JP2009006316A - Apparatus and method for continuously treating waste water containing cod component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for continuously treating waste water containing a sulfur-based COD component, in each of which the required amount of an oxidizer to be added to the waste water to be treated is determined by at least two-stage different feedforward controls, and consequently the COD concentration can be stabilized in a proper range equal to or below an effluent standard with a short time lag even when the COD concentration of the waste water to be treated is fluctuated greatly. <P>SOLUTION: The apparatus for continuously treating waste water containing the COD component has: one pretreatment apparatus for continuously treating the waste water by the feedforward control using a first monitoring means capable of predicting the COD concentration in a comparatively short measuring time; and at least one post-treatment apparatus for continuously treating the waste water by the feedforward control using another monitoring means capable of highly accurately measuring the COD concentration though requiring the comparatively longer measuring time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a continuous treatment apparatus and method for wastewater containing a COD component, and in particular, even when the COD concentration in the wastewater to be treated fluctuates greatly, the time lag is small and the COD concentration is determined based on the drainage standard. The present invention relates to a continuous treatment apparatus and a continuous treatment method for sulfur wastewater that can be stabilized within the following appropriate range.

Conventionally, an oxidizing agent has been widely used for the treatment of wastewater containing a COD component. Regarding control of the injection amount of the oxidizing agent, for example, Patent Document 1 uses hydrogen peroxide as an oxidizing agent, and JIS K0102: 1998. Disclosed is a method of treating wastewater by adding 0.5 to 50 times the hydrogen peroxide to the COD _Mn concentration value measured in accordance with the prescribed method and irradiating with ultraviolet rays.
Japanese Patent Laid-Open No. 8-141581

Further, Patent Document 2 uses both hydrogen peroxide and ozone as oxidizing agents, and the dissolved ozone concentration calculated in the treated water at the first process outlet and / or second process outlet is experimentally and empirically calculated. A wastewater treatment method by two-stage feedback control in which ozone is added so as to be 0.1 to 10 mg / L that is a target value of ozone concentration is disclosed.
Japanese Patent Laid-Open No. 11-10171

  However, since the method described in Patent Document 1 does not analyze the quality of the treated water, there is no means for suppressing the COD concentration below the drainage standard when the COD concentration of wastewater fluctuates rapidly. Further, in the method based on the two-stage feedback control described in Patent Document 2, when the COD concentration of the inflowing wastewater largely fluctuates, a time lag occurs only with the feedback control, and the COD concentration is quickly controlled below the drainage standard. There was a problem that the amount of ozone added temporarily excessively or insufficiently.

  The object of the present invention is to determine the required amount of oxidant in the wastewater to be treated by at least two different feedforward controls, so that even if the COD concentration in the wastewater to be treated varies greatly. Another object of the present invention is to provide a continuous treatment apparatus and a continuous treatment method for sulfur-based wastewater that have a small time lag and can stabilize the COD concentration within an appropriate range below the drainage standard.

In order to achieve the above object, the gist of the present invention is as follows.
(1) A first treatment tank having a first inlet through which waste water containing a COD component flows in and a first outlet through which primary treated water that is treated water of the waste water flows out, upstream of the first inlet. A first monitoring means for measuring a first property value having a correlation with the COD concentration of waste water, a first oxidant injection means for adding a first oxidant to the first treatment tank, and Based on the first COD concentration predicted value predicted by the first monitoring means from the first physical property value, the addition amount of the first oxidant to be added to the first treatment tank is determined, and by the first oxidant injection means One pretreatment system device having a first control means for controlling the amount of the first oxidant added to the first treatment tank, and the primary treated water flowing out from the first outlet of the first treatment tank are introduced. Second treated inlet and treated water of the primary treated water A second treatment tank having a second outlet for allowing the secondary treated water to flow out; a second monitoring means for measuring the COD concentration of the primary treated water provided upstream of the second inlet; the second Second oxidant injection means for adding the second oxidant to the treatment tank, and the amount of the second oxidant added to the second treatment tank based on the second COD concentration measurement value measured by the second monitoring means And at least one aftertreatment system device having second control means for controlling the amount of the second oxidant added to the second treatment tank by the second oxidant injection means. Continuous treatment equipment for wastewater containing COD components.

  (2) Third monitoring for measuring a second physical property value having a predetermined relationship with the COD concentration of the secondary treated water flowing out from the second outlet of the second treatment tank of the post-treatment system apparatus located at the most subsequent stage. And the second oxidant into the second treatment tank by the second oxidant injection means of the post-treatment device located at the rearmost stage based on the second physical property measurement value measured by the third monitoring means. The continuous treatment apparatus for wastewater containing a COD component according to the above (1), further comprising an additional treatment apparatus having a third control means for controlling the addition amount.

  (3) The continuous treatment apparatus for wastewater containing a COD component as described in (1) or (2) above, wherein the first oxidizing agent and the second oxidizing agent are sodium hypochlorite aqueous solutions.

  (4) The continuous treatment apparatus for wastewater containing a COD component according to any one of (1) to (3), wherein the first monitoring means is a UV meter.

  (5) The continuous treatment apparatus for wastewater containing a COD component according to any one of (1) to (4), wherein the second monitoring means is one or a plurality of COD meters.

  (6) The continuous treatment apparatus for wastewater containing a COD component according to any one of (2) to (5) above, wherein the third monitoring means is an ORP meter and / or a residual chlorine meter.

  (7) The continuous treatment apparatus for wastewater containing a COD component as described in any one of (1) to (6) above, wherein the wastewater is sulfur-based wastewater.

  (8) The first physical property value having a correlation with the COD concentration of the wastewater containing the COD component is measured, and the first COD concentration necessary for obtaining the target COD concentration based on the predicted first COD concentration value predicted from the measured value. A pre-treatment step by feedforward control for determining an addition amount of the first oxidant and adding the determined amount of the first oxidant to the waste water to form a primary treated water; and the primary treated water The COD concentration is measured, and based on the measured second COD concentration measurement, the amount of the second oxidant added to reach the target COD concentration is determined, and the determined amount of the second oxidant is added to the primary oxidant. A method for treating wastewater containing a COD component, characterized by comprising at least one post-treatment step by feedforward control that is added to treated water to form secondary treated water.

  (9) Measure the second physical property measurement value having a predetermined relationship with the COD concentration of the secondary treated water in the post-treatment step located in the most subsequent stage, and the relationship between the measured second physical property measurement value and the target COD concentration And an additional treatment step by feedback control for controlling the amount of the second oxidant added to the primary treated water by the second oxidant injection means in the second post-treatment step located in the most subsequent stage based on The continuous processing method of the wastewater containing the COD component as described in said (8).

  (10) The continuous treatment method for wastewater containing a COD component according to (8) or (9) above, wherein the first oxidant and the second oxidant are aqueous sodium hypochlorite solutions.

  (11) The continuous treatment method of wastewater containing a COD component according to any one of (8) to (10), wherein the first COD concentration predicted value is a value predicted by a UV meter.

  (12) The continuous treatment method for wastewater containing a COD component according to any one of (8) to (11) above, wherein the second COD concentration measurement value is a value measured by a COD meter.

  (13) The continuous treatment method of waste water containing a COD component according to (12), wherein the second COD concentration measurement value is a value measured by shifting by a predetermined time with two or more COD meters.

  (14) The waste water containing the COD component according to any one of (8) to (13), wherein the second physical property measurement value is a value measured with an ORP meter and / or a residual chlorine meter. Continuous processing method.

  (15) When an ORP meter and a residual chlorine meter are used for the measurement of the second physical property measurement value, the second of the post-processing steps positioned at the last stage based on the relationship between the measured residual chlorine concentration value and the target COD concentration The method for continuously treating wastewater containing a COD component according to (14) above, wherein the amount of the second oxidant added to the second treatment tank by the oxidant injection means is controlled.

  (16) The continuous treatment method for wastewater containing a COD component according to any one of (8) to (15) above, wherein the wastewater is sulfur-based wastewater.

  According to the present invention, even if the COD concentration in the wastewater to be treated varies greatly by determining the required amount of oxidizer in the wastewater to be treated by at least two different feedforward controls. Therefore, it is possible to provide a continuous treatment apparatus and a continuous treatment method for sulfur-based wastewater with a small time lag and capable of stabilizing the COD concentration within an appropriate range below the drainage standard.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a process diagram showing an embodiment of a continuous treatment apparatus for wastewater containing a COD component according to the present invention. The waste water containing the COD component is preferably a sulfur waste water. The apparatus shown in FIG. 1 is mainly composed of a pre-processing system apparatus I and a post-processing system apparatus II.

The pretreatment system apparatus I is mainly composed of a first treatment tank 3, first monitoring means 5, first oxidant injection means 7, and first control means 6.
The 1st processing tank 3 has the 1st inflow port 2 which flows in the waste water 1 containing a COD component, and the 1st outflow port 4 which flows out the primary treated water 9 which is the treated water of the said waste water.
The first monitoring means 5 measures a first physical property value having a correlation with the COD concentration of the wastewater 1 provided on the upstream side of the first inflow port 2.
The first oxidant injection means 7 adds the first oxidant to the first treatment tank 3. An example of the first oxidant injection means 7 is a pump.
The first control means 6 determines the addition amount of the first oxidant to be added to the first treatment tank 3 based on the first COD concentration predicted value predicted by the first monitoring means 5 from the first physical property value, and the first This is feedforward control for controlling the amount of the first oxidant added to the first treatment tank 3 by the oxidant injection means 7 so as to be the determined amount added.

The post-treatment system apparatus II is mainly composed of a second treatment tank 11, second monitoring means 13, second oxidant injection means 15, and second control means 14.
The second treatment tank 11 is a second treated water 16 that is treated water of the second treated inlet 10 and the first treated water 9 for flowing in the first treated water 9 flowing out from the first outlet 4 of the first treating tank 3. And a second outlet 12 through which the gas flows out.
The second monitoring unit 13 measures the COD concentration of the primary treated water 9 provided on the upstream side of the second inlet 10.
The second oxidant injection means 15 adds the second oxidant to the second treatment tank 11. An example of the second oxidant injection means 15 is a pump.
The second control means 14 determines the amount of the second oxidant added to the second treatment tank 11 based on the second COD concentration measurement value measured by the second monitoring means 13, and the second oxidant injection means 15. Is a feedforward control for controlling the amount of the second oxidizing agent added to the second treatment tank 11 to be the determined amount added.

The continuous treatment apparatus for wastewater containing a COD component according to the present invention preferably further includes an additional treatment system apparatus II.
The additional processing system apparatus III is mainly composed of third monitoring means 17 and third control means 18.
The third monitoring means 17 has a second physical property having a predetermined relationship with the COD concentration of the secondary treated water 16 flowing out from the second outlet 12 of the second treatment tank 11 of the post-treatment system apparatus II located at the most subsequent stage. Measure the value.
Based on the second physical property measurement value measured by the third monitoring means 17, the third control means 18 is supplied to the second treatment tank 11 by the second oxidant injection means 15 of the post-treatment system apparatus II located at the most rear stage. Feedback control for controlling the amount of the second oxidant added, for example, PID control.

Examples of the first oxidizing agent and the second oxidizing agent include sodium hypochlorite aqueous solution, ozone, hydrogen peroxide, and the like. In particular, the reaction rate is fast and a large-capacity reaction tank is not required. A sodium hypochlorite aqueous solution is preferable.
Moreover, it is preferable that the density | concentration of sodium hypochlorite shall be 2-15 mass% in order to ensure a suitable reaction rate. More preferred is 5 to 12% by mass.

  The first monitoring means 5 is preferably a UV meter. The UV meter can predict the COD concentration value from the measured value of absorbance by utilizing the fact that the COD component has absorption light in the ultraviolet region and utilizing the linear correlation between the absorbance and the COD concentration value. The measurement time is relatively short and continuous measurement is possible.

  The second monitoring means 13 is preferably one or a plurality of COD meters. The COD meter is consumed by the method specified in JIS K0102: 1998, that is, when a specified amount of potassium permanganate, sulfuric acid and silver nitrate is added to a sample (treated water) and reacted in a boiling water bath for 30 minutes. From the amount of potassium permanganate, the oxygen demand (COD) can be measured with high accuracy. This is a relatively long measurement time of about 1 hour for one measurement time.

The third monitoring means 17 is preferably an ORP meter and / or a residual chlorine meter.
The ORP meter uses a metal electrode (gold, platinum, etc.) as a sensor and measures the oxidation-reduction potential in the water to be treated. The measurement time is relatively short and prediction can be made continuously. Further, the oxidation-reduction potential measured with the ORP meter has a predetermined relationship with the COD concentration, and therefore is preferable as a monitoring means for feedback to the addition of the oxidizing agent in the final post-treatment system.
The residual chlorine meter can be used when sodium hypochlorite is used as the oxidizing agent. The residual chlorine concentration which is the remaining oxidizing agent has a predetermined relationship with the COD concentration.
As the residual chlorine meter, the following two methods can be mentioned.
1) A method for predicting the residual chlorine concentration by mixing with a DPD reagent and measuring the absorbance at 528 nm.
2) After adding potassium iodide to react chlorine and potassium iodide to liberate iodine, titrate the liberated iodine with a reducing agent, and immerse the electrode in the titrated solution to obtain residual chlorine (oxidant) ), The current flows and the current value decreases as the residual chlorine concentration decreases. Using the amount of reducing agent added until the current does not decrease, the residual chlorine concentration How to measure.
One prediction time by the residual chlorine meter is characterized by being as short as 5 minutes. Therefore, the residual chlorine meter is preferable as a monitoring means for feedback to the oxidizer addition of the final aftertreatment system.

  Next, an embodiment of a continuous treatment method for wastewater containing a COD component according to the present invention will be described by taking as an example the case of continuously treating sulfur wastewater.

  The sulfur-based wastewater 1 flows into the first treatment tank 3 from the first inlet 2. A part of the waste water 1 flowing upstream of the first inlet 2 is collected, and the first property value having a correlation with the COD concentration is measured by the first monitoring means 5. Next, an addition amount of the first oxidant necessary for obtaining the target COD concentration value is determined based on the predicted first COD concentration value predicted from the measured value, and the determined amount of the first oxidant is set to the first amount. Add to the waste water 1 in the treatment tank 3. Thus, it has one pretreatment process by feedforward control which makes primary treated water. The first oxidant is stored in the oxidant storage means 8. The first injection means 7 mixes the first oxidant and the waste water 1 in the first treatment tank 3 to obtain a primary treatment water 9, and the primary treatment water 9 is a first flow in the first treatment tank 3. It flows out from the outlet 4.

  The primary treated water 9 flows into the second treatment tank 11 from the second inlet 10. A part of the primary treated water 9 flowing upstream from the second inlet 10 is collected, and the COD concentration of the primary treated water 9 is measured by the second monitoring means 13. Next, the addition amount of the second oxidant necessary for achieving the target COD concentration value is determined based on the second COD concentration measurement value, and the determined amount of the second oxidant is stored in the second treatment tank 11. Add to primary treated water 9. Thus, it has at least 1 post-processing process by feedforward control made into secondary treated water. The second oxidant is stored in the oxidant storage means 8. The second injection means 15 mixes the second oxidant and the primary treated water 9 in the second treatment tank 11 to obtain the secondary treated water 16, and the secondary treated water 16 is added to the second treatment tank 11. It flows out from the second outlet 12.

  The second physical property value having a predetermined relationship with the COD concentration of the secondary treated water 16 in the post-treatment step located in the most subsequent stage is measured, and the most based on the relationship between the measured second physical property measured value and the target COD concentration. It further has an additional processing step by feedback control for controlling the amount of the second oxidant added to the primary treated water 9 in the second treatment tank 11 by the second oxidant injection means 15 of the post-treatment step located in the subsequent stage. Is preferred. Here, in the case of having a plurality of post-treatment steps, the second oxidant controlled in the additional treatment step is added to the primary treatment water 9 in the second treatment tank 11 located at the most subsequent stage, This primary treated water is treated water that has been sequentially treated in the post-treatment process preceding the post-treatment process located in the most subsequent stage, and is referred to as primary treated water for convenience.

Examples of the first oxidizing agent and the second oxidizing agent include sodium hypochlorite aqueous solution, ozone, hydrogen peroxide, and the like. In particular, the reaction rate is fast and a large-capacity reaction tank is not required. A sodium hypochlorite aqueous solution is preferable.
Moreover, it is preferable that the density | concentration of sodium hypochlorite shall be 2-15 mass% in order to ensure a suitable reaction rate. More preferred is 5 to 12% by mass.

  The first COD concentration predicted value is preferably a value predicted by a UV meter. This is because the UV meter can measure in a relatively short time and can monitor even when the COD concentration fluctuates rapidly.

  The second COD concentration measurement value is preferably a value measured by a COD meter. This is because the COD meter requires a relatively long time for measurement but is highly accurate and has a value necessary for reliable processing in the second processing tank.

  The second COD concentration measurement value is preferably a value measured by shifting by a predetermined time with two or more COD meters. This is because a more precise measurement of COD concentration is possible by measuring with two or more COD meters.

  The second physical property measurement value is preferably a value measured with an ORP meter and / or a residual chlorine meter. This is because these values can be continuously monitored, and feedback to the addition of the oxidizing agent can be performed as a final treatment.

  When an ORP meter and a residual chlorine meter are used to measure the second physical property measurement value, the second oxidant injection means in the post-processing step located at the most subsequent stage based on the relationship between the measured residual chlorine concentration value and the target COD concentration It is preferable to control the amount of the second oxidizing agent added to the primary treated water in the second treatment tank.

When a residual chlorine meter is used for measurement of the second physical property measurement value, it is assumed that a chlorine-containing oxidizing agent such as a sodium hypochlorite solution is used as the second oxidizing agent. When the residual chlorine concentration of the secondary treated water 16 measured by the residual chlorine meter is lower than the set residual chlorine concentration range, the amount of addition of the second oxidant is increased and is higher than the residual chlorine concentration range. The amount of the second oxidant added is decreased. When an ORP meter is used to measure the second physical property measurement value, the second oxidizing agent is used when the redox potential of the secondary treated water 16 measured by the ORP meter is lower than the set redox potential range. The amount of the second oxidant is decreased when the amount is higher than the range of the oxidation-reduction potential. Furthermore, when using both an ORP meter and a residual chlorine meter for the measurement of the second physical property measurement value, it is preferable to control according to the residual chlorine concentration of the secondary treated water 16 measured by the residual chlorine meter.

Next, the correlation between measured values by the COD monitoring means will be described.
FIG. 2 shows the correlation between the measured value of the UV meter (absorbance at 254 nm) and the measured value of the COD meter in sulfur wastewater. It can be seen that a linear proportional correlation is obtained although the proportionality constant is slightly different depending on the wastewater.
3 shows the correlation between the measured value of the UV meter (absorbance at 254 nm) and the thiosulfate ion concentration, and FIG. 4 shows the correlation between the measured value of the UV meter (absorbance at 254 nm) and the sulfide ion concentration. From these figures, it can be seen that both have a linear proportional relationship. However, when the composition of sulfide ions and thiosulfate ions changes, the measured value of the UV meter and the measured value of the COD meter deviate from the linear proportional relationship, and if chlorine is present, chlorine is detected by the UV meter, resulting in an error. Considering the characteristics, it is preferable to measure the COD concentration using a COD meter capable of measuring with high accuracy as the second monitoring means for measuring the primary treated water which is the inflow water to the post-treatment tank.

  However, since the COD meter takes about one hour for one measurement, two or more COD meters are used to determine the amount of oxidizer added more accurately by making the time lag as small as possible against sudden water quality fluctuations. It is preferable to perform the analysis alternately to narrow the analysis time interval.

  FIG. 5 shows the correlation between the measured value by the COD meter and the measured value by the ORP meter. In addition, the leachate A in FIG. 5 is obtained by adding sodium thiosulfate to water, the leachate B is obtained by adding sodium sulfide to water, and the leachate C is sulfur waste water. From this result, it is understood that when the COD concentration is close to 0 mg / L, the measured value of the ORP meter increases rapidly and takes a value of +400 mV or more. Further, FIG. 6 shows the correlation between the measured value by the COD meter and the residual chlorine concentration value when sodium hypochlorite is used as the oxidizing agent. When COD remains, when chlorine is consumed and the COD component disappears, sodium hypochlorite is not used for the oxidation-reduction reaction and remains in the leachate as residual chlorine. Is detected. As described above, from the results of FIGS. 5 and 6, when the ORP is +400 mV or more or the residual chlorine is detected, it can be predicted that the COD satisfies the drainage standard of 20 mg / L or less.

Example 1
Examination of Treatment Flow FIGS. 7, 8 and 9 show the treatment flow for examining an example of applying the wastewater generation amount of 10 L / h and the COD concentration fluctuation pattern shown in Table 1 as a model of sulfur wastewater. 7 is a processing flow according to the present invention (Example), FIG. 8 is a processing flow (Comparative Example 1) in which only one-stage feedforward control is performed, and FIG. 9 is a processing flow (Comparison) in which only one-stage feedback control is performed. Example 2). In addition, the sodium hypochlorite aqueous solution whose density | concentration is 10 mass% was used as an oxidizing agent.

  In the embodiment shown in FIG. 7, the first treatment tank 21 and the second treatment tank 27 have an internal volume of 20L. Further, a UV meter 22 is used as the first monitoring means, and an oxidizing agent is added in the first treatment tank 21 so as to be 100% oxidized with respect to the predicted COD concentration value. As the second monitoring means, one COD meter 28 with a measurement interval of once / hour is used, and the error of this COD meter 28 is about 0%. In the second treatment tank 27, an oxidizing agent is added so that the COD concentration value of the secondary treated water 31 becomes 10 mg / L with respect to the latest output value of the COD meter 28. As described above, since the COD meter 28 takes about 1 hour to measure, an output value cannot be obtained for 1 hour after the start of the experiment. During this time, the second oxidant in the second treatment tank 27 has a COD concentration value of the primary treatment water 26 calculated from the output value of the UV meter 22 and the oxidant addition amount in the first treatment tank 21. It is added so that the COD concentration value of the secondary treated water 31 is 10 mg / L. When the ORP meter 32 is used as the third monitoring means for feedback control and the set value is 10 ± 5 mg / L, the COD concentration value converted from the measured value of the ORP meter 32 is out of the set value range. The amount of the third oxidizing agent added is set so that the COD concentration value changes by 2 mg / L per 10 minutes.

  In Comparative Example 1 shown in FIG. 8, the COD concentration value of the sulfur waste water 101 is measured by the COD meter 103, and an oxidizing agent is added so that the COD concentration value of the treated water 107 becomes 10 mg / L. Also in this comparative example 1, since the analysis frequency of the COD meter 103 is 1 time / 1 hour and there is no measurement result for 1 hour after the start of the experiment, it is assumed that the initial COD value of the generated wastewater is known. .

  In Comparative Example 2 shown in FIG. 9, the COD concentration value of the sulfur-based wastewater 201 is not measured, and the oxidizer addition amount by the ORP meter 206 so that the COD concentration value of the treated water 207 becomes 10 ± 5 mg / L. Adjust. In the example, when the COD concentration value converted from the measured value by the ORP meter 206 is out of the set range, the addition amount is set so that the COD concentration value changes by 2 mg / L per 10 minutes.

  FIG. 10 shows the COD concentration of the treated water in each example in the COD concentration fluctuation pattern 1 of the wastewater shown in Table 1. Similarly, FIG. 11 shows the treated water of each example in the COD concentration fluctuation pattern 2 of the wastewater shown in Table 1. COD concentration is shown. In FIG. 10, when an oxidizing agent is excessively added, the oxidizable COD concentration calculated from the oxidizing agent addition amount is shown as a negative value. From the results of FIG. 10, even when waste water with a low COD concentration flows in, in the example of the present invention, the comparative example 1 and the case where either one-stage feedforward control or feedback control is performed and Compared to 2, the negative value of the COD concentration is small, and it can be seen that excessive addition of the oxidizing agent can be avoided. Further, from the results of FIG. 11, even when wastewater having a high COD concentration flows in, compared to Comparative Examples 1 and 2 in which one of the one-stage feedforward control or feedback control is performed, In the present invention, the possibility that the COD concentration greatly exceeds the target value is also kept small.

(Example 2)
Examination of Addition Amount of Oxidant in Treatment Tank The method of adding the first oxidant in the first treatment tank is described. Table 2 shows the method of adding the first oxidizing agent. As Example A, it was added so that 100% of the COD concentration of wastewater could be oxidized. As Example B, the oxidizing agent was injected so that the COD concentration value of the secondary treated water flowing out from the first treatment tank was 30 mg / L. Here, the model wastewater has a wastewater generation amount of 10 L / h, and the COD concentration fluctuation pattern is as shown in Table 3. Other operation items (UV meter error, time interval of COD meter, determination method of initial value of oxidizer addition amount in second treatment tank, treated water COD target value, ORP meter set value, etc.) are the same as in Example 1. It is.

  FIG. 12 shows the COD concentration value of the treated water in each oxidizer addition method in the COD concentration fluctuation pattern 3 of the wastewater. Similarly, FIG. 13 shows the treated water in each oxidizer addition method in the COD concentration fluctuation pattern 4 of the wastewater. The COD concentration value is shown. From FIG. 12, it can be seen that in Example A, when the inflowing COD concentration is drastically reduced, the oxidant is excessively added. In addition, FIG. 13 shows that the treated water COD concentration becomes higher in Example A when the inflow COD concentration increases rapidly. As these causes, a COD meter is used as the second monitoring means. Although the COD meter has high measurement accuracy, it can only measure with an analysis frequency of about once per hour. Therefore, when an oxidant is introduced at a constant rate with respect to the inflow COD, the first processing is performed in accordance with the fluctuation of the inflow COD. Since the treated water COD concentration in the tank fluctuates, a change in the COD concentration in one hour, which is the measurement interval of the COD meter, is affected. On the other hand, in Example B, since the error of the UV meter which is the COD first monitoring means of the wastewater is only affected, the treatment water is injected when the oxidizing agent is injected so that the treatment water concentration becomes constant. It can be seen that the COD concentration value is stable and a value closer to the target value can be easily obtained.

  However, the sodium hypochlorite solution is added to the treatment tank so that the COD removal rate in the first treatment tank becomes a set value (target removal rate) with respect to the COD measurement predicted value of the wastewater. By increasing the number of water COD meters, the measurement interval is shortened and the target value can be satisfied. Furthermore, when the COD concentration of wastewater is high, an error is likely to occur in the predicted COD concentration. For example, in the treatment of wastewater with a COD of 1000 mg / L, the method 1) the treated water COD concentration value of the first treatment tank is 50 mg. / L (constant) method and method 2) A method of treating 100% COD in the first treatment tank is compared. At this time, if the measured value has a 10% error and the actual wastewater COD concentration is 900 mg / L, the actual treated water COD concentration is -50 mg / L in Method 1) and -100 mg / L in Method 2). L. That is, the case where the COD removal rate is constant with respect to the COD measurement value may be effective.

FIG. 1 is a process diagram of a continuous treatment apparatus for wastewater containing a COD component. FIG. 2 is a graph showing the correlation between the measured value of the UV meter and the measured value of the COD meter in wastewater containing a COD component. FIG. 3 is a graph showing the correlation between the measured value of the UV meter and the thiosulfate ion concentration. FIG. 4 is a graph showing the correlation between the measured value of the UV meter and the sulfide ion concentration. FIG. 5 is a graph showing the correlation between the COD concentration and the measured value of the ORP meter. FIG. 6 is a graph showing the correlation between the COD concentration and the residual chlorine concentration value. FIG. 7 is a process diagram showing an embodiment. FIG. 8 is a process diagram showing Comparative Example 1 in which only one-stage feedforward control is performed. FIG. 9 is a process diagram showing a comparative example 2 in which only one-stage feedback control is performed. FIG. 10 is a graph showing the COD concentration change when the waste water is treated in the COD concentration fluctuation pattern 1 of the example and the comparative examples 1 and 2. FIG. 11 is a graph showing the COD concentration change when the wastewater is treated in the COD concentration fluctuation pattern 2 of the example and the comparative examples 1 and 2. FIG. 12 is a graph showing changes in COD concentration when treated in Examples A and B in the COD concentration fluctuation pattern 3 of wastewater. FIG. 13 is a graph showing changes in COD concentration when treated in Examples A and B in the COD concentration fluctuation pattern 4 of wastewater.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste water 2 1st inflow port 3 1st processing tank 4 1st outflow port 5 1st monitoring means 6 1st control means 7 1st oxidizing agent injection | pouring means 8 Oxidant storage means 9 Primary treated water 10 2nd inflow port 11 Second treatment tank 12 Second outlet 13 Second monitoring means 14 Second control means 15 Second oxidant injection means 16 Secondary treated water 17 Third monitoring means 18 Third control means 20 Waste water 21 First treatment tank 22 UV Total 23 First control means 24 First oxidant injection means 25 Oxidant storage means 26 Primary treated water 27 Second treatment tank 28 COD meter 29 Second control means 30 Second oxidant injection means 31 Secondary treated water 32 ORP Total 33 Third control means 101 Sulfur waste water 102 First treatment tank 103 COD meter 104 Control means 105 Injection means 106 Oxidant storage means 107 Treated water 201 Sulfur system Waste water 202 First treatment tank 203 Injection means 204 Oxidant storage means 205 Control means 206 ORP meter 207 Treated water

Claims (16)

A first treatment tank having a first inlet through which waste water containing a COD component flows in and a first outlet through which primary treated water, which is the treated water of the waste water, flows out, is provided upstream of the first inlet. First monitoring means for measuring the first physical property value correlated with the COD concentration of the wastewater, first oxidant injection means for adding the first oxidant to the first treatment tank, and the first An addition amount of the first oxidant to be added to the first treatment tank is determined based on a first COD concentration predicted value predicted by the first monitoring unit from a physical property value, and the first oxidant injection unit performs the first One pretreatment system device having a first control means for controlling the amount of the first oxidant added to the treatment tank, and a second for flowing in the primary treated water flowing out from the first outlet of the first treatment tank. Secondary that is treated water of the inlet and the primary treated water A second treatment tank having a second outlet for discharging treated water; a second monitoring means for measuring a COD concentration of primary treated water provided upstream of the second inlet; and the second treatment tank The second oxidant injection means for adding the second oxidant to the second treatment agent and the amount of the second oxidant added to the second treatment tank are determined based on the second COD concentration measurement value measured by the second monitoring means. And a COD component having at least one post-treatment system device having second control means for controlling the amount of the second oxidant added to the second treatment tank by the second oxidant injection means. Continuous treatment equipment for wastewater containing   Third monitoring means for measuring a second physical property value having a predetermined relationship with the COD concentration of the secondary treated water flowing out from the second outlet of the second treatment tank of the post-treatment system apparatus located at the most subsequent stage; and Based on the second physical property measurement value measured by the third monitoring means, the amount of the second oxidant added to the second treatment tank by the second oxidant injection means of the post-treatment device located at the most rear stage is determined. The continuous treatment apparatus for wastewater containing a COD component according to claim 1, further comprising an additional treatment apparatus having a third control means for controlling.   The continuous treatment apparatus for wastewater containing a COD component according to claim 1 or 2, wherein the first oxidizing agent and the second oxidizing agent are aqueous sodium hypochlorite solutions.   The said 1st monitoring means is UV meter, The continuous processing apparatus of the wastewater containing the COD component as described in any one of Claims 1-3 characterized by the above-mentioned.   The continuous processing apparatus for wastewater containing a COD component according to any one of claims 1 to 4, wherein the second monitoring means is one or a plurality of COD meters.   The continuous treatment apparatus for wastewater containing a COD component according to any one of claims 2 to 5, wherein the third monitoring means is an ORP meter and / or a residual chlorine meter.   The said waste water is a sulfur type waste water, The continuous processing apparatus of the waste water containing the COD component as described in any one of Claims 1-6 characterized by the above-mentioned. A first oxidant necessary for measuring a first physical property value having a correlation with a COD concentration of wastewater containing a COD component and obtaining a target COD concentration based on a predicted first COD concentration value predicted from the measured value One pretreatment step by feedforward control, wherein the amount of the first oxidant is determined and the determined amount of the first oxidant is added to the wastewater to form primary treated water;
The COD concentration of the primary treated water is measured, and based on the measured second COD concentration value, the amount of the second oxidant added to reach the target COD concentration is determined, and the second amount of the determined amount is determined. A method for treating wastewater containing a COD component, comprising: at least one post-treatment step by feedforward control in which an oxidant is added to the primary treated water to form a secondary treated water.   A second physical property measurement value having a predetermined relationship with the COD concentration of the secondary treated water in the post-treatment step located at the most subsequent stage is measured, and based on the relationship between the measured second physical property measurement value and the target COD concentration. The method further comprises an additional treatment step by feedback control for controlling the amount of the second oxidant added to the primary treated water by the second oxidant injection means of the post-treatment step located in the most subsequent stage. Item 9. A continuous treatment method of wastewater containing a COD component according to Item 8.   10. The continuous treatment method for wastewater containing a COD component according to claim 8, wherein the first oxidizing agent and the second oxidizing agent are sodium hypochlorite aqueous solutions.   The continuous treatment method for wastewater containing a COD component according to any one of claims 8 to 10, wherein the first COD concentration predicted value is a value predicted by a UV meter.   The continuous treatment method for wastewater containing a COD component according to any one of claims 8 to 11, wherein the second COD concentration measurement value is a value measured by a COD meter.   13. The continuous treatment method for wastewater containing a COD component according to claim 12, wherein the second COD concentration measurement value is a value measured by shifting a predetermined time with two or more COD meters.   The continuous treatment method for wastewater containing a COD component according to any one of claims 8 to 13, wherein the second physical property measurement value is a value measured with an ORP meter and / or a residual chlorine meter.   When an ORP meter and a residual chlorine meter are used for the measurement of the second physical property measurement value, the second oxidant injection in the post-processing step located at the last stage based on the relationship between the measured residual chlorine concentration value and the target COD concentration The continuous treatment method for wastewater containing a COD component according to claim 14, wherein the amount of the second oxidizing agent added to the second treatment tank by means is controlled.   The said waste water is a sulfur type waste water, The continuous processing method of the waste water containing the COD component as described in any one of Claims 8-15 characterized by the above-mentioned.

Images