JP4831782B2 - Wastewater treatment method and system - Google Patents

Description

  The present invention relates to a wastewater treatment method and system particularly suitable for wastewater having a relatively high concentration.

Conventionally, there are various types of wastewater such as liquid crystal factory wastewater, kitchen wastewater, etc. These wastewaters were originally clean water, but after use they are contaminated with organic components and others.
There are various types of drainage, but the amount and quality of water varies depending on the day and time. For example, even on the same day, depending on the time of day, the COD (chemical oxygen demand) is close to 2,000 ppm when it is high, and when it is low, it drops below 1,000 ppm. Therefore, during treatment, the amount of water and water quality are averaged, and in order to dilute to a predetermined concentration that can be treated (in the case of biological treatment, it is said to be about 500 ppm of COD), one day's worth of water is stored in the adjustment tank . That is, if the amount to be processed daily is 1,000 tons, an adjustment tank (pit) having a size of 1,000 tons + α is provided and stored there. In this way, even if the COD fluctuates by a factor of half from 1,000 to 2,000 ppm, the water quality is gradually and uniformly averaged as it is stored in the adjustment tank, and at the next day, it reaches about 1,500 ppm. When the treatment is performed after averaging in this way, the influence of the up-down of the original amount and quality of the wastewater can be reduced and the treatment can be stabilized.
However, there is a problem that a large pit of the adjustment tank is necessary to store the wastewater, and even if the adjustment tank is used, the water quality during processing may fluctuate due to daily fluctuations. there were.
Japanese Patent Laid-Open No. 11-347596

  Therefore, the present invention is intended to provide a wastewater treatment method and system that do not necessarily require a regulating tank and can absorb daily fluctuations in water quality.

In order to solve the above problems, the present invention takes the following technical means.
(1) In the wastewater treatment method of the present invention, the treated clean water is fed back to and mixed with the wastewater before treatment to adjust the water to be treated by this treatment method, and the treated clean water for the wastewater before treatment is treated. The amount of the mixture is set so that the concentration index and flow rate of the water to be treated are within a predetermined range suitable for treatment, and the concentration index of the water to be treated is detected by a sensor. It is characterized in that the feedback amount of the clean water after the treatment to the waste water before the treatment and the discharge amount from this treatment system are controlled so that the concentration index of the water to be treated falls within a predetermined range.
Examples of the treatment of waste water include biological treatment, treatment by electrolysis, treatment of adding an oxidizing agent (sodium hypochlorite, etc.), and the like. Examples of the concentration index include COD (chemical oxygen demand), BOD (biochemical oxygen demand), TOC, TN, and n-hexane.

According to this wastewater treatment method, “clean water after treatment (for example, less than COD of 5 ppm)” is fed back to “untreated wastewater (for example, COD 1000 to 2000 ppm)” and mixed to adjust “treatment water” by this treatment method. However, the amount of “clean water after treatment” with respect to “drain water before treatment” is the concentration of “water to be treated” for the type of waste water treatment (biological treatment or electrolysis treatment, etc.) The index and the flow rate are set so as to be within a predetermined range suitable for treatment, and the concentration indicators of the “drain before treatment”, “clean water after treatment”, and “treatment water” are sensors (for example, COD The “treatment water” concentration index is within a specified range (for example, COD of 50 to 100 ppm in the case of treatment by electrolysis or addition of an oxidizing agent). `` After clean water '' feedback amount and this processing Since the amount of discharge from the science system is controlled, by adjusting the water to be treated by feeding back clean water after treatment, the impact on the treatment due to fluctuations in the concentration of the original wastewater itself can be reduced. Smooth processing can be performed. In addition, clean water after treatment is used for adjustment, which can save water resources and contribute to environmental problems.
Here, if the sensor detects not only the water to be treated but also the concentration index of the waste water before the treatment and the purified water after the treatment, the concentration index of the original waste water and the clean water discharged from the system is also grasped. Since it is possible, it is preferable about clean water to be discharged in practice.
By the way, when the treatment mode is electrolysis, an electrolyte such as sodium chloride is dissolved in the waste water as necessary to give an appropriate conductivity so that a current flows, and the anodic oxidation and generated OH radicals, etc. Reduces COD by oxidizing and decomposing organic components contained in wastewater by oxidizing action. The pH during treatment (during treatment) of the water to be treated is adjusted to a range in which an oxidizing action such as hypochlorous acid generated by electrolysis is strong. Unlike the biological treatment, this electrolysis treatment has an advantage that oxidative decomposition is performed instantaneously and sludge is not generated.

(2) An oxidant generation electrolysis mechanism that electrolyzes water containing an electrolyte to generate hypohalous acid, and the oxidant-containing water generated by the oxidant generation electrolysis mechanism is applied to the water to be treated. The concentration index is reduced, and the electrolyte separated from the treated clean water is fed back and mixed with the wastewater before treatment, and the separated and recovered electrolyte is supplied to the oxidant-generating electrolysis mechanism. Good.
Here, examples of the electrolyte include sodium chloride (sodium chloride) and sodium bromide. For example, seawater can be used as the water containing the electrolyte. Examples of the hypohalous acid include hypochlorous acid and hypobromous acid. As a means for separating the electrolyte, an RO membrane, an ion exchange resin, electrodialysis, or an ion separator can be used.
Constructed in this way, the oxidant-containing water generated by the oxidant-generating electrolysis mechanism is applied to the water to be treated to reduce the concentration index, and the electrolyte separated from the treated clean water is fed back Since it was mixed with the wastewater before treatment, the electrolyte was separated from the clean water after treatment that was fed back and mixed with the wastewater before treatment, and the electrolyte concentration increased cumulatively during treatment. Can be avoided. In addition, since the separated and recovered electrolyte is supplied to the oxidant-generating electrolysis mechanism, the electrolyte contained in the oxidant-containing water can be circulated to the oxidant-generating mechanism and effectively used.

(3) The wastewater treatment system of the present invention comprises a treated water tank for treating wastewater and a return flow path for feeding back the treated clean water, and the treated water in the treated water tank is treated as wastewater before treatment. The amount of water to be treated is adjusted by feeding back and mixing through the return flow path, and the amount of clean water after treatment with respect to the waste water before treatment is the concentration index and flow rate of the water to be treated for the aspect of the waste water treatment. Is set so as to be within a predetermined range suitable for treatment, and the concentration index of the water to be treated is detected by a sensor, and the waste water before treatment is treated so that the concentration index of the water to be treated falls within the predetermined range. It is characterized in that the amount of feedback of the subsequent clean water and the amount of discharge from this treatment system are controlled.
This waste water treatment system has the same action as the waste water treatment method. Here, it is preferable to store tap water (or clean water after the previous treatment) at the start of the treatment (because there is no clean water after treatment) in the treated water tank that performs the treatment by supplying wastewater.

The present invention is configured as described above and has the following effects.
By adjusting the water to be treated by feeding back clean water after treatment, the effect on the treatment due to fluctuations in the concentration of the original wastewater itself can be reduced and smooth treatment can be performed. It can absorb daily fluctuations in water quality without need.

There are various types of wastewater, such as factory wastewater, kitchen wastewater, etc., but the treatment methods include biological treatment methods, coagulation sedimentation methods, treatment methods by electrolysis, treatment methods that add oxidizing agents (such as sodium hypochlorite), etc. There are also BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), TOC, TN, n-Hexane, etc. as concentration indicators for evaluating the degree of contamination of wastewater.
By the way, the amount of water and the quality of drainage vary considerably depending on the time and time zone. For example, in the case of an LCD TV manufacturing plant, the operating status of production facilities varies greatly depending on the demand environment of the world, such as the timing of the preparation for bonus sales, and even if it is designed to be planned production A large amount of wastewater is generated during full operation, but after that time it may change completely and become almost closed. Also, the amount of drainage differs considerably between the time when there are many people and the amount of water used is high and the time when there are few people. Therefore, although a large pit was excavated as a wastewater storage tank on the site (requires a considerable site area), the wastewater was stored in this pit to try to average and equalize the water volume and water quality as much as possible. The quality of the wastewater to be treated coming out of this is changing unexpectedly. Therefore, there were cases where the BOD concentration and COD concentration were too high or low during the actual treatment, so that proper treatment could not be performed. In other words, the wastewater could not be purified properly.
For this reason, a plurality of large evaporators are arranged side by side, and each waste water is evaporated and reliquefied (concentrated to a residue without concentrating high-concentration organic components), and the re-liquefied portion (high-concentration organic components are reduced). COD has also been reduced to some extent), and attempts have been made to dispose of the evaporation residue as waste, but if there is a large amount of wastewater, a large amount of fuel is required and it is said to be the best policy. It is difficult and also requires great costs and labor to transport the waste residue.
This wastewater treatment method and system is based on how to reduce and absorb this fluctuation while accepting that the quantity and quality of the wastewater is fluctuating. It is composed.

Embodiments of the present invention will be described below.
(Embodiment 1)
In this wastewater treatment method, the treated wastewater (COD 1000 to 2000 ppm) 1 is fed back to the treated clean water (COD less than 5 ppm, preferably almost 0 ppm) 2 and mixed. The water 4 to be treated is adjusted by a treatment method in which 3 sodium hypochlorite is added to oxidatively decompose. In this embodiment, wastewater having a COD of 1000 to 2000 ppm is treated. However, any concentration of wastewater, for example, wastewater having a high concentration of COD of 300,000 ppm can be applied.
On the other hand, this waste water treatment system is an apparatus of the above waste water treatment method, and includes a treated water tank 5 for treating waste water and a return flow path 6 for feeding back clean water 2 after the treatment. The treated clean water 2 in the treated water tank 5 is fed back through the return flow path 6 and mixed to adjust the treated water 4. The treated clean water 2 is fed back and mixed with the untreated waste water 1 to adjust the treatment target water 4. However, external clean water such as tap water may also be mixed. (Not shown).
The amount of clean water 2 after treatment with respect to the waste water 1 before treatment is an aspect of the waste water treatment (whether it is an oxidant addition method, an electrolysis treatment method, a biological treatment method, etc.) Is set so that the concentration index (COD) and the flow rate of the water to be treated 4 are within a predetermined range suitable for the treatment, the waste water 1 before the treatment, the clean water 2 after the treatment, and the water to be treated 4 Is detected by a sensor (COD meter), and the concentration index of the water 4 to be treated can be within a predetermined range (for example, COD of 50 to 100 ppm in the treatment by electrolysis or addition of an oxidizing agent, In this case, the feedback amount A of the clean water 2 after the treatment to the waste water 1 before the treatment and the discharge amount B from this treatment system are controlled so as to be about 400 to 600 ppm. In addition, the sensor of the density | concentration index of the waste water 1 before a process is shown by S1, the sensor of the density | concentration index of the clean water 2 after a process is shown by S2, and the sensor of the density | concentration index of the process target water 4 is shown by S3.

  By the way, the predetermined range in which the concentration index (COD) and the flow rate of the water to be treated 4 are suitable for treatment is specific to each treatment device (electrolysis or oxidant addition) or treatment facility (biological treatment or coagulation sedimentation). It depends on the specific specifications. That is, in the treatment by electrolysis or addition of an oxidizing agent, the COD of 10 to 20 ppm or other ranges are preferable instead of the above-mentioned COD of 50 to 100 ppm depending on the specification and concept of the apparatus. That is, when the predetermined range of the concentration index of the water to be treated 4 is set to a lower concentration range (COD 10 to 20 ppm), there is an advantage that fluctuations in drainage water quality and the like can be reduced and absorbed. . On the other hand, when the predetermined range of the concentration index of the water 4 to be treated is set to COD 50-100 ppm, the total amount of treatment can be reduced by reducing the amount of feedback of the treated clean water 2. There is. Nevertheless, in view of the specifications and concepts of the treatment apparatus and treatment facility, there is clearly a predetermined range in which the concentration index (COD) and flow rate of the treatment target water 4 are suitable for treatment.

  If the concentration range (COD) and flow rate of the water 4 to be treated is a predetermined range suitable for treatment of COD of 50 to 100 ppm, the basic setting is 1 amount of waste water (COD 1000 to 2000 ppm) 1 before treatment. The amount of clean water (COD less than 5ppm, preferably less than 0ppm) 2 after treatment 19 is fed back and mixed to adjust the water to be treated (COD 50-100ppm) 4 and treated with sodium hypochlorite. The water tank 5 is oxidized and decomposed, and the amount 1 of clean water 2 after treatment is discharged out of the treatment system, but the feedback amount A and the discharge amount B from the treatment system can be changed according to changes in water quality. I have control. That is, when the COD of the concentration index of the water 4 to be treated is detected to be higher than the predetermined concentration range (50 to 100 ppm) by the sensor COD meter, the feedback amount A is increased and the discharge amount B from the processing system is decreased. To control. Conversely, when the COD of the concentration index of the water to be treated 4 is detected to be lower than the predetermined concentration range (50 to 100), control is performed to reduce the feedback amount A and increase the discharge amount B from the processing system.

In addition, as described above, this embodiment is a treatment method in which sodium hypochlorite (oxidant) is added, and an oxidant-generating electrolysis mechanism 7 that electrolyzes water containing an electrolyte to generate hypohalous acid. It comprises. 8 is an electrolytic electrode. And the oxidizing agent containing water 3 produced | generated by the said oxidizing agent production | generation electrolysis mechanism 7 is exerted on the said process target water 4 (it is made to inject | pour into the return flow path 6 in this embodiment), and the reduction process of the density | concentration parameter | index is performed. In the electrolyte separation means 9, the separated electrolyte from the treated clean water 2 is fed back and mixed with the wastewater 1 before treatment, and the separated and recovered electrolyte is supplied to the oxidant-generating electrolysis mechanism 7. ing. Here, since the amount of water supplied as the electrolyte to the oxidant-generating electrolysis mechanism 7 is reduced from the treated clean water 2, tap water is replenished to the return flow path 6 to compensate for the reduced amount. May be.
Examples of the electrolyte include sodium chloride (sodium chloride) and sodium bromide. For example, seawater can be used as the water containing the electrolyte. Examples of the hypohalous acid include hypochlorous acid and hypobromous acid. As the electrolyte separation means 9, an RO membrane, an ion exchange resin, electrodialysis, or an ion separator can be used.
In addition, since the treated water tank 5 that performs the wastewater treatment does not yet have the treated clean water 2 at the start of the treatment, it is preferable to store the tap water or the treated water 2 after the previous treatment. Moreover, when ss components etc. are mixed in the waste water, it is filtered in advance with a sand filter or the like.

Next, the use state of the waste water treatment method and system of this embodiment will be described.
According to this wastewater treatment method and system, the wastewater before treatment (COD 1000 to 2000 ppm) 1 is fed back to the treated clean water 2 (COD less than 5 ppm, preferably almost 0 ppm) and mixed to this treatment method (oxidizer) The amount of water 4 to be treated is adjusted by a treatment method in which sodium hypochlorite is added and oxidatively decomposed, and the amount of clean water 2 after treatment with respect to waste water 1 before treatment is determined according to the mode of wastewater treatment (of oxidant). And the concentration index and flow rate of the water to be treated 4 are set to be within a predetermined range suitable for the treatment, as to whether it is an addition method, a treatment method by electrolysis, a biological treatment method, etc. The concentration index of the treatment target water 4 is detected by a sensor (COD meter), and the treated waste water 1 is cleaned after treatment so that the concentration index of the treatment target water 4 falls within a predetermined range (COD 50-100 ppm). Water 2 feedback amount A and this Since the amount of discharge B from the system is controlled, the treated water 4 is adjusted by feeding back the treated clean water 2 so that the effect on the treatment due to fluctuations in the concentration of the original wastewater itself can be reduced. It is possible to reduce and smooth the treatment, and there is an advantage that the adjustment tank is not always necessary and can absorb the daily fluctuation of the water quality. Moreover, the clean water 2 after processing is used for adjustment, and there exists an advantage that a water resource can be saved and it can contribute to an environmental problem.

Further, the oxidant-containing water 3 generated by the oxidant-generating electrolysis mechanism 7 is applied to the water 4 to be treated to reduce its concentration index, and the electrolyte separation means 9 separates the electrolyte from the treated clean water 2. Since the wastewater 1 was fed back and mixed with the wastewater 1 before treatment, the electrolyte was separated from the treated clean water 2 fed back and mixed with the wastewater 1 before treatment. It can be avoided that the concentration of the electrolyte of the target water 4 increases cumulatively during the treatment. Furthermore, since the separated and recovered electrolyte is supplied to the oxidant-generating electrolysis mechanism 7, there is an advantage that the electrolyte contained in the oxidant-containing water 3 can be circulated to the oxidant-generating mechanism and effectively used. is there.
In addition, since the treated clean water 2 has a reduced concentration of the soil evaluation index as described above (less than 5 ppm COD), it can be recycled for various uses and contributes to environmental problems through provision of water resources. There is an advantage that you can. Moreover, there exists an advantage that it can process directly in real time, without storing the waste_water | drain 1 before a process in an adjustment tank etc.

(Embodiment 2)
In this embodiment, the wastewater treatment mode is electrolysis (not shown), and an electrolyte such as sodium chloride is dissolved in the wastewater to give an appropriate conductivity as required when the wastewater conductivity is low. By causing an electric current to flow, the organic components contained in the wastewater are oxidatively decomposed to reduce its COD by anodic oxidation and oxidizing action such as generated OH radicals. The pH during treatment (during treatment) of the water to be treated is adjusted to a range in which an oxidizing action such as hypochlorous acid generated by electrolysis is strong.
Specifically, an electrolyte such as sodium chloride is added so that the electrolysis can be performed with respect to the conductivity of the water to be treated, and an electrolytic electrode is inserted into the treatment water tank to directly electrolyze the water to be treated. . Unlike the biological treatment, this electrolysis treatment has an advantage that oxidative decomposition is performed instantaneously and sludge is not generated.

  By adjusting the water to be treated by feeding back clean water after treatment, the effect on the treatment due to fluctuations in the concentration of the original wastewater itself can be reduced and smooth treatment can be performed. It can absorb daily fluctuations of water quality without necessity, and can be applied and applied to water treatment of liquid crystal factory wastewater, kitchen wastewater and other various wastewater.

The processing flowchart explaining embodiment of the waste water treatment system of this invention.

Explanation of symbols

1 Wastewater before treatment 2 Clean water after treatment 3 Water containing oxidant 4 Water to be treated 5 Treated water tank 6 Return flow path 7 Oxidant production electrolysis mechanism

Claims (2)

The treated clean water 2 is fed back and mixed with the waste water 1 before treatment to adjust the treatment target water 4 by this waste water treatment method, and the mixing amount of the treated clean water 2 with respect to the waste water 1 before treatment is: About the aspect of the wastewater treatment, the concentration index and flow rate of the treatment target water 4 are set to be within a predetermined range suitable for treatment, and the concentration index of the treatment target water 4 is detected by a sensor, and the treatment target water 4 The amount of feedback of clean water 2 after treatment to the waste water 1 before treatment and the amount discharged from this treatment system are controlled so that the concentration index of 4 falls within a predetermined range, and the water containing the electrolyte is An oxidizing agent generation electrolysis mechanism 7 that decomposes to generate hypohalous acid is provided, and the oxidizing agent-containing water 3 generated by the oxidizing agent generation electrolysis mechanism 7 is applied to the water 4 to be treated to reduce its concentration index. And after processing With mixing from the clean water 2 to wastewater 1 pretreatment by feeding back the one separating the electrolyte, the waste water treatment method is separated and recovered electrolyte characterized by being adapted to supply to the oxidant generating electrolytic mechanism 7. A treated water tank 5 for treating the waste water and a return flow path 6 for feeding back the treated clean water 2 are provided, and the treated clean water 2 after treatment in the treated water tank 5 is passed through the return flow path 6 to the waste water 1 before treatment. The water to be treated 4 is mixed to adjust the treatment target water 4, and the mixed amount of the treated clean water 2 with respect to the waste water 1 before the treatment is the concentration index and flow rate of the treatment target water 4 for the aspect of the waste water treatment. Is set so as to be within a predetermined range suitable for treatment, and the concentration index of the water to be treated 4 is detected by a sensor, and the waste water 1 before treatment so that the concentration index of the water to be treated 4 falls within the predetermined range. An oxidant-generating electrolysis mechanism 7 for controlling the feedback amount of the clean water 2 after the treatment and the discharge amount from the treatment system and electrolyzing the water containing the electrolyte to produce hypohalous acid. Comprising the oxidant-generating electrolysis The oxidizing agent-containing water 3 generated in the structure 7 is applied to the water 4 to be treated to reduce its concentration index, and the electrolyte separated from the treated clean water 2 is fed back to the wastewater 1 before treatment. A wastewater treatment system characterized in that while being mixed, the separated and recovered electrolyte is supplied to an oxidant-generating electrolysis mechanism 7 .