JPH0581282B2 - - 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 a flocculant injection control method for controlling the injection amount of flocculant according to the properties of raw water during injection, in particular, a set value of flowing current selected according to at least one of the hydrogen ion concentration index and temperature of 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 correcting the flow current according to the turbidity of the treated water.

[Prior Art] Conventionally, this type of flocculant injection control method includes:
When a flocculant (inorganic flocculant or organic flocculant) is injected into raw water to flocculate suspended solids, remove precipitates, and discharge as treated water, it is determined based on empirical rules according to the measurement results of treated water turbidity. It has been proposed that a control device determines the amount of coagulant to be injected so that the measured value of the flowing current approaches the target value of the flowing current.

[Problems to be solved] However, in the conventional flocculant injection control method, the measured value of the flowing current approaches the target value of the flowing current determined based on empirical rules according to the measurement results of the turbidity of the treated water. Since the amount of coagulant to be injected was determined, even if the amount of coagulant to be injected was changed immediately when the turbidity of the treated water changed, the rapid stirring pond,
This method has the disadvantage that the injection control of the flocculant is delayed by the residence time in the slow stirring pond and sedimentation pond, and as a result, it is not possible to sufficiently suppress fluctuations in the turbidity of the treated water due to fluctuations in the raw water properties. As a result, the injection amount of coagulant must always be set large in order to maintain the turbidity of the treated water at the desired level regardless of fluctuations in the raw water properties. Ta.

Therefore, in order to eliminate these drawbacks, the present invention corrects the set value of the flowing current selected according to at least one of the hydrogen ion concentration index and the temperature of the raw water according to the turbidity of the treated water. It is an object of the present invention to provide 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.

(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; (e) a fifth step of determining the amount of coagulant to be injected according to the results compared in the fourth step; (f) a sixth step of measuring the turbidity of the treated water; (g) a seventh step of correcting the set value of the flowing current selected in determining the target value of the flowing current in the third step according to the turbidity of the treated water measured in the sixth step; A coagulant injection control method characterized by comprising:

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; (f) a sixth step of measuring the turbidity of the treated water; and (g) a method selected in determining the target value of the flowing current in the third step. and a seventh step of correcting the set value of the flowing current according to the turbidity of the treated water measured in the sixth step.''

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 the 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 second 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; and (g) a seventh step of measuring the turbidity of the treated water; (h) measuring the set value of the flowing current selected in determining the target value of the flowing current in the fourth step of the treated water measured in the seventh step; and an eighth step of correcting according to the turbidity of the flocculant injection.

[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 seventh steps listed in item (g), it (i) 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) ) Acts to correct the amount of coagulant injected in immediate response to changes in the turbidity of the treated water, and in turn (iii) acts to suppress fluctuations in the turbidity of the treated water, and also (iv) adjusts the amount of coagulant injected. It acts to reduce the

The second 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 stated in the middle section of the second solution, (a) ~
Since it includes the first to seventh steps listed in item (g), (v) it acts to determine the amount of coagulant to be injected in immediate response to changes in raw water temperature, and (vi) it prevents turbidity of treated water. This functions to correct the injection amount of the flocculant in response to the change in the temperature, and as a result, the above-mentioned functions () and () are performed similarly to the first flocculant injection control method described above.

The third flocculant injection control method according to the present invention includes:
When injecting a flocculant into raw water to flocculate suspended matter from the 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. Point solution] As specified in the latter part as the third solution, (a) ~
Since it includes the first to eighth steps listed in paragraph (h), (vii) it has the function of determining 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. None, and (viii) acts to correct the amount of flocculant injection in response to changes in the turbidity of the treated water, and as a result, compared to the first and second flocculant injection control methods described above, to suit the effect of

[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 FIG. 1.

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.

(Configuration of the first embodiment) First, with reference to FIGS. 1 and 2, the first embodiment of the flocculant injection control method according to the present invention will be explained, whereby the flocculant injection control is executed. The configuration will be explained in detail while explaining the configuration of the coagulation and sedimentation processing apparatus.

10 is a coagulation-sedimentation treatment apparatus in which injection control of a coagulant is executed by the coagulant injection control method according to the present invention; “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 a flocculant is injected from the rapid stirring basin 13 and rapidly stirred to form aggregates (hereinafter referred to as "rapid stirring"). a slow agitation pond 14 for slowly agitating the rapid agitation pond effluent to enlarge the aggregates;
A flocculant is applied to the settling basin 15 for allowing suspended water (hereinafter referred to as "slow stirring basin effluent water") given from the water to settle to settle aggregates, and the rapid stirring basin 13 for forming aggregates. A flocculant injection device 16 for injecting (an inorganic flocculant or an organic flocculant) is provided. The rapid stirring pond 13 is provided with a stirring member 13B that is rapidly rotated (that is, rotated at a relatively high speed) by a drive source (for example, an electric motor) 13A. Slow stirring pond 1
4 is provided with a stirring member 14B that is driven to rotate slowly (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, which is installed for 1B and measures the hydrogen ion concentration index (hereinafter also referred to as "raw water PH") of raw water, and a rapid stirring pond. A flow current meter 19 for measuring the flow current of raw water (i.e. suspended water) in which a flocculant has been injected, which is disposed in relation to 13.
It is arranged for the treated water discharge pipe 11C for discharging the treated water from the settling tank 15 as shown by arrow B, and measures the turbidity of the treated water (hereinafter also referred to as "treated water turbidity"). It is equipped with a treated water turbidity meter 20. Incidentally, the flowing current meter 19 temporarily holds raw water injected with a flocculant collected from the rapid stirring pond 13B via the water sampling pipe 19a and the water sampling pump 19a ⁺ as a sample, and provides it for measuring the flowing current. Thereafter, the cylindrical container 19 discharges the sample (that is, the raw water into which the flocculant has been injected) toward the rapid stirring pond 13B via the drainage pipe 19b.
A, two electrodes 19B and 19C spaced apart from each other on the inner peripheral surface of the cylindrical container 19A, and the cylindrical container 19
A piston 19E, which is disposed inside the cylindrical container 19A and is reciprocated by a power source 19D located outside the cylindrical container 19A, to move the sample (that is, raw water injected with a flocculant); and electrodes 19B, 1.
It is connected to electrodes 19C and 19C via connecting wires 19c and 19d, and measures the current generated between electrodes 19B and 19C due to the movement of the sample (i.e. raw water injected with flocculant) as the piston 19E reciprocates. It includes an ammeter 19F that amplifies and outputs the amplified flowing current to the comparator circuit 22. The measured value of the flowing current by the flowing current meter 19 will decrease if the amount of coagulant injection is not increased when the raw water flow rate or raw water turbidity increases, and if the raw water flow rate or raw water turbidity decreases, the value of the flowing current will decrease if the amount of flocculant injection is not increased. If the amount is not decreased, it will increase, so in the present invention, by controlling the injection amount of the flocculant so that it matches the set value of the flowing current output from the setting device 21, the raw water flow rate and raw water turbidity can be adjusted. It eliminates the need for attention.

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. The optimal flowing current (i.e., the set value of the flowing current) is appropriately selected according to the measured value of PH, and the selected optimal flowing current (that is, the set value of the flowing current) is given from the treated water turbidity meter 20. A setting device 21 for appropriately correcting the measured value of the turbidity of the treated water and outputting it as a target value of the flowing current is connected to the flowing ammeter 19 and the setting device 21. A comparison circuit 22 is connected to the comparison circuit 22 for comparing the measurement value of the given flowing current and the target value of the flowing current given from the setting device 21, and the comparison result of the comparison circuit 22 (i.e. and a control device 23 for determining the amount of coagulant to be injected according to the difference between the target value of the flowing current and the measured value of the flowing current and giving it to the coagulant injection device 16 as a coagulant injection control signal. ing.

(Operation of the first embodiment) Furthermore, 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 treated as raw water after large foreign substances are precipitated and removed in the landing well 12. It is supplied to the rapid stirring pond 13 via the supply pipe 11B.

The 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 basin 13 is supplied to the slow stirring basin 14 as rapid stirring basin outflow water.

In the slow agitation pond 14, the water flowing out of the rapid agitation pond is slowly agitated to enlarge the aggregates. The rapid agitation basin effluent that has been slowly agitated in the slow agitation basin 14 is supplied to the sedimentation basin 15 as slowly agitated effluent.

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). The waste is supplied to the public, or is discharged or reused as is.

Coagulant injection control setting operation Prior to the start of operation of the coagulation and sedimentation treatment device 10 , the raw water PH and the optimum flowing current (i.e., "the flowing current corresponding to when the desired coagulation state is achieved") are measured in an appropriate manner. . The measurement of the raw water PH and the optimum flowing current may be achieved by preliminary operation of the coagulation sedimentation treatment device 10 , or by creating a scaled-down model of the coagulation sedimentation treatment device 10 , but here, The following description assumes that this is achieved using a PH meter, a jar test device, and a flowing ammeter attached to the jar test device.

Raw water PH is measured 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 ( (See Figure 3a).

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 the setting value of the flowing current.

Injection control operation When the operation of the coagulation sedimentation processing device 10 is started,
The hydrogen ion concentration index (that is, raw water PH) of suspended water supplied from the landing well 12 to the rapid stirring pond 13 as raw water starts to be measured by the raw water PH meter 18 . The measured value of the raw water PH is given to the setting device 21.

In the setting device 21, each time the measured value of raw water PH is given from the raw water PH meter 18, the optimum flowing current (that is, the flow current set value) was appropriately selected, and the selected optimal flowing current (i.e., the set value of the flowing current) was appropriately corrected according to the measured value of treated water turbidity given from the treated water turbidity meter 20. Thereafter, it is outputted to the comparator circuit 22 as the target value of the flowing current. Correction of the set value of the flowing current selected by the setting device 21 does not necessarily need to be performed all the time, and may be performed when the measured value of the treated water turbidity fluctuates beyond a predetermined value, if desired. (Hereinafter, explanation will be given assuming that the process is executed when the measured value of treated water turbidity varies by 0.3 from the target value of treated water turbidity, for example).

In the comparison circuit 22, the difference between the target value of the 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 the difference is outputted to the control device 23 as a comparison result. be done.

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 is injected from the flocculant 16A toward the rapid stirring pond 13.

As described above, according to the present invention, the amount of coagulant to be injected can be immediately changed in the rapid stirring pond 13 according to changes in raw water PH and turbidity of treated water, thereby avoiding unnecessary increases in the amount of coagulant to be injected. It is possible to reliably suppress fluctuations in the turbidity of the treated water.

(Specific Example 1) In addition, with reference to FIG. 1 and FIGS. 4 a to 4 d, in order to further deepen the understanding of the first embodiment of the flocculant injection control method according to the present invention, specific numerical values will be explained. 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 tank, a slow stirring tank, and a settling tank that have the same structure, and the residence time of the rapid stirring tank, slow stirring tank, and settling tank 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 measured by the raw water PH meter and given to the setting device is constant at 7.5 (see Figure 4 a), and the elapsed time from the start of operation is the rapid stirring tank, slow stirring tank, and settling tank. As described below, the turbidity of the treated water had not yet been measured for less than the residence time (i.e. 3 hours), so the setting value of the flowing current selected according to the raw water PH (7.5 in this case) in the setting device was corrected. It was output as the target value of the flowing current and given to the comparator circuit. Therefore, the target value of the flowing current 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 given from 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
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 agitated 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 (see Figure 4d) and were not used to determine the target value of the flowing current in the setting device as described above.

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 (4th
(See Figure a), the turbidity of the treated water increased during the period from 1:00 to 3:00 when 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 sedimentation tank (see below). However, at 4 o'clock, when the elapsed time from the start of operation exceeded the residence time in the rapid agitation tank, slow agitation tank, and sedimentation tank, the turbidity of the treated water increased by more than 2.3 degrees. Since I started, I set the raw water PH in the setting device.
The set value of the flowing current selected in accordance with
The target value of the flowing current was outputted without being corrected during the period up to and given to the comparator circuit. Therefore, the target value of the flowing current gradually increases from -3 to nearly -1.8 during the period from 1 o'clock to 4 o'clock,
After being corrected to increase by 0.3 at 4 o'clock, it gradually increased to -1 in the period up to 5 o'clock (Fig. 4b)
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. 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 comparative results gradually increased, the injection amount of flocculant was increased to 10 mg/day in the period up to 4:00 p.m.
Gradually increased from 1 to 14mg/1 at 4:00
mg/increased by almost 15 mg/g in the period up to 5 p.m.
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 fed to the slow stirring pond 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 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.
It gradually increased from nearly 2 degrees between
It increased from 2.3 degrees to nearly 2.5 degrees during the period from 4 o'clock to 5 o'clock, corresponding to the beginning of the phase (see Figure 4 d).

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), 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)
As mentioned below, the turbidity of the treated water gradually decreased from 2.5 degrees and remained within the range of 1.7 to 2.3 degrees with almost no fluctuation. The set value was output as the target value of the flowing current and given to the comparator circuit without being corrected. Therefore, the target value of the flowing current was maintained at -1 (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 given from 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 injection amount of coagulant was maintained at 15 mg/,
This signal was given to the flocculant injection device as a flocculant injection control signal (see FIG. 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 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 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 settling pond gradually decreased from 2.5 degrees during the period from 5 o'clock to 8 o'clock, which corresponds to the middle to late stage of the second stage. Close to 2 degrees (i.e. 1.7
The temperature remained close to 2 degrees (i.e. within the range of 1.7 to 2.3 degrees) with almost no fluctuation during the period from 08:00 to 13:00, which corresponds to the early to middle stage of the third stage. (See Figure 4d).

Stage 4 (i.e. period from 13:00 to 17:00)
, 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 (4th
As described below, the turbidity of the treated water gradually decreased from around 2 degrees and started to decrease beyond 1.7 degrees at 4 p.m., so the setting value of the flowing current was selected in the setting device according to the raw water PH. is output as the target value of the flowing current without being corrected during the period from 13:00 to 16:00, and after being corrected at 16:00, is output as the target value of the flowing current without being corrected during the period until 17:00. , given to the comparison circuit. Therefore, the target value of the flowing current is - during the period from 13:00 to 16:00.
It gradually decreased from 1 to -2, decreased by 0.5 at 16:00, and then gradually decreased to -3 in the period up to 17:00 (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. The comparison results showed that the target value of flowing current decreased gradually as the raw water pH increased.

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

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 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 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 settling pond gradually decreased from nearly 2 degrees Celsius during the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, and then reached 16 degrees Celsius. It decreased by more than 1.7 degrees at times, and from 1.7 degrees to nearly 1.5 degrees during the period from 16:00 to 17:00, corresponding to the beginning of stage 4 (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 constant at 7.5 (see Figure 4 a), and the turbidity of the treated water changes from around 1.5 degrees to 2 degrees as described below.
After increasing to almost 1.5 degrees, it remained within the range of 1.7 to 2.3 degrees with almost no fluctuation, so the setting value of the flowing current selected according to the raw water PH in the setting device was
It was outputted as the target value of the flowing current and given to the comparison circuit without being corrected. Therefore, the target value of the flowing current was maintained at -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 given from 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 injection amount of coagulant was maintained at 10 mg/,
This signal was given to the flocculant injection device as a flocculant injection control signal (see FIG. 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 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 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 fluctuated slightly around 2 degrees during the period from 17:00 to 20:00, which corresponds to the middle to late stage of the 4th stage. , was maintained at 2 degrees during the period from 20:00 to 24:00, corresponding to the early to middle stage of stage 5 (see Figure 4 d).

Comparative Example 1 In the first stage (that is, the period from 0:00 to 1:00), the raw water PH measured by the raw water PH meter and given to the setting device was constant at 7.5 (see Figure 4 a). ,
Since the elapsed time from the start of operation was less than the retention period (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 based on a rule of thumb (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, 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/, depending on the comparison results (see Figure 4c). The injection amount of the flocculant was 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 agitated 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 or used to determine the target value of the flowing current (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 is from 1:00 to 3:00 when the elapsed time from the start of operation is 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 has not yet been measured as described below. Based on the empirical rule, the turbidity of the treated water was maintained at -3 degrees as in the first stage during the period up to 3:00 and 4:00, when the turbidity of the treated water was 2 degrees as described below. It was maintained at -3 based on the rule of thumb at 4 o'clock, when the turbidity of the treated water began to increase corresponding to the beginning of the second stage, and was maintained at -2 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 injection amount of flocculant decreases monotonically from 10 mg/ to 5 mg/ in the period from 1 o'clock to 4 o'clock and from 5 mg/ to 7.5 in the period from 4 o'clock to 5 o'clock, depending on the comparison result. mg/
determined (see Figure 4c). 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 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 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 degrees in the period from 4 o'clock to 5 o'clock, corresponding to the beginning of the second stage (Fig. 4 d 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),
Due to the effects of the second stage, as described below, the turbidity of the treated water continued to increase from 4 degrees to nearly 9 degrees between 5:00 and 7:00, and from 7:00 to 1:00 pm it rose to nearly 9 degrees.
Since it continued to decrease to less than 1.5 degrees, the target value of the flowing current output from the setting device and given to the comparison circuit was set to -1 based on the empirical rule at 5 o'clock, maintained until 6 o'clock, and then set again at 6 o'clock. After it was set to 0 based on the empirical rule, it was maintained until 11 o'clock, and at 11 o'clock it was again set to -1 based on the empirical rule, and 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, from 17.5 mg/ to 15 mg/ after 11 o'clock
It was decided that the temperature would decrease to 1:00 p.m. and then be maintained until 1:00 p.m. (see Figure 4c). 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 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 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 nearly 9 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. After that, the temperature decreased again to nearly 6 degrees, and gradually decreased from 6 degrees to less than 1.5 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
Based on the empirical rule, it was maintained at -1 during the period from 1:00 to 16:00, and after being reduced to -2 based on the empirical rule at 16:00, it was maintained until 17:00 (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.

The control device maintains the injection amount of coagulant at 15 mg/during the period from 13:00 to 14:00, and from 15 mg/mt to 25 mg/distance during the period from 14:00 to 16:00, depending on the comparison results.
It was determined that the amount increased monotonically from 16:00 to 17:00 and then rapidly decreased from 25 mg/ to 16 mg/mg 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 agitated and then fed to the settling pond as 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 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 5:00 p.m., temperatures remained below 2 degrees Celsius (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 constant at 7.5 (see Figure 4 a), and the turbidity of the treated water is below 2 degrees due to the influence of the 4th 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 -2.5 based on the empirical rule at 5:00 p.m.
It is maintained until 19:00 and then again at 19:00 based on the rule of thumb.
3 and was 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.

The control device adjusts the injection amount of coagulant from 16 mg/kg to 16 mg/kg between 5:00 pm and 8:00 pm, depending on the comparison results.
It was decided to gradually decrease the dose to 10 mg/ and maintain it at 10 mg/ during the period from 20:00 to 24:00 (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 agitated and then fed to the settling pond as 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 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 decreased from less than 2 degrees to less than 1 degree during the period from 17:00 to 19:00, which corresponds to the middle to late stage of stage 4. It gradually decreases and gradually increases from 1 to 2 degrees during the period from 19:00 to 22:00, corresponding to the late stage 4 or early stage 5, and from 22:00, corresponding to the middle of stage 5. It was maintained at 2 degrees Celsius during the period up to 24 hours (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 better follow the fluctuations in the raw water PH, and as a result, the flocculation There were no problems with the injection amount of the agent, and as a result, fluctuations in the turbidity of the treated water were 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 explained in order to further deepen the understanding of the second embodiment of the flocculant injection control method according to the present invention. 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 agitation tank, a slow agitation 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 m2 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. Also,
The target turbidity of the treated water was 2 degrees.

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 setting value of the flowing current selected according to the temperature of the raw water (25°C in this case) in the setting device is , was output as the target value of the flowing current without being corrected and given to the comparator circuit. Therefore, the target value of the flowing current was -3 (see FIG. 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. 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 injection amount of flocculant was maintained at 15 mg/.
This was given to the flocculant injection device as a flocculant injection control signal (see Figure 7c). By the way, 15mg/
was determined by a separately performed jar test (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 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 (see Figure 7d) and were not used to determine the target value of the flowing current in the setting device as described above.

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 decreases from 25℃ to 15℃ (see Figure 7a), and the elapsed time from the start of operation changes between the rapid stirring pond and the slow stirring pond. As described below, the turbidity of the treated water has not yet been measured during the period from 1 o'clock to 3 o'clock, when the residence time in the rapid stirring pond and sedimentation basin was less than 3 hours (i.e. 3 hours), and the time elapsed from the start of operation was rapid. The measurement result of treated water turbidity is 2.3 at 4:00, which exceeds the residence time in the stirring pond, slow stirring pond, and settling pond.
The setting value of the flowing current selected according to the temperature of the raw water in the setting device was output as the target value of the flowing current without being corrected during the period from 1 o'clock to 4 o'clock. , after being corrected at 4 o'clock, it was outputted as the target value of the flowing current without being corrected in the period up to 5 o'clock, and was given to the comparison circuit. Therefore, the target value of the flowing current gradually increases from -3 to close to -2.2 during the period from 1 o'clock to 4 o'clock, increases by 0.2 at 4 o'clock, and then gradually increases to close to -1.9 during the period 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. 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 comparative results gradually increased, the injection amount of flocculant was gradually increased from 15 mg/ to nearly 19 mg/ in the period from 1 o'clock to 4 o'clock,
After increasing by 2 mg/at 4 o'clock, the amount was gradually decreased to nearly 20 mg/in the period up to 5 o'clock, and was given to the coagulant injection device as a coagulant injection control signal (see Fig. 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 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 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.
It gradually increased from nearly 2 degrees between
It increased from 2.3 degrees to nearly 2.5 degrees during the period from 4 o'clock to 5 o'clock, which corresponds to the early stage of (see Figure 7d).

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 is 15°C (see Figure 7a).
The elapsed time from the start of operation exceeded the residence time (i.e. 3 hours) in the rapid agitation pond, slow agitation pond, and settling pond, and the turbidity of the treated water gradually decreased from around 2.5 degrees as described below, but remained almost unchanged. 1.7~2.3
Therefore, the setting value of the flowing current selected by the setting device according to the temperature of the raw water was outputted as the target value of the flowing current and given to the comparison circuit without being corrected. . The target value of the flowing current was maintained near -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 given from 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 close 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 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 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 settling pond gradually decreased from 5:00 to 8:00, which corresponds to the middle to late stage of the second stage, and then reached 2°C. near degrees (i.e. 1.7 to 2.3
During the period from 8:00 to 13:00, which corresponds to the early to middle stage of the third stage, the temperature remained close to 2 degrees (i.e., within the range of 1.7 to 2.3 degrees) with almost no fluctuation. (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 increases from 15°C to 25°C (see Figure 7a), and the turbidity of the treated water increases from around 2°C as described below. The temperature gradually decreased and started to drop beyond 1.7 degrees at 16:00, so the setting value of the flowing current selected according to the temperature of the raw water in the setting device was not corrected during the period from 13:00 to 16:00. It is output as the target value of the flowing current, and after being corrected at 4:00 p.m.
During the period up to 5:00 p.m., it was output as the target value of the flowing current without being corrected and given to the comparison circuit.
Therefore, the target value of flowing current gradually decreases from -2 to -2.75 during the period from 13:00 to 16:00, and 16:00.
After decreasing by 0.25 at the time, -3 during the period 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. The comparison results showed that the target value of the flowing current gradually decreased as the temperature of the raw water increased.

In the control device, the comparison results gradually decreased, so the injection amount of flocculant was changed from around 20mg/ to 15mg/
The signal was gradually decreased to a point close to the level shown in Fig.
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 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 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 settling pond gradually decreased from nearly 2 degrees Celsius during the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, and then reached 16 degrees Celsius. Sometimes it exceeds 1.7 degrees and begins to decrease,
It decreased from 1.7 degrees to nearly 1.5 degrees during the period from 16:00 to 17:00, which corresponds to the beginning of the fourth stage (Fig. 7d).
reference).

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 about 1.5°C to 2°C as described below.
After increasing to almost 1.5 degrees, it remained within the range of 1.7 to 2.3 degrees with almost no fluctuation, so the setting value of the flowing current selected according to the temperature of the raw water in the setting device was not corrected, and the flowing current is output as the target value and given to the comparison circuit. For this reason,
The target value of the 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 given from 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 between 15 mg/ and 16 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 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 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 fluctuated slightly around 2 degrees during the period from 17:00 to 20:00, which corresponds to the middle to late stage of the 4th stage. , which was maintained at two degrees during the period from 20:00 to 24:00, corresponding to the early to middle stage of stage 5 (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:
Based on empirical rules, it 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, 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 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 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)
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 flowing current is
The period from 1:00 to 3:00 when 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. Based on the empirical rule, it is maintained at −3 as in the first stage, and the first
Corresponding to the beginning of the second stage, the turbidity of the treated water was maintained at -3 based on the empirical rule during the period from 3 o'clock to 4 o'clock, when it was 2 degrees as described below. -2.5 based on the empirical rule at 4 o'clock when it started to increase
It was then 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 decreases monotonically from 15 mg/ to nearly 5 mg/in the period from 1 o'clock to 4 o'clock, and from nearly 5 mg/in to 5 mg/in the period from 4 o'clock to 5 o'clock, depending on the comparison result. It was decided to increase the amount up to 10 mg/ml (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 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 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 due to the influence of the second stage, the turbidity of the treated water was 5°C as described below. The temperature continued to increase from 3 degrees to nearly 5 degrees during the period from 7:00 to 1:00 p.m.
The target value of the flowing current output from the setting device and given to the comparator circuit was set to -2 based on the empirical rule at 5 o'clock and was maintained until 6 o'clock. At that time, it was set to -1 again based on the empirical rule and was maintained until 11 o'clock, and at 11 o'clock it was again set to -2 based on the empirical rule and 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 injection amount of flocculant is increased from 10 mg/ to 15 mg/ at 5 o'clock and maintained until 6 o'clock depending on the comparison result, and then from 6 o'clock to 7 o'clock.
It was decided that the dose should be increased from 15 mg/ to 22.5 mg/ and maintained until 11 o'clock, and then decreased from 22.5 mg/ to 20 mg/ at 11 o'clock and maintained until 13:00 (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 slow stirring pond effluent.

In the sedimentation basin, the water flowing out of the slow stirring basin was allowed to stand still to precipitate and remove aggregates, and then was output 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 nearly 1.5 degrees during the period from 8:00 to 13:00, which corresponds to the early to middle stage of the third stage (see Figure 7 d).

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 Based on this, it was maintained at -2, and at 16:00, it was reduced to -3.5 based on the empirical rule and then 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 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 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 turbidity from 13:00 to 16:00, which corresponds to the latter half of the third stage, also corresponds to the early stage of the fourth stage16. 2:00 to 5:00 p.m.
The temperature was maintained at less than 100°C, and there was 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 based on the empirical rule at 5:00 p.m.
It is maintained until 19:00 and then again at 19:00 based on the rule of thumb.
3 and was maintained until 24:00 (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 decreases from 20 mg/ to 17.5 mg/ at 5:00 p.m. and is maintained until after 7:00 p.m., depending on the comparison results.
It was decided to reduce the amount from 1 to 15 mg/min and maintain it for 24 hours (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 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 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 decreased from less than 2 degrees to less than 1 degree during the period from 17:00 to 19:00, which corresponds to the middle to late stage of stage 4. It gradually decreases and 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 at 22:00, corresponding to the middle of stage 5. It was maintained at 2 degrees during the period from 24:00 to 24:00 (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 reference numerals as in the first embodiment are given to the same members as those in the first embodiment, so that they will be referred to as such. A detailed explanation will be omitted.

(Specific Example 3) Also, with reference to FIGS. 8 to 11 a to e, the third example of the flocculant 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 tank, a slow stirring tank, and a settling tank that have the same structure, and the residence time of the rapid stirring tank, slow stirring tank, and settling tank 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. Incidentally, the turbidity of the raw water was almost constant at 20 degrees. Furthermore, the turbidity of the treated water was targeted at 2 degrees.

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 constant at 7.5 (see Figure 11a),
In addition, the temperature of the raw water measured by the raw water thermometer and given to the setting device is constant at 25°C (see Figure 11b), and the elapsed time from the start of operation is the rapid stirring pond.
As described below, the turbidity of the treated water had not yet been measured for less than the residence time (i.e. 3 hours) in the slow stirring pond and sedimentation basin, so the setting device was used to set the raw water PH (here 7.5) and the raw water temperature (here The set value of the flowing current selected according to the current temperature (25°C) was output as the target value of the flowing current without being corrected, and was given to the comparator circuit. For this reason,
The target value of the flowing current was -3 (Fig. 11c)
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. 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 injection amount of coagulant was maintained at 8 mg/,
It is given to the flocculant injection device as a flocculant injection control signal (see FIG. 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 agitated 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 (see Figure 11e) and were not used to determine the target value of the flowing current in the setting device as described above.

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 1 a), and the temperature of the raw water given to the setting device measured by the raw water thermometer is between 25°C and 15°C.
℃ (see Figure 11b), and from 1 o'clock to 3 o'clock, when the elapsed time from the start of operation was less than the residence time (i.e. 3 hours) in the rapid stirring basin, slow stirring basin and settling basin. As mentioned below, the turbidity of the treated water has not been measured yet during this period, and the turbidity of the treated water was measured at 4:00, when the elapsed time from the start of operation exceeded the residence time in the rapid stirring pond, slow stirring pond, and sedimentation pond. As the results started increasing beyond 2.3 degrees,
The set value of the flowing current selected in the setting device according to the raw water PH and raw water temperature is output as the target value of the flowing current without being corrected during the period from 1 o'clock to 4 o'clock, and after being corrected at 4 o'clock. During the period up to 5 o'clock, it was outputted as the target value of the flowing current without being corrected and given to the comparison circuit. Therefore, the target value of the flowing current increases monotonically from -3 to nearly -1.25 in the period from 1 o'clock to 4 o'clock, increases by 0.5 at 4 o'clock, and then gradually increases to near 0 in the period until 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 given from 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 comparative results gradually increased, the injection amount of flocculant was gradually increased from 8 mg/ to nearly 14 mg/ in the period from 1 o'clock to 4 o'clock,
The amount was increased by 1 mg/l at 4 o'clock and then maintained at approximately 15 mg/l for the period up to 5 o'clock, 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 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 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.
It gradually increased from nearly 2 degrees between
In the period from 4 o'clock to 5 o'clock, corresponding to the early stage of the
The temperature increased from 2.3 degrees to nearly 3 degrees (see Figure 11e).

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 temperature of the raw water measured by the raw water thermometer and given to the setting device is 15°C. (See Figure 11b), the elapsed time from the start of operation exceeds 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 has increased from 3 degrees as described below. After gradually decreasing, it hardly changed and was maintained within the range of 1.7 to 2.3 degrees, so the setting value of the flowing current selected according to the raw water PH and raw water temperature in the setting device was not corrected. It was output as the target value of the flowing current and given to the comparison circuit. Therefore, the target value of the flowing current was maintained at 0 (see FIG. 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 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 injection amount of coagulant was maintained at 15 mg/,
This signal 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 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 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 gradually decreased from around 3 degrees during the period from 5:00 to 8:00, which corresponds to the middle to late stage of the second stage. Later, nearly twice (i.e.
during the period from 08:00 to 13:00, which corresponds to the early to middle stage of the third stage, the temperature remained close to 2 degrees (i.e. within the range 1.7-2.3 degrees). (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 (first
(see Figure 1 a), and the temperature of the raw water measured by the raw water thermometer and given to the setting device is between 15℃ and 25℃.
(see Figure 11b), and the turbidity of the treated water gradually decreased from around 2 degrees, as described below, until 4:00 p.m.
As the temperature started to drop beyond 1.7 degrees, the setting value of the flowing current selected according to the raw water PH and raw water temperature in the setting device was changed to the target flowing current without being corrected during the period from 13:00 to 16:00. After being corrected at 16:00, it was outputted as a target value of the flowing current without being corrected until 17:00, and was given to the comparison circuit. Therefore, the target value of the flowing current gradually decreases from 0 to -2 during the period from 13:00 to 16:00, decreases by 0.5 at 16:00, and then decreases to 17:00.
gradually decreased to -3 in the period up to (11th
(see figure c).

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 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, since the comparison result gradually decreased, the injection amount of flocculant was gradually decreased from 15 mg/ to 10 mg/ in the period from 13:00 to 14:00, and then at 16:00.
After rapidly decreasing from 10 mg/ to nearly 8 mg/, it gradually decreased to 8 mg/ in the period up to 5:00 pm, 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 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 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 settling pond gradually decreased from nearly 2 degrees Celsius during the period from 13:00 to 16:00, which corresponds to the latter half of the third stage, and then reached 16 degrees Celsius. Sometimes it exceeds 1.7 degrees and begins to decrease,
The temperature decreased from 1.7 degrees to nearly 1.5 degrees during the period from 16:00 to 17:00, which corresponds to the beginning of the fourth stage (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 increased from nearly 1.5 degrees to nearly 2 degrees, but remained within the range of 1.7 to 2.3 degrees without changing much, so the setting device raw water
The set value of the flowing current selected according to the pH and the temperature of the raw water was outputted as the target value of the flowing current and given to the comparison circuit without being corrected. Therefore, the target value of the flowing current was maintained at -3 (see FIG. 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 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 injection amount of coagulant was maintained at 8 mg/,
It was given to the flocculant injection device as a flocculant injection control signal (see FIG. 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 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 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 fluctuated slightly around 2 degrees during the period from 17:00 to 20:00, which corresponds to the middle to late stage of the 4th stage. , was maintained at approximately 2 degrees during the period from 20:00 to 24:00, corresponding to the early to middle stage of stage 5 (see Figure 11e).

Comparative 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 constant at 7.5 (see Figure 11a),
In addition, the temperature of the raw water measured by the raw water thermometer and given to the setting device is constant at 25°C (see Figure 11b), and the elapsed time from the start of operation is the rapid stirring pond.
Since the turbidity of the treated water has not yet been measured during the residence time (i.e. 3 hours) in the slow stirring basin and settling basin as described below, the target value of the flowing current output from the setting device and given to the comparison circuit is , was maintained at -3 based on empirical rules (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 given 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 flocculant injection 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 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 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 1 a), and the temperature of the raw water given to the setting device measured by the raw water thermometer is between 25°C and 15°C.
℃ (see Figure 11b), the target value of the flowing current output from the setting device and given to the comparator circuit is determined by During the period from 1 o'clock to 3 o'clock, when the residence time in the pond was less than 3 hours (i.e. 3 hours) and the turbidity of the treated water had not yet been measured as described below, based on the empirical rule, -3 as in the first stage.
Corresponding to the first stage, the turbidity of the treated water was maintained at -3 based on empirical rules during the period from 3 o'clock to 4 o'clock, when it was 2 degrees as described below, and corresponded to the beginning of the third stage. At 4 o'clock, when the turbidity of the treated water began to increase, it was set to -2 based on empirical rules and was maintained until 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 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/day between 1:00 and after 4:00, depending on the comparison results.
It decreased monotonically from 4 to 5 mg/day.
It was decided to increase from nearly 4 mg/d to nearly 7.5 mg/d in the period up to (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 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 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 given to the setting device is 6.5 (see Figure 11a), and the temperature of the raw water measured by the raw water thermometer and given to the setting device is 15°C. (See Figure 11b)
However, due to the effects of the second stage, the turbidity of the treated water continued to increase from 4.5 degrees to nearly 9 degrees between 5:00 and 7:00, and from nearly 9 degrees to 1.5 degrees between 7:00 and 1:00 p.m. Therefore, the target value of the flowing current output from the setting device and given to the comparator circuit was set to -1 based on the empirical rule at 5 o'clock, and then maintained until 6 o'clock, and at 6 o'clock the target value of the flowing current was set to -1 based on the empirical rule again. After being set to 0 based on the rule of thumb, it was maintained until 7 o'clock, and at 7 o'clock it was set to 0.5 again based on the empirical rule, and then it was maintained until 12 o'clock.
At 12 o'clock, it was set to 0 again based on the empirical rule and 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, 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 15 mg/ in the period from 6 o'clock to 7 o'clock, depending on the comparison result. from 7 a.m. to 8 p.m.
It increased from 15mg/ to 18mg/ in the period up to 12:00 and was maintained until 12:00, and from 18mg/ to 15mg/ after 12:00.
It was decided to decrease the amount to 13:00 and maintain it until 13:00 (see Figure 11d). The injection 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 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 precipitate and remove aggregates, and then was discharged as treated water.

The turbidity of the treated water discharged from the settling pond increased from 4.5 degrees to nearly 9 degrees during the period from 5:00 to 8:00, which corresponds to the middle to late stage of the second stage, as measured by a treated water turbidity meter. After that, it decreased again to nearly 6 degrees, and the temperature reached 8 degrees, which corresponds to the early to middle stage of the third stage.
10:00 to 10:30, which monotonically decreased from 6 degrees to nearly 1.5 degrees, corresponding to the middle of the third stage.
The temperature remained close to 1.5 degrees from 1:30 to 1:00 p.m. (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 (first
(see Figure 1 a), and the temperature of the raw water measured by the raw water thermometer and given to the setting device is between 15℃ and 25℃.
(see Figure 11b), but due to the influence of the late stage 3 to early stage 4, the turbidity of the treated water was maintained at less than 2 degrees as described below, so the output from the setting device The target value of the flowing current given to the comparator circuit was maintained at 0 based on the empirical rule from 13:00 to 16:00, and after being set to -1 based on the empirical rule 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 is adjusted to 15:00 between 1:00 p.m. and after 3:30 p.m., depending on the comparison results.
mg/ to nearly 40 mg/, increasing monotonically from 15:00
40mg/nearly from 30 minutes to 5pm
It was decided to reduce the amount to nearly 30 mg/kg (see Figure 11c). The flocculant injection 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 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 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 case, the raw water PH measured by the raw water PH meter and given to the setting device is constant at 7.5 (see Figure 11a),
In addition, the temperature of the raw water measured by the raw water thermometer and given to the setting device is constant at 25°C (see Figure 11b), and the turbidity of the treated water is less than 2°C due to the influence of the 4th stage as described below. Therefore, the target value of the flowing current output from the setting device and given to the comparator circuit was set to -2 based on the empirical rule at 5:00 pm, then maintained until 7:00 pm, and then set again at 7:00 pm based on the empirical rule. -3 and was 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.

In the control device, depending on the comparison results, the injection amount of coagulant rapidly decreases from around 30 mg/ to around 20 mg/in the period from 17:00 to 18:00, is maintained until 19:00, and then decreases to around 20 mg/in at 19:00. It was determined that the concentration should be rapidly decreased from 1 to 8 mg/d and maintained for up to 24 hours (see Figure 11d). The flocculant injection 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 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 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 flocculant injection control method is to control the injection amount of flocculant according to the properties of the raw water when injecting the flocculant into raw water in order to flocculate suspended water from raw water, remove precipitates, 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 has the first to seventh steps listed in items (a) to (g), so (i) Hydrogen in raw water (ii) It has the effect of being able to determine the injection amount of flocculant in immediate response to a change in the ion concentration index, and (ii) it has the effect of correcting the injection amount of flocculant in immediate response to a change in the turbidity of the treated water. (iii) It has the effect of suppressing fluctuations in the turbidity of treated water, and (iv) It has the effect of reducing the amount of coagulant injection.

The second 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 stated in the middle section of the second solution, (a) ~
Since it includes the first to seventh steps listed in item (g), (v) it has the effect of being able to determine the amount of coagulant to be injected in response to changes in raw water temperature, and (vi) This method has the effect of being able to correct the injection amount of the flocculant in response to a change in turbidity, and thus has the effects () and () above, similarly to the first flocculant injection control method described above.

The third flocculant injection control method according to the present invention includes:
When injecting a flocculant into raw water to flocculate suspended matter from the 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. Point solution] As specified in the latter part as the third solution, (a) ~
Since the first to eighth steps listed in (h) are included, (vii) the amount of coagulant to be injected can be determined immediately in response to changes in the hydrogen ion concentration index of raw water and changes in raw water temperature. and (viii) has the effect of being able to correct the amount of coagulant injection in response to changes in the turbidity of the treated water, and has the effect of () above in comparison with the first and second coagulant injection control methods described above. It preferably has the effect of ().

[Brief explanation of the drawing]

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. 8, and FIGS. 10 a-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...Measuring 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, 19
d... Connection line, 19A... Cylindrical container, 19B, 1
9C... 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 fifth step of determining the injection amount; (f) a sixth step of measuring the turbidity of the treated water; and (g) a step of measuring the flow current selected in determining the target value of the flow current in the third step. A flocculant injection control method comprising: a seventh step of correcting the set value according to the turbidity of the treated water measured in the sixth step. 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; (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 sixth step of measuring the turbidity of the treated water; (g) a set value of the flowing current selected in determining the target value of the flowing current in the third step; A coagulant injection control method, comprising: a seventh step of correcting according to water turbidity. 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 second step; (f) a sixth step of determining the amount of coagulant to be injected according to the results compared in the fifth step; (g) a seventh step of measuring the turbidity of the treated water; ) an eighth step of correcting the set value of the flowing current selected in determining the target value of the flowing current in the fourth step according to the turbidity of the treated water measured in the seventh step; A flocculant injection control method characterized by: