JP2002028663A - Method for determining chemical feeding rate of coagulating agent and chemical feeding controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform efficient COD removal by adding both of an inorganic coagulating agent and organic coagulating agent at the optimum amounts of addition meeting the target treatment value for COD removal, i.e., in the state optimum on both of a treatment cost and treatment efficiency regardless of the daily fluctuation in the quality of waste water in waste water treatment to obtain treated water by separation of solid from the liquid after adding the inorganic coagulating agent and the organic coagulating agent to the COD- containing waste water. SOLUTION: This method for determining the chemical feeding rate consists in setting the suspended solid concentration corresponding to the CODMN concentration of the treated water which is the target from the relation between the CODMN concentration and suspended solid concentration of the treated water of the waste water previously determined by a jar test and determining the required amounts of addition of the inorganic coagulating agent and/or the organic coagulating agent in such a manner that the suspended solid concentration of the treated water obtained by the waste water treatment attains this set value of the suspended solid concentration. The chemical feeding controller controls the amounts of addition of at least one of the inorganic coagulating agent and/or the organic coagulating agent in accordance with the necessary amounts of addition determined by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inorganic coagulant and an organic coagulant for wastewater containing COD components discharged from various industrial fields such as paper, pulp, steel, machinery, automobile, petroleum, chemical, pharmaceutical, food, etc. The present invention relates to a method for simply and accurately determining the required amount of both coagulants when removing COD components by adding an agent and performing solid-liquid separation, and to a device for controlling chemical injection based on the results.

[0002]

2. Description of the Related Art Wastewater generated from various industrial fields such as paper, pulp, steel, machinery, automobiles, petroleum, chemicals, pharmaceuticals, and foods often contains a large amount of COD components. Biological treatment such as activated sludge treatment is used for the removal of non-soluble COD components and suspended solid components. Usually, a coagulant is added and then a polymer flocculant is added to remove the sediment. A method of performing a treatment or a pressure flotation treatment is employed.

In this case, the addition of an inorganic coagulant as a coagulant leads to an increase in the amount of sludge generated by metal hydroxides such as aluminum and iron. Therefore, in order to reduce the amount of generated sludge, an inorganic coagulant and an organic coagulant are generally used. Application of a combination treatment with a coagulant has been performed. It should be noted that addition of only an organic coagulant is often insufficient in terms of both treatment cost and treatment effect, and is usually treated in combination with an inorganic coagulant.

In such a treatment, generally, as an organic coagulant, polyethyleneimine, dicyandiamide / formalin polycondensate, dimethylamine / epichlorohydrin polycondensate, dimethylaminoethyl methacrylate / styrene copolymer, melamine / formalin polycondensate object,
Polydimethyldiacrylammonium salts and the like are used. As the inorganic coagulant, a sulfuric acid band (aluminum sulfate), polyaluminum chloride, ferric chloride, polyferric sulfate and the like are used.

[0005]

The combined treatment of an inorganic coagulant and an organic coagulant is a treatment using two coagulants, and the quality of the wastewater is more variable than that of a treatment using one coagulant. In this case, there is a problem that it is difficult to adjust a medicine injection amount.

[0006] On the other hand, wastewater generated from various industrial fields is rarely homogeneous, and water quality fluctuates greatly with changes in production volume and manufacturing conditions in factories.

According to the present invention, both inorganic coagulants and organic coagulants are used regardless of the fluctuation of water quality of daily wastewater.
With the optimal addition amount that matches the processing target value of OD removal,
It is an object of the present invention to provide a method for determining a coagulant dosing amount and a dosing control device for performing efficient COD removal by adding in an optimum state in terms of both processing cost and processing effect.

[0008]

SUMMARY OF THE INVENTION The method for determining the amount of coagulant to be injected according to the present invention is a method for wastewater treatment in which an inorganic coagulant and an organic coagulant are added to COD-containing wastewater and then solid-liquid separated to obtain treated water. A method for determining the required amount of the inorganic coagulant and / or the organic coagulant, wherein a target and a target are determined from the relationship between the COD _Mn concentration of the treated water of the waste water and the concentration of suspended solids, which is obtained in advance by a jar test The concentration of the suspended substance corresponding to the COD _Mn concentration of the treated water to be treated is set, and the inorganic coagulant and / or the inorganic coagulant and / or the like are set so that the suspended substance concentration of the treated water obtained by the wastewater treatment becomes the set value of the suspended substance concentration. Alternatively, the amount of the organic coagulant to be added is determined.

The chemical injection control device of the present invention is a chemical injection control device for wastewater treatment in which an inorganic coagulant and an organic coagulant are added to COD-containing wastewater and then separated into solid and liquid to obtain treated water. The amount of at least one of the inorganic coagulant and the organic coagulant is controlled on the basis of the required amount determined by the method for determining the amount of coagulant to be injected according to the present invention.

[0010] There is a correlation between the concentration of insoluble COD _{Mn and the} concentration of suspended solids in COD-containing wastewater discharged from various industrial fields.

In the present invention, the target COD _Mn is used by utilizing the correlation between the COD _Mn concentration and the suspended substance concentration.
The concentration is replaced by the concentration of the suspended substance, and the chemical dosing control of the inorganic coagulant and / or the organic coagulant is performed with this value as a target.

Since the concentration of the suspended substance in the treated water is proportional to the turbidity, in the present invention, the concentration of the suspended substance can be replaced by the turbidity.

Although the chemical injection control of the present invention can be applied to a wastewater treatment facility employing a coagulation sedimentation tank as a solid-liquid separating means, the present invention is particularly applicable to a pressurized solid-liquid separating means. It is effective for wastewater treatment equipment that employs a floating device. That is, the residence time of the coagulation treatment water in the tank is usually about 2 hours or more in the coagulation sedimentation tank, whereas the pressurized flotation tank is generally about 30 minutes or less. When the present invention is applied to wastewater treatment equipment employing a coagulation sedimentation tank, due to the length of the residence time, it is not possible to sufficiently follow fluctuations in the water quality of the wastewater, and control performance may be reduced. A wastewater treatment facility that performs solid-liquid separation with a pressurized flotation device with a short length can sufficiently respond to fluctuations in the quality of wastewater and achieve good effects.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of a method for determining a coagulant dosing amount and a dosing control device according to the present invention.

In this wastewater treatment equipment, COD-containing wastewater is first sent to a first reaction tank 1, an inorganic coagulant in an inorganic coagulant storage tank 2 is added, and then sent to a second reaction tank 3 for organic discharge. The organic coagulant in the coagulant storage tank 4 is added. After that, pH adjustment tank 5
And the pH is adjusted by adding an acid or an alkali based on the measured value of the pH meter 5A, and then fed to the coagulation tank 6 to add a polymer coagulant to perform coagulation treatment. The water is supplied to the pressurized floating tank 7 together with the pressurized water from the pressurized water tank 8 and separated by pressurized floating. The treated water in the pressurized floating tank 7 is discharged through the treated water tank 9. Further, the sludge scum separated by flotation is fed to the dehydrator 10 through the scum take-out section 7A and subjected to dehydration processing.

In the wastewater treatment equipment shown in FIG.
The suspended matter concentration of the treated water is measured by an SS meter (which may be of any type such as a transmitted light type or an ultrasonic type) provided at Is measured. These measured values are input to the control calculator 13,
The required amount of the inorganic coagulant and the organic coagulant to be added is calculated by the control calculator 13. The calculation result is outputted to the pump controller 14 of the inverter such as a control signal for chemical feed pump P ₂ of chemical feed pump P ₁ and an organic coagulant inorganic coagulant,
The pump controller 14 controls the chemical injection pumps P ₁ and P ₂ to perform appropriate chemical injection of the inorganic coagulant and the organic coagulant.

In the wastewater treatment equipment shown in FIG. 1, the required amounts of the inorganic coagulant and the organic coagulant are determined, for example, by the following method.

First, the wastewater to be treated is subjected to the same treatment in advance by a jar test to obtain treated water, the relationship between the COD _Mn concentration of the treated water and the concentration of suspended solids is determined, and a calibration curve is prepared. deep. The COD _Mn concentration and the suspended _solid concentration have a correlation as shown in the examples below. From this calibration curve, the concentration of the suspended solids corresponding to the target COD _Mn concentration of the treated water is determined and set to a set value (hereinafter referred to as “SS set value”).
Called. Note that the SS set value has a certain width within the allowable range. ) Is input to the control calculator 13. The addition amount of the inorganic coagulant and the addition amount of the organic coagulant at this time are input to the control calculator 13 as reference addition amounts.

On the other hand, the flow rate of the wastewater was measured by the flow meter 12 and the concentration of suspended solids in the treated water was measured by the SS meter 11.
These measured values are input to the control calculator.

In the control calculator 13, for example, the following calculations (1) and (2) are performed in combination to determine the required addition amount.

Calculation (1): Set value of flow rate and measured value of flow rate measured by flow meter 12 (hereinafter referred to as "flow rate measured value")
When the measured flow rate is within the range of the set flow rate, the measured value of the suspended solid concentration measured by the SS meter 11 (hereinafter referred to as “SS measured value”) is compared with the SS set value. Then S
When the S measurement value is within the range of the SS set value, the inorganic coagulant and the organic coagulant are each controlled by a standard addition amount. SS
If the measured value exceeds the SS set value, the added amount of the inorganic coagulant and / or the organic coagulant is increased from the reference added amount. For this increase, control may be performed to increase the addition amount in two or more steps based on the difference between the SS measured value and the SS set value. If the SS measured value is lower than the SS set value, the added amount of the inorganic coagulant and / or the organic coagulant is reduced from the reference amount. Even in this reduction, control may be performed to reduce the addition amount in two or more steps based on the difference between the SS measurement value and the SS set value.

Calculation (2): In the above (1), when the measured flow rate is out of the range of the set flow rate, the reference addition amount of the inorganic coagulant and / or the organic coagulant is calculated or calculated according to the increase or decrease of the flow rate. The addition amount of the inorganic coagulant and / or the organic coagulant determined by the above is increased or decreased.

As described above, the addition amount of the inorganic coagulant and / or the organic coagulant is determined based on the comparison result between the SS measured value of the treated water and the SS set value, and the addition amount is corrected by the fluctuation of the drainage flow rate. Thereby, appropriate chemical injection control of the inorganic coagulant and / or the organic coagulant can be performed.

In the wastewater treatment facility shown in FIG. 1, the measurement results of the SS meter 11 and the flow meter 12 and the calculation results of the control calculator 13 at the site where the wastewater is treated are remotely transmitted via a communication terminal 15 via a telephone line. The information is transmitted to and monitored by the remote monitoring device 16 at the local center, and the setting is changed from the remote monitoring device 16 (for example, the setting value of the SS is changed, and the calculation formula of the appropriate dose is calculated from the measured value). Communication terminal 15 via telephone line
Can be transmitted to the control computing unit 13 via
It is configured so that the processing status in a remote place can be grasped, monitored, and remotely controlled by data communication between the centers.

FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one unless it exceeds the gist of the present invention.

In FIG. 1, the injection amounts of both the inorganic coagulant and the organic coagulant are controlled, but in the present invention, one of the inorganic coagulant and the organic coagulant is added in a fixed amount, and only the other is added. Chemical injection control may be performed. In FIG. 1, the flow rate of the wastewater into the wastewater treatment facility is measured by the flow meter 12, and the amounts of the inorganic coagulant and the organic coagulant are corrected based on the measured values. Then, the inflow amount of the coagulation treated water flowing into the pressurized floating tank 7 and the treated water outflow amount from the pressurized floating tank 7 may be measured, and correction may be performed based on the results. The correction based on the flow rate is not essential, and may be omitted when the fluctuation of the drainage amount is small.

In FIG. 1, an SS meter is used to measure the concentration of suspended solids in the treated water. However, the means for measuring the concentration of suspended solids in the treated water is not particularly limited. In addition, it can be performed using a turbidity meter or the like.

In the present invention, the inorganic coagulant, organic coagulant, polymer coagulant and acid and alkali for pH adjustment to be added to the wastewater are those conventionally used in such wastewater treatment equipment. Can be used.

The amount of the chemical added and the adjusted pH vary depending on the quality of the wastewater to be treated and the target quality of the treated water. In general, the amount of the inorganic coagulant added: 50 to 2000 mg / L The amount of the organic coagulant : 1 to 50 mg / L Adjusted pH: 5.5 to 7.5 Addition amount of polymer coagulant: about 0.1 to 10.0 mg / L.

[0031]

The present invention will be described more specifically with reference to the following examples.

Example 1 A wastewater treatment facility shown in FIG. 1 in which the following inorganic coagulant, organic coagulant and polymer coagulant are added sequentially to wastewater of the following quality discharged from a paper mill and subjected to pressure flotation treatment. In accordance with the present invention, the required addition amounts of the inorganic coagulant and / or the organic coagulant were determined, and the injection control was performed based on the results. [Wastewater quality] pH: 7.4 SS: 1900 mg / L COD _Mn : 510 mg / L [Chemical] Inorganic coagulant: Liquid sulfuric acid band Organic coagulant: "Zeta Ace C3" manufactured by Kurita Water Industries Ltd.
01 ”Polymer flocculant: Kurifa Kogyo Co., Ltd.“ Clifflock PA3 ”
62 "First, a jar test in which the above-mentioned chemicals were sequentially added to the wastewater was performed, and the relationship between the COD _Mn concentration of the treated water and the turbidity was examined. As shown in FIG. 2, it was confirmed that there was a correlation. .

Further, the addition amount of the organic coagulant was kept constant at 2 mg / L, the addition amount of the inorganic coagulant was changed, and the relationship between the addition amount of the inorganic coagulant and the turbidity of the treated water was examined. It was shown to.

Further, the amount of the inorganic coagulant added was 200 mg /
L, the amount of the organic coagulant added was changed, and the relationship between the amount of the organic coagulant added and the turbidity of the treated water was examined. The results are shown in FIG.

The following chemical injection control was performed based on the above results. The wastewater treatment amount is 200 to 400 m ³ / H, and the adjusted pH after adding the inorganic coagulant and the organic coagulant.
The value was 6.5, and the amount of the polymer coagulant added was 1.0 mg /
L, and the residence time of the pressure floating tank was 30 minutes.

Chemical Injection Control Example 1 (Injection Control of Inorganic Coagulant) The target COD _Mn of treated water is set to 150 mg / L, and the turbidity set value of treated water is set to 100 to 150 degrees from FIG. . On the other hand, the operation was carried out with the addition amount of the organic coagulant constant at 2 mg / L and the addition amount of the inorganic coagulant at 250 mg / L from FIG.

The turbidity of the treated water was measured, and the turbidity was 100 to 1
When it is within the range of 50 degrees, the addition amount of the inorganic coagulant is not changed. When the turbidity increases outside this range, the addition amount of the inorganic coagulant is increased by 20%, and when the turbidity decreases. Was controlled by chemical injection to reduce the amount of inorganic coagulant added by 20%.

As a result, the COD _Mn concentration of the treated water was 12
It was maintained within the range of 0 to 140 mg / L, and stable processing was performed.

Chemical Injection Control Example 2 (Chemical Injection Control of Organic Coagulant) The target COD _Mn of the treated water was set to 150 mg / L, and the set value of the turbidity of the treated water was set to 100 to 150 degrees from FIG. . On the other hand, the addition amount of the inorganic coagulant was kept constant at 200 mg / L, and the operation was performed with the addition amount of the organic coagulant being 2 mg / L from FIG.

The turbidity of the treated water was measured, and the turbidity was 100 to 1
When it is within the range of 50 degrees, the addition amount of the organic coagulant is not changed. When the turbidity increases outside this range, the addition amount of the organic coagulant is increased by 20%, and when the turbidity decreases. Was controlled by chemical injection to reduce the amount of organic coagulant added by 20%.

As a result, the COD _Mn concentration of the treated water was 12
It was maintained within the range of 0 to 140 mg / L, and stable processing was performed.

Chemical Injection Control Example 3 (Chemical Injection Control of Inorganic Coagulant and Organic Coagulant) The target COD _Mn of the treated water is set to 150 mg / L, and the turbidity set value of the treated water is set to 100 to 100 mg / L from FIG. It was set to 150 degrees. On the other hand, when the operation is performed with the addition amount of the organic coagulant being 2 mg / L and the addition amount of the inorganic coagulant being 200 mg / L, the turbidity of the treated water is measured, and when the turbidity is in the range of 100 to 150 degrees. Does not change the addition amount of the inorganic coagulant and the organic coagulant, and when the turbidity increases outside this range, the addition amount of the inorganic coagulant is increased by 10%, and the addition amount of the organic coagulant is increased by 10%. When the turbidity decreased, chemical injection control was performed to reduce the amount of the inorganic coagulant added by 10% and the amount of the organic coagulant by 10%.

As a result, the COD _Mn concentration of the treated water was 12
It was maintained within the range of 0 to 140 mg / L, and stable processing was performed.

Chemical Injection Control Example 4 (Chemical Injection Control of Inorganic Coagulant and Correction by Wastewater Treatment Amount) In Chemical Injection Control Example 1, the reference value of the wastewater treatment amount is further increased by 25.
0 m ³ / H, the amount of wastewater treatment was measured, and when the amount of wastewater treatment increased by 25 m ³ / H or more from this reference value, the amount of addition of the inorganic coagulant was increased by 10%, and the amount of wastewater treatment was reduced to this reference value. When the amount decreased by 25 m ³ / H or more, the amount of the inorganic coagulant added was corrected by 10% to correct the chemical injection amount.

As a result, the COD _Mn concentration of the treated water was 13
0 to 140 mg / L, which is maintained in a much narrower range than in the case of the dosing control 1, while the amount of the inorganic coagulant used is 1
0% reduction was achieved.

[0046]

As described above in detail, according to the method for determining the coagulant dosing amount and the dosing control device of the present invention, paper, pulp,
Removal of COD components by adding an inorganic coagulant and an organic coagulant to wastewater containing COD components discharged from various industrial fields such as steel, machinery, automobiles, petroleum, chemicals, pharmaceuticals, and foods, followed by solid-liquid separation. In doing so, the required addition amount of both coagulants can be determined simply and accurately, and based on this value, efficient chemical dosing control can be performed and the treatment can be stabilized. On the other hand, operation within the processing reference value is always possible. Cost savings: Irrespective of fluctuations in the quality of wastewater, the optimal amount of chemicals can always be injected, and the amount of chemicals used can be reduced. Labor saving: Eliminates the need to change the chemical injection volume setting due to fluctuations in drainage, thus reducing operation and maintenance work. And other excellent effects can be obtained.

According to the second aspect of the present invention, accurate chemical injection control can be performed even when the amount of wastewater treatment varies.

According to the chemical dosing control device of the fifth aspect, it is possible to monitor the processing status in a remote place, change the setting of the processing target value, and so on, and it is possible to achieve further labor saving by unmanned operation.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a method for determining a coagulant dosing amount and a dosing control device according to the present invention.

FIG. 2 is a graph showing the relationship between the COD _Mn concentration and the turbidity of the treated wastewater in Example 1.

FIG. 3 is a graph showing the relationship between the amount of an inorganic coagulant added to wastewater and the turbidity of treated water in Example 1.

FIG. 4 is a graph showing the relationship between the amount of an organic coagulant added to wastewater and the turbidity of treated water in Example 1.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 First reaction tank 2 Inorganic coagulant storage tank 3 Second reaction tank 4 Organic coagulant storage tank 5 pH adjustment tank 6 Coagulation tank 7 Pressurized flotation tank 8 Pressurized water tank 9 Treatment water tank 10 Dehydrator 11 SS meter 12 Flow meter 13 Control operation Device 14 pump controller 15 communication terminal 16 remote monitoring device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/52 C02F 1/52 CK ZAB ZABA (72) Inventor Yoshiyuki Kanda 3-chome Nishishinjuku, Shinjuku-ku, Tokyo No. 4-7 F-term in Kurita Kogyo Co., Ltd. (Reference) 4D037 AA13 AB01 AB02 BA02 CA08 4D062 BA21 BB09 BB12 CA04 CA05 CA18 DA04 DA05 DA13 DA16 DB09 DB19 DB25 DC02 EA03 EA12 EA33 FA03 FA19

Claims (5)

[Claims] Claims 1. An inorganic coagulant and / or an organic coagulant are added to a COD-containing wastewater, and then the required amount of the inorganic coagulant and / or the organic coagulant is determined in a wastewater treatment in which solid-liquid separation is performed to obtain treated water. The COD of the treated water of the wastewater obtained in advance by a jar test.
_From the relationship between the _Mn concentration and the suspended matter concentration, a suspended matter concentration corresponding to the target COD _Mn concentration of the treated water is set, and the suspended matter concentration of the treated water obtained by the wastewater treatment is adjusted to the suspended matter concentration. The inorganic coagulant and / or
Alternatively, a method for determining the amount of coagulant to be injected, comprising determining the required amount of organic coagulant. 2. The method according to claim 1, wherein the flow rate of the wastewater supplied to the wastewater treatment or the obtained treated water is measured, and an inorganic coagulant and / or an organic coagulant is required based on a fluctuation in the measured value of the flow rate. A method for determining a coagulant dispensing amount, comprising correcting an addition amount. 3. The method according to claim 1 or 2, wherein solid-liquid separation is performed by pressure flotation treatment. 4. A chemical injection control device for wastewater treatment, wherein after adding an inorganic coagulant and an organic coagulant to COD-containing wastewater, solid-liquid separation is performed to obtain treated water. A chemical dosing control device characterized by controlling the addition amount of at least one of an inorganic coagulant and an organic coagulant on the basis of the required addition amount determined by the method described in the paragraph. 5. The remote control system according to claim 4, wherein the measurement result and the control result are transmitted to a remote place via a communication line to monitor the result at the remote place and change the control setting value of the apparatus from the remote place. A drug injection control device for performing control.