JP5686465B2 - Water treatment method and water treatment system using the same - Google Patents

Description

  The present invention relates to a water treatment method and a water treatment system using the same.

  In this specification, “water treatment” means “water purification”, and in addition to operations for reducing chemical oxygen demand (hereinafter referred to as COD) in wastewater, the wastewater is disinfected, sterilized, decolorized, etc. And operations for reducing biological oxygen demand (hereinafter referred to as BOD) in wastewater, decomposing non-biodegradable substances and organic substances, improving transparency, and the like.

  Furthermore, waste water (sometimes referred to as treated water) in the present invention is leached water, sewage, secondary treated water for sewage treatment, human waste, wastewater after septic tank sludge treatment, wastewater after coagulation sedimentation treatment, waste incineration facility Wastewater from the factory, general wastewater from factories, etc.

  In recent years, interest in water has been greatly increased, as it is said that “the 21st century is the century of water”, and the supply of safe water and the spread of sewage treatment (wastewater treatment) facilities are serious problems. In addition, since water resources are limited, the importance of purifying and reusing wastewater has been recognized again.

  In general, a biological treatment method represented by an activated sludge method is used for wastewater treatment. However, although the biological treatment method has a very high BOD reduction effect, the effect of reducing COD derived from hardly biodegradable substances is small. Therefore, a separate process is required to obtain a high COD reduction effect. Particularly in recent years, there are many places where COD in closed waters has not achieved environmental standards, and reduction of COD is often regarded as important.

  For example, in order to reduce the COD of wastewater, attempts have been made to reduce the COD using ozone gas. When ozone gas is used, for example, it is known that running costs can be reduced compared to treatment using activated carbon. However, when the COD reduction process is performed using ozone gas, although the COD can be quickly reduced at the beginning of the reaction, the process effect is limited.

  Usually, after reducing the COD of about 30 to 60% of the wastewater, even if the injection amount of ozone gas is increased, the effect of reducing the COD is not so much obtained. Therefore, such treatment with ozone gas is not effective unless the target COD reduction rate is low. In addition, it is generally known that when wastewater is treated with ozone gas, the hardly biodegradable substance in the wastewater is converted into an easily biodegradable substance, resulting in an increase in BOD.

  Thus, it has been proposed so far to perform treatment with hydrogen peroxide in addition to ozone treatment as described above on wastewater (for example, see Patent Document 1 below).

  In addition to ozone treatment, treatment with hydrogen peroxide (treatment of ozone treatment and hydrogen peroxide collectively, hereinafter referred to as accelerated oxidation treatment) reacts with dissolved ozone and hydrogen peroxide in wastewater. As a result, hydroxyl radicals (OH radicals), which are strong oxidizing agents, are generated. Then, the strong oxidizing power of the OH radical makes it possible to completely oxidize and decompose organic substances such as COD that could not be completely decomposed by ozone treatment.

  However, when hydrogen peroxide is excessively injected into the wastewater in the above-described accelerated oxidation treatment, the activity of the microorganism group is caused by the bactericidal action of the hydrogen peroxide remaining in the wastewater, for example, when biological treatment is performed thereafter. Is inhibited, and in some cases, the microorganism group is killed.

  Furthermore, depending on the amount of ozone gas and hydrogen peroxide injected into the wastewater (especially when hydrogen peroxide is insufficient relative to the ozone gas), impurities (chloride ions, bromide ions) in the wastewater are oxidized by dissolved ozone, Oxidizing substances (halogen oxides such as hypochlorous acid and hypobromite) may be generated. Since this oxidizing substance has a stronger bactericidal action against microbial groups than the above-mentioned bactericidal action of hydrogen peroxide remaining in the wastewater, there is a concern about adverse effects on biological treatment.

  In general, the amount of ozone gas and hydrogen peroxide injected into the wastewater is controlled to achieve a certain condition (optimum dissolved ozone concentration in the wastewater or optimum dissolved hydrogen peroxide concentration in the wastewater) in the accelerated oxidation treatment. In order to maintain, the numerical value which becomes the parameter | index of the state of the wastewater in the said accelerated oxidation process is measured with various measuring devices. And in order to suppress the processing cost in the accelerated oxidation treatment (saving of the injection amount of ozone gas and hydrogen peroxide), it is indispensable to control the injection amount of ozone gas and hydrogen peroxide according to the measurement result (for example, below) Patent Documents 2 and 3).

  For example, as an index for grasping the state of wastewater during accelerated oxidation treatment, “dissolved ozone concentration” and “dissolved hydrogen peroxide concentration” of wastewater during accelerated oxidation treatment, or impurities generated in wastewater are oxidized. There is a “residual chlorine concentration” that is an index of how much oxidizing substances are present in the wastewater during the accelerated oxidation treatment. In addition, some sensors dedicated to measuring these indices have been put into practical use and are commercially available.

  However, many of the above-mentioned dedicated sensors can be used when there is little mixing of substances that cause an error in the measured value (for example, fresh water). It is very difficult to measure each index, and it is necessary to use a special device. Therefore, wastewater cannot be processed at low cost.

  In other words, if hydrogen peroxide remains in the wastewater after the accelerated oxidation treatment, not only the microbial group is sterilized in the subsequent biological treatment, but also the injection rate of ozone gas and hydrogen peroxide in the accelerated oxidation treatment is not appropriate. In this case, there has been a problem that an oxidizing substance having a stronger bactericidal action on the microorganism group than hydrogen peroxide is generated in the wastewater.

JP 2010-58078 A JP 2006-272080 A JP 2006-272081 A

  Therefore, there has been a demand for a water treatment method and a water treatment system using the water treatment method that do not adversely affect biological treatment even if the accelerated oxidation treatment is performed on the wastewater by a simple method while suppressing cost.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a water treatment method capable of obtaining stable treated water at a low cost and a simple method, and a water treatment system using the same. And

In order to achieve the above object, the present invention provides a water treatment method for purifying water to be treated containing at least iron or manganese, and a coloring component that becomes colorless and transparent by the coexistence of ozone gas and hydrogen peroxide. A first step of performing an accelerated oxidation treatment with ozone gas and hydrogen peroxide on the treated water, a second step of performing a hydrogen peroxide decomposition treatment after the first step, and a third step of performing a biological treatment after the second step with the door, in a first step, the color of the water to be treated, without being colored brown or pink color from iron or manganese in the vicinity of the injection point of the ozone gas, and colorless at a distance from the injection point of the ozone gas If no Do et transparent is characterized by increasing the injection quantity of hydrogen peroxide, water treatment method, and a water treatment system using the water treatment method, the line a first step A water treatment system comprising an accelerated oxidation treatment tank, a hydrogen peroxide decomposition treatment tank that performs the second step after the accelerated oxidation treatment tank, and a biological treatment tank that performs the third step after the hydrogen peroxide decomposition treatment tank It is.

In the second step, activated carbon is added to and mixed with the accelerated oxidation treated water in the first step, and hydrogen peroxide remaining in the accelerated oxidized treated water is decomposed .

  The water treatment method according to the present invention and the water treatment system using the water treatment method are particularly characterized in that the chemical oxygen demand (COD) in the water to be treated is reduced.

  According to the present invention, for example, the reaction of impurities (chloride ions and bromide ions) in treated water to be oxidized by ozone to become an oxidizing substance (halogen oxides such as hypochlorous acid and hypobromite) is suppressed. Therefore, even if hydrogen peroxide is injected slightly excessively, in the biological treatment which is the subsequent treatment, the activity of the microorganism group responsible for the biological treatment is not inhibited. That is, stable treated water can be obtained by a simple method of providing a hydrogen peroxide decomposition tank after the accelerated oxidation treatment tank without inhibiting the activity of the microorganism group responsible for biological treatment.

  In addition, the decomposition of hydrogen peroxide does not use adsorption of hydrogen peroxide by the activated carbon but uses a catalytic reaction, and activated carbon can be used sufficiently even with used activated carbon. Therefore, hydrogen peroxide can be decomposed at low cost, and as a result, treated water can be obtained at low cost.

  Furthermore, it is possible to control the appropriate injection amount of ozone gas and hydrogen peroxide by a simple method such as confirming the color of the water to be treated in the first step without using special equipment or equipment, etc. The reaction state of the water to be treated in the oxidation treatment tank 1 can be immediately and easily grasped, and the appropriate reaction state (for example, dissolved ozone concentration 0 to 0.1 mg / L, residual chlorine concentration 0 to 2 mg / L) Can keep.

The schematic diagram which shows the water treatment system using the water treatment method which concerns on 1st Embodiment. The schematic diagram which shows the water treatment system using the water treatment method which concerns on 2nd Embodiment.

  A water treatment method and a water treatment system using the water treatment method according to the present invention are characterized by performing an oxidation treatment in which ozone gas and hydrogen peroxide are injected into water to be treated, and then performing a hydrogen peroxide decomposition treatment. To do. In the following description, the oxidation treatment for supplying ozone gas and hydrogen peroxide to the water to be treated is referred to as accelerated oxidation treatment.

  Furthermore, the water treatment method and the water treatment system using the same according to the present invention perform the biological treatment after the hydrogen peroxide decomposition treatment, and reuse the biologically treated water by the biological treatment in the accelerated oxidation treatment. . That is, it is also characterized in that the water to be treated is subjected to circulation treatment between accelerated oxidation treatment, hydrogen peroxide decomposition treatment, and biological treatment.

  In addition, as described above, in order to obtain stable treated water that is safe and has very little fluctuation in water quality, it is required to control the injection amounts of ozone gas and hydrogen peroxide within an appropriate range in the above-described accelerated oxidation treatment. It is done. As a result of diligent examination, the present applicant pays attention to the color change of the water to be treated during the accelerated oxidation treatment, and uses the color change as an index of the accelerated oxidation treatment, so that it is a simple method and at a low cost. It has also been found that the injection amounts of ozone gas and hydrogen peroxide can be controlled within an appropriate range.

  Hereinafter, a water treatment method according to the present invention and a water treatment system using the same will be described with reference to the drawings. Note that these descriptions do not limit the present invention, and it goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

  In addition, although there is no particular limitation on the “treated water” that is the subject of the present invention, for example, those requiring water treatment such as final disposal site leachate, sewage secondary treated water, factory effluent, agricultural effluent, and garbage effluent. Say. In particular, the water treatment method of the present invention and the water treatment system using the water treatment system include a final disposal site leachate having a high chloride ion concentration and easily generating hypochlorous acid, the necessity of water purification, and the treated water obtained. This is particularly suitable for water treatment of sewage secondary treated water having higher utility. Although there is no particular limitation, for example, COD is 50 mg / L or more, or COD is 15 to 30 mg / L, and it is effective in reducing COD of water to be treated containing a biodegradable substance, and the chloride ion concentration is 200 mg / L. Of course, the water to be treated can also be treated water whose chloride ion concentration exceeds 200 mg / L, and further exceeds 5000 mg / L.

(First embodiment)
First, a water treatment method according to a first embodiment of the present invention and a water treatment system using the water treatment method will be described.

  Drawing 1 is a mimetic diagram showing the water treatment system using the water treatment method concerning a 1st embodiment of the present invention. In FIG. 1, 1A is an accelerated oxidation treatment tank that performs an accelerated oxidation treatment on the water to be treated α, and 2 is a hydrogen peroxide decomposition tank for decomposing hydrogen peroxide in waste water from the accelerated oxidation treatment tank. Reference numeral 3 denotes a biological treatment tank that performs biological treatment on the wastewater from the hydrogen peroxide decomposition tank.

  The waste water from the biological treatment tank 3 flows into the treated water tank 4 and is circulated between accelerated oxidation treatment, hydrogen peroxide decomposition treatment, and biological treatment by a circulation pump 41 provided in the treated water tank 4. It has a configuration. The accelerated oxidation treatment is an example of the first step described in the claims, the hydrogen peroxide decomposition treatment is an example of the second step of the claims, and the biological treatment is an example of the third step of the claims. Each corresponds.

  Below, first, the structure and operation | movement of 1 A of accelerated oxidation processing tanks, the hydrogen peroxide decomposition tank 2, and the biological treatment tank 3 are demonstrated in order, respectively. Then, control of the injection amount of ozone gas and hydrogen peroxide focusing on the color change of the water to be treated α will be described.

1. Configuration of Water Treatment System First, the configuration of the accelerated oxidation treatment tank 1A and the treatment in the accelerated oxidation treatment tank 1A will be described.

  As shown in FIG. 1, the accelerated oxidation treatment tank 1 </ b> A is a tank that performs accelerated oxidation treatment with ozone gas and hydrogen peroxide on the water to be treated α with ozone gas β and hydrogen peroxide γ. Further, as will become apparent from the description below, the accelerated oxidation treatment tank 1A is provided with observation windows 11a to 11c that can confirm the state of the water 12 to be treated in the accelerated oxidation treatment tank 1A.

  First, the water to be treated α is transferred to the accelerated oxidation treatment tank 1A by a pump (not shown), and ozone gas β is supplied to the treated water α in the accelerated oxidation treatment tank 1A.

  Furthermore, as shown in FIG. 1, the aqueous solution of hydrogen peroxide γ from the hydrogen peroxide tank 6 is supplied to the water to be treated α with respect to the water to be treated α before being transferred to the accelerated oxidation treatment tank 1A. .

  Thus, by supplying the ozone gas β and hydrogen peroxide γ, in the accelerated oxidation tank 1A, the dissolved ozone in the water to be treated α reacts with hydrogen peroxide to generate a hydroxyl radical (hereinafter referred to as a strong oxidizing agent). , And sometimes referred to as OH radicals), and the oxidizable substance is oxidized, for example, the pollutant such as the hardly biodegradable substance in the water to be treated α is decomposed by the strong oxidizing power of the OH radical. COD and the like are reduced.

  The ozone gas β is supplied from the ozone gas generator 5 as shown in FIG. 1, but is not particularly limited as long as it is various means capable of generating ozone gas. For example, the ozone gas generator 5 may generate the ozone gas β with oxygen supplied from an oxygen generator (not shown).

  A part of the ozone gas β used for the reaction in the accelerated reaction treatment tank 1A is transferred from the accelerated reaction treatment tank 1A to the waste ozone decomposition apparatus 7, decomposed, and discharged outside the system. (Dashed arrow in FIG. 1).

  Next, the configuration of the hydrogen peroxide decomposition tank 2 and the processing in the hydrogen peroxide decomposition tank 2 will be described. First, an outline of the hydrogen peroxide decomposition tank 2 will be briefly described.

  As shown in FIG. 1, to-be-treated water α oxidized in the accelerated oxidation treatment tank 1A is transferred to the hydrogen peroxide decomposition tank 2. The hydrogen peroxide contained in the water to be treated α is decomposed in the hydrogen peroxide decomposition tank 2.

  By the way, generally, in the reaction in the accelerated oxidation treatment tank 1A, the injection amount of hydrogen peroxide γ with respect to the injection amount of ozone gas β according to the property of the water to be treated α is known. For example, generally, the properties of treated water to be treated in a wastewater treatment facility are measured in advance by various measuring methods to obtain an optimal ozone gas injection amount. In many cases, hydrogen peroxide is injected into the water to be treated while being fixed within a range of about 10% to 50% with respect to the injection amount of ozone gas.

  On the other hand, in general, hydrogen peroxide was not excessively injected into the treated water in order to reduce running costs in the wastewater treatment facility.

  However, by injecting hydrogen peroxide into the treated water in a slight excess, impurities (chlorine ions and bromide ions) in the treated water are oxidized by ozone gas and oxidized (hypochlorous acid, hypochlorous acid). It has also become clear that it is possible to suppress the reaction that becomes a halogen oxide). Further, in the water treatment method and the water treatment system using the same according to the present invention, it is planned to inject hydrogen peroxide into the water to be treated a little excessively for the above purpose.

  Therefore, the activity of microorganisms responsible for biological treatment in the biological treatment tank 3 is inhibited by the sterilization action of hydrogen peroxide remaining in the treated water α by the treated water α transferred to the biological treatment tank 3 described later. There is no doubt. Therefore, in the water treatment method and the water treatment system using the water treatment method according to the present invention, hydrogen peroxide (residual hydrogen peroxide which is excessively injected into the water to be treated α before being transferred to the biological treatment tank 3 described later). ) Is immediately transferred to the hydrogen peroxide decomposition tank 2 before being transferred to the biological treatment tank 3, and the hydrogen peroxide decomposition tank 2 Decomposes hydrogen peroxide remaining in the water to be treated α.

  Hereinafter, the configuration of the hydrogen peroxide decomposition tank 2 and the treatment in the hydrogen peroxide decomposition tank 2 will be described.

  Activated carbon for decomposing hydrogen peroxide in the water α to be treated is placed in the hydrogen peroxide decomposition tank 2 shown in FIG. Further, when the activated carbon is a fixed bed in the hydrogen peroxide decomposition tank 2, there is a risk of clogging or the like, and therefore, the activated carbon is preferably in a granular state. Further, in order to bring the activated carbon into a floating flow state in the hydrogen peroxide decomposition tank 2, as shown in FIG. 1, for example, a stirrer 21 (in FIG. 1, a motor that drives the stirring blade together with the stirring blade is also illustrated. It is preferable to stir and mix the water to be treated α in the hydrogen peroxide decomposition tank 2 and the activated carbon.

  The activated carbon charged into the hydrogen peroxide decomposition tank 2 is preferably about 10% to 30% in volume ratio in the hydrogen peroxide decomposition tank 2, but is not limited to this ratio. That is, as described above, the activated carbon only needs to be maintained in a floating flow state in the hydrogen peroxide decomposition tank 2, and depends on the shape (weight, particle size, etc.) of the activated carbon and the stirring ability of the stirrer 21. What is necessary is just to adjust the quantity of the activated carbon thrown into the said hydrogen peroxide decomposition tank 2 suitably.

  In addition, the decomposition of hydrogen peroxide by activated carbon in the hydrogen peroxide decomposition tank 2 does not use adsorption of hydrogen peroxide by the activated carbon, but a catalytic reaction (catalysis of decomposition reaction that decomposes into water and oxygen). Is to be used. Therefore, the activated carbon thrown into the hydrogen peroxide decomposition tank 2 can be used sufficiently even with used activated carbon.

In addition, the SV value of activated carbon in the hydrogen peroxide decomposition tank 2 (Space Velocity: space velocity; SV value (1 / h) = [(air flow rate (m ³ / h)) / (fill volume (m ³ )) ] Is preferably about 20 to 100.

  In this way, the water to be treated α is decomposed in the hydrogen peroxide decomposition tank 2 and then transferred to the biological treatment tank 3. As described above, since the granular activated carbon is in a floating flow state in the hydrogen peroxide decomposition tank 2, when the water to be treated α is transferred from the hydrogen peroxide decomposition tank 2 to the biological treatment tank 3. For example, an arbitrary configuration (such as a screen) may be provided between the hydrogen peroxide decomposition tank 2 and the biological treatment tank 3 so that the granular activated carbon does not flow out together with the water to be treated α.

  Next, the biological treatment tank 3 will be described. The biological treatment tank 3 is a tank for performing biological treatment on the water to be treated α. The biological treatment method performed on the water to be treated α in the biological treatment tank 3 is not particularly limited. For example, a biofilm method, an aerobic filter bed method, an activated sludge treatment method, or the like is adopted. be able to.

  The biofilm method is a method using a film of various microorganisms, and for example, a contact aeration method is often used. The contact aeration method is, for example, a method of treating with a carrier-supporting biofilm in which a microorganism film is attached to a plastic contact material, and organic matter is ingested and decomposed by the microorganism.

  The aerobic filter bed method uses a biofilm filtration type aerobic filter bed filled with a filter medium, and includes a moving bed type method and a fixed bed type method. Examples of the filter medium include porous ceramics, and the organic substances are decomposed by aerobic microorganisms on the surface of the filter medium to reduce BOD.

  The activated sludge treatment method is a method using activated sludge containing various microorganisms, in which the treated water α in the biological treatment tank 3 is stirred and aerated with activated sludge to oxidize and decompose organic matter in the treated water. It is. A part of the generated sludge after separating and precipitating the treated product to obtain the supernatant water is sent to the biological treatment tank 3 as return sludge and used for adjusting the microbial concentration of the sludge in the tank.

  In addition, among the above methods, the organic substance decomposition effect and the BOD reduction effect are large, and even if a small amount of ozone in the preceding accelerated oxidation treatment flows into the biological treatment tank 3, the biological function is easily retained. The biofilm method can be preferably used. Examples of microorganisms that can be used for biological treatments include heterotrophic bacteria, nitrifying bacteria, Escherichia coli, protozoa, rotifers, oligochaetes, nematodes and the like. In many cases, water to be treated is naturally adapted to the water quality and treatment method.

  Furthermore, the conditions for biological treatment of the water to be treated α in the biological treatment tank 3 are not particularly limited as long as a sufficient treatment effect can be obtained, the quality of the water to be treated α, the quality of the target treated water, and the activity of the microorganisms used. Although it can change suitably according to application temperature etc., for example, it is preferable that biological treatment time (residence time) is about 5 to 600 minutes, Furthermore, it is about 7 to 60 minutes.

  In addition to the above-mentioned methods, biological activated carbon treatment methods are also known as biological treatment methods. However, when the COD is high, the biological activated carbon tank is blocked and the frequency of backwashing of the biological activated carbon tank is increased. Therefore, it is preferable not to employ the biological activated carbon treatment method. Further, the biological treatment tank 3 may be usually backwashed to prevent clogging due to the growth of microorganisms.

  As described above, the hydrogen peroxide decomposition tank 2 is disposed downstream of the accelerated oxidation treatment tank 1A (backward in the direction in which the treated water α is treated), and the treatment target transferred from the accelerated oxidation treatment tank 1A. Since the hydrogen peroxide remaining in the water α can be decomposed, in the biological treatment performed in the biological treatment tank 3 as the subsequent treatment, the activity of the microorganism group responsible for the biological treatment is not inhibited.

  Returning to the description of FIG. 1, after that, the treated water α is subjected to biological treatment in the biological treatment tank 3, and a part of the treated water δ transferred to the treated water tank 4 is sterilized in the next step. Although necessary treatment is performed and discharged, or reused for various purposes, most of the treated water δ is again returned to the accelerated oxidation treatment tank 1A by the pump 41 installed in the treated water tank 4. It is transferred (arrow α1 in FIG. 1). That is, the treated water δ is circulated a plurality of times between the accelerated oxidation treatment tank 1A, the hydrogen peroxide decomposition treatment tank 2 and the biological treatment tank 3.

  In addition, when actually operating the water treatment system which concerns on this invention, it is more preferable to incorporate the sand filtration process in the front | former stage of the accelerated oxidation treatment tank 1A.

2. Control of injection amount of ozone gas and hydrogen peroxide Next, a method of controlling the injection amount of ozone gas β and hydrogen peroxide γ, focusing on the change in the color of the water to be treated α during the accelerated oxidation treatment will be described.

  Generally treated water α (leached water, sewage, secondary treated water, human waste, wastewater after septic tank sludge treatment, wastewater after coagulation sedimentation treatment, wastewater from waste incineration facilities, from general factories In many cases, wastewater and the like are colored by some coloring component. In addition, when the water to be treated α is subjected to accelerated oxidation treatment in the accelerated oxidation treatment tank 1A, the colored component contained in the water to be treated α is decomposed relatively quickly, and the water to be treated α is colorless and transparent. It becomes. Then, by continuing the accelerated oxidation treatment, the decomposition of the hardly decomposable substance proceeds.

  At this time, if the injection amounts of ozone gas β and hydrogen peroxide γ in the accelerated oxidation treatment are appropriate, the decomposition of the hardly decomposable substance proceeds rapidly, but at least one of ozone gas β and hydrogen peroxide γ is excessive or insufficient. In this case, not only the decomposition of the hardly decomposable substance but also the decomposition of the COD component does not proceed as intended. In other words, in order to efficiently promote the accelerated oxidation treatment for the water to be treated α, it is necessary to balance the injection amounts of ozone gas β and hydrogen peroxide γ.

  Hereinafter, the relationship between the injection amount of ozone gas β and hydrogen peroxide γ in the accelerated oxidation treatment and the color of the water to be treated α will be described.

[1] When the injection amounts of ozone gas β and hydrogen peroxide γ in the accelerated oxidation treatment are appropriate If the injection amounts of ozone gas β and hydrogen peroxide γ injected into the accelerated oxidation treatment tank 1A are appropriate, The colored component contained in the treated water α is decomposed relatively quickly, and the treated water α once becomes colorless and transparent. In addition, the color of the to-be-processed water (alpha) in the accelerated oxidation processing tank 1A can be directly confirmed visually with the observation windows 11a-11c shown in FIG.

  Thereafter, by continuing the accelerated oxidation treatment in the accelerated oxidation treatment tank 1A, the decomposition of the hardly decomposable substance progresses, and the injection point of ozone gas β in the accelerated oxidation treatment tank 1A is reduced along with the reduction of the hardly decomposed substance. In the vicinity of, a minute amount of metal ions (iron ions, manganese ions, etc.) contained in the water to be treated α react, and the water to be treated α is colored, for example, brown or pink. That is, the to-be-processed water (alpha) is colored in the color originating in the said metal ion accompanying the oxidation of a metal ion. Such a change in the color of the water to be treated α can be directly confirmed visually in the vicinity of the injection point of the ozone gas β in the accelerated oxidation treatment tank 1A, that is, particularly in the observation window 11c.

  On the other hand, the color change of the water to be treated α is confirmed in the vicinity of the injection point of the ozone gas β in the accelerated oxidation treatment tank 1A, but the water to be treated α is slightly above the injection point of the ozone gas β. Becomes colorless and transparent again. Changes in the color of the water to be treated α can be visually confirmed particularly through the observation windows 11a and 11b.

  The water to be treated α of the colored portion in the vicinity of the injection point of the ozone gas β in the accelerated oxidation treatment tank 1A is that the metal contained in the water to be treated α becomes an oxide. It shows that the inside of the accelerated oxidation treatment tank 1A is in an oxidizing atmosphere. If the injection amounts of the ozone gas β and hydrogen peroxide γ injected into the accelerated oxidation treatment tank 1A are appropriate, such coloring can be confirmed only in the vicinity of the injection point of the ozone gas β.

[2] When the amount of ozone gas and hydrogen peroxide injected in the accelerated oxidation treatment is inappropriate As an example of the case where the amount of ozone gas β and hydrogen peroxide γ injected into the accelerated oxidation treatment tank 1A is inappropriate The case where the injection amount of ozone gas β is excessive (for example, the dissolved ozone concentration in the accelerated oxidation treatment tank 1A is 0.1 mg / L or more) and the injection amount of hydrogen peroxide γ is insufficient will be described. In such a state, when the accelerated oxidation treatment is performed on the water to be treated α, the oxidizing power due to dissolved ozone works, and therefore the color of the water to be treated α when the injection amount described in [1] is appropriate. Compared with the change in the above, after becoming colorless and transparent, the one that is brown or pink only in the vicinity of the ozone gas β injection point is colored in the accelerated oxidation treatment tank 1A. In this state, impurities (for example, chloride ions and bromide ions) in the water to be treated α react with excess ozone gas β to oxidize substances (halogen oxides such as hypochlorous acid and hypobromous acid). Will be generated.

  Further, in the accelerated oxidation treatment, if the injection amount of hydrogen peroxide γ is initially insufficient with respect to the injection amount of ozone gas β, generation of an oxidizing substance occurs immediately after the start of the accelerated oxidation treatment, and decomposition of COD and the like. Therefore, the generated oxidizing substance accumulates in the water to be treated α. Then, for example, since hypobromous acid and the like exhibit a yellow color, the color of the water to be treated α is rather dark because the color of the hypobromite and the like is added to the original color of the water to be treated α.

Thus, when the phenomenon in [2] described above (change in color of the water to be treated α) is confirmed, for example, in the observation windows 11a to 11c, for example, an operator who manages the water treatment system Is
(1) Temporarily interrupting the injection of ozone gas β injected into the accelerated oxidation treatment tank 1A (2) Temporarily excessing the injection amount of hydrogen peroxide γ injected into the accelerated oxidation treatment tank 1A (3) Take measures such as changing the injection amount of hydrogen peroxide γ with respect to the preset ozone gas β.

  In addition, when it is determined that it takes a long time to change the color of the water to be treated α as described above (colorless and transparent, pink), the injection amount of ozone gas β and hydrogen peroxide γ may be increased.

  That is, the reaction state of the water to be treated α in the accelerated oxidation treatment tank 1A can be immediately and easily grasped using the color of the water to be treated α as an index. For example, the operations (1) to (3) described above are performed. By carrying out, proper reaction states (for example, dissolved ozone concentration of 0 to 0.1 mg / L, residual chlorine concentration of 0 to 2 mg / L) can be maintained.

  In the above description, an example in which three observation windows (observation windows 11a to 11c) are provided has been described, but the number is not limited to this.

  In the above description, for example, the system operator checks the color of the water to be treated α with the observation windows 11a to 11c and adjusts the injection amounts of ozone gas β and hydrogen peroxide γ. For example, the following method is also conceivable.

  For example, for example, an optical camera is installed in each of the observation windows 11a to 11c of the accelerated oxidation treatment tank 1A, and a change in the color of the water to be treated 12 in the accelerated oxidation treatment tank 1A is detected by image analysis using the optical camera. May be. Then, based on the detection result, for example, ozone gas β and hydrogen peroxide γ from the ozone gas generator 5 and the hydrogen peroxide tank 6 are adjusted so that the injection amounts of ozone gas β and hydrogen peroxide γ in the accelerated oxidation treatment become appropriate. This amount may be automatically controlled. Moreover, if it is an apparatus which can detect the change of the color of the to-be-processed water 12 in 1 A of accelerated oxidation treatment tanks, it will not be restricted to an optical camera.

(Second Embodiment)
Next, a second embodiment will be described. FIG. 2 is a schematic diagram showing a water treatment system using a water treatment method according to the second embodiment of the present invention. In FIG. 2, 1A to 1C are accelerated oxidation treatment tanks for subjecting the water to be treated α to accelerated oxidation treatment, and 2 is hydrogen peroxide decomposition for decomposing hydrogen peroxide in the treated wastewater from the accelerated oxidation treatment tank. 3 is a biological treatment tank for performing biological treatment on the treated wastewater from the hydrogen peroxide decomposition tank.

  In the following description, only differences from the above-described first embodiment will be described.

  The second embodiment is different from the first embodiment in that the accelerated oxidation treatment tank is provided in multiple stages. Specifically, if the accelerated oxidation treatment tank 1A is referred to as a first accelerated oxidation treatment tank, in the second embodiment, the latter stage of the first accelerated oxidation treatment tank 1A (the direction in which the water to be treated α is treated). The second accelerated oxidation treatment tank 1 </ b> B and the third accelerated oxidation treatment tank 1 </ b> C are arranged at the rear of the above. 2 shows an example in which three stages of accelerated oxidation treatment tanks are provided, it is needless to say that this is merely an example and is not limited to three stages.

  Also in the second embodiment, similarly to the first embodiment described above, control of the injection amount of ozone gas β and hydrogen peroxide γ focusing on the color change of the water to be treated α during the accelerated oxidation treatment. May be performed. In addition, in FIG. 2, although 1 A of 1st accelerated oxidation process tanks showed the example provided with the observation windows 11a-11c, the number of observation windows is not restricted to this. Furthermore, although illustration is omitted, for example, a peep window is provided in the second accelerated oxidation treatment tank 1B and / or the third accelerated oxidation treatment tank 1C, and the second accelerated oxidation treatment tank 1B and / or the third accelerated oxidation treatment tank 1C. The injection amount of ozone gas β and hydrogen peroxide γ may be controlled. Furthermore, similarly to the first embodiment described above, for example, the amounts of ozone gas β and hydrogen peroxide γ may be controlled by an optical camera or the like.

  Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples 1 and 2, but the present invention is not limited only to the Examples. Moreover, the Example and Comparative Examples 1 and 2 which are demonstrated below were performed using the waste water after the accelerated oxidation process of the final disposal site leach waste water in the water treatment system shown in the schematic diagram of FIG.

(Example 1)
(1-1) Water to be treated α
100 mg / L of hydrogen peroxide was additionally added to the wastewater after the accelerated oxidation treatment of the final disposal site leachate wastewater, and the wastewater in which the hydrogen peroxide was in excess was designated as the water to be treated α.
Dissolved ozone concentration: 0 mg / L
Dissolved hydrogen peroxide concentration: 120 mg / L

(1-2) Treatment conditions in the accelerated oxidation treatment tank 1A Ozone gas injection amount: 150 mg / L
Hydrogen peroxide injection amount: 75 mg / L
Residence time in the accelerated oxidation treatment tank 1A: 18 minutes

(1-3) Treatment conditions in hydrogen peroxide decomposition tank 2 Capacity of tank: 1 L
Activated carbon: granular activated carbon for water treatment Activated carbon amount: 0.2L
Residence time: (See Table 1)

  In accordance with the above conditions, the residual hydrogen peroxide concentration of the treated water α after treatment in the hydrogen peroxide decomposition tank 2 was measured in the water treatment system shown in the schematic diagram of FIG. The results are shown in Table 1.

(Comparative Example 1)
In Comparative Example 1, the residual hydrogen peroxide concentration of the water to be treated α when the activated carbon was not charged into the hydrogen peroxide decomposition tank 2 was measured. In other words, the comparative example 1 is different from the above example in that activated carbon is not charged into the hydrogen peroxide decomposition tank 2 in the water treatment system shown in the schematic diagram of FIG. The results are shown in Table 2.

  As is apparent from Tables 1 and 2, it was found that the decomposition of hydrogen peroxide progressed with activated carbon, and the residual hydrogen peroxide concentration rapidly decreased.

(Comparative Example 2)
In Comparative Example 2, the amount of oxidizing substances generated in the water to be treated when accelerated oxidation treatment (for example, insufficient injection amount of hydrogen peroxide γ into the accelerated oxidation treatment tank) is performed in a state where hydrogen peroxide is insufficient. Was measured. The conditions are as follows, and the results are shown in Table 3.

(2-1) Water to be treated α
The tertiary (biological treatment + coagulation sedimentation treatment + sand filtration treatment) treated water from the final disposal site leachate was treated water α.
COD concentration: 60 mg / L
Residual chlorine concentration: 0 mg / L

(2-2) Treatment conditions in the accelerated oxidation treatment tank 1A Ozone injection rate: 120 mg / L (total amount 120 mg / L injected in 30 minutes)
Hydrogen peroxide injection amount: 20 mg / L (initially charged into the treatment tank)
Reaction time: (Table 3)

  As shown in Table 3, it was found that the residual chlorine concentration in the water to be treated α in the accelerated oxidation treatment tank 1A increases when hydrogen peroxide is insufficient. This comparative example 2 shows that the accelerated oxidation treatment was performed on the assumption that the injection amount of hydrogen peroxide γ is insufficient in the accelerated oxidation treatment tank 1A, for example. In other words, if the injection amount of hydrogen peroxide is insufficient, excess dissolved ozone exists in the water to be treated, and impurities (for example, chloride ions and bromide ions) in the water to be treated react with dissolved ozone to oxidize. It shows that substances (halogen oxides such as hypochlorous acid and hypobromous acid) are formed.

  Although the present invention has been described in detail above, the above description is merely illustrative of the present invention in all respects and is not intended to limit the scope thereof. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

  The water treatment method according to the present invention and a water treatment system using the same are, for example, final disposal site leach wastewater, sewage, secondary treated water for sewage treatment, human waste, wastewater after septic tank sludge treatment, wastewater after coagulation sedimentation treatment, It can be used effectively for water treatment of treated water such as wastewater from waste incineration facilities and wastewater from general factories.

1A, 1B, 1C ... accelerated oxidation treatment tank 2 ... hydrogen peroxide decomposition tank 3 ... biological treatment tank 4 ... treated water tank 5 ... ozone gas generator 6 ... hydrogen peroxide tank 7 ... waste ozone decomposition apparatus

Claims (5)

A water treatment method for purifying water to be treated containing at least iron or manganese, which is colorless and transparent due to the coexistence of ozone gas and hydrogen peroxide ,
A first step of performing an accelerated oxidation treatment with ozone gas and hydrogen peroxide on the water to be treated;
A second step of performing a hydrogen peroxide decomposition treatment after the first step;
A third step of performing biological treatment after the second step,
In the first step, color before Symbol water to be treated, without being colored brown or pink color from iron or manganese in the vicinity of the injection point of the ozone gas, and a colorless transparent at a distance from the injection point of the ozone gas DOO in the case name should not be characterized by increasing the injection quantity of hydrogen peroxide, water treatment process.   The water treatment method according to claim 1, wherein the biologically treated water in the third step is circulated between the first step and the third step by using it in the first step.   2. The second step is characterized in that activated carbon is added to and mixed with the accelerated oxidation water in the first step to decompose hydrogen peroxide remaining in the accelerated oxidation water. 2. The water treatment method according to 2. The water treatment method according to any one of claims 1 to 3 , wherein the item to be purified in the treated water is COD (chemical oxygen demand). A water treatment system using the water treatment method according to any one of claims 1 to 4 ,
An accelerated oxidation treatment tank for performing the first step;
A hydrogen peroxide decomposition treatment tank for performing the second step after the accelerated oxidation treatment tank;
A water treatment system comprising: a biological treatment tank that performs the third step after the hydrogen peroxide decomposition treatment tank.

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