin effluent was allowed to stand still in order to settle and remove aggregates. however,
Since the residence time in the sedimentation tank was 2 hours and 30 minutes, the raw water given to the rapid stirring tank at the start of operation was
The treated water had not yet been discharged from the settling pond. Therefore, the measurement results of the treated water turbidity meter were not plotted or used to determine the target value of the flowing current (see Figure 7d).

Second phase (i.e. period from 1:00 to 5:00)
In this case, the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually decreased from 25°C to 15°C (see Figure 7a), but it is output from the setting device and given to the comparison circuit. The target value of flowing current is (i)
Since the elapsed time from the start of operation was less than the residence time (i.e. 3 hours) in the rapid stirring tank, slow stirring tank, and settling tank, and the turbidity of the treated water had not yet been measured as described below, from 1:00 to 3:00 (ii) Since the treated water turbidity was constant during the period from 3:00 to 4:00, which corresponds to the first stage, it was maintained at -3, and (iii) during the second stage. The turbidity of the treated water began to increase at 4 o'clock, corresponding to the beginning of the turbidity, so it was set to -2 and maintained until 5 o'clock (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant injected was gradually decreased from 15 mg/ to 5 mg/ in the period from 1 o'clock to 4 o'clock, increased to 10 mg/ at 4 o'clock, and maintained until 5 o'clock, depending on the comparison result. (See Figure 7c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and the raw water from the first stage had not yet been discharged as treated water between 1:00 and 3:00. Not done, first
2 degrees in the period from 3 o'clock to 4 o'clock, corresponding to the second stage, and increased monotonically from 2 degrees to 3 degrees in the period from 4 o'clock to 5 o'clock, corresponding to the beginning of the second stage (Fig. 7d). reference).

Third stage (i.e. period from 5:00 to 13:00)
In this case, the temperature of the raw water measured by the raw water thermometer and given to the setting device was 15°C (see Figure 7a), but the turbidity of the treated water fluctuated as described below due to the influence of the second stage. Therefore, the target value of the flowing current output from the setting device and given to the comparator circuit was set to -2 at 5 o'clock and then maintained until 6 o'clock;
After being set to 1, it was maintained until 11:00, and after being set to -2 at 11:00, it was maintained until 13:00 (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant to be injected was increased to 15 mg/at 5 o'clock and maintained until 6 o'clock, increased to 22.5 mg/at 6 o'clock and maintained until 11 o'clock, and increased to 20 mg/at 11 o'clock, depending on the comparison results. It was decided that the temperature would decrease to 1:00 p.m. and then be maintained until 1:00 p.m. (see Figure 7c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the coagulant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the effluent from the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond increased from 3 to 5 degrees during the period from 5 o'clock to 8 o'clock, which corresponds to the middle to late stage of the second stage, as measured by a treated water turbidity meter. Later, it decreased again to nearly 4 degrees, and gradually decreased from 4 degrees to less than 2 degrees during the period from 08:00 to 13:00, which corresponds to the early to middle stage of the third stage (see Figure 7d).

Stage 4 (i.e. period from 13:00 to 17:00)
In this case, the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually increased from 15°C to 25°C (see Figure 7a). As explained below, the turbidity of the treated water was maintained at less than 2 degrees due to the influence of It was maintained at -3.5 at 16:00 and maintained until 17:00 (see Figure 7b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant injected is maintained at 20 mg/during the period from 13:00 to 14:00, and from 20 mg/deg/during the period from 14:00 to 16:00, depending on the comparison results.
It was determined that the amount increased monotonically to 22.5 mg/, rapidly decreased to 20 mg/ at 16:00, and was maintained until 17:00 (see Figure 7c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling basin was measured using a treated water turbidity meter, and it was found that the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, was also the same from 16:00, which corresponds to the early stage of the fourth stage. During the period from 17:00 to 17:00, the temperature remained below 2 degrees, with almost no change (see Figure 7d).

Stage 5 (i.e. period from 17:00 to 24:00)
In this case, the temperature of the raw water measured by the raw water thermometer and given to the setting device is 25°C (see Figure 7a), and the turbidity of the treated water is below 2°C due to the influence of the fourth stage, as described below. Therefore, the target value of the flowing current output from the setting device and given to the comparison circuit was set to -2.75 at 17:00 and maintained until 19:00, and then set to -3 at 19:00 and maintained until 24:00. (7th
(see figure b).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, depending on the comparison results, the injection amount of coagulant is reduced to 17.5mg/ from 17:00 and maintained until after 19:00, and then reduced to 15mg/ after 19:00 and maintained until 24:00. (See Figure 7c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent is slowly agitated and then fed to the settling pond as slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

As measured by a treated water turbidity meter, the turbidity of the treated water discharged from the sedimentation pond gradually decreased from 2 degrees to less than 1 degree from 17:00 to 19:00, which corresponds to the middle to late stage of the 4th stage. It gradually increases from less than 1 degree to 2 degrees in the period from 19:00 to 22:00, corresponding to the late stage 4 to early stage 5, and from 22:00, corresponding to the middle of stage 5. It was maintained at 2 degrees during the period up to 24 hours (see Figure 7 d).

Comparison of Example 2 and Comparative Example 2 As is clear from the above, in Example 2, compared to Comparative Example 2, the target value of the flowing current given to the comparison circuit can suitably follow fluctuations in the temperature of raw water, and as a result, There was no apparent excess or deficiency in the amount of coagulant injected, and as a result, fluctuations in the turbidity of the treated water could be reliably suppressed.

(Structure and operation of third embodiment) Also, with reference to FIGS. 8 to 11 a to e, the third embodiment of the flocculant injection control method according to the present invention
The structure and operation of the embodiment will be explained in detail while explaining the coagulation and sedimentation processing apparatus in which the injection control of the coagulant is executed.

As is clear from a comparison between FIG. 1 and FIG. 8, the third embodiment has an additional raw water thermometer of 18A compared to the first embodiment to measure raw water PH, raw water temperature, and flowing current. This embodiment has substantially the same structure and operation as the first embodiment, except that the amount of coagulant to be injected is determined from the measured value.

That is, in the third embodiment, the raw water PH measured by the raw water PH meter 18 and the raw water temperature measured by the raw water thermometer 18A are used as indicators equivalent to the raw water PH in the first embodiment. Functioning (see Figures 9a-c and 10a-c).

Therefore, in order to simplify the explanation, the same members as those included in the first embodiment are designated by the same reference numerals as in the first embodiment. Detailed explanation will be omitted.

Specific Example 3 Referring also to FIGS. 8 to 11 a to c, the third example of the coagulant injection control method according to the present invention
In order to further deepen the understanding of the embodiment, a detailed explanation will be provided using specific numerical values.

Here, dam stored water is used as raw water, and a first coagulation and sedimentation treatment device in which coagulant injection control is executed by the coagulant injection control method according to the present invention, and a coagulant injection method disclosed as a prior art. The second control method executes coagulant injection control according to the control method.
was supplied to the coagulation and sedimentation processing equipment.

The first and second coagulation and sedimentation treatment devices are both equipped with a rapid stirring basin, a slow stirring basin, and a settling basin of the same structure, and the residence time of the rapid stirring basin, slow stirring basin, and settling basin is 3. minutes, 27 minutes and 2 hours
The treatment time was 30 minutes, the raw water (ie suspended water) throughput was 100 m ³ /h, and polyaluminum chloride (so-called "PAC") was used as the flocculant.

Raw water PH changes over time from the start of operation.
It changed between 7.5 and 6.5 as shown in Figure 11a. Furthermore, the temperature of the raw water varied between 25°C and 15°C as time elapsed from the start of operation, as shown in Figure 11a. By the way, the raw water turbidity is 20
The temperature remained almost constant. In addition, the turbidity of the treated water is 2
degree was the goal.

Example 3 First stage (i.e. period from 0:00 to 1:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device is 7.5 (see Figure 11a),
The temperature of the raw water measured by the raw water thermometer and fed to the setting device was 25°C (see Figure 10b).
Therefore, the target value of the flowing current that is output from the setting device and given to the comparison circuit (here, the optimal flowing current)
was -3 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current tolerated from the setting device (ie, the optimum flowing current), and the comparison result was provided to the control device. The comparison result was that the flowing current was maintained at zero since the nominal value was constant.

In the control device, since the comparison result was maintained at 0, the injection amount of flocculant was maintained at 8 mg/, and was given to the current injection device as a flowing current injection control signal (see Figure 11d). By the way, 8mg/
was determined by a separately performed jar test.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly stirred and then fed to the settling pond as slow stirring pond effluent.

In the settling basin, the slow stirring basin effluent was allowed to stand still in order to settle and remove aggregates. however,
Since the residence time in the sedimentation tank was 2 hours and 30 minutes, the raw water given to the rapid stirring tank at the start of operation was
The treated water had not yet been discharged from the settling pond. Therefore, the measurement results of the treated water turbidity meter are not plotted (see Figure 11e).

Second phase (i.e. period from 1:00 to 5:00)
, the raw water PH measured by the raw water PH meter and given to the setting device gradually decreased from 7.5 to 6.5 (first
(See Figure 1a), the temperature of the raw water fed to the setting device measured by the raw water thermometer gradually decreased from 25℃ to 15℃ (See Figure 11b), so the temperature output from the setting device The target value of the flowing current (here the optimum flowing current) applied to the comparator circuit was monotonically increased from -3 to 0 during the period from 1 o'clock to 5 o'clock (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison results showed that the target value of flowing current gradually increased as the raw water PH decreased and the raw water temperature decreased.

In the control device, as the comparison results gradually increased, the injection amount of flocculant was gradually increased from 8 mg/ to 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (Fig. 11d). reference).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and the turbidity was 3, which corresponds to the first stage.
2 degrees in the period from reference).

Third stage (i.e. period from 5:00 to 13:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device is 6.5 (see Figure 11a), and the raw water temperature measured by the raw water thermometer and given to the setting device is 15°C. Therefore, the target value of the flowing current (in this case, the optimum flowing current) is output from the setting device and given to the comparison circuit.
was maintained at 0 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison result was maintained at 0, the flocculant injection amount was maintained at 15 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 11d).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to settle and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the sedimentation basin was measured using a treated water turbidity meter, and the turbidity of the treated water rose twice during the period from 5 o'clock to 8 o'clock, which corresponds to the middle to late stage of the second stage.
After decreasing to 1.5 degrees, it increases from 1.5 degrees to 3 degrees, and from 8 o'clock, corresponding to the early to middle stage of the third stage.
It was maintained at 2 degrees in the period until 13:00 (11th
(see figure e).

Stage 4 (i.e. period from 13:00 to 17:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device gradually increases from 6.5 to 7.5 (first
As the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually increased from 15℃ to 25℃ (see Figure 11b), the temperature of the raw water measured by the raw water thermometer and given to the setting device gradually increased from 15℃ to 25℃ (see Figure 11b), so the temperature was output from the setting device and compared. The target value of the flowing current given to the circuit (optimal flowing current here) is from 0 to -
It gradually decreased to 3 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison results showed that the target value of flowing current gradually decreased as the raw water PH increased and the raw water temperature increased.

In the control device, as the comparison progress gradually decreased, the flocculant injection amount was gradually reduced from 15 mg/ to 8 mg/, and was given to the flocculant injection device as a flocculant injection control signal (Fig. 11d). reference).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and was maintained at 2 degrees Celsius during the period from 13:00 to 16:00, which corresponds to the latter half of the third stage.
During the period from 16:00 to 17:00, corresponding to the beginning of the fourth stage, it increased to nearly 2 to 3 degrees and then decreased to 2 degrees (see Figure 11e).

Stage 5 (i.e. period from 17:00 to 24:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device is 7.5 (see Figure 11a),
Since the temperature of the raw water measured by the raw water thermometer and given to the setting device is 25°C (see Figure 11b), the target value of the flowing current output from the setting device and given to the comparison circuit (here, optimal flowing current)
was maintained at -3 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current (in this case, the optimum flowing current) given by the setting device, and the comparison result was given to the control device. The comparison result was that the target value of flowing current was kept constant, so it was maintained at zero.

In the control device, since the comparison progress was maintained at 0, the flocculant injection rate was maintained at 8 mg/, and was given to the flocculant injection device as a flocculant injection control signal (see Figure 11d).

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly stirred and then fed to the settling pond as slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still to settle and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the sedimentation basin was measured with a treated water turbidity meter, and it fluctuated around 2 degrees during the period from 17:00 to 20:00, which corresponds to the middle to late stage of the 4th stage. It was maintained at 2 degrees during the period from 20:00 to 24:00, which corresponds to the early to middle stage of the fifth stage (see Figure 11e).

Comparative Example 3 First stage (i.e. period from 0:00 to 1:00)
In this case, the raw water PH given to the setting device as measured by the raw water PH meter is 7.5 (see Figure 11a). and the temperature of the raw water measured by the raw water thermometer and given to the setting device is 25°C (see Figure 11b),
Since the elapsed time from the start of operation was less than the residence time (i.e. 3 hours) in the rapid stirring tank, slow stirring tank, and settling tank, and the turbidity of the treated water had not yet been measured as described below, the turbidity of the treated water was not output from the setting device. The target value of the flowing current applied to the comparator circuit was maintained at -3 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current, and the comparison result was provided to the control device.

In the control device, the injection rate of flocculant was determined to be maintained at 8 mg/d according to the comparison results (see Figure 11d). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal. Incidentally, 8 mg/ was determined by a jar test conducted separately.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond according to the flocculant injection control signal.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the sedimentation basin, the effluent from the slow stirring basin was left to settle and remove aggregates. however,
Since the residence time in the stirring pond was 2 hours and 30 minutes, the raw water given to the rapid stirring pond at the start of operation was:
The treated water had not yet been discharged from the settling pond. Therefore, the measurement results of the treated water turbidity meter were not plotted and were not used to determine the target value of the flowing current (see Figure 11e).

Second phase (i.e. period from 1:00 to 5:00)
, the raw water PH measured by the raw water PH meter and given to the setting device gradually decreased from 7.5 to 6.5 (first
(See Figure 1a), the temperature of the raw water fed to the setting device measured by the raw water thermometer gradually decreased from 25℃ to 15℃ (See Figure 11b), so the temperature output from the setting device The target value of the flowing current given to the comparison circuit is set when the elapsed time from the start of operation is less than the residence time (i.e. 3 hours) in the rapid stirring tank, slow stirring tank and sedimentation tank, and the turbidity of the treated water is still measured as described below. During the period from 1:00 to 3:00 when the
It was maintained at -3 during the period from 10:00 to 4:00, and after being set to -2 at 4:00, which corresponds to the beginning of the second phase, it was maintained until 5:00 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant to be injected was adjusted to 8 mg/kg between 1:00 and after 4:00, depending on the comparison results.
It gradually decreased from 4 mg/ to 7.5 after 4 o'clock.
It was decided to increase to 500 mg/mg/ml and maintain it by 5:00 (see Figure 11d). The injection amount of flocculant is
This signal was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond was measured using a treated water turbidity meter, and the raw water from the first stage had not yet been discharged as treated water between 1:00 and 3:00. Not done, first
2 degrees in the period from 3 o'clock to 4 o'clock, corresponding to the second stage, and increased monotonically from 2 degrees to 4.5 degrees in the period from 4 o'clock to 5 o'clock, corresponding to the beginning of the second stage (Fig. 11e). reference).

Third stage (i.e. period from 5:00 to 13:00)
In this case, the raw water PH measured by the raw water PH meter and fed to the setting device is 6.5 (see Figure 11a), and the raw water temperature measured by the raw water thermometer and fed to the setting device is 15°C. Atsuta (see Figure 11b)
As the turbidity of the treated water was fluctuating as described below due to the influence of the second stage, the target value of the flowing current output from the setting device and given to the comparison circuit was set to -1 at 5 o'clock and maintained until 6 o'clock. It was set to 0 at 6 o'clock, maintained until 7 o'clock, set to 0.5 at 7 o'clock, and then set to 0.5 at 7 o'clock.
It was maintained until 12 o'clock, and after being set to 0 at 12 o'clock, it was maintained until 13 o'clock (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, depending on the comparison results, the injection amount of the flocculant was increased to 12 mg/at 5 o'clock and maintained until 6 o'clock, increased to 15 mg/at 6 o'clock and maintained until 7 o'clock, and increased to 17.5 mg/at 7 o'clock. It was decided to increase the dose to 12:00 and maintain it until 12:00, decrease to 15 mg/l at 12:00 and maintain until 13:00 (see Figure 11d).
The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond increased from 4 degrees to 9 degrees during the period from 5 o'clock to 8 o'clock, corresponding to the middle to late stage of the second stage, as measured by a treated water turbidity meter. Later, it decreased again to nearly 6 degrees, and during the period from 8:00 to 10:30, corresponding to the early to middle stage of the third stage, it decreased from 4 degrees to less than 2 degrees, corresponding to the middle stage of the third stage. The temperature remained below 2 degrees Celsius from 10:30 to 13:00 (see Figure 11e).

Stage 4 (i.e. period from 13:00 to 17:00)
In this case, the raw water PH measured by the raw water PH meter and given to the setting device gradually increases from 6.5 to 7.5 (see Figure 11a), and the raw water PH measured by the raw water thermometer and given to the setting device gradually increases from 6.5 to 7.5 (see Figure 11a). The temperature of the raw water is between 15℃ and 25℃.
℃ (see Figure 11b), but the third
Because the turbidity of the treated water was maintained at less than 2 degrees due to the effects of the latter stages or the early stages of the fourth stage, as described below, the target value of the flowing current output from the setting device and given to the comparison circuit was set at 1:00 p.m. It was maintained at 0 during the period from 16:00 to 16:00, and after being set to -1 at 16:00, it was maintained until 17:00 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

In the control device, the amount of coagulant injected increases monotonically from 15 mg/ to 40 mg/in the period from 13:00 to 15:30, and increases to 40 mg/in the period from 15:30 to 14:00, depending on the comparison results. decreased from to 30mg/
It was decided that it would be maintained until 17:00 (see Figure 11c). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling basin was measured using a treated water turbidity meter, and it was found that the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, was also the same from 16:00, which corresponds to the early stage of the fourth stage. During the period from 17:00 to 17:00, the temperature remained below 2 degrees, with almost no change (see Figure 11e).

Stage 5 (i.e. period from 17:00 to 24:00)
In this example, the raw water PH measured by the raw water PH meter and fed to the setting device is 7.5 (see Figure 11a), and the temperature of the raw water measured by the raw water thermometer and fed to the setting device is 25°C. (See Figure 11b), and as described below, the turbidity of the treated water was maintained at less than 2 degrees due to the influence of the fourth stage, so the target value of the flowing current output from the setting device and given to the comparison circuit is 17
After being set to -2 at the time, it was maintained until 19:00, and at 19:00, it was set to -3 and maintained until 24:00 (see Figure 11c).

In the comparison circuit, the measured value of the flowing current by the flowing ammeter was compared with the target value of the flowing current given from the setting device, and the comparison result was given to the control device.

The control device adjusts the amount of coagulant injected from 30 mg/day to 20 mg/day from 5:00 p.m. to 6:00 p.m., depending on the comparison results.
mg/mg and was maintained until 19:00.
It was determined that the amount of water was rapidly decreased to 8 mg/day and maintained for up to 24 hours (see Figure 11d). The injection amount of the flocculant was given to the flocculant injection device as a flocculant injection control signal.

In the flocculant injection device, the flocculant was injected into the rapid stirring pond in response to a flocculant injection control signal given from the control device.

The raw water into which the flocculant was injected in the rapid stirring pond was rapidly stirred and then fed to the slow stirring pond as rapid stirring pond effluent.

In the slow stirring pond, the rapid stirring pond effluent was slowly agitated and then fed to the settling pond as the slow stirring pond effluent.

In the settling basin, the water flowing out of the slow stirring basin was allowed to stand still in order to precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the sedimentation basin was measured using a treated water turbidity meter, and the turbidity of the treated water reached 1 during the period from 17:00 to 18:30, which corresponds to the middle to late stage of the 4th stage.
It gradually decreases from around 0.5 degrees to nearly 0.5 degrees, and gradually increases from around 0.5 degrees to 2 degrees in the period from 18:30 to 22:00, which corresponds to the late stage 4 or early stage 5. From 22:00 to 24:00 corresponding to the middle period of
It was maintained at 2 degrees during the period up to (see Figure 11e).

Comparison of Example 3 and Comparative Example 3 As is clear from the above, in Example 3, compared to Comparative Example 3, the target value of the flowing current given to the comparison circuit better follows fluctuations in the raw water PH and the temperature of the raw water. As a result, fluctuations in the turbidity of the treated water were reliably suppressed as there was no apparent excess or deficiency in the amount of coagulant injected.

(3) Effects of the invention As is clear from the above, the first effect of the present invention is
The coagulant injection control method is to control the amount of coagulant injection according to the properties of the raw water when injecting the coagulant into the raw water to make the suspended water a coagulant, remove the precipitate, and discharge it as treated water. In particular, as specified as the first solution in the previous section of [Means for solving the problem], it includes the first to fifth steps listed in items (a) to (e). (i) It has the effect of being able to determine the injection amount of flocculant in immediate response to changes in the hydrogen ion concentration index of raw water, and (ii) It has the effect of suppressing fluctuations in treated water turbidity.
In addition, (iii) it has the effect of reducing the amount of coagulant to be injected.

The second flocculant injection control method according to the present invention is characterized in that when a flocculant is injected into raw water in order to flocculate suspended water from raw water, remove precipitates, and discharge it as treated water, the flocculant is injected into the raw water according to the properties of the raw water. In particular, as specified as the second solution in the middle section of [Means for solving the problem], the amount of injection is controlled, and in particular, the
(iv) It has the effect of being able to determine the injection amount of flocculant in immediate response to changes in the raw water temperature, and as a result, it has the effect of (ii) as well as the first flocculant injection control method described above. It has the effect of (iii).

The third flocculant injection control method according to the present invention is characterized in that when a flocculant is injected into raw water in order to flocculate suspended solids from raw water, remove precipitates, and discharge as treated water, the flocculant is flocculated according to the properties of the raw water. The injection amount of the agent is controlled, and in particular, as specified as the third solution in the latter part of [Means for solving the problem], the first to sixth methods listed in items (a) to (f) are
(v) It has the effect of being able to determine the amount of coagulant to be injected in immediate response to changes in the hydrogen ion concentration index of raw water and changes in raw water temperature. Compared to the flocculant injection control method, this method preferably has the effects (ii) and (iii) above.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing a flocculant-sedimentation treatment apparatus in which flocculant injection control is executed according to the first embodiment of the flocculant injection control method according to the present invention, and FIG. An enlarged sectional view showing a part of the coagulation and sedimentation treatment apparatus shown in the figure, FIGS. 3 a to c are operation explanatory diagrams for explaining the embodiment in FIG. 1, and FIGS. 4 a to d are Fig. 1 is an operation explanatory diagram for explaining a specific example of the embodiment, and Fig. 5 shows the injection control of the coagulant being executed according to the second embodiment of the flocculant injection control method according to the present invention. A conceptual diagram to show the coagulation sedimentation processing apparatus, FIG. 6 a to c are operation explanatory diagrams to explain the embodiment in FIG.
d is an operation explanatory diagram for explaining a specific example of the embodiment shown in FIG. 5, and FIG. 9a-c are operational explanatory diagrams for explaining the embodiment in FIG. 5, and FIGS. 10a-c are diagrams for explaining the embodiment in FIG. 8. Other operation explanatory diagrams, FIGS. 11a to 11e, are operation explanatory diagrams for explaining a specific example of the embodiment of FIG. 10 ... Coagulation sedimentation processing device, 11A, 11B...
... Raw water supply pipe, 11C... Treated water discharge pipe, 12...
...Water landing well, 13... Rapid stirring pond, 13A... Drive source, 13B... Stirring member, 14... Slow stirring pond,
14A... Drive source, 14B... Stirring member, 15...
...Sedimentation tank, 16...Flocculant injection device, 16A...
Coagulant storage tank, 16B...metering pump, 18...raw water PH meter, 18A...raw water temperature meter, 19...flowing ammeter, 19a...water sampling pipe, 19a ⁺ ...water sampling pump, 19b...drainage pipe, 19c, 19d
... Connection wire, 19A ... Cylindrical container, 19B, 19
C... Electrode, 19D... Power source, 19E... Piston, 19F... Ammeter, 20... Treated water turbidity meter, 21... Setting device, 22... Comparison circuit, 23
……Control device.

Claims (1)

[Claims] 1. When a flocculant is injected into raw water in order to flocculate suspended solids from the raw water, remove precipitates, and discharge as treated water, the amount of flocculant injected is controlled according to the properties of the raw water. A flocculant injection control method comprising: (a) a first step of measuring the hydrogen ion concentration index of the raw water; (b) a second step of measuring the flowing current of the raw water into which the flocculant has been injected; c) a third step of selecting a set value of the flowing current according to the hydrogen ion concentration index of the raw water measured in the first step and determining it as a target value of the flowing current; (e) comparing the determined target value of the flowing current with the measured value of the flowing current measured in the second step; A flocculant injection control method, comprising: a fifth step of determining an injection amount. 2. Coagulant injection control that controls the injection amount of coagulant according to the properties of raw water when coagulant is injected into raw water in order to coagulate suspended solids from raw water, remove precipitates, and discharge as treated water. The method includes (a) a first step of measuring the temperature of the raw water, (b) a second step of measuring the flowing current of the raw water into which a flocculant has been injected, and (c) a step of measuring the temperature of the raw water measured in the first step. (d) selecting a set value of the flowing current according to the temperature of the raw water and determining it as the target value of the flowing current; a fourth step of comparing the measured value of the flowing current measured in the step; and (e) a fifth step of determining the amount of coagulant to be injected according to the results of the comparison in the fourth step. A flocculant injection control method characterized by: 3. Coagulant injection control that controls the injection amount of coagulant according to the properties of raw water when coagulant is injected into raw water in order to coagulate suspended solids from raw water, remove precipitates, and discharge as treated water. The method includes (a) a first step of measuring the hydrogen ion concentration index of the raw water, (b) a second step of measuring the temperature of the raw water, and (c) a flowing current of the raw water into which a flocculant has been injected. and (d) selecting a set value of the flowing current according to the hydrogen ion concentration index of the raw water measured in the first step and the temperature of the raw water measured in the second step. (e) a fifth step of comparing the target value of the flowing current determined in the fourth step with the measured value of the flowing current measured in the third step; and (f) a sixth step of determining the amount of coagulant to be injected according to the results compared in the fifth step.