Neutralization apparatus of wastewater and neutralization method of wastewater

Abstract

To provide a neutralization apparatus capable of corresponding to rapid increase of wastewater.SOLUTION: A neutralization apparatus of wastewater for neutralizing pH of wastewater in a wastewater passage includes a rain gauge 16 for estimating a rainfall amount around a wastewater passage 12, a medicament feeder 18 for supplying a medicament for neutralizing pH to wastewater, and a controller 24 for controlling the supply of the medicament supplied from the medicament feeder. The controller 24 includes a prediction unit 40 for predicting a drainage volume of a wastewater passage from a rainfall amount measured by the rain gauge and a supply amount control unit 42 for controlling a supply amount of the medicament in a manner that wastewater of a drainage volume predicted by the prediction unit has a pH falling in an objective range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for neutralizing wastewater. [Background technology]

[0002] Neutralizing the pH of wastewater means adding an acidic or alkaline chemical solution to wastewater stored in a mixing tank or other device to adjust the pH to a level that allows the wastewater to be discharged. The pH of wastewater is neutralized in a neutralization device that is composed of a mixing tank, a chemical solution addition device, etc.

[0003] The amount of chemical solution added to neutralize the pH of the wastewater is determined by the pH measured by a pH meter installed at either the wastewater inlet or outlet of the neutralization device, or at both. Patent Document 1 discloses a method in which, instead of retaining the wastewater in a mixing tank, a barrier is provided in the wastewater flow path to slow down the flow rate of the wastewater, thereby achieving the same effect as retaining the wastewater in a mixing tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-261379 Summary of the Invention [Problem to be solved by the invention]

[0005] When a sudden downpour occurs, which has become more frequent in recent years, a large amount of rain falls in a short period of time, causing a sudden increase in the amount of wastewater flowing into the neutralization device and a sudden change in the pH of the wastewater. Conventional methods cannot handle such sudden changes, and there is a problem that the pH of the wastewater falls outside the range of water quality standards for discharge.

[0006] The present invention has been made in consideration of the problems with the conventional technology, and its object is to provide a wastewater neutralization device and a wastewater neutralization method that can maintain the pH of wastewater within the range of water quality standards even if the wastewater increases suddenly. [Means for solving the problem]

[0007] The means for solving the above problems are as follows. [1] A wastewater neutralization device that neutralizes the pH of wastewater in a drainage flow path, comprising: a rain gauge that measures the amount of rainfall around the drainage flow path; a chemical supply device that supplies a chemical that neutralizes the pH to the wastewater; and a control device that controls the supply of the chemical supplied from the chemical supply device. The control device includes a prediction unit that predicts the amount of wastewater in the drainage flow path from the amount of rainfall measured by the rain gauge, and a supply amount control unit that controls the amount of the chemical supplied so that the amount of wastewater predicted by the prediction unit falls within a target pH range. [2] The wastewater neutralization apparatus described in [1], wherein the chemical is strongly acidic or strongly basic. [3] A wastewater neutralization device as described in [1] or [2], further comprising a pH meter for measuring the pH of the wastewater, wherein the supply amount control unit continues supplying the chemical when the pH of the wastewater to which the chemical has been supplied is within a target pH range, and stops supplying the chemical when the pH of the wastewater measured by the pH meter is outside the target pH range. [4] A wastewater neutralization device described in any of [1] to [3], wherein the prediction unit predicts the discharge volume of the drainage flow path when the amount of rainfall is equal to or greater than a predetermined threshold, and supplies the chemical to the wastewater without predicting the discharge volume of the drainage flow path when the amount of rainfall is less than a predetermined threshold. [5] The wastewater neutralization device described in [4], wherein the supply amount control unit supplies the chemical agent a predetermined time after the rainfall amount becomes equal to or exceeds a predetermined threshold. [6] A method for neutralizing the pH of wastewater in a drainage flow path, comprising: a rainfall measurement step for measuring the amount of rainfall around the drainage flow path; and a chemical supply step for supplying a chemical that neutralizes the pH to the wastewater in the drainage flow path, wherein in the chemical supply step, the amount of wastewater in the drainage flow path is predicted from the amount of rainfall measured in the rainfall measurement step, and a supply amount of chemical is supplied to the wastewater such that the predicted amount of wastewater is within a target pH range. [7] The method for neutralizing wastewater described in [6], wherein the agent is strongly acidic or strongly basic. [8] A method for neutralizing wastewater described in [6] or [7], further comprising a pH measurement step of measuring the pH of the wastewater after the chemical supply step, continuing the supply of the chemical when the pH of the wastewater measured in the pH measurement step is within a target pH range, and stopping the supply of the chemical when the pH of the wastewater measured in the pH measurement step is outside the target pH range. [9] A method for neutralizing wastewater described in any of [6] to [8], wherein in the chemical supply step, the discharge volume of the drainage flow path is predicted when the amount of rainfall is equal to or greater than a predetermined threshold, and the chemical is supplied to the wastewater without predicting the discharge volume of the drainage flow path when the amount of rainfall is less than a predetermined threshold.

[10] The method for neutralizing wastewater described in [9], wherein in the chemical supplying step, the chemical is supplied a predetermined time after the amount of rainfall becomes equal to or greater than a predetermined threshold. Effect of the Invention

[0008] According to the present invention, even when a large amount of rain falls in a short period of time, such as in a sudden downpour, wastewater can be stably neutralized, and the pH of the wastewater can be maintained within the range of water quality standards. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a wastewater neutralization device 10 capable of carrying out the wastewater neutralization method according to this embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of the control device 24. As shown in FIG. [Diagram 3] FIG. 3 is a graph showing an example of a regression equation showing the correspondence relationship between the amount of rainfall and the amount of drainage. [Figure 4] FIG. 4 is a graph showing the correspondence relationship between the pH of 500 mL of wastewater and the amount of sulfuric acid added. [Diagram 5] FIG. 5 is a graph showing the relationship between the change in rainfall amount and the change in water level of the drainage channel 12 and time. [Figure 6] FIG. 6 is a flow diagram illustrating the method for neutralizing wastewater according to this embodiment. [Figure 7] FIG. 7 is a flow diagram illustrating another example of the method for neutralizing wastewater according to this embodiment. [Figure 8] FIG. 8 is a graph showing the pH of wastewater and the amount of rainfall before and after the installation of the wastewater neutralization device according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described below through the embodiments of the present invention. FIG. 1 is a schematic diagram showing an example of a wastewater neutralization apparatus 10 in which the wastewater neutralization method according to the present embodiment can be implemented. The wastewater neutralization apparatus 10 and the wastewater neutralization method according to the present embodiment will be described below using an example in which the wastewater neutralization apparatus 10 and the wastewater neutralization method according to the present embodiment are used to neutralize wastewater 14 with a pH of 11 flowing through a wastewater flow path 12 provided within the site of a steelworks. However, the wastewater neutralization apparatus 10 and the neutralization method according to the present embodiment are not limited to the wastewater 14, and can be applied to various wastewaters by changing the type of chemical agent supplied from the wastewater neutralization apparatus 10 according to the pH of the wastewater 14.

[0011] The wastewater neutralization device 10 has a rain gauge 16, a chemical supply device 18, a control device 24, and a pH meter 26. The rain gauge 16 is provided around the drainage flow path 12 and measures the amount of rainfall around the drainage flow path 12. The rain gauge 16 is, for example, a commonly used tipping bucket type rain gauge.

[0012] The chemical supply device 18 supplies a chemical that neutralizes the pH of the wastewater 14 to the wastewater 14 flowing through the drainage flow path 12. The chemical supply device 18 has a tank 20 that stores the chemical, and a pump 22 that supplies the chemical in the tank 20 to the wastewater 14. It is preferable to use a strongly acidic chemical as the chemical that neutralizes the pH of the wastewater 14. By using a strongly acidic chemical, the amount of change in pH relative to the amount of chemical added increases, so that the wastewater 14 can be stably neutralized even when the wastewater 14 increases rapidly.

[0013] In addition, when the wastewater 14 flowing through the drainage flow path 12 is acidic, it is preferable to use a strong basic chemical, which can provide the same effect as when a strong acidic chemical is used. Furthermore, a powdered or granular solid chemical may be used as the chemical, but a liquid chemical is preferable. By using a liquid chemical, the time from chemical supply to pH neutralization is shorter than that of a solid chemical, so that the wastewater 14 can be neutralized more stably against a sudden increase in the wastewater 14. In the following, in the wastewater neutralization device 10 according to this embodiment, an example in which strongly acidic sulfuric acid is used as a chemical to neutralize the pH of the wastewater 14 will be described, but it is not limited to sulfuric acid, and hydrochloric acid may also be used. The type of chemical used in the wastewater neutralization device 10 may be determined in consideration of precipitates and the like that are generated by reaction with substances contained in the wastewater 14.

[0014] The pH meter 26 is provided downstream of the drainage flow path 12 with respect to the chemical supply device 18, and measures the pH of the drainage 14 flowing through the drainage flow path 12. There is no particular limitation on the type of pH meter 26, and any commonly used pH meter may be used. The pH meter 26 may be provided upstream of the chemical supply device 18 in addition to the downstream of the drainage flow path 12. By providing the pH meter 26 downstream and upstream of the chemical supply device 18, it is possible to grasp not only the pH of the drainage 14 downstream of the chemical supply device 18, but also the pH of the drainage 14 upstream and the amount of change in pH due to chemical supply.

[0015] The control device 24 controls the supply amount of sulfuric acid supplied from the chemical supply device 18. The control device 24 acquires information indicating the amount of rainfall around the drainage flow path 12 from the rain gauge 16, and predicts the amount of drainage water 14 flowing through the drainage flow path 12 using the amount of rainfall. The control device 24 also controls the supply amount of chemicals supplied from the chemical supply device 18 so that the predicted amount of drainage water falls within a target pH range. The target pH range is determined in advance by multiplying the range of water quality standards (e.g., pH 5.8 to 8.6) determined by the local government in which the steelworks is located by a predetermined safety factor.

[0016] The control device 24 also acquires information indicating the pH of the wastewater 14 from the pH meter 26. The control device 24 determines whether to continue or stop the supply of sulfuric acid to the wastewater 14 based on the pH of the wastewater 14. By controlling the supply of sulfuric acid based on the pH of the wastewater 14 in this manner, it is possible to shorten the time during which the predicted wastewater volume significantly differs from the actual wastewater volume, resulting in an oversupply or undersupply of sulfuric acid, thereby making it possible to neutralize the wastewater 14 more stably.

[0017] 2 is a diagram showing a schematic example of the configuration of the control device 24. The control device 24 is, for example, a general-purpose computer such as a workstation or a personal computer. The control device 24 has a control unit 30, an input unit 32, an output unit 34, and a storage unit 36. The control unit 30 is, for example, a CPU or the like, and executes a program read from the storage unit 36 ​​to cause the control unit 30 to function as an acquisition unit 38, a prediction unit 40, and a supply amount control unit 42.

[0018] The input unit 32 is, for example, a keyboard, a touch panel integral with a display, etc. The output unit 34 is, for example, an LCD or CRT display, etc. The storage unit 36 ​​is, for example, an information recording medium such as an updatable flash memory, a built-in hard disk or a hard disk connected via a data communication terminal, a memory card, etc., and a read / write device for the information recording medium. The storage unit 36 ​​stores programs for the control unit 30 to execute each function, data used by the programs, etc.

[0019] Next, the processing of the acquisition unit 38, prediction unit 40, and supply amount control unit 42 of the control device 24 will be described. The acquisition unit 38 acquires information indicating the amount of rainfall from the rain gauge 16. The acquisition unit 38 outputs the acquired information indicating the amount of rainfall to the prediction unit 40. The acquisition unit 38 also acquires information indicating the pH of the wastewater 14 from the pH meter 26. The acquisition unit 38 outputs the acquired information indicating the pH of the wastewater 14 to the supply amount control unit 42.

[0020] When the prediction unit 40 acquires information indicating the amount of rainfall, the prediction unit 40 first judges whether the acquired amount of rainfall is equal to or greater than a predetermined threshold amount of rainfall. The threshold amount of rainfall is predetermined based on the amount of rainfall at which the pH of the wastewater 14 cannot be maintained within a target pH range in normal operation, which will be described later. The threshold amount of rainfall may be stored in the storage unit 36 ​​in advance, or may be input by the operator through the input unit 32.

[0021] When it is determined that the amount of rainfall is less than a predetermined rainfall threshold, the prediction unit 40 outputs to the supply amount control unit 42 that the amount of rainfall is less than the threshold. In this case, the supply amount control unit 42 controls the chemical supply device 18 to continue normal operation. Here, normal operation is an operation in which a predetermined supply amount of sulfuric acid is supplied based on the past records of the amount of wastewater and the pH of the wastewater 14. In addition, two chemical supply devices may be provided, one of which supplies sulfuric acid to the wastewater 14, and the other chemical supply device may supply carbonic acid to the wastewater 14, and in the case of normal operation, carbonic acid, which is a weak acidic chemical, may be supplied to the wastewater 14 as a chemical. Since the pH of the wastewater 14 does not decrease significantly even if a large amount of the weak acidic chemical is supplied, this makes it possible to neutralize the wastewater 14 more stably.

[0022] On the other hand, when a large amount of rain falls in a short period of time, such as in a sudden downpour, the prediction unit 40 determines that the amount of rainfall is equal to or greater than a predetermined threshold. When the prediction unit 40 determines that the amount of rainfall is equal to or greater than a predetermined threshold, the prediction unit 40 predicts the amount of drainage water 14 flowing through the drainage channel 12 using information indicating the amount of rainfall and a regression equation indicating the correspondence between the amount of rainfall and the amount of drainage water. The regression equation indicating the correspondence between the amount of rainfall and the amount of drainage water is obtained in advance and stored in the storage unit 36.

[0023] FIG. 3 is a graph showing an example of a regression equation showing the correspondence relationship between rainfall and drainage volume. In FIG. 3, the horizontal axis represents rainfall (mm / h) and the vertical axis represents drainage volume (m 3 / s). As shown in FIG. 3, there is a correlation between the amount of rainfall and the amount of drainage, and a regression equation showing the correlation between the two can be obtained. For this reason, by obtaining a regression equation showing the correlation between the amount of rainfall and the amount of drainage using actual data on the amount of rainfall and the amount of drainage in the past, and storing the regression equation in the storage unit 36, the prediction unit 40 can predict the amount of drainage of the drainage 14 flowing through the drainage channel 12 using information indicating the amount of rainfall and the regression equation. The prediction unit 40 outputs the predicted amount of drainage to the supply amount control unit 42. The prediction unit 40 may cause the output unit 34 to display the predicted amount of drainage of the drainage 14.

[0024] Furthermore, when the supply amount control unit 42 obtains the predicted value of the wastewater amount from the prediction unit 40, it specifies the supply amount of sulfuric acid that can bring the pH of the wastewater 14 of the corresponding amount into the target pH range. Fig. 4 is a graph showing the correspondence relationship between the pH of the wastewater and the dripping amount of sulfuric acid for 500 mL of wastewater. In Fig. 4, the horizontal axis is the dripping amount of sulfuric acid (mL), and the vertical axis is the pH (-) of the wastewater after dripping of sulfuric acid. The unit (-) indicates that the value is dimensionless.

[0025] For example, the amount of sulfuric acid to be dropped to lower the pH of the wastewater 14 from 11 to 9 can be calculated from the amount of sulfuric acid to be dropped on the horizontal axis where the vertical axis of Figure 4 corresponds to pH 9. That is, it is found that 1.25 mL of sulfuric acid should be dropped to lower the pH of 500 mL of wastewater 14 from 11 to pH 9.

[0026] For example, if the rainfall is 20 mm / h, the drainage volume calculated using the regression equation shown in Figure 3 is 5.2 × 10 3 L / h. To lower the pH of this wastewater 14 from 11 to 9, the wastewater volume (5.2 × 10 3 13 L / h is obtained by dividing 13 L / h by 500 mL and multiplying the result by 1.25 mL. In other words, in this case, it is understood that 13 L / h of sulfuric acid should be supplied from the chemical supply device 18 to the wastewater 14.

[0027] 4 is obtained in advance by performing an experiment or the like, and the corresponding relationship is stored in the storage unit 36. In this way, the supply amount control unit 42 can specify the supply amount of sulfuric acid that neutralizes the pH of the wastewater 14 to within the target pH range by using the predicted wastewater amount of the wastewater 14 and the corresponding relationship.

[0028] Referring again to Fig. 2, when the supply amount control unit 42 specifies the supply amount of sulfuric acid, it controls the pump 22 of the chemical supply device 18 to supply the specified supply amount of sulfuric acid to the wastewater 14. In this way, in the wastewater neutralization device 10 according to this embodiment, the wastewater amount is predicted from the amount of rainfall, and the pH of the wastewater 14 is neutralized by supplying an amount of sulfuric acid that allows the predicted amount of wastewater 14 to fall within a target pH range. This allows the wastewater to be stably neutralized even in the case of a large amount of rainfall in a short period of time, such as a sudden downpour, and the pH of the wastewater 14 discharged from the steelworks to be maintained within the range of water quality standards set by the local government.

[0029] Furthermore, it is preferable that the supply amount control unit 42 controls so that sulfuric acid is supplied from the chemical supply device 18 to the wastewater 14 after a predetermined time has elapsed since the prediction unit 40 determined that the amount of rainfall was equal to or greater than a predetermined rainfall threshold. Figure 5 is a graph showing the relationship between the change in rainfall amount and the change in the water level of the drainage flow path 12 and time. Figures 5(a), (b), and (c) show the change in rainfall amount (solid line) and the change in the water level of the drainage flow path 12 (dashed line) on different days. The change in rainfall amount was measured using a tipping bucket rain gauge, and the water level of the drainage flow path 12 was measured using an ultrasonic level gauge.

[0030] From Figs. 5(a), (b), and (c), it can be seen that after 7 to 9 minutes, the peak of rainfall is observed in the drainage flow path 12 in which the drainage neutralizer 10 is installed, and therefore, it is 7 to 9 minutes before the water volume change due to rainfall appears in the drainage flow path 12. For this reason, it is preferable that the supply amount control unit 42 controls the supply of sulfuric acid 7 minutes after the prediction unit 40 judges that the rainfall is equal to or greater than the predetermined rainfall threshold. This makes it possible to supply an amount of sulfuric acid that brings the increased amount of drainage 14 into the target pH range in accordance with the timing of the increase in the drainage 14, and to neutralize the drainage 14 more stably. Note that if sulfuric acid is supplied 7 minutes after the peak of rainfall is observed, there may be an excess supply of sulfuric acid, but since the excess supply of sulfuric acid can be detected by the pH meter 26 as described later, the supply of sulfuric acid may be stopped when an excess supply of sulfuric acid is detected.

[0031] The predetermined time at which the water level in the drainage flow path 12 changes due to rainfall may vary depending on the locations of the rain gauge 16 and the chemical supply device 18. For this reason, the predetermined time can be specified by creating a graph showing the change in rainfall amount and the change in water level in the drainage flow path, and determining the time difference between the time when the peak of rainfall amount appears and the time when the peak of the water level in the drainage flow path 12 appears. Then, the supply amount control unit 42 may control the chemical supply device 18 to supply sulfuric acid to the drainage 14 after the specified predetermined time has elapsed since the prediction unit 40 determined that the amount of rainfall is equal to or greater than a predetermined rainfall amount threshold.

[0032] Furthermore, the supply amount control unit 42 acquires information indicating the pH of the wastewater 14 from the acquisition unit 38, and determines whether the acquired pH of the wastewater 14 is within a target pH range. If the pH of the wastewater 14 is within the target pH range, the supply amount control unit 42 continues the supply of sulfuric acid from the chemical supply device 18. On the other hand, if the pH of the wastewater 14 is outside the target pH range, the supply amount control unit 42 stops the supply of sulfuric acid from the chemical supply device 18.

[0033] If the predicted wastewater volume differs greatly from the actual wastewater volume and sulfuric acid is oversupplied, the pH of the wastewater 14 drops and falls below the target pH range. For the same reason, if sulfuric acid is undersupplied, the pH of the wastewater 14 exceeds the target pH range. Therefore, by determining whether the pH of the wastewater 14 obtained by the supply volume control unit 42 is within the target pH range, it is possible to detect an oversupply or undersupply of sulfuric acid. In addition, the supply volume control unit 42 determines whether to continue or stop the supply of sulfuric acid from the chemical supply device 18 according to the detection result. This makes it possible to shorten the time when sulfuric acid is oversupplied or undersupplied, thereby making it possible to neutralize the wastewater 14 more stably.

[0034] In the wastewater neutralization device 10 according to the present embodiment, an example having the pH meter 26 has been described, but the present invention is not limited to this, and the device may not have the pH meter 26. However, as described above, the pH of the wastewater 14 is measured by the pH meter 26, and by determining whether the pH is within a target pH range, an excess or insufficient supply of sulfuric acid can be detected. Therefore, it is preferable that the wastewater neutralization device 10 has the pH meter 26.

[0035] Next, a method for neutralizing wastewater in a case where the wastewater neutralization device 10 does not have a pH meter 26 will be described with reference to Fig. 6. Fig. 6 is a flow diagram for explaining a method for neutralizing wastewater according to this embodiment. In principle, the flow shown in Fig. 6 continues to operate 24 hours a day, 365 days a year, but can be terminated at any step by the input unit 32 receiving an instruction to terminate from an operator.

[0036] First, the rainfall is measured using the rain gauge 16 (step S101). This process is the rainfall measurement step. Next, the prediction unit 40 judges whether the rainfall measured in the rainfall measurement step is less than a predetermined threshold (step S102). If it is judged that the rainfall is less than the predetermined threshold (step S102: Yes), the prediction unit 40 outputs to the supply amount control unit 42 that the rainfall is less than the threshold, and operates the drug supply device 18 as a normal operation (step S103). On the other hand, if it is judged that the rainfall is less than the predetermined threshold (step S102: No), the prediction unit 40 predicts the drainage amount using the rainfall (step S104) and outputs the predicted drainage amount to the supply amount control unit 42.

[0037] When the predicted value of the wastewater volume is obtained from the prediction unit 40, the supply volume control unit 42 specifies a supply volume of sulfuric acid that will bring the pH of the wastewater 14 of that volume into the target pH range (step S105), and supplies the specified supply volume of sulfuric acid from the chemical supply device 18 to the wastewater 14 (step S106). The process from step S104 to S106 constitutes the chemical supply step. Thereafter, the process returns to step S101, and the process from step S101 is executed again repeatedly.

[0038] In this way, in the method for neutralizing wastewater according to the present embodiment, the amount of wastewater is predicted from the amount of rainfall, and sulfuric acid is supplied in an amount that allows the pH of the wastewater of that amount to fall within the target pH range. This allows the wastewater to be stably neutralized even in the case of a large amount of rain falling in a short period of time, such as in a torrential downpour, and the pH of the wastewater can be maintained within the control value range.

[0039] Next, a method for neutralizing wastewater in the case where the wastewater neutralization device 10 has a pH meter 26 will be described with reference to Fig. 7. Fig. 7 is a flow diagram for explaining another example of the method for neutralizing wastewater according to this embodiment. In Fig. 7, the same steps as those in Fig. 6 are given the same step numbers, and their description will be omitted. In principle, the flow shown in Fig. 7 also continues to operate 24 hours a day, 365 days a year, but can be terminated at any step by the input unit 32 receiving an instruction to terminate from the operator.

[0040] After the supply amount of sulfuric acid specified in step S106 is supplied from the chemical supply device 18 to the wastewater 14, the pH of the wastewater 14 is measured using the pH meter 26 (step 201). This process corresponds to the pH measurement step. Information indicating the measured pH of the wastewater 14 is output to the supply amount control unit 42 via the acquisition unit 38.

[0041] The supply amount control unit 42 judges whether the pH of the wastewater 14 is within the target pH range (step S202). If it is judged that the pH of the wastewater 14 is not within the target pH range (step 202: No), the supply amount control unit 42 stops the supply of sulfuric acid from the chemical supply device 18 (step S203), returns the process to step S101, and repeats the process from step S101 again. On the other hand, if it is judged that the pH of the wastewater 14 is within the target pH range (step S202: Yes), the supply amount control unit 42 continues the supply of sulfuric acid from the chemical supply device 18, returns the process to step S101, and repeats the process from step S101 again.

[0042] In this way, in the case where the pH meter 26 is provided, the method for neutralizing wastewater according to the present embodiment further determines whether to continue or stop the supply of sulfuric acid to the wastewater 14 based on the pH of the wastewater 14. This makes it possible to shorten the time during which the predicted wastewater volume significantly differs from the actual wastewater volume, resulting in an oversupply of sulfuric acid or an undersupply of sulfuric acid, thereby making it possible to neutralize the wastewater 14 more stably.

[0043] In the wastewater neutralization method according to the present embodiment, the pH of the wastewater 14 is 11, and the wastewater volume is predicted from the amount of rainfall, but the present invention is not limited to this. For example, when the pH of the wastewater 14 varies depending on the amount of rainfall, the amount of change in pH may be specified using a regression equation showing the correspondence between the amount of rainfall and pH. Then, the amount of chemical to be supplied from the chemical supply device 18 may be specified using the specified amount of change in pH and the amount of wastewater 14. This allows the wastewater 14 to be stably neutralized even when the pH of the wastewater 14 varies depending on the amount of rainfall. EXAMPLES

[0044] Next, an example will be described in which wastewater in a 1.5 m wide drainage channel was actually neutralized using the wastewater neutralization device 10 (chemical: sulfuric acid) shown in Figure 1. The wastewater flowing through the target drainage channel is always alkaline (pH 11), and even during rainfall, the pH does not change, with only the amount of wastewater changing.

[0045] The amount of wastewater flowing through the drainage channel was calculated from the water level of the drainage channel, the channel width (1.5m), and the flow velocity of the wastewater. The water level of the drainage channel was measured with an ultrasonic level gauge, and the flow velocity of the wastewater was measured with a propeller-type current meter. The rain gauge was also measured with a tipping bucket-type rain gauge. The water level of the drainage channel, the flow velocity of the wastewater, and the amount of rainfall were constantly recorded, and a regression equation between rainfall and the amount of wastewater was determined. The regression equation between rainfall and the amount of wastewater of drainage 14 was given by the following equation (1).

[0046] Q = 0.0072 × R + 0.0006 (1) In the above formula (1), Q is the displacement (m 3 / s) and R is the rainfall (mm / h).

[0047] The drainage volume was predicted from the rainfall volume using the above formula (1). The supply volume of sulfuric acid was specified using the graph shown in Figure 4. Furthermore, since there was a correlation between the change in rainfall volume and the change in drainage volume, with a time difference of about 7 to 9 minutes, the supply of sulfuric acid was started 7 minutes after the rainfall volume exceeded a predetermined threshold value.

[0048] Fig. 8 is a graph showing the pH of wastewater and the amount of rainfall before and after the installation of the wastewater neutralization device according to this embodiment. Fig. 8(a) is the graph before the installation of the wastewater neutralization device, and Fig. 8(b) is the graph after the installation of the wastewater neutralization device. In Fig. 8, the triangular plot shows the pH (-) of the waterway drainage, and the bar graph shows the amount of rainfall (mm / 10 min).

[0049] Before the installation of the wastewater neutralization device according to the present embodiment, as shown in FIG. 8(a), when rainfall of more than 3.5 mm / 10 min fell in a short time, the pH of the wastewater flowing through the drainage flow path greatly exceeded the range of pH 5.8 to 8.6, which is the water quality standard. In contrast, after the installation of the wastewater neutralization device according to the present embodiment, as shown in FIG. 8(b), even if rainfall of more than 3.5 mm / 10 min fell in a short time, the pH of the wastewater flowing through the drainage flow path was within the range of pH 5.8 to 8.6, which is the water quality standard, as before the installation. From this result, it was confirmed that by using the wastewater neutralization device according to the present embodiment, wastewater can be stably neutralized even when a large amount of rain falls in a short time, and the pH of the wastewater can be maintained within the range of the water quality standard. [Explanation of symbols]

[0050] 10. Wastewater neutralization device 12 Drainage channel 14 Drainage 16 Rain gauge 18 Drug supply device 20. Tank 22 Pump 24 Control device 26 pH meter 30 Control section 32 Input section 34 Output section 36 Storage area 38 Acquisition Department 40 Prediction Department 42 Supply amount control section

Claims

1. A wastewater neutralization device that neutralizes the pH of wastewater in a wastewater flow path, A rain gauge for measuring the amount of rainfall around the drainage channel; A chemical supplying device that supplies a chemical to neutralize the pH to the wastewater; A control device that controls the supply of the medicine supplied from the medicine supply device; Equipped with The control device is a wastewater neutralization device that has a prediction unit that predicts the amount of wastewater in the drainage flow path from the rainfall measured by the rain gauge, and a supply amount control unit that controls the supply amount of the chemical so that the amount of wastewater predicted by the prediction unit is within a target pH range.

2. The wastewater neutralization apparatus according to claim 1 , wherein the chemical is strongly acidic or strongly basic.

3. Further comprising a pH meter for measuring the pH of the wastewater; The wastewater neutralization device according to claim 1 or claim 2, wherein the supply amount control unit continues supplying the chemical when the pH of the wastewater to which the chemical has been supplied is within a target pH range, and stops supplying the chemical when the pH of the wastewater measured by a pH meter is outside the target pH range.

4. The wastewater neutralization device of claim 1 or claim 2, wherein the prediction unit predicts the amount of discharge in the drainage flow path when the amount of rainfall is equal to or greater than a predetermined threshold, and supplies the chemical to the wastewater without predicting the amount of discharge in the drainage flow path when the amount of rainfall is less than a predetermined threshold.

5. The wastewater neutralization device described in claim 3, wherein the prediction unit predicts the amount of discharge in the drainage flow path when the amount of rainfall is greater than or equal to a predetermined threshold, and supplies the chemical to the wastewater without predicting the amount of discharge in the drainage flow path when the amount of rainfall is less than a predetermined threshold.

6. The wastewater neutralization device according to claim 4 , wherein the supply amount control unit supplies the chemical agent a predetermined time after the amount of rainfall becomes equal to or greater than a predetermined threshold.

7. The wastewater neutralization device according to claim 5 , wherein the supply amount control unit supplies the chemical agent a predetermined time after the amount of rainfall becomes equal to or greater than a predetermined threshold.

8. A method for neutralizing a pH of wastewater in a wastewater flow path, comprising: A rainfall measuring step for measuring the amount of rainfall around the drainage channel; A chemical supply step of supplying a chemical that neutralizes the pH to the wastewater in the drainage flow path; having In the chemical supply step, the amount of wastewater discharged from the drainage flow path is predicted from the amount of rainfall measured in the rainfall measurement step, and a supply amount of chemical is supplied to the wastewater such that the predicted amount of wastewater reaches a target pH range.

9. The method for neutralizing wastewater according to claim 8, wherein the chemical is strongly acidic or strongly basic.

10. 10. The method for neutralizing wastewater according to claim 8 or claim 9, further comprising a pH measurement step of measuring the pH of the wastewater after the chemical supply step, and continuing the supply of the chemical when the pH of the wastewater measured in the pH measurement step is within a target pH range, and stopping the supply of the chemical when the pH of the wastewater measured in the pH measurement step is outside the target pH range.

11. A method for neutralizing wastewater as described in claim 8 or claim 9, wherein in the chemical supply step, the amount of discharged water in the drainage flow path is predicted when the amount of rainfall is equal to or greater than a predetermined threshold, and the chemical is supplied to the wastewater without predicting the amount of discharged water in the drainage flow path when the amount of rainfall is less than a predetermined threshold.

12. The method for neutralizing wastewater described in claim 10, wherein in the chemical supply step, the amount of discharged water in the drainage flow path is predicted when the amount of rainfall is equal to or greater than a predetermined threshold, and the chemical is supplied to the wastewater without predicting the amount of discharged water in the drainage flow path when the amount of rainfall is less than a predetermined threshold.

13. The method for neutralizing wastewater according to claim 11, wherein in the chemical supplying step, the chemical is supplied a predetermined time after the amount of rainfall becomes equal to or greater than a predetermined threshold.

14. The method for neutralizing wastewater according to claim 12, wherein in the chemical supplying step, the chemical is supplied a predetermined time after the amount of rainfall becomes equal to or greater than a predetermined threshold.

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