JP2003047805A - Water treatment apparatus and apparatus for adjusting quantity of flocculant to be added - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus in which the degradation of the quality of treated water or the excessive addition of a flocculant is prevented. SOLUTION: The water treatment apparatus is provided with a flocculation reaction tank 1, a flocculant supply part 2, a settling tank 3 and apparatuses 4 and 5 for adjusting the quantity of a flocculant to be added. The apparatus 5 for adjusting the quantity of the flocculant to be added is provided with a detecting means 11 for detecting the turbidity of the treated water and an adjusting means 13 for adjusting the quantity of the flocculant to be added based on the detected value of the detecting means 11. When the detected value by the detecting means 11 is in a predetermined range, the flocculant of the quantity corresponding to the detected value is added and when the detected value becomes lower than the lower limit S1 in the set range, the flocculant is added upto a prescribed value V1 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment device for aggregating suspended substances contained in irrigation water (river water, lake water, well water, etc.), industrial wastewater, etc. using a coagulant and separating the same. The present invention relates to a coagulant addition amount adjusting device used.

[0002]

2. Description of the Related Art Conventionally, when a suspended substance contained in water, waste water, etc. is coagulated and precipitated using a coagulant to separate it, the coagulant is added just enough to detect the turbidity of treated water. It has been proposed to control the addition amount of the coagulant by PI control, PID control, fuzzy control, etc. based on the value. For example, JP-A-2-261505 and JP-A-2-258004 disclose a method of controlling the coagulant addition amount by fuzzy control based on the turbidity of treated water and the like.

FIG. 3 shows an example of a conventional water treatment device. In FIG. 3, reference numeral 1 indicates a flocculation reaction tank into which water to be treated is introduced, reference numeral 2 indicates a flocculant supply unit for supplying a flocculant, and reference numeral 3 indicates a precipitation tank for settling and separating flocculates. Reference numeral 4 denotes a coagulant addition amount adjusting device for adjusting the addition amount of the coagulant from the coagulant supply unit 2 and adding it to the coagulation reaction tank 1. The coagulant supply unit 2 includes a coagulant storage tank 6 that stores the coagulant solution. The coagulant addition amount adjusting device 4 outputs a drive signal based on a flow meter 7 for detecting the flow rate of the water to be treated, a turbidity meter 8 for detecting the turbidity of the water to be treated, and detection signals from these. The controller 9 and the liquid feed pump 10 that adjusts the flow rate of the coagulant solution from the coagulant storage tank 6 based on the drive signal from the controller 9 are provided.

In this water treatment apparatus, the water to be treated is introduced into the flocculation reaction tank 1 through the supply path L1, and the flocculant solution from the flocculant storage tank 6 is added to the flocculation reaction tank 1.
Suspended substances, etc. in the water to be treated are aggregated, and the aggregates are settling tank 3
To separate treated water to obtain treated water.

The addition amount of the coagulant is determined based on the flow rate and turbidity of the water to be treated detected by the flow meter 7 and the turbidity meter 8. That is, a drive signal is output from the control unit 9 based on the detection signals from the flow meter 7 and the turbidimeter 8, the liquid feed pump 10 is driven according to this drive signal, and the coagulant solution from the supply path L4 is discharged. The flow rate is defined. As a result, an amount of the aggregating agent depending on the flow rate and turbidity of the water to be treated is added to the aggregating reaction tank 1.

FIG. 4 shows another example of the conventional water treatment apparatus. The water treatment apparatus shown here supplies the flocculant solution from the flocculant storage tank 6 to the flocculation reaction tank 1 at a constant flow rate. The coagulant supply unit 14 is provided. The coagulant supply unit 14 includes a supply path L6 and a liquid feed pump 15. In this water treatment device, the coagulant in an amount corresponding to the flow rate of the water to be treated and the detected value of turbidity is added to the coagulation reaction tank 1 by the controller 4, and the coagulant supply unit 14 coagulates the coagulant at a constant flow rate. Agent is added.

[0007]

However, in the above-mentioned conventional technique, the detected value may be inaccurate due to adhesion of suspended solids to the turbidimeter, inclusion of bubbles, failure of the turbidimeter, and the like. If the detected value becomes lower than the actual turbidity of the treated water, the amount of coagulant added will be insufficient and the quality of the treated water will deteriorate. Further, when the detected value becomes higher than the actual turbidity of the treated water, the amount of the coagulant added becomes excessive and the cost required for the coagulant increases.

In order to prevent the malfunction of the turbidimeter, it is effective to add a cleaning function to the turbidimeter or deaerate the treated water to prevent the adherence of suspended substances and the inclusion of air bubbles. . However, even if these measures are taken,
At present, it is difficult to completely prevent the malfunction of the turbidimeter, and the deterioration of the quality of the treated water and the excessive addition of the coagulant may occur. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water treatment device capable of preventing deterioration of treated water quality and excessive addition of a coagulant.

[0009]

The water treatment apparatus of the present invention comprises:
A coagulation reaction tank into which water to be treated is introduced, a coagulant supply unit that supplies a coagulant, a solid-liquid separation unit that separates coagulates, and a coagulation reaction by adjusting the amount of coagulant added from the coagulant supply unit. A plurality of coagulant addition amount adjusting devices to be added to the tank, wherein at least one of the coagulant addition amount adjusting devices detects the turbidity of the treated water, and the coagulant based on the detection value of the detecting device. With the adjusting means for adjusting the addition amount, when the detection value of the detecting means is within a predetermined setting range, an amount of the aggregating agent according to the detection value is added, and the detection value is the lower limit value of the setting range. When it becomes less than S ₁ , the coagulant addition amount is a predetermined value V ₁
It is characterized in that it can be set so that The water treatment apparatus of the present invention includes a flocculation reaction tank into which water to be treated is introduced, a flocculant supply unit that supplies a flocculant, a solid-liquid separation unit that separates aggregates, and a flocculant from the flocculant supply unit. A plurality of coagulant addition amount adjusting devices for adjusting the addition amount of the coagulant and adding the coagulant to the aggregating reaction tank, wherein at least one of the coagulant adding amount adjusting devices is a detection means for detecting the turbidity of the treated water; Equipped with adjusting means for adjusting the coagulant addition amount based on the detection value of the means, when the detection value of the detection means is within a predetermined setting range, the amount of coagulant according to the detection value is added, And the detected value is the predetermined time T or more, the upper limit value S of the setting range
When the number exceeds ₂ , the coagulant addition amount can be set to a predetermined value V ₂ so that it can be set. The coagulant addition amount adjusting device can be set so that the coagulant addition amount becomes a predetermined value V ₁ when the detection value of the detecting means becomes less than the setting range lower limit value S _1. .

The coagulant addition amount control apparatus of the present invention comprises a coagulation reaction tank into which water to be treated is introduced, a coagulant supply section for supplying a coagulant, and a solid-liquid separation section for separating coagulates. A coagulant addition amount adjusting device used for a water treatment device, which adjusts an addition amount of a coagulant from a coagulant supply unit and adds the coagulant to a coagulation reaction tank, and a detection means for detecting turbidity of treated water, Equipped with adjusting means for adjusting the coagulant addition amount based on the detection value of the means, when the detection value of the detection means is within a predetermined setting range, the amount of coagulant according to the detection value is added, Moreover, when the detected value is less than the lower limit value S _{1 of the} setting range, the coagulant addition amount can be set to a predetermined value V ₁ . The coagulant addition amount control device of the present invention is a water treatment device including a coagulation reaction tank into which water to be treated is introduced, a coagulant supply unit that supplies a coagulant, and a solid-liquid separation unit that separates coagulates. A coagulant addition amount adjusting device for controlling the addition amount of the coagulant from the coagulant supply part and adding it to the coagulation reaction tank, the detecting means detecting the turbidity of the treated water, and the detection of the detecting means. The amount of coagulant added is adjusted based on the value, and when the detection value of the detection unit is within a predetermined setting range, the amount of the coagulant according to the detection value is added, and the detection value Exceeds the upper limit value S ₂ of the set range for a predetermined time T or more, the coagulant addition amount is a predetermined value V ₂
The configuration can be set so that This aggregating agent addition amount adjusting device can be set so that the aggregating agent addition amount becomes a predetermined value V ₁ when the detection value of the detection means becomes less than the setting range lower limit value S _1. .

[0011]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a water treatment device of the present invention. In FIG.
Reference numeral 1 represents a coagulation reaction tank into which water to be treated is introduced, reference numeral 2 represents a coagulant supply unit that supplies a coagulant, and reference numeral 3
Indicates a settling tank (solid-liquid separation section) for solid-liquid separation of the agglomerates, and reference numeral 4 indicates a first agglomeration for adjusting the addition amount of the aggregating agent from the aggregating agent supply unit 2 and adding it to the aggregating reaction tank 1. The reference numeral 5 denotes a second coagulant addition amount adjusting device for adjusting the addition amount of the coagulant from the coagulant supply unit 2 and adding the coagulant to the coagulation reaction tank 1. The water treatment device shown in FIG. 1 has a configuration in which a second coagulant addition amount adjusting device 5 is added to the conventional water treatment device shown in FIG.

The coagulant supply unit 2 has a coagulant storage tank 6 for storing the coagulant solution. The first coagulant addition amount adjusting device 4 includes a flow meter (process water flow rate detecting means) 7 for detecting the flow rate of the water to be treated and a turbidity meter (turbidity of the water to be treated) for detecting the turbidity of the water to be treated. Degree detecting means) 8, a controller 9 for outputting a drive signal based on detection signals from these, and a flow rate of the coagulant solution from the coagulant reservoir 6 based on the drive signal from the controller 9. And a liquid feed pump 10 for
The flow meter 7 and the turbidity meter 8 are provided in the feed path L1 for the water to be treated. The liquid feeding pump 10 supplies a coagulant solution from the coagulant storage tank 6 to the coagulation reaction tank 1 through a supply path L4.
It is provided in. Inverter control can be adopted as a control method for the liquid feed pump 10.

The second coagulant addition amount adjusting device 5 is a turbidimeter (treated water turbidity detecting means) 11 for detecting the turbidity of the treated water.
And a control unit 12 that outputs a drive signal based on a detection signal from the turbidimeter 11, and a transmission unit that adjusts the flow rate of the coagulant solution from the coagulant storage tank 6 based on the drive signal from the control unit 12. A liquid pump (adjusting means) 13 is provided. The turbidity meter 11 is provided in the treated water discharge path L3. The liquid feed pump 13 is provided in the supply path L5 that supplies the coagulant solution from the coagulant storage tank 6 to the coagulation reaction tank 1. Inverter control can be adopted as a control method for the liquid feed pump 13.

A first example of a treatment method using the above water treatment device will be described below. The water to be treated is introduced into the coagulation reaction tank 1 through the supply path L1, and the coagulant solution from the coagulant storage tank 6 is added to the coagulation reaction tank 1 through the supply paths L4 and L5. In the coagulation reaction tank 1, suspended substances and the like in the water to be treated are aggregated by being crosslinked and neutralized by charge by an aggregating agent. Aggregate is route L along with the water to be treated
It is introduced through 2 into a settling tank 3 where it is separated by settling. The treated water from which the aggregates have been separated is discharged out of the system through the discharge path L3.

The addition amount of the coagulant is determined by the first and second coagulant addition amount adjusting devices 4 and 5 as follows. In the first coagulant addition amount adjusting device 4, the flowmeter 7
The turbidity meter 8 detects the flow rate and turbidity of the water to be treated and outputs a detection signal. A drive signal is output from the control unit 9 based on this detection signal, the liquid feed pump 10 is driven according to this drive signal, and the flow rate of the coagulant solution from the supply path L4 is determined.

The minimum amount of coagulant (optimum amount of coagulant) required for aggregating the suspended solids in the water to be treated in the flocculation reaction tank 1 is the suspended solid introduced into the flocculation reaction tank 1. The value depends on the quantity. This optimum amount of coagulant is usually an amount that is approximately proportional to the product of the flow rate of the water to be treated and the turbidity. When there is no change in the flow rate of the water to be treated, the optimum amount of coagulant is an amount that is almost proportional to the turbidity of the water to be treated. Further, when the turbidity of the water to be treated does not change, the optimum amount of the coagulant is substantially proportional to the flow rate of the water to be treated. Therefore, the setting value of the addition amount of the coagulant by the first coagulant addition amount adjusting device 4 is one of the flow rate turbidity product (product of flow rate and turbidity), the flow rate, and the turbidity of the water to be treated. It is preferable to set it according to the detected value of (preferably so as to be approximately proportional to the detected value). Since the coagulant is also added from the second coagulant addition amount adjusting device 5, in the first coagulant addition amount adjusting device 4, the set value of the coagulant adding amount is lower than the optimum coagulant amount, For example, it is preferable to set it to be about 50% of the optimum amount of the coagulant.

When the flow rate or turbidity of the water to be treated fluctuates, the detection value in the flow meter 7 or the turbidity meter 8 changes, and a drive signal is sent from the control section 9 based on the deviation between the detected value and the set value. Is output, and the flow rate of the coagulant solution is adjusted by the liquid feed pump 10. The control method for the amount of coagulant added is P
I control, PID control, fuzzy control, etc. can be adopted. As a result, the aggregating agent is constantly added to the aggregating reaction tank 1 in an amount corresponding to the flow rate of the water to be treated and the detected value of turbidity.

In the second coagulant addition amount adjusting device 5, the turbidity meter 11 detects the turbidity of the treated water and outputs a detection signal. A drive signal is output from the control unit 12 based on this detection signal, and the liquid delivery pump 13 is output according to this drive signal.
Is driven, and the flow rate of the coagulant solution from the supply path L5 is determined. Since the amount of suspended solids in the treated water will be a value according to the amount of unaggregated suspended solids in the flocculation reaction tank 1, the amount of coagulant necessary to aggregate the unaggregated suspended solids is It becomes a value corresponding to the water turbidity (for example, a value almost proportional to the treated water turbidity).

In the processing method of this example, the second coagulant addition amount adjusting device 5 sets the detected value of the turbidimeter 11 to the detected value when the detected value is within a predetermined setting range (S ₁ or more). When an appropriate amount of coagulant is added and the detected value is less than the lower limit value S _{1 of the} setting range, the coagulant addition amount is the predetermined value V ₁
Is set. The lower limit value S ₁ can be any value. When the turbidimeter 11 is in a normally operating state, its detected value is usually 0 or more, and therefore the lower limit value S ₁ is preferably 0. This is because the coagulant can be added even when the detected value of the turbidimeter 11 becomes less than 0 due to a failure or the like.

When the detected value of the treated water turbidity is within the set range (S ₁ or more), the set value of the coagulant addition amount by the second adjusting device 5 is determined so as to be substantially proportional to this detected value. Is preferred. This set value is the total amount of coagulant added (first
And the total amount of coagulant added by the second adjusting devices 4 and 5) is preferably set to be approximately equal to the optimum coagulant amount.

When the turbidity of the treated water changes, the detection value in the turbidity meter 11 changes, and a drive signal is output from the control unit 12 based on the deviation between the detection value and the set value, and the liquid feed pump. The coagulant solution flow rate is adjusted by 13. PI control, PID control, fuzzy control and the like can be used to control the coagulant addition amount. As a result, the aggregating agent is constantly added to the aggregating reaction tank 1 in an amount corresponding to the detected value of the turbidity of the treated water.

[0022] V ₁ detected value of the turbidimeter 11 is a set value of the flocculant amount when a lower limit value S less than _1, the total amount of coagulant (first and second adjusting device 4 It is preferable that the total amount of coagulant added according to 5) be as close as possible to the optimum amount of coagulant.

Hereinafter, the coagulant addition amount by the first adjusting device 4 is set to 50% with respect to the optimum coagulant amount, and the coagulant adding amount by the second adjusting device 5 is proportional to the treated water turbidity detection value. The process will be described in detail by taking a value (when the detected value of the treated water turbidity is 0 degree or more) or a predetermined value V ₁ (when the detected value is less than 0 degree) as an example. Treated water turbidity detection value is 0
The setting value of the addition amount of the aggregating agent by the second adjusting device 5 when it is equal to or higher than the degree is determined so that the unaggregated suspended substance in the aggregating reaction tank 1 can be aggregated. The predetermined value V ₁ is 0
And a value that is 50% or less of the optimum amount of the coagulant.

In the first coagulant addition amount adjusting device 4, based on the detection values from the flow meter 7 and the turbidimeter 8, the coagulant in an amount corresponding to 50% of the optimum coagulant amount is supplied from the supply path L4. It is added to the flocculation reaction tank 1. When the detected value of the turbidity of the treated water by the turbidimeter 11 is 0 degree or more, the amount of the aggregating agent that can agglomerate the unaggregated suspended matter is based on the detected value, and the second adjusting device is used. 5 supply path L5 to agglutination reaction tank 1
Added to. The total amount of the coagulant added by the first and second adjusting devices 4 and 5 is an amount substantially equivalent to the optimum amount of the coagulant.

In the processing method of this example, when the detected value falls below 0 degrees due to a failure of the turbidimeter 11, the addition amount of the coagulant from the second adjusting device 5 is a predetermined value V ₁ (0
Value of 50% or less of the optimum amount of coagulant). Therefore, even if the turbidity detection value becomes lower than the turbidity of the actual treated water due to a failure of the turbidimeter 11, it is possible to prevent the coagulant addition amount to the coagulation reaction tank 1 from being extremely insufficient. it can. Therefore, even if an abnormality occurs in the turbidity meter 11, it is possible to prevent deterioration of the quality of treated water.

Further, in general, the feedforward control has a problem that it is not possible to correct an unexpected disturbance, and the feedback control has a problem that the countermeasure against the disturbance may be delayed and the control amount may fluctuate. In the above-mentioned water treatment device, based on the first adjusting device 4 adopting the feedforward control in which the coagulant is added based on the detected value of the flow rate of the treated water or the turbidity, and the detected value of the turbidity of the treated water. 2nd which adopted the feedback control which adds the coagulant
Since it is used together with the adjusting device 5 of No. 5, it is possible to quickly deal with fluctuations in the flow rate and turbidity of the water to be treated, and even if the turbidity of the water to be treated increases due to unexpected factors, good treated water can be obtained. be able to.

Next, a second example of the water treatment method using the above water treatment apparatus will be described. In the method of this example, when the detected value of the turbidimeter 11 is within a predetermined setting range (S ₂ or less), the second coagulant addition amount adjusting device 5 adjusts the amount according to the detected value. When the coagulant is added and the detected value exceeds the set range upper limit value S ₂ for a predetermined time T or more, the coagulant addition amount is set to the predetermined value V ₂ . When the detected value of the treated water turbidity is within the set range (S ₂ or less), the set value of the coagulant addition amount is preferably determined so as to be substantially proportional to the detected value. This set value is preferably determined so that the total amount of coagulant added (the total amount of coagulant added by the first and second adjusting devices 4, 5) is approximately equal to the optimum amount of coagulant.

If the detected value of the turbidity meter 11 is a predetermined time T or more,
V ₂ which is the set value of the coagulant addition amount when it becomes less than the setting range upper limit value S ₂ is the total coagulant addition amount (the total of the coagulant addition amounts by the first and second adjusting devices 4 and 5). ) Is preferably set so as to be as close as possible to the optimum coagulant amount. The time T is preferably set according to the properties of the water to be treated. If the water to be treated is surface water (river water, lake water) or wastewater (industrial wastewater, etc.) whose turbidity changes drastically, time T
Is preferably 1 to 4 times (preferably 2 to 3 times) the residence time of the water to be treated from the coagulant addition point (aggregation reaction tank 1) to the detection point (turbidity meter 11). . When the water to be treated is tertiary treated water (wastewater that has undergone coagulation treatment and activated sludge treatment) or well water in which turbidity fluctuation is small, the time T can be set to 0.

When the detected value of the turbidity of the treated water by the turbidimeter 11 is within the set range (S ₂ or less), based on this detected value, the amount of agglomeration of the unaggregated suspended matter can be agglomerated. The agent is fed from the supply path L5 of the second adjusting device 5 to the aggregation reaction tank 1
Added to.

In the treatment method of this example, when the detected value of the turbidimeter 11 exceeds the upper limit S ₂ for a predetermined time T or more due to the adherence of suspended substances or bubbles to the turbidimeter 11, ,
The addition amount of the coagulant from the second adjusting device 5 becomes the predetermined value V ₂ . Therefore, even if the turbidity detection value becomes higher than the actual turbidity of the treated water due to the adherence of suspended matter or bubbles to the turbidimeter 11, the amount of the coagulant added to the coagulation reaction tank 1 becomes excessive. Can be prevented. Therefore, it is possible to prevent the processing cost from rising due to the excessive addition of the coagulant.

Next, a third example of a water treatment method using the above water treatment apparatus will be described. In the method of this example, when the detection value of the turbidity meter 11 is within a predetermined setting range (S ₁ or more, S ₂ or less), the second adjusting device 5 adjusts the amount according to the detection value. The coagulant is set to be added. In the adjusting device 5, when the detected value becomes less than the lower limit value S _{1 of the} setting range, the coagulant addition amount becomes the predetermined value V ₁ , and the detected value exceeds the upper limit value S _{2 of the} setting range for a predetermined time T or more. In this case, the coagulant addition amount is set to a predetermined value V ₂ . The set value of the coagulant addition amount when the detected value is within the set range (S ₁ or more and S ₂ or less) is preferably determined so as to be substantially proportional to the detected value. This set value is preferably determined so that the total amount of coagulant added is approximately equal to the optimum amount of coagulant. The predetermined value V ₂ and the predetermined value V ₁ may be equal to each other.

When the detected value of the turbidity of the treated water by the turbidimeter 11 is within the set range (S ₁ or more and S ₂ or less), the unaggregated suspended solids are aggregated based on this detected value. The amount of flocculant to be obtained is added to the flocculation reaction tank 1 from the supply path L5 of the second controller 5.

In the treatment method of this example, the turbidimeter 11
The detected value is the lower limit value S due to a failure, etc. ₁(For example, 0 degrees)
If it is below the range, the addition of the coagulant from the second adjusting device 5
The added amount is a predetermined value V₁Becomes Suspended substances and gas to the turbidimeter 11
The value detected by the turbidity meter 11 may be changed for a certain period of time due to the adhesion of bubbles.
T or higher, upper limit S₂Second adjustment device
The amount of coagulant added from 5 is the predetermined value V₂Becomes others
Therefore, if the turbidity detection value becomes lower than the turbidity of the actual treated water,
Even if the amount of coagulant added to the coagulation reaction tank 1 is extremely insufficient
It is possible to prevent the turbidity detection value from actually
Even if it becomes higher than the turbidity of water,
It is possible to prevent the addition amount of the coagulant from becoming excessive. Obey
Prevent excessive addition of coagulant and improve the quality of treated water.
It can prevent the deterioration.

FIG. 2 shows another embodiment of the water treatment apparatus of the present invention. In the water treatment apparatus shown here, the flocculant solution from the flocculant storage tank 6 is fed at a constant flow rate to the flocculation reaction tank 1. The water treatment device shown in FIG. 1 is different from the water treatment device shown in FIG. The coagulant supply unit 14 supplies the supply path L
6 and a liquid feed pump 15. The water treatment device shown in FIG. 2 has a configuration in which a second coagulant addition amount adjusting device 5 is added to the conventional water treatment device shown in FIG.

In this water treatment device, the first adjusting device 4 adds the coagulant in an amount according to the flow rate of the water to be treated and the detected value of the turbidity to the coagulation reaction tank 1, and the coagulant supply unit 14
The coagulant is added at a constant flow rate. Further, in the second adjusting device 5, when the detection value of the turbidity meter 11 is within a predetermined setting range, the detection value is changed to the detection value in the same manner as in the water treatment methods of the above-described first to third examples. A corresponding amount of the coagulant is added, and when the detected value is out of the set range, a predetermined amount (constant flow rate) of the coagulant is added.

Further, in the water treatment device of the present invention, an alarm device (not shown) is provided to issue an alarm when the detected value of the turbidity meter 11 is less than the lower limit value S ₁ or exceeds the upper limit value S _2. You can also allow it. As a result, when an abnormality (fault, adhesion of suspended solids, etc.) occurs in the turbidimeter 11,
You will be able to detect this immediately. Therefore, it is possible to take prompt measures (repair, cleaning, etc. of the turbidity meter 11). Therefore, normal operation can be achieved in a short time. Further, it is preferable that the liquid feed pumps 10 and 13 of the first and second adjusting devices 4 and 5 be configured to stop the supply of the coagulant when the supply of the water to be treated is stopped.

The water treatment apparatus shown in FIGS. 1 and 2 has a construction in which a second adjusting device 5 is added to the conventional water treatment apparatus shown in FIGS. 3 and 4, respectively. That is, the configuration of the water treatment device of the above embodiment can be obtained by installing the second adjustment device 5 in the existing water treatment device.

[0038]

EXAMPLES Using the water treatment apparatus shown in FIG. 1, the waste water was coagulated as shown below. As the target wastewater, wastewater from a paper mill (SS concentration 1000 mg / l) was used. The coagulant addition amount set value of the first controller 4 was set to be about 50% of the optimum coagulant amount calculated from the product of the flow rate of the water to be treated and the detected value of turbidity. When the detected value of the turbidimeter 11 is within a predetermined setting range (S ₁ : 0 degrees or more and S ₂ : 100 degrees or less), the second adjusting device 5 is an amount proportional to the detected value (optimum). The amount of flocculant (corresponding to about 50% of the amount of flocculant) was set to be added. This adjusting device 5
When the detected value is lower than the lower limit value S ₁ : 0 degrees, the coagulant addition amount becomes V ₁ : 700 mg / l, and the detected value is a predetermined time T: 120 minutes or more, the upper limit value S ₂ : 100 degrees. When it exceeds the above, the addition amount of the coagulant was set to V ₂ : 700 mg / l. In addition, the time T is the aggregation reaction tank 1
It is the time corresponding to twice the residence time of the water to be treated from the turbidity meter to the turbidimeter 11. As the control method of the second adjusting device 5 (when the detected value of the turbidity meter 11 is within the above setting range),
PI control was adopted, P value was 100% and S value was 0.1S. In the second adjusting device 5, the turbidimeter 1 is added from the addition of the coagulant.
Considering the time until turbidity detection in 1), hold operation for 60 minutes (no control) after control operation for 3 minutes
Was repeated.

When the above water treatment device was operated for one year,
During the period, there were two accidents in which the detected value became abnormally higher than the turbidity of the actual treated water due to dirt on the turbidimeter 11, and the turbidimeter 11 was stopped twice for the purpose of testing. It was possible to maintain the turbidity of the treated water at 50 mg / l or less.

[0040]

As described above, in the water treatment device of the present invention, at least one of the coagulant addition amount adjusting devices is
When the detected value of the treated water turbidity is within a predetermined setting range, when an amount of the coagulant corresponding to the detected value is added and the detected value is less than the lower limit value S _{1 of the} set range, Since the coagulant addition amount can be set to a predetermined value V ₁ , even if the turbidity detection value becomes lower than the actual turbidity of the treated water due to a failure of the turbidity detection means or the like, It is possible to prevent the coagulant addition amount from being extremely insufficient. Therefore, even if an abnormality occurs in the turbidity detection means, it is possible to prevent deterioration of the treated water quality.

Further, the coagulant addition amount adjusting device is set so that the coagulant addition amount becomes the predetermined value V ₂ when the turbidity detection value exceeds the upper limit value S ₂ of the setting range for a predetermined time T or more. By making it possible, even when the turbidity detection value becomes higher than the actual turbidity of the treated water, it is possible to prevent the coagulant addition amount from becoming excessive.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a water treatment device of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the water treatment device of the present invention.

FIG. 3 is a schematic configuration diagram showing an example of a conventional water treatment device.

FIG. 4 is a schematic configuration diagram showing another example of a conventional water treatment device.

[Explanation of symbols]

1 ... Aggregation reaction tank, 2 ... Flocculant supply part, 3 ... Precipitation tank,
4 ... 1st coagulant addition amount adjustment device, 5 ... 2nd coagulant addition amount adjustment device, 11 ... Turbidimeter (process water turbidity detection means), 13 ... Liquid sending Pump (adjusting means)

Claims (6)

[Claims] 1. A water treatment apparatus for adding a coagulant to water to be treated to separate coagulates to obtain treated water, wherein a coagulation reaction tank into which the water to be treated is introduced and coagulation for supplying the coagulant are provided. The coagulant is provided with a coagulant supply unit, a solid-liquid separation unit that separates coagulants, and a plurality of coagulant addition amount control devices that control the coagulant addition amount from the coagulant supply unit and add the coagulant to the coagulation reaction tank. At least one of the addition amount adjusting devices is provided with a detecting means for detecting the turbidity of the treated water and an adjusting means for adjusting the coagulant addition amount based on the detection value of the detecting means. When the coagulant is added in an amount corresponding to the detected value when it is within the predetermined setting range, and when the detected value is less than the lower limit value S _{1 of the} set range, the coagulant addition amount is a predetermined value. A water treatment device characterized in that it can be set to V ₁ . 2. A water treatment apparatus for adding a coagulant to treated water to separate coagulates to obtain treated water, wherein a coagulation reaction tank into which the treated water is introduced and coagulation for supplying the coagulant are provided. The coagulant is provided with a coagulant supply unit, a solid-liquid separation unit that separates coagulants, and a plurality of coagulant addition amount control devices that control the coagulant addition amount from the coagulant supply unit and add the coagulant to the coagulation reaction tank. At least one of the addition amount adjusting devices is provided with a detecting means for detecting the turbidity of the treated water and an adjusting means for adjusting the coagulant addition amount based on the detection value of the detecting means. When the coagulant is added in an amount corresponding to the detected value when it is within the predetermined setting range, and when the detected value exceeds the upper limit S ₂ of the set range for a predetermined time T or more, the coagulant addition amount Is set so as to be a predetermined value V ₂ . 3. The detection value of the detection means is set range lower limit value S ₁
The water treatment device according to claim 2, wherein the amount of the coagulant added can be set to a predetermined value V ₁ when the amount is less than the predetermined value. 4. A flocculation reaction tank into which water to be treated is introduced,
It is used in a water treatment device equipped with a coagulant supply unit that supplies a coagulant and a solid-liquid separation unit that separates coagulates. The coagulant from the coagulant supply unit is added to the coagulation reaction tank by adjusting the addition amount. A coagulant addition amount adjusting device for detecting the turbidity of the treated water, and an adjusting unit for adjusting the coagulant addition amount based on the detection value of the detecting means. When the coagulant is added in an amount corresponding to the detected value when it is within the predetermined setting range, and when the detected value is less than the lower limit value S _{1 of the} set range, the coagulant addition amount is a predetermined value. A coagulant addition amount adjusting device, characterized in that it can be set to V ₁ . 5. A coagulation reaction tank into which water to be treated is introduced,
It is used in a water treatment device equipped with a coagulant supply unit that supplies a coagulant and a solid-liquid separation unit that separates coagulates. The coagulant from the coagulant supply unit is added to the coagulation reaction tank by adjusting the addition amount. A coagulant addition amount adjusting device for detecting the turbidity of the treated water, and an adjusting unit for adjusting the coagulant addition amount based on the detection value of the detecting means. When the coagulant is added in an amount corresponding to the detected value when it is within the predetermined setting range, and when the detected value exceeds the upper limit S ₂ of the set range for a predetermined time T or more, the coagulant addition amount There flocculant amount adjusting apparatus characterized by being to be set to a predetermined value V _2. 6. The detection value of the detection means is set range lower limit value S ₁
The coagulant addition amount adjusting device according to claim 5, wherein the coagulant addition amount can be set to a predetermined value V ₁ when the amount is less than the predetermined value.