Wastewater treatment method

Abstract

To provide a wastewater treatment method capable of stably suppressing generation of hydrogen sulfide at a low cost when wastewater containing sulfate is treated.SOLUTION: A wastewater treatment method of an embodiment 1 is a method for treating wastewater W containing sulfate. In the method, the wastewater W is allowed to flow into a treatment tank 1, a value of pH that is a water quality indicator of in-tank water Wa stored in the treatment tank 1 is detected, and an alkaline solution D1 is added to the in-tank water Wa to increase the value of pH based on a detection result of pH.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating wastewater. [Background technology]

[0002] It has been known that hydrogen sulfide is generated within wastewater treatment facilities that treat wastewater containing sulfates. Hydrogen sulfide is one of the specific odorous substances designated by the Offensive Odor Prevention Law, and is stipulated to be a substance that can cause unpleasant odors and damage the living environment. In addition, hydrogen sulfide is highly corrosive, and there are concerns about its adverse effects on facilities and the human body. Therefore, in the design of this type of wastewater treatment facility, technology to suppress the generation of hydrogen sulfide is required.

[0003] The following Patent Document 1 discloses a sewage treatment method, which is one of the techniques for suppressing the generation of hydrogen sulfide. In this sewage treatment method, sewage containing hydrogen sulfide is introduced into an aeration tank as inflow water, and electrolyzed alkaline water having a pH of 13.0 or more is mixed into the water in the tank. According to this sewage treatment method, electrolyzed alkaline water of, for example, 0.04 [wt %] or more is added to the sewage flowing into the aeration tank. This is intended to suppress the generation of hydrogen sulfide in the aeration tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-117242 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the sewage treatment method of the cited document 1, electrolyzed alkaline water is added according to the ratio of the amount of electrolyzed alkaline water to the amount of sewage. Therefore, when the quality of the inflow water flowing into the aeration tank changes, it is difficult to grasp the optimal amount of electrolyzed alkaline water to be added. For example, even if a planned amount of electrolyzed alkaline water is added to the aeration tank, there is little certainty that the amount of hydrogen sulfide generated will be stably suppressed. In particular, when the inflow water is wastewater such as industrial wastewater, the quality of the industrial wastewater varies greatly from one business entity to another, so that the amount of electrolyzed alkaline water to be added must be set individually, which may result in a problem of low versatility.

[0006] As another method for suppressing the generation of hydrogen sulfide, it is possible to use an activated carbon deodorizer or soil deodorizer attached to the treatment tank. The activated carbon deodorizer adsorbs and removes hydrogen sulfide generated in the treatment tank using activated carbon. The soil deodorizer sends hydrogen sulfide generated in the treatment tank into soil, where it is adsorbed or dissolved by soil particles or moisture in the soil, and decomposes it into odorless components using the action of microorganisms in the soil. However, the activated carbon deodorizer has a problem in that the running costs for replacing the activated carbon are high. The deodorizing effect of the soil deodorizer is greatly affected by the external environment, so there is little certainty in stably suppressing the amount of hydrogen sulfide generated. It is also known that devices that remove hydrogen sulfide once generated, such as the activated carbon deodorizer and soil deodorizer, can be a factor that increases the initial cost of wastewater treatment facilities.

[0007] The present invention has been made in view of the above problems, and aims to provide a wastewater treatment method capable of stably suppressing the generation of hydrogen sulfide when treating wastewater containing sulfates, at low cost. [Means for solving the problem]

[0008] One aspect of the present invention is A method for treating wastewater containing sulfate, comprising the steps of: The wastewater is introduced into a treatment tank; Detecting the value of the water quality index of the water in the treatment tank; a chemical for increasing at least one of pH and oxidation-reduction potential based on the detection result of the water quality index, is located. Effect of the Invention

[0009] According to the wastewater treatment method of the above embodiment, a chemical agent is used for increasing at least one of the water quality indicators, pH and redox potential, of acidic wastewater containing sulfate. The chemical agent is added to the water in the tank based on the detection result of the water quality indicator of the water in the tank. By adding the chemical agent at this time, the pH of the water in the treatment tank can be increased to the alkaline side, or the redox potential of the water in the tank can be increased, or both the pH and the redox potential of the water in the tank can be increased, and in either case, a condition can be formed in which sulfate ions derived from sulfate are likely to remain in the water in the tank. In other words, this condition is a sulfate ion concentration reduction suppression condition that can suppress the reduction in the sulfate ion concentration in the water in the tank, and is also a hydrogen sulfide generation suppression condition that can suppress the generation of hydrogen sulfide in a gaseous state in the treatment tank.

[0010] Therefore, by adding a chemical to the water in the treatment tank, the generation of hydrogen sulfide in the treatment tank can be suppressed. Moreover, unlike simply adding a chemical to the water in the tank, the chemical is added while checking the detection results of the water quality index of the water in the tank. This makes it possible to reliably suppress the amount of hydrogen sulfide generated. Moreover, since the generation of hydrogen sulfide can be suppressed by simply adding a chemical addition device and a water quality index detection device to the treatment tank, this is effective in keeping the initial cost of the wastewater treatment facility low compared to using a device that removes hydrogen sulfide once it has been generated, such as an activated carbon deodorization device or a soil deodorization device.

[0011] As described above, according to the above-mentioned embodiment, it is possible to provide a wastewater treatment method capable of stably suppressing the generation of hydrogen sulfide when treating wastewater containing sulfates at low cost. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 is a diagram showing a schematic configuration of a wastewater treatment device according to a first embodiment. [Diagram 2] 1 is a flowchart of a wastewater treatment method according to the first embodiment. [Diagram 3] A graph showing the results of experiment A, in which sludge transport water from a septic tank was used as a sample. [Figure 4] FIG. 4 is a graph showing the correlation between hydrogen sulfide concentration and pH in the results of Experiment A in FIG. 3. [Diagram 5] FIG. 4 is a graph showing the correlation between sulfate ion concentration and pH in the results of Experiment A in FIG. 3. [Figure 6] A list of the results of experiment B, which used industrial wastewater as a sample. [Figure 7] FIG. 7 is a graph showing the correlation between hydrogen sulfide concentration and pH in the results of Experiment B in FIG. 6. [Figure 8] FIG. 7 is a graph showing the correlation between sulfate ion concentration and pH in the results of Experiment B in FIG. 6. [Figure 9] Correlation diagram between the redox potential of sulfur species and pH. [Figure 10] The results of Experiment A are plotted on the correlation diagram in Figure 9 . [Figure 11] FIG. 1 is a diagram showing a schematic configuration of a wastewater treatment device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Preferred embodiments of the above aspects are described below.

[0014] In the wastewater treatment method of the above embodiment, it is preferable to use an alkaline solution as the chemical agent to increase the pH value, and the water quality index is pH. According to this wastewater treatment method, it is possible to control the water quality of the water in the tank by using pH as the water quality index.

[0015] In the wastewater treatment method of the above aspect, when an alkaline solution is used as the chemical agent, the target pH value of the water in the tank is preferably set to 8 or more. According to this wastewater treatment method, it is possible to increase the reliability of the effect of suppressing the generation of hydrogen sulfide.

[0016] In the wastewater treatment method of the above aspect, when an alkaline solution is used as the chemical agent, it is preferable that the target pH value of the water in the tank is set to 8 or more when the redox potential of the wastewater is in the range of -0.4 [V] to 0.3 [V]. This wastewater treatment method can increase the reliability of the effect of suppressing the generation of hydrogen sulfide.

[0017] In the wastewater treatment method of the above aspect, it is preferable to use a chlorine-based disinfectant as the chemical agent for increasing the value of the redox potential, and the water quality index is the redox potential. According to this wastewater treatment method, it is possible to manage the water quality of the water in the tank by using the redox potential as the water quality index.

[0018] In the wastewater treatment method of the above aspect, the wastewater is preferably industrial wastewater. According to this wastewater treatment method, the wastewater treatment target is industrial wastewater whose water quality varies greatly from one business entity to another, thereby making it possible to increase the versatility of the wastewater treatment.

[0019] In the wastewater treatment method of the above aspect, the wastewater is preferably domestic wastewater. This wastewater treatment method makes it possible to treat domestic wastewater whose water quality varies depending on differences in household lifestyles. Furthermore, domestic wastewater is organic wastewater containing organic matter, and it is known that in water treatment in the presence of sulfate-reducing bacteria, the sulfate-reducing bacteria feed on the organic matter and live there, causing the generation of hydrogen sulfide. Therefore, if the wastewater treatment method of this aspect is adopted when treating domestic wastewater, it is particularly effective in suppressing the generation of hydrogen sulfide in the treatment tank.

[0020] Hereinafter, specific examples of the wastewater treatment method according to the above-mentioned embodiment will be described with reference to the drawings.

[0021] (Embodiment 1) 1. Structure of wastewater treatment device 101 1, a wastewater treatment device 101 of the first embodiment receives wastewater W from the outside and continuously treats it. The wastewater treatment device 101 includes a treatment tank 1, a chemical tank 10, a chemical supply pump 11, and a water quality sensor 12.

[0022] The wastewater W contains sulfate. That is, sulfate ions may be present in the wastewater W. In this embodiment, the wastewater W may be industrial wastewater generated in business entities such as factories, or domestic wastewater generated in houses. The wastewater W may be organic or inorganic.

[0023] The treatment tank 1 has an inlet pipe 1a and an outlet pipe 1b, and is a hollow tank-shaped body. Wastewater W flows into the internal space 2 of the treatment tank 1 through the inlet pipe 1a and is temporarily stored therein. Although not shown, the internal space 2 of the treatment tank 1 is partitioned into a plurality of treatment areas, and each treatment area performs separate water treatment. After being treated in the treatment tank 1, the treated water Wb flows out of the treatment tank 1 through the outlet pipe 1b.

[0024] The chemical tank 10 is a tank capable of storing a chemical D. As the chemical D, for example, an alkaline solution D1 such as a sodium hydroxide solution, a potassium hydroxide solution, a calcium carbonate solution, or electrolytic alkaline water can be used. The alkaline solution D1 is a chemical used to increase the pH value. Note that a chlorine-based disinfectant D2 can be used instead of the alkaline solution D1. The chlorine-based disinfectant D2 is a chemical used to increase the oxidation-reduction potential value.

[0025] The chemical supply pump 11 is a pump for supplying the chemical D stored in the chemical tank 10 to any one of the multiple treatment areas 3 of the treatment tank 1. The chemical supply pump 11 can add the chemical D to the tank water Wa stored in the treatment area 3 of the treatment tank 1.

[0026] The water quality sensor 12 is a sensor that detects the value of a water quality index of the tank water Wa in the treatment area 3 of the treatment tank 1. Examples of the water quality sensor 12 include a pH sensor for detecting the pH of the tank water Wa and an ORP sensor for detecting the oxidation-reduction potential of the tank water Wa.

[0027] It is preferable to select an arbitrary region in which hydrogen sulfide is particularly likely to be generated among the multiple treatment regions in the treatment tank 1 as the treatment region 3. For example, a region in which the water quality of the tank water Wa is substantially the same as that of the wastewater W, such as the most upstream treatment region, or a region that is likely to become anaerobic and does not contain oxygen, may be selected as the treatment region 3. This allows the chemical D to be effectively added to the tank water Wa in the region limited to the region in which hydrogen sulfide is likely to be generated.

[0028] 2. Wastewater treatment methods Next, a wastewater treatment method of the first embodiment will be described with reference to Figures 1 and 2. This wastewater treatment method is made possible by using the wastewater treatment device 101 of Figure 1 and sequentially executing each step from step S101 to step S106 of Figure 2. If necessary, one or more steps may be added to these steps, at least one step may be divided into multiple steps, or at least one step may be deleted.

[0029] The wastewater treatment method of the first embodiment is carried out on the condition that the wastewater W is acidic. First, if the wastewater W is acidic (if "Yes" in step S101), proceed to step S102. For example, step S101 is determined based on the results of a pH sensor, test paper, or the like. Note that if it has been confirmed in advance that the wastewater W is acidic, or if it is not necessary to determine whether the wastewater W is acidic or not (for example, if it is not necessary to determine whether the water quality of the wastewater W is acidic, neutral, or alkaline), step S101 may be omitted.

[0030] In step S102, the water quality sensor 12 is used to detect the value of a predetermined water quality index of the tank water Wa in the treatment area 3. Then, in step S103, it is determined whether or not the addition of chemical D is necessary based on the detection result of step S102 (the value of the water quality index of the tank water Wa). This determination is made by comparing the value of the water quality index of the tank water Wa with a preset target value of the water quality index. For example, if the pH of the tank water Wa is below a preset target value, it is determined that the addition of chemical D is necessary. If it is determined in step S103 that the addition of chemical D is necessary (if "Yes" in step S103), the process proceeds to step S104, and the addition of chemical D is started.

[0031] Thereafter, in step S105, similarly to step S102, the water quality sensor 12 is used to detect the value of the water quality index of the tank water Wa in the treatment area 3. Then, in step S106, it is determined whether or not to end the addition of the chemical D based on the detection result of step S105 (the value of the water quality index of the tank water Wa). This determination is the same as in step S103. If it is determined in step S106 that the addition of the chemical D is to be ended (if "Yes" in step S106), the wastewater treatment is ended.

[0032] 3. Setting target values ​​for water quality indexes The inventors carried out the following Experiments A and B in order to determine the target values ​​of the water quality indexes to be used in the determination in step S103.

[0033] 3-1. Experiment A In experiment A, sludge transfer water from a septic tank was used as sample water (sample water: A-1 to A-7) (see Figure 3). Each sample water was 500 [mL]. Each sample water was placed in a container, and 0.1N HCL (hydrogen chloride) or NaOH (sodium hydroxide) adjustment solution was added under sealed conditions to adjust the pH of each sample water to the respective target value. The amount of adjustment solution added at this time was determined from a preliminary experiment conducted in advance. In this preliminary experiment, the amount of adjustment solution added to the sample water was changed with the container open to determine the appropriate amount to add to adjust the pH to the target value. In addition, the oxidation-reduction potential [V] of each sample water after adjustment was measured using an existing ORP meter.

[0034] Subsequently, each container was placed in a water bath to maintain a constant temperature of 30°C, and after 24 hours, the hydrogen sulfide concentration and sulfate ion concentration were measured. First, the tip of a known hydrogen sulfide detector tube was inserted into the gas phase of each sealed container, and the concentration of gaseous hydrogen sulfide generated in each sample water was measured by drawing gas into the hydrogen sulfide detector tube. Next, the sample water in each container was collected, and the sulfate ion concentration in each sample water was measured using a known analytical method called ion chromatography.

[0035] The following findings were obtained from the results of Experiment A above.

[0036] As shown in Figures 3 to 5, the concentration of gaseous hydrogen sulfide and the concentration of sulfate ions in the sample water both changed significantly before and after the pH of the sample water reached 8. Specifically, when the pH of the sample water was 8 or higher, there was a tendency for the amount of gaseous hydrogen sulfide generated to be less than when the pH was 7 or lower (see Figures 3 and 4). In addition, there was a tendency for the amount of sulfate ions contained in the sample water to be greater when the pH of the sample water was 8 or higher than when the pH was 7 or lower (see Figures 3 and 5).

[0037] According to the results of Experiment A, it was confirmed that a pH of 8 or higher for the sludge transfer water is a condition in which sulfates are likely to exist in the water as sulfate ions or sulfide ions, and that this also corresponds to a condition in which the generation of gaseous hydrogen sulfide can be suppressed.

[0038] 3-2.Experiment B In experiment B, industrial wastewater generated at the actual site was used as sample water (sample water: B-1 to B-3) instead of sludge transfer water from a septic tank. Based on the knowledge gained from experiment A, this experiment B was carried out by narrowing down the pH of the sample water to three patterns: 6, 7, and 8. Each sample was 900 [mL]. In addition, in order to always maintain the pH of the sample water at the target pH, a drip program (amount dripped per unit time) was adopted to continuously drip NaOH (sodium hydroxide). Other conditions, such as the measurement method, were the same as in experiment A.

[0039] The following findings were obtained from the results of Experiment B above.

[0040] As shown in Figures 6 and 7, the amount of gaseous hydrogen sulfide generated was reduced to 0 (zero) by maintaining the pH of the sample water at 8. Also, as shown in Figures 6 and 8, when the pH of the sample water was maintained at 8, sulfate ions were detected that were not detected when the pH was 6 and 7.

[0041] The results of Experiment B, like those of Experiment A, confirmed that a pH of 8 or higher for industrial wastewater is a condition in which sulfates are likely to exist in water as sulfate ions or sulfide ions, and also corresponds to a condition in which the generation of gaseous hydrogen sulfide can be suppressed.

[0042] 3-3. Correlation between the redox potential of sulfur species and pH As shown in Figure 9, the correlation between the redox potential of sulfur species and pH is generally known. According to this correlation, a pH of 8 or higher is a condition in which hydrogen sulfide (H2S) is unlikely to be generated, and sulfate ions (SO4 2-) is likely to exist in water. Therefore, the results of Experiment A and Experiment B above are supported by the correlation in Figure 9.

[0043] In Fig. 10, each sample used in experiment A is plotted with a black circle on the correlation diagram of Fig. 9. According to Fig. 10, samples A-1, A-2, and A-3 belong to the hydrogen sulfide region, and samples A-5, A-6, and A-7 belong to the sulfate ion region. Sample A-4 belongs to the boundary region between the hydrogen sulfide region and the sulfate ion region. Therefore, for samples A-1, A-2, and A-3, the hydrogen sulfide concentration is relatively high and the sulfate ion concentration is relatively low, which is consistent with the actual measurement results. Similarly, for samples A-5, A-6, and A-7, the hydrogen sulfide concentration is relatively low and the sulfate ion concentration is relatively high, which is consistent with the actual measurement results.

[0044] 3-4. Target values ​​for water quality indexes 9, when treating acidic wastewater W (see FIG. 1), it is understood that the effect of suppressing the generation of hydrogen sulfide can be obtained by increasing the pH of the wastewater W or the tank water Wa. Also, when the oxidation-reduction potential Eh of the wastewater W is in the range of -0.4 [V] to 0.3 [V], it is understood that the effect of suppressing the generation of hydrogen sulfide can be obtained by increasing the pH of the wastewater W or the tank water Wa. In either case, the effect of suppressing the generation of hydrogen sulfide can be increased by increasing the pH of the wastewater W or the tank water Wa to 8 or more. For example, in FIG. 10, when the water quality of the wastewater W or the tank water Wa is similar to that of the samples A-1, A-2, and A-3, if the pH is increased to 8 or more, the water quality state can be forcibly shifted from the hydrogen sulfide region (region where hydrogen sulfide is easily generated) to the sulfate ion region (region where hydrogen sulfide is not easily generated). Therefore, in order to reliably suppress the generation of hydrogen sulfide, it is effective to set the target pH, which is a water quality index, at 8 or higher.

[0045] 4. Control in wastewater treatment device 101 In a wastewater treatment device 101 (see FIG. 1) that receives wastewater W in a treatment tank 1 and continuously treats it, for example, the pH value of the tank water Wa stored in the treatment tank 1 is detected by a water quality sensor 12, and the conditions for adding alkaline solution D1 (addition amount, addition timing, etc.) are determined based on the detection result (detected pH value) and a target pH value. At this time, by adding alkaline solution D1 so that the pH of the tank water Wa becomes 8 or higher, the generation of hydrogen sulfide in the treatment tank 1 can be reliably suppressed.

[0046] 5. Effects According to the above-mentioned first embodiment, the following advantageous effects are achieved.

[0047] According to the wastewater treatment method of the first embodiment, an alkaline solution D1 is used to increase the pH value of acidic wastewater W containing sulfate salts. The alkaline solution D1 is added to the tank water Wa based on the detection result of the pH of the tank water Wa. By adding the alkaline solution D1 at this time, the pH of the tank water Wa in the treatment tank 1 can be increased to the alkaline side, and a condition in which sulfate ions derived from sulfate salts are likely to remain in the tank water Wa can be created. In other words, this condition is a sulfate ion concentration reduction suppression condition that can suppress the reduction in the sulfate ion concentration in the tank water Wa, and is also a hydrogen sulfide generation suppression condition that can suppress the generation amount of gaseous hydrogen sulfide in the treatment tank 1.

[0048] Therefore, by adding the alkaline solution D1 to the water Wa in the treatment tank 1, the generation of hydrogen sulfide in the treatment tank 1 can be suppressed. Moreover, unlike simply adding the alkaline solution D1 to the water Wa in the tank, the alkaline solution D1 is added while checking the detection result of the pH of the water Wa in the tank. This makes it possible to obtain a certainty of stably suppressing the amount of hydrogen sulfide generated. Furthermore, since the generation of hydrogen sulfide can be suppressed by only adding an adding device for the alkaline solution D1 (a device mainly consisting of a chemical tank 10 and a chemical supply pump 11) and a detection device for a water quality index (a water quality sensor 12) to the treatment tank 1, it is effective in keeping the initial cost of the wastewater treatment facility low compared to using a device that removes hydrogen sulfide once generated, such as an activated carbon deodorizer or a soil deodorizer.

[0049] According to the above-mentioned first embodiment, it is possible to provide a wastewater treatment method capable of stably suppressing the generation of hydrogen sulfide when treating wastewater W containing sulfates at low cost.

[0050] Furthermore, according to the above-described first embodiment, it is possible to manage the water quality of the tank water Wa with pH as the water quality index by using an alkaline solution D1 for increasing the pH value as the chemical D. In this case, the reliability of the effect of suppressing the generation of hydrogen sulfide can be increased by setting the target pH value of the tank water Wa to 8 or more, or by setting the target pH value of the tank water Wa to 8 or more when the redox potential of the wastewater W is in the range of -0.4 [V] to 0.3 [V].

[0051] Furthermore, according to the above-described first embodiment, by treating industrial wastewater, the quality of which varies greatly from one business entity to another, as the wastewater W, it is possible to increase the versatility of the wastewater treatment.

[0052] Moreover, according to the above-mentioned embodiment 1, the wastewater W to be treated can be domestic wastewater, the quality of which varies depending on the lifestyle of the household, thereby making it possible to increase the versatility of the wastewater treatment. Moreover, domestic wastewater is organic wastewater W containing organic matter, and it is known that in water treatment in the presence of sulfate-reducing bacteria, the sulfate-reducing bacteria feed on the organic matter and live there, causing the generation of hydrogen sulfide. Therefore, when the wastewater W is domestic wastewater, the wastewater treatment method of this embodiment is particularly effective in suppressing the generation of hydrogen sulfide in the treatment tank 1.

[0053] In the above-mentioned embodiment 1, the water quality index may be the oxidation-reduction potential Eh, and a chlorine-based disinfectant D2 may be used as the chemical D to increase the value of the oxidation-reduction potential Eh. The value of the oxidation-reduction potential Eh of the tank water Wa may be detected by the water quality sensor 12, and the addition conditions (addition amount, addition timing, etc.) of the chlorine-based disinfectant D2 may be determined based on the detection result and the target value of the oxidation-reduction potential Eh. With reference to FIG. 9, when the oxidation-reduction potential Eh of the tank water Wa is in the range from -0.4 [V] to 0.3 [V], the target value of the oxidation-reduction potential Eh may be set to, for example, 0.3 [V] or more. At this time, the generation of hydrogen sulfide may be reliably suppressed by adding the chlorine-based disinfectant D2 so that the oxidation-reduction potential Eh of the tank water Wa becomes 0.3 [V] or more.

[0054] Hereinafter, other embodiments related to the above-mentioned embodiment 1 will be described with reference to the drawings. In the other embodiments, the same reference numerals as those in the above-mentioned embodiment 1 are used, and the description of the same elements will be omitted.

[0055] (Embodiment 2) In the second embodiment, a wastewater treatment device 102 shown in FIG. 11 is used. The wastewater treatment device 102 differs from the wastewater treatment device 101 of the first embodiment in that it includes a deodorizing device 20 connected to the upper part of the treatment tank 1. The deodorizing device 20 is an auxiliary device and communicates with the internal space 2 of the treatment tank 1. Therefore, gas remaining in the internal space 2 of the treatment tank 1 is introduced into the deodorizing device 20. The deodorizing device 20 performs a deodorizing function by removing hydrogen sulfide remaining in the internal space 2 of the treatment tank 1. For example, an activated carbon deodorizing device or a soil deodorizing device of a known structure can be used as the deodorizing device 20. The other configurations are the same as those of the first embodiment.

[0056] According to the second embodiment, when the generation of hydrogen sulfide cannot be completely suppressed by the wastewater treatment in the treatment tank 1, the hydrogen sulfide generated in the internal space 2 of the treatment tank 1 can be removed by the deodorizing device 20. In addition, the same effects as those of the first embodiment are achieved.

[0057] The present invention is not limited to the above-described embodiment, and various applications and modifications are possible without departing from the scope of the present invention. For example, the following embodiments can be embodied by applying the above-described embodiment.

[0058] In the above embodiment, when the pH of the tank water Wa is used as a water quality index, a preferable target pH value is set to 8 or more, but the target pH value may be a value within the range of 7 to 8.

[0059] In the above-described embodiment, examples have been given of increasing the pH of the tank water Wa by adding an alkaline solution D1, and increasing the redox potential Eh of the tank water Wa by adding a chlorine-based disinfectant D2, but alternatively, both the pH and the redox potential Eh of the tank water Wa may be increased by adding an appropriate chemical D. [Explanation of symbols]

[0060] 1...Treatment tank D: Drug D1: Alkaline solution D2: Chlorine-based disinfectant Eh: Redox potential S101~S106…Wastewater treatment methods W…Wastewater Wa…tank water

Claims

1. A method for treating wastewater containing sulfate, comprising the steps of: The wastewater is introduced into a treatment tank; Detecting a water quality index value of the water in the treatment tank; Adding a chemical to the water in the tank to increase at least one of the pH and the oxidation-reduction potential based on the detection result of the water quality index. Wastewater treatment methods.

2. 2. The wastewater treatment method according to claim 1, wherein the water quality index is pH, and an alkaline solution is used as the chemical agent for increasing the pH value.

3. 3. The wastewater treatment method according to claim 2, wherein the target pH value of the water in the tank is 8 or higher.

4. The wastewater treatment method according to claim 2, wherein the target pH value of the water in the tank is set to 8 or more when the oxidation-reduction potential of the wastewater is in the range of -0.4 [V] to 0.3 [V].

5. 2. The wastewater treatment method according to claim 1, wherein the water quality index is an oxidation-reduction potential, and a chlorine-based disinfectant is used as the chemical agent for increasing the value of the oxidation-reduction potential.

6. The method for treating wastewater according to any one of claims 1 to 5, wherein the wastewater is industrial wastewater.

7. The wastewater treatment method according to any one of claims 1 to 5, wherein the wastewater is domestic wastewater.

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