JP5259311B2 - Water treatment method and water treatment system used therefor - Google Patents

Description

  The present invention relates to a water treatment method and a water treatment system used therefor. More specifically, for example, chemical oxygen demand (hereinafter referred to as COD) in treated water such as final disposal site leachate and sewage secondary treated water is significantly reduced, and hypochlorous acid is sufficiently generated. The present invention relates to a water treatment method and a water treatment system used therefor, which can obtain stable treated water that is safe and has little fluctuation in water quality at low cost.

  In this specification, “water treatment” means “water purification”, in addition to operations for reducing COD in treated water, operations for disinfecting, sterilizing, and decolorizing treated water, This includes operations for reducing biological oxygen demand (hereinafter referred to as BOD), non-biodegradable substances, fungi, etc., decomposing organic substances, and improving transparency.

  In recent years, since water resources are limited, the importance of purifying and reusing wastewater has been recognized again. On the other hand, contamination by trace pollutants is a problem in water supply sources, and in addition to the conventional advanced treatment aimed at removing nitrogen and phosphorus, treatment methods aimed at deodorizing, decolorizing, sterilizing and removing trace pollutants The introduction of is being considered.

  In general, biological treatment methods represented by the activated sludge method are applied to wastewater treatment. However, although the biological treatment method has a very high BOD reduction effect, the effect of reducing the COD derived from a hardly biodegradable substance is small. Therefore, a separate treatment 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 regarded as important.

  Therefore, in order to reduce COD after biological treatment, activated carbon treatment has been conventionally performed. However, activated carbon after adsorption must be discarded or regenerated, which increases the maintenance cost of wastewater treatment. there were.

  In contrast, attempts have been made to reduce COD using ozone instead of the activated carbon treatment. When ozone is used, it is possible to reduce the running cost as compared with the case where activated carbon treatment is performed. However, although ozone can reduce COD quickly at the beginning of the reaction, its treatment effect is limited, and after reducing COD of about 30-60% of normal wastewater, the ozone injection rate Even if it increases, the reduction effect of COD will fall. Therefore, the ozone treatment is not effective unless the target COD reduction rate is low. Moreover, in general, when ozone treatment is performed, the hardly biodegradable substance is converted into an easily biodegradable substance, resulting in an increase in BOD.

  Therefore, various methods for reducing COD while suppressing increase in BOD in wastewater using ozone treatment and the biological treatment in combination have been proposed (see, for example, Patent Documents 1 to 8).

  However, when biological activated carbon is used in biological treatment, the load of biological activated carbon rises when wastewater with high COD is treated, and the amount of sludge generated with a reduction in COD increases. As a result, the risk of clogging the biological activated carbon layer increases, the frequency of backwashing the biological activated carbon layer increases, and the water treatment system cannot be operated satisfactorily.

  In addition, injecting a large amount of ozone into wastewater during ozone treatment not only increases running costs, but ozone is used to oxidize oxidizable substances and reacts with chlorine ions in wastewater. The amount of hypochlorous acid generated increases in proportion to the amount of injected hydrogen. The generated hypochlorous acid kills organisms in the next biological treatment, and thus has an adverse effect that the expected COD reduction effect cannot be obtained. When ozone-treated water is not used in the next process, it must be discharged after decomposing hypochlorous acid because it contains high-concentration hypochlorous acid.

As described above, when a high COD reduction effect is to be obtained, the amount of ozone required for the ozone treatment increases. Therefore, simply performing the ozone treatment and the biological treatment is expected to achieve the target COD reduction effect. In addition, there is a problem that an adverse effect caused by the generation of hypochlorous acid occurs particularly when the chlorine ion concentration in the wastewater is high.
JP 09-511448 A Japanese Patent Laid-Open No. 10-192892 JP 11-342398 A JP 2000-000595 A JP 2000-079384 A JP 2001-149982 A Japanese Patent Laid-Open No. 2001-300576 JP 2002-292395 A

  The present invention has been made in view of the background art described above. For example, COD is significantly reduced in water to be treated such as waste water, and hypochlorous acid is sufficiently generated from water to be treated having high COD. It is an object of the present invention to provide a water treatment method and a water treatment system used therefor, which can obtain stable treated water that is suppressed, is safe and has very little fluctuation in water quality, at low cost.

That is, the present invention
A water treatment method for performing at least ozone treatment (1A) for supplying ozone to a water to be treated and biological treatment (2) for decomposing organic matter by microorganisms,
The treated water is treated water having a chemical oxygen demand (COD _Mn ) exceeding 20 mg / L,
In the ozone treatment (1A), the ozone injection rate is controlled so that the dissolved ozone concentration in the treated water is within the determined range by measuring the dissolved ozone concentration in the treated water, and the ozone The injection rate is controlled to be 1 to 3 times (weight ratio) the chemical oxygen demand in the water to be treated,
After the ozone treatment (1A), the biological treatment (2) is performed with a plastic carrier-holding biofilm,
By using the biologically treated water from the biological treatment (2) for the ozone treatment (1A), the water treatment is carried out between the ozone treatment (1A) and the biological treatment (2). A water treatment system comprising at least a treatment method, an ozone treatment tank for ozone treatment (1A), and a biological treatment tank for biological treatment (2),
Used to treat water to be treated with chemical oxygen demand (COD _Mn ) exceeding 20 mg / L,
The ozone treatment tank includes a dissolved ozone concentration measurement unit, and controls the ozone injection rate so that the dissolved ozone concentration measured by the dissolved ozone concentration measurement unit falls within the determined range. but has a structure capable of controlling so that the a 1-3 times the chemical oxygen demand of the water to be treated (weight ratio),
Subsequent to the ozone treatment tank, the biological treatment tank having a plastic carrier holding biofilm is provided,
It is related with the water treatment system used for the said water treatment method characterized by the circulation structure between the said ozone treatment tank and the said biological treatment tank.

  According to the water treatment method of the present invention and the water treatment system used therefor, for example, COD is remarkably reduced in water to be treated such as waste water, and hypochlorous acid is sufficiently generated even from water to be treated having a high COD. It is possible to obtain stable treated water that is suppressed, is safe, and has very little fluctuation in water quality. Moreover, regardless of the quality of the water to be treated, compared to the case where the water to be treated with the same water quality is treated by the conventional method, it can be treated with a small amount of ozone and efficiently at a low running cost. The excellent effect of being able to operate is expressed at the same time.

  In the water treatment method of the present invention, at least ozone treatment (1A) for supplying ozone and biological treatment (2) for decomposing organic matter by microorganisms are performed on the water to be treated. By controlling the injection rate within a certain range, performing the biological treatment (2) after the ozone treatment (1A), and using the biologically treated water from the biological treatment (2) for the ozone treatment (1A), A circulation process is performed between 1A) and the biological process (2).

There is no particular limitation on the “treated water” that is the subject of the present invention. For example, final disposal site leachate, secondary sewage treatment water, river water, groundwater, lakes, factory wastewater, agricultural wastewater, wastewater treatment wastewater, etc. The water treatment method and the water treatment system of the present invention, which require water treatment, have a high chloride ion concentration, and the final disposal site leachate that easily generates hypochlorous acid, and the necessity and need for water purification. It is particularly suitable for water treatment of sewage secondary treated water with higher utilization of treated water. Moreover, the water treatment method and the water treatment system of the present invention are effectively used for COD reduction of water to be treated with COD _Mn exceeding 20 mg / L, not to mention the water to be treated having a chlorine ion concentration of about 300 mg / L, chlorine It is possible to target treated water having an ion concentration exceeding 500 mg / L.

  Below, the water treatment method of this invention and the water treatment system used for this are demonstrated based on drawing.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a water treatment system used in the water treatment method according to Embodiment 1 of the present invention. In FIG. 1, 1a is an ozone treatment tank for performing ozone treatment (1A) on the water to be treated, 4a1 is a dissolved ozone concentration measuring unit provided in the ozone treatment tank 1a, and 4a2 is a waste provided in the ozone treatment tank 1a. An ozone gas concentration measuring unit 2 is a biological treatment tank that performs biological treatment (2) on the water to be treated.

  As will be described later, the ozone treatment tank 1a has a structure capable of controlling the ozone injection rate within a certain range in the ozone treatment (1A). Moreover, between the ozone treatment tank 1a and the biological treatment tank 2, as will be described later, there is a circulation structure capable of performing circulation treatment between the ozone treatment (1A) and the biological treatment (2).

  First, the water to be treated α in the water tank 5 to be treated is transferred to the ozone treatment tank 1 a by the pump 51. Next, ozone β which has passed through the ozone generator 8 is supplied from the oxygen generator 7 to the water to be treated α transferred to the ozone treatment tank 1a. The supplied ozone β is absorbed in contact with the water to be treated α, and thereby, the oxidizable material is oxidized, such as decomposition of the pollutant such as a non-biodegradable material in the water to be treated α, COD, Fungi and the like are reduced. The ozone β may be supplied from the oxygen generator 7 via the ozone generator 8 as shown in FIG. 1 and FIGS. 2 and 4 described below. 8 may be supplied by means of supplying directly without going through 8, and the supply method of ozone β is not limited.

  In the ozone treatment (1A), the supply amount of ozone β to the water to be treated α, that is, the ozone injection rate is controlled within a certain range. Such ozone injection rate can be controlled, for example, by measuring the concentration of dissolved ozone in the water to be treated α or measuring the concentration of waste ozone gas discharged in the ozone treatment (1A).

  When the dissolved ozone concentration in the water to be treated α is measured to control the ozone injection rate, the dissolved ozone concentration is measured by the dissolved ozone concentration measuring unit 4a1 provided in the ozone treatment tank 1a. As described above, when the ozone treatment (1A) is performed in the ozone treatment tank 1a, the dissolved ozone concentration in the treated water α is measured, and the ozone injection rate is accurately controlled within a certain range, whereby the treated water α Even when the water quality fluctuates, it is possible to obtain stable treated water in which the water quality fluctuation is extremely small and the water quality is maintained within a certain good range.

  The ozone injection rate is preferably controlled by determining the range of the dissolved ozone concentration according to the quality of the water to be treated α and the target quality of the treated water, but if the ozone injection rate is too high, Not only is it used to oxidize oxidizable substances, but also reacts with chlorine ions in the water to be treated α to generate hypochlorous acid, so the dissolved ozone concentration is 10 mg / L or less, and further 5 mg It is preferable to control the ozone injection rate so as to be / L or less, particularly 1 mg / L or less. On the other hand, when the ozone injection rate is too low, oxidation of the oxidizable substance in the water to be treated α becomes insufficient and COD, fungi, etc. may not be sufficiently reduced, so that dissolved ozone is detected. It is preferable to control the ozone injection rate so that the concentration becomes higher than the concentration.

Incidentally, the ozone is reacted with oxidizable substances, and in consideration of suppressing the generation of hypochlorous acid, ozone injection rate in ozone treatment (1A), by weight, in the water to be treated α was controlled so that the COD of 3 times or less, also in consideration of ensuring the dissolved ozone concentration, the ozone injection rate, by weight, such as a 1-fold or more COD in the water to be treated α It controls to.

  As the dissolved ozone concentration measurement unit 4a1 provided in the ozone treatment tank 1a, for example, the dissolved ozone concentration can be easily measured, and the dissolved ozone concentration can be more accurately controlled within a certain range. A meter is preferably used.

  As the dissolved ozone concentration meter, for example, an ultraviolet absorption type concentration meter or a diaphragm polarographic type concentration meter is preferable because it is excellent in accuracy and handleability. Since the measured value of the dissolved ozone concentration may vary depending on the distance from collection of the treated water to monitoring and the amount of treated water, etc., such a dissolved ozone concentration meter is, for example, a detection unit and a control unit. Which can continuously measure the dissolved ozone concentration in the water to be treated α by connecting the ozone treatment tank 1a and the detection part, or continuously from the ozone treatment tank 1a to the detection part. What can introduce | transduce (alpha) etc. are used suitably. Moreover, it is preferable to appropriately adjust the usage environment of the dissolved ozone concentration meter such as the flow rate of the water to be treated, the water temperature, and the humidity during use according to the application range of the concentration meter to be used.

  In the first embodiment, means other than the dissolved ozone concentration meter can be used as the dissolved ozone concentration measuring unit 4a1.

  Besides measuring the concentration of dissolved ozone in the water to be treated α, for example, as described above, the ozone injection rate can be controlled by measuring the concentration of waste ozone gas discharged in the ozone treatment (1A).

  Since the waste ozone gas concentration is correlated with the dissolved ozone concentration within a certain range, the ozone concentration is provided in the ozone treatment tank 1a instead of measuring the dissolved ozone concentration in the water to be treated α within that range. The ozone injection rate may be controlled by measuring the waste ozone gas concentration in the waste ozone gas concentration measuring unit 4a2.

  As described above, the ozone injection rate is preferably determined by controlling the range of the waste ozone gas concentration according to the quality of the treated water α and the target treated water quality, but the ozone injection rate is too high. In this case, ozone is not only used for oxidizing the oxidizable substance, but may react with chlorine ions in the water to be treated α to generate hypochlorous acid. However, since the waste ozone gas concentration varies depending on the initial ozone concentration and the absorption efficiency in the ozone reaction tower, it is preferable that the waste ozone gas concentration is appropriately determined experimentally and empirically according to the system.

  As the waste ozone gas concentration measurement unit 4a2 provided in the ozone treatment tank 1a, for example, an ozone gas concentration meter is preferably used from the viewpoint of easy and accurate measurement of the waste ozone gas concentration.

  As the ozone gas concentration meter, the most popular ultraviolet absorption type concentration meter is preferable from the viewpoint of economy and performance, but is not limited thereto.

  In the first embodiment, means other than the ozone gas concentration meter can be used as the waste ozone gas concentration measuring unit 4a2.

  When the water quality variation of the water to be treated is not large, the relationship between the ozone injection rate and the dissolved ozone concentration in the water to be treated α can be determined in advance, and the ozone injection rate can be controlled according to this determined relationship.

  The ozone treatment condition of the water to be treated α in the ozone treatment tank 1a is not particularly limited as long as the ozone injection rate into the water to be treated α is controlled within a certain range and a desired effect is sufficiently exhibited. However, the ozone treatment time (residence time) is preferably about 3 to 60 minutes, and more preferably about 5 to 15 minutes.

  A part of the ozone used in the ozone treatment (1A) is transferred from the ozone treatment tank 1a to the waste ozone decomposing apparatus 10 and decomposed, and then discharged out of the system by the pump 101.

  The treated water α that has been subjected to the ozone treatment (1A) in the ozone treatment tank 1a as described above is transferred to the biological treatment tank 2. In the biological treatment tank 2, organic substances in the water to be treated α are decomposed by microorganisms, and readily biodegradable substances mainly contained in the water to be treated α are decomposed.

  Thus, when the biological treatment (2) is performed after the ozone treatment (1A), the hardly biodegradable substance in the water to be treated α is easily decomposed into microorganisms by the ozone treatment (1A). In the biological treatment (2), the organic matter (easily biodegradable substance) is sufficiently decomposed by the microorganisms. In addition, since biodegradable substances are decomposed in the subsequent biological treatment (2), the ozone treatment (1A) does not completely decompose organic substances (refractory biodegradable substances), Since it is sufficient to increase the biodegradability, there is an advantage that the ozone injection rate can be reduced as compared with the conventional method. At the same time, the BOD of the water to be treated α is reduced by the biological treatment (2), and the BOD is increased by the ozone used in the ozone treatment (1A) performed prior to the biological treatment (2). , Such BOD can be sufficiently reduced.

The method of biological treatment (2), for example, biofilm process, aerobic filter bed method, there are activated sludge treatment method, we adopt biofilm process in the first embodiment. In addition to these, biological activated carbon treatment is generally used as a biological treatment method. However, when COD is high, the biological activated carbon layer may be blocked and the frequency of back washing of the biological activated carbon layer may increase. since large, the organism activated carbon treatment method do not want to adopt.

  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 carrier, 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 uses activated sludge containing various microorganisms. The treated water in the biological treatment tank is agitated and aerated with activated sludge to oxidize and decompose organic matter in the treated water. . Part of the generated sludge after separating and precipitating the treated product to obtain the supernatant water is sent to the biological treatment tank as return sludge and used for adjusting the microorganism concentration of the sludge in the tank.

  Among these biological treatment methods (2), the organic matter decomposition effect and the BOD reduction effect are large, and even if a small amount of ozone in the preceding ozone treatment (1A) flows into the biological treatment tank 2, the biological function is retained. The biofilm method is preferably employed because it is easily performed. Examples of microorganisms that can be used in the biological treatment (2) are usually heterotrophic bacteria, nitrifying bacteria, Escherichia coli, protozoa, rotifers, oligochaetes, nematodes, etc. In the present invention, In many cases, microorganisms that are suitable for the quality of the water to be treated and the treatment method are naturally adapted.

  The biological treatment conditions of the water to be treated α in the biological treatment tank 2 are not particularly limited as long as a sufficient treatment effect can be obtained. Water quality of the water to be treated α, water quality of the target treated water, active application temperature of microorganisms to be used, etc. The biological treatment time (residence time) is, for example, preferably about 5 to 600 minutes, more preferably about 7 to 60 minutes.

  The biological treatment tank 2 is usually backwashed to prevent clogging due to the growth of microorganisms.

  After the biological treatment (2) is performed in the biological treatment tank 2, the biological treatment water by the biological treatment (2) is used for the ozone treatment (1A), so that the ozone treatment (1A) and the biological treatment (2 ).

  As in the conventional case, when ozone treatment and biological treatment are sequentially repeated several times, the concentration of pollutants in the water to be treated decreases and the dissolved ozone concentration easily rises as the treatment in the later stage. As a result, hypochlorous acid is likely to be generated, and a problem arises that the treatment becomes unstable under the influence of water quality fluctuations such as the concentration of water to be treated. However, in the water treatment method of the present invention, since the circulation treatment is performed between the ozone treatment (1A) and the biological treatment (2), such a conventional problem does not occur, and the water quality fluctuation is safe and extremely small. Stable treated water can be efficiently obtained at a low running cost with a small amount and an appropriate amount of ozone regardless of the quality of the water to be treated.

  There is no particular limitation on the number of times that the circulation treatment is performed between the ozone treatment (1A) and the biological treatment (2). For example, the number of treatments may be appropriately determined according to the quality of the treated water and the target treated water quality. Usually, it is preferable to perform the ozone treatment (1A) and the biological treatment (2) for about 2 to 20 times.

  After performing a desired number of circulation treatments between the ozone treatment (1A) and the biological treatment (2), the treated water δ transferred from the biological treatment tank 2 to the treated water tank 11 is reused according to various purposes. Is done. If necessary, the treated water δ in the treated water tank 11 may be transferred to the biological treatment tank 2 by the pump 111 and backwashed in the biological treatment tank 2 may be performed.

(Embodiment 2)
In the water treatment method according to Embodiment 1 performed in the water treatment system shown in FIG. 1, ozone treatment (1A) is performed on the water to be treated by controlling the ozone injection rate within a certain range in the ozone treatment tank 1a. Then, in the biological treatment tank 2, the biological treatment (2) is performed on the water to be treated, and the circulation treatment is performed between the ozone treatment (1A) and the biological treatment (2). In the water treatment method according to 2, in place of ozone treatment (1A) in the ozone treatment tank 1a, ozone and hydrogen peroxide are supplied to the water to be treated in the accelerated oxidation treatment tank 1b to perform accelerated oxidation treatment (1B). .

  Thus, since the water treatment method according to the second embodiment is the same as the water treatment method according to the first embodiment except for the ozone treatment (1A), the accelerated oxidation treatment that replaces the ozone treatment (1A) is performed. Only (1B) will be described in detail below.

  FIG. 2 is a schematic diagram showing a water treatment system used in the water treatment method according to Embodiment 2 of the present invention. In FIG. 2, 1b is an accelerated oxidation treatment tank for performing accelerated oxidation treatment (1B) on the water to be treated, 4b1 is a dissolved ozone concentration measuring unit provided in the accelerated oxidation treatment tank 1b, and 4b2 is placed in the accelerated oxidation treatment tank 1b. The waste ozone gas concentration measuring unit 2 provided is a biological treatment tank that performs biological treatment (2) on the water to be treated.

  As will be described later, the accelerated oxidation treatment tank 1b has a structure capable of controlling the ozone injection rate within a certain range in the accelerated oxidation treatment (1B). Moreover, between the acceleration | stimulation oxidation treatment tank 1b and the biological treatment tank 2, it is a circulation structure which can perform a circulation process between an accelerated oxidation process (1B) and a biological treatment (2) so that it may mention later. .

  First, the to-be-treated water α in the to-be-treated water tank 5 is transferred to the accelerated oxidation treatment tank 1b by the pump 51. Next, the ozone β that has passed through the ozone generator 8 is supplied from the oxygen generator 7 to the water to be treated α transferred to the accelerated oxidation treatment tank 1 b, and the hydrogen peroxide γ is supplied by the pump 91 of the hydrogen peroxide tank 9. An aqueous solution of is supplied. By supplying these ozone β and hydrogen peroxide γ, the dissolved ozone in the water to be treated α reacts with hydrogen peroxide to generate hydroxyl radicals (hereinafter referred to as OH radicals) which are strong oxidizing agents, and the OH Oxidizable substances are oxidized and COD, fungi and the like are reduced, for example, pollutants such as hardly biodegradable substances in the water to be treated α are decomposed by the strong oxidizing power of radicals. The ozone β may be supplied from the oxygen generator 7 via the ozone generator 8 as shown in FIG. 2, but by means of supplying directly without passing through the oxygen generator 7 and the ozone generator 8. The method of supplying ozone β is not limited.

  In the accelerated oxidation treatment (1B), the supply amount of ozone β to the water to be treated α, that is, the ozone injection rate is controlled within a certain range. Such ozone injection rate can be controlled, for example, by measuring the concentration of dissolved ozone in the water to be treated α or measuring the concentration of waste ozone gas discharged in the accelerated oxidation treatment (1B).

  When the dissolved ozone concentration in the water to be treated α is measured to control the ozone injection rate, the dissolved ozone concentration is measured by the dissolved ozone concentration measuring unit 4b1 provided in the accelerated oxidation treatment tank 1b. As described above, when the accelerated oxidation treatment (1B) is performed in the accelerated oxidation treatment tank 1b, the dissolved ozone concentration in the water to be treated α is measured, and the ozone injection rate is accurately controlled within a certain range. Even when the water α changes in water quality, it is possible to obtain stable treated water in which the water quality change is extremely small and the water quality is maintained within a certain good range.

  The ozone injection rate is preferably controlled by determining the range of the dissolved ozone concentration according to the quality of the water to be treated α and the target quality of the treated water, but if the ozone injection rate is too high, In addition to being used to oxidize oxidizable substances, it may react with chlorine ions in the water to be treated α to generate hypochlorous acid, and the generated OH radicals can decompose pollutants, COD, Before the effect of reducing fungi and the like is manifested, it reacts with dissolved ozone and disappears, and there is a possibility that a sufficient effect cannot be obtained. Therefore, the dissolved ozone concentration is 10 mg / L or less, further 5 mg / L or less, especially It is preferable to control the ozone injection rate so as to be 1 mg / L or less. On the other hand, when the ozone injection rate is too low, oxidation of the oxidizable substance in the water to be treated α becomes insufficient and COD, fungi, etc. may not be sufficiently reduced, so that dissolved ozone is detected. It is preferable to control the ozone injection rate so that the concentration becomes higher than the concentration.

Incidentally, the ozone is reacted with oxidizable substances, and in consideration of suppressing the generation of hypochlorous acid, ozone injection rate in advanced oxidation processes (1B), a weight ratio of the water to be treated α Medium controlled to be less than three times the COD, also in consideration of ensuring the dissolved ozone concentration, the ozone injection rate, by weight, of 1 or more times the COD in the water to be treated α that controls so.

  As the dissolved ozone concentration measuring unit 4b1 provided in the accelerated oxidation treatment tank 1b, for example, the dissolved ozone concentration can be easily measured, and the dissolved ozone concentration can be more accurately controlled within a certain range, for example, dissolved ozone. A densitometer is preferably used.

  As the dissolved ozone concentration meter, for example, the one exemplified in the first embodiment is mentioned. However, since the diaphragm polarographic concentration meter may malfunction, in that case, an ultraviolet absorption concentration meter is suitable. is there. In addition, it is preferable to appropriately adjust the usage environment of the dissolved ozone concentration meter such as the flow rate of water to be treated, the water temperature, and the humidity during use according to the application range of the concentration meter to be used.

  In the second embodiment, means other than the dissolved ozone concentration meter can be used as the dissolved ozone concentration measuring unit 4b1.

  In addition to measuring the dissolved ozone concentration in the water to be treated α, for example, as described above, the ozone injection rate can be controlled by measuring the concentration of waste ozone gas discharged in the accelerated oxidation treatment (1B).

  Since the waste ozone gas concentration has a correlation with the dissolved ozone concentration within a certain range, it is included in the accelerated oxidation treatment tank 1b instead of measuring the dissolved ozone concentration in the water to be treated α within that range. The waste ozone gas concentration may be measured by the waste ozone gas concentration measuring unit 4b2 to control the ozone injection rate.

  As described above, the ozone injection rate is preferably determined by controlling the range of the waste ozone gas concentration according to the quality of the treated water α and the target treated water quality, but the ozone injection rate is too high. In addition to being used for the oxidation of oxidizable substances, ozone may react with chlorine ions in the water to be treated α to generate hypochlorous acid, and the generated OH radicals are polluted substances. It may disappear due to the reaction with dissolved ozone before the effect of reducing COD, COD, fungi, etc. is manifested, and a sufficient effect may not be obtained. However, since the waste ozone gas concentration varies depending on the initial ozone concentration and the absorption efficiency in the ozone reaction tower, it is preferable that the waste ozone gas concentration is appropriately determined experimentally and empirically according to the system.

  As the waste ozone gas concentration measuring unit 4b2 provided in the accelerated oxidation treatment tank 1b, for example, an ozone gas concentration meter is preferably used from the viewpoint that the measurement of the waste ozone gas concentration is easy and accurate. Examples of the ozone gas concentration meter include those exemplified in the first embodiment.

  In the second embodiment, means other than the ozone gas concentration meter can be used as the waste ozone gas concentration measuring unit 4b2.

  When the water quality variation of the water to be treated is not large, the relationship between the ozone injection rate and the dissolved ozone concentration in the water to be treated α can be determined in advance, and the ozone injection rate can be controlled according to this determined relationship.

  Furthermore, in the water treatment method according to the second embodiment, the ozone injection rate into the water to be treated α is controlled within a certain range in the accelerated oxidation treatment (1B), and at the same time, hydrogen peroxide is injected into the water to be treated α. The rate may also be controlled within a certain range. In this way, when not only the ozone injection rate but also the hydrogen peroxide injection rate is controlled within a certain range and the accelerated oxidation treatment (1B) is performed, even if the water to be treated α changes in water quality, the water quality changes. It is possible to obtain stable treated water whose water quality is maintained within a certain good range, and that it can be treated with extremely small amounts of ozone and hydrogen peroxide regardless of the quality of the treated water. There is an advantage that an excellent effect is greatly expressed.

  In the accelerated oxidation treatment (1B), in order to control the supply amount of hydrogen peroxide γ to the water to be treated α, that is, the hydrogen peroxide injection rate within a certain range, for example, the dissolved hydrogen peroxide concentration in the water to be treated α Can be measured.

  In order to control the dissolved hydrogen peroxide concentration in the water to be treated within a certain range, a dissolved hydrogen peroxide concentration measuring unit is installed in the accelerated oxidation treatment tank 1b (not shown in FIG. 2), and the dissolved peroxidation is performed. What is necessary is just to measure the dissolved hydrogen peroxide concentration in the hydrogen concentration measuring section.

  The hydrogen peroxide injection rate is preferably controlled by determining the range of dissolved hydrogen peroxide concentration according to the quality of the water to be treated α and the target water quality of the treated water and the control range of the ozone injection rate. If the hydrogen peroxide injection rate is too high, the generated OH radicals will disappear by reacting with dissolved hydrogen peroxide before the degradation effect of pollutants and the effect of reducing COD, fungi, etc. will be lost. Since the effect may not be obtained, it is preferable to control the hydrogen peroxide injection rate so that the dissolved hydrogen peroxide concentration is 10 mg / L or less, more preferably 5 mg / L or less. Conversely, if the hydrogen peroxide injection rate is too low, the generation of OH radicals is small, and there is a risk that the decomposition of pollutants and the reduction of COD, fungi, etc. will be insufficient. It is preferable to control the hydrogen peroxide injection rate so as to be 0.01 mg / L or more, and further 0.1 mg / L or more.

  The dissolved hydrogen peroxide concentration measuring unit provided in the accelerated oxidation treatment tank 1b is easy to measure the dissolved hydrogen peroxide concentration, and can be controlled within a certain range more accurately, for example, dissolved peroxidation. A hydrogen concentration meter is preferably used.

  Examples of the dissolved hydrogen peroxide concentration meter include an acid potassium permanganate titration meter, an ultraviolet transmission absorption concentration meter, and an iodine coulometric titration method (reverse titration method). From the viewpoint of excellent properties, an acid potassium permanganate titration type concentration meter is preferable. However, in this case, ozone in the water to be treated α may also affect the measurement concentration. Therefore, it is desirable to remove the ozone in the water to be treated α by aeration or the like before use in the measurement. Further, since the dissolved hydrogen peroxide concentration may vary depending on the distance from collection of the treated water to monitoring and the amount of water to be treated, etc., the dissolved hydrogen peroxide concentration meter includes, for example, a detection unit and Having a control unit and connecting the accelerated oxidation treatment tank 1b and the detection unit to continuously measure the dissolved hydrogen peroxide concentration in the water to be treated α, or continuously from the accelerated oxidation treatment tank 1b What can introduce the to-be-processed water (alpha) into a detection part etc. are used suitably. It is preferable to appropriately adjust the usage environment of the dissolved hydrogen peroxide concentration meter such as the flow rate of water to be treated, the water temperature, and the humidity during use according to the application range of the concentration meter to be used.

  In the second embodiment, means other than the dissolved hydrogen peroxide concentration meter can be used as the dissolved hydrogen peroxide concentration measuring unit.

  Thus, the hydrogen peroxide injection rate into the water to be treated α in the accelerated oxidation treatment (1B) can be controlled, for example, by measuring the dissolved hydrogen peroxide concentration in the water to be treated α. The hydrogen oxide injection rate is preferably 0.01 or more, more preferably 0.02 or more with respect to the ozone injection rate 1, and is preferably 0.5 or less, and more preferably 0.3 or less.

  In the accelerated oxidation treatment (1B), when the ozone injection rate into the water to be treated α is controlled within a certain range by measuring the dissolved ozone concentration, the dissolved hydrogen peroxide concentration is also measured simultaneously with the dissolved ozone concentration. You may adjust it.

  The accelerated oxidation treatment conditions for the water to be treated α in the accelerated oxidation treatment tank 1b are such that the ozone injection rate into the water to be treated α and, if necessary, the hydrogen peroxide injection rate are controlled within a certain range, and the desired effect is sufficiently obtained. There is no particular limitation as long as it is expressed, and it can be appropriately changed according to the quality of the water to be treated α, the quality of the target treated water, etc. For example, the accelerated oxidation treatment time (residence time) is about 3 to 60 minutes. Furthermore, it is preferably about 5 to 15 minutes.

  A part of ozone used in the accelerated oxidation treatment (1B) is transferred from the accelerated oxidation treatment tank 1b to the waste ozone decomposing apparatus 10 and decomposed, and then discharged to the outside by the pump 101. .

  In the second embodiment, ozone and hydrogen peroxide are supplied to the water to be treated to perform the accelerated oxidation treatment (1B). Instead of such a combination of ozone and hydrogen peroxide, ozone and hydrogen peroxide are used. A combination with ultraviolet rays can also be employed. By supplying ozone to the water to be treated and irradiating it with ultraviolet rays, the effect of the accelerated oxidation treatment (1B) similar to that when ozone and hydrogen peroxide are supplied as described above can be obtained.

  The treated water α that has been subjected to the accelerated oxidation treatment (1B) in the accelerated oxidation treatment tank 1b as described above is transferred to the biological treatment tank 2, and the organism is treated in the same manner as the water treatment method according to the first embodiment. Biological treatment (2) is performed in the treatment tank 2.

  After the biological treatment (2) is performed in the biological treatment tank 2, the biological treatment water by the biological treatment (2) is used for the accelerated oxidation treatment (1B), whereby the accelerated oxidation treatment (1B) and the biological treatment are performed. Cycle processing with (2).

  As in the past, in the case where the accelerated oxidation treatment and the biological treatment are sequentially repeated several times, the concentration of pollutants in the water to be treated decreases and the dissolved ozone concentration and dissolved hydrogen peroxide increase as the treatment in the later stage. The concentration is likely to increase, and thus OH radicals and hypochlorous acid are likely to be generated, which causes a problem that the treatment becomes unstable due to the influence of water quality fluctuations such as the concentration of water to be treated. However, in the water treatment method of the present invention, since the circulation treatment is performed between the accelerated oxidation treatment (1B) and the biological treatment (2), such a conventional problem does not occur, and the water quality variation is extremely safe. Regardless of the quality of the water to be treated, a small amount of stable treated water can be efficiently obtained at a low running cost with a small amount and an appropriate amount of ozone.

  There is no particular limitation on the number of times that the circulation treatment is performed between the accelerated oxidation treatment (1B) and the biological treatment (2). For example, the number may be appropriately determined according to the quality of the water to be treated and the quality of the target treated water. However, it is preferable to perform the set of the normal oxidation treatment (1B) and the biological treatment (2) about 2 to 20 times.

  After performing the desired number of circulation treatments between the accelerated oxidation treatment (1B) and the biological treatment (2), the treated water δ transferred from the biological treatment tank 2 to the treated water tank 11 is recycled according to various purposes. Used. If necessary, the treated water δ in the treated water tank 11 may be transferred to the biological treatment tank 2 by the pump 111 and backwashed in the biological treatment tank 2 may be performed.

  In the water treatment method according to Embodiment 2, the accelerated oxidation treatment (1B) can be performed in multiple stages.

  FIG. 3 is a schematic diagram showing accelerated oxidation treatment tanks provided in multiple stages in the water treatment system used in the water treatment method according to Embodiment 2 of the present invention. In FIG. 3, 1b1, 1b2, and 1b3 are all accelerated oxidation treatment tanks that perform accelerated oxidation treatment (1B) on the water to be treated.

  First, an aqueous solution of ozone β1 and hydrogen peroxide γ1 is supplied to the treated water transferred to the accelerated oxidation treatment tank 1b1, and then the treated water is transferred to the accelerated oxidation treatment tank 1b2, where ozone β2 and peroxidation are transferred. An aqueous solution of hydrogen γ2 is supplied. Next, the water to be treated is transferred to the accelerated oxidation treatment tank 1b3, and after supplying an aqueous solution of ozone β3 and hydrogen peroxide γ3, the water to be treated is transferred to the biological treatment tank 2 at the subsequent stage.

  In this way, when the accelerated oxidation treatment (1B) is performed in multiple stages, the injection of ozone and hydrogen peroxide can be performed separately. For example, the dissolved ozone concentration or dissolved hydrogen peroxide concentration in the water to be treated Is not too high at the same time, and even with the same amount of oxidant, a higher treatment effect is exhibited, and further, generation of hypochlorous acid is suppressed and excessive generation of OH radicals is prevented at one time. There is an advantage that can be. Therefore, by performing the accelerated oxidation treatment (1B) in multiple stages, it is possible to obtain stable treated water that is safe and has very little fluctuation in water quality, more efficiently and at a lower running cost.

  When the accelerated oxidation treatment (1B) is performed in multiple stages, the number of times is not particularly limited. For example, the number may be appropriately determined according to the quality of the water to be treated and the target quality of the treated water. It is preferable to carry out about 2 to 4 steps.

(Embodiment 3)
Furthermore, as one embodiment of the water treatment method of the present invention, the sand filtration treatment (3) can be performed before the ozone treatment (1A) or the accelerated oxidation treatment (1B). One embodiment in the case of performing such sand filtration processing (3) is described based on a drawing. The following is a water treatment method in which sand filtration treatment (3) is performed in advance in the embodiment in which ozone treatment (1A) is performed, but accelerated oxidation treatment (1B) instead of ozone treatment (1A). The same applies to the embodiment that performs the above.

  FIG. 4 is a schematic diagram showing a water treatment system used in the water treatment method according to Embodiment 3 of the present invention. In FIG. 4, 1a is an ozone treatment tank for performing ozone treatment (1A) on the water to be treated, 4a1 is a dissolved ozone concentration measuring unit provided in the ozone treatment tank 1a, and 4a2 is a waste provided in the ozone treatment tank 1a. The ozone gas concentration measuring unit 2 is a biological treatment tank 2 for subjecting the water to be treated to biological treatment (2), and 3 is a sand filter for subjecting the water to be treated to sand filtration (3).

  As described above, the ozone treatment tank 1a has a structure capable of controlling the ozone injection rate within a certain range in the ozone treatment (1A). Moreover, between the ozone treatment tank 1a and the biological treatment tank 2, as described above, a circulation structure capable of performing a circulation treatment between the ozone treatment (1A) and the biological treatment (2).

  First, the water to be treated α in the water tank 5 to be treated is transferred to the sand filter 3 by the pump 51. In the sand filter 3, suspended substances, phosphorus, etc. contained in the water to be treated α are removed in advance, or BOD is reduced in advance. By such sand filtration (3), the required amount of dissolved ozone in the subsequent ozone treatment (1A) can be reduced, and the amount of ozone used can be reduced.

  In addition, when it is desired to remove phosphorus in the water to be treated α, a flocculant is added as a pretreatment, and the flocculant and the water to be treated α are mixed in a static mixer to contain phosphorus contained in the water to be treated α. Can be solidified and subjected to sand filtration (3).

  The flocculant includes inorganic flocculants and organic flocculants. Examples of inorganic flocculants include aluminum flocculants such as aluminum sulfate and polyaluminum chloride (hereinafter referred to as PAC), and iron flocculants such as ferric chloride. Examples of organic flocculants include polyacrylamide polymer flocculants. Such a flocculant is preferably added to the water to be treated α in an amount according to the type and purpose of the water to be treated α in consideration of the manifestation of the effect.

  Although there is no limitation in particular in the sand filter 3 used for sand filtration process (3), for example, an upward flow moving bed type sand filter etc. are illustrated, and the filter gravel layer and the filter sand layer are laminated | stacked sequentially on the filter bed. Is usually used. As such filtration sand, it is preferable to use a hard, uniform sand that does not contain many impurities, flatness, and fragile sand, is rich in quartz, and is hard. For example, filter sand having an effective diameter of about 0.8 to 2.5 mm and a uniformity coefficient of about 1.5 or less can be suitably used.

The sand filtration treatment conditions of the water to be treated α in the sand filter 3 are not particularly limited as long as a sufficient treatment effect can be obtained, and appropriately changed according to the quality of the water to be treated α, the quality of the target treated water, and the like. For example, the filtration rate is preferably about 100 to 1000 m / day, and more preferably about 200 to 700 m / day. Further, during the sand filtration treatment, it is preferable to supply air appropriately at a flow rate of about 10 to 30 L / m ² / min for washing the filtration sand.

  In the sand filter 3, the filter bed is usually washed in parallel with the filtration of the water to be treated α. The dirty filter bed is mixed and washed with air and water. Thereafter, the filter bed separated from the backwash waste water is washed with filtered water and counterflow, and returns to the filter bed surface again.

  The water to be treated α subjected to the sand filtration process (3) in the sand filter 3 is similar to the water treatment system of the first embodiment shown in the schematic diagram of FIG. 1 in the ozone treatment tank 1a. The ozone treatment (1A) and the biological treatment (2) in the biological treatment tank 2 are circulated and the treated water δ transferred to the treated water tank 11 may be reused for various purposes. If necessary, the treated water δ in the treated water tank 11 may be transferred to the biological treatment tank 2 by the pump 111 and backwashed in the biological treatment tank 2 may be performed.

  In the water treatment system of the present invention, although not shown in the schematic diagrams of FIGS. 1, 2, and 4, the dissolved ozone concentration measuring units 4a1, 4b1 are provided so that the entire system can be operated efficiently, safely and accurately. , Waste ozone gas concentration measuring units 4a2, 4b2, pump 51 of water tank 5 to be treated, oxygen generator 7, ozone generator 8, pump 91 of hydrogen peroxide tank 9, pump 101 of waste ozone decomposition apparatus 10, and water tank 11 Each of the pumps 111 and the like is controlled for operation.

  Thus, according to the present invention, for example, COD in treated water such as waste water is remarkably reduced, and generation of hypochlorous acid is sufficiently suppressed even from treated water having a high COD, so that the water quality can be changed safely. Therefore, stable treated water can be obtained. Moreover, regardless of the quality of the water to be treated, compared to the case where the water to be treated with the same water quality is treated by the conventional method, it can be treated with a small amount of ozone and efficiently at a low running cost. Can operate.

  Next, although the water treatment method of this invention and the water treatment system used therewith are demonstrated more concretely based on the following Examples, this invention is not limited only to this Example.

Example 1 (circulation treatment of ozone treatment (1A) + biological treatment (2))
In the water treatment system shown in the schematic diagram of FIG. 1, the final disposal site leachate biological treatment water was treated continuously for 24 hours. The COD _Mn of the final disposal site leachate biological treatment water used was 80 mg / L, and the chloride ion concentration was 10000 mg / L. The conditions for each process are as follows.

(A) Ozone treatment dissolved ozone concentration: timely confirmation by manual analysis Ozone injection rate: hand-adjusted residence time so that the dissolved ozone concentration is about 0.3 mg / L or less: 10 minutes

(I) Biological treatment method: Contact aeration method (using carrier-supported biofilm)
Treatment temperature: Final disposal site leachate biological treatment water temperature 20 ° C
Residence time: 20 minutes

(C) Set of circulation treatment ozone treatment and biological treatment: 3 times

As a result of performing the treatment under the above-mentioned conditions, the COD _Mn of the obtained treated water was 21 mg / L, which was sufficiently reduced as compared with that before the treatment. In addition, the chlorine smell from the treated water was not felt.

Example 2 (accelerated oxidation treatment (1B) + biological treatment (2) circulation treatment)
In Example 1, the final disposal site leachate biological treatment water was treated in the same manner as in Example 1 except that the accelerated oxidation treatment was performed instead of the ozone treatment. As the water treatment system, the water treatment system shown in the schematic diagram of FIG. 2 was used. The conditions for the accelerated oxidation treatment and the circulation treatment are as follows.

(A) Accelerated oxidation treatment dissolved ozone concentration: timely confirmed by manual analysis Ozone injection rate: hand-adjusted hydrogen peroxide injection rate so that the dissolved ozone concentration is about 0.3 mg / L or less: 3 mg / L (constant)
Residence time: 10 minutes

(C) Set of circulatory treatment-promoting oxidation treatment and biological treatment: 3 times

As a result of the treatment under each of the above conditions, the COD _Mn of the obtained treated water was 12 mg / L, which was significantly reduced as compared to before treatment. In addition, the chlorine smell from the treated water was not felt.

Comparative Example 1 (only ozone treatment)
In Example 1, biological treatment (circulation treatment between ozone treatment and biological treatment) was not performed, and only ozone treatment was continuously performed for 24 hours, and the final disposal site leachate biological treatment was performed in the same manner as in Example 1. Water treatment was performed. In addition, as a water treatment system, in the water treatment system shown in the schematic diagram of FIG. 1, the biological treatment tank 2 is not provided after the ozone treatment tank 1 a, and the treated water from the ozone treatment tank 1 a is directly transferred to the treatment water tank 11. Using what will be.

As a result of the treatment under the above conditions, the COD _Mn of the obtained treated water was 35 mg / L, which was not sufficiently reduced as compared with that before the treatment. Further, a strong chlorine odor was felt from the treated water.

As in Examples 1 and 2, when the ozone injection rate is controlled within a certain range in the ozone treatment or accelerated oxidation treatment, and the circulation treatment is performed between the ozone treatment or accelerated oxidation treatment and the biological treatment, Despite the extremely high COD _Mn of leachate and biological treatment water of final disposal site 80 mg / L, the ozone injection rate can be controlled low, and COD _Mn is extremely low, about 10 to 20 mg / L. It can be seen that generation of hypochlorous acid is sufficiently suppressed, and stable treated water that is safe and has little fluctuation in water quality can be easily obtained.

  Further, comparing Example 1 and Example 2, it can be seen that the effect of reducing COD is greater when the accelerated oxidation treatment is performed as in Example 2.

In contrast, in Comparative Example 1, only ozone treatment was performed without performing biological treatment (circulation treatment between ozone treatment and biological treatment), so COD _Mn remained as high as 35 mg / L and hypochlorous acid was present. It can be seen that only the generated treated water can be obtained.

  The water treatment method and water treatment system of the present invention are used for water treatment of treated water such as final disposal site leachate, secondary sewage treatment water, river water, ground water, lakes, factory effluent, agricultural effluent, garbage treatment effluent, etc. Effective use is possible.

The schematic diagram which shows the water treatment system used for the water treatment method which concerns on Embodiment 1. FIG. The schematic diagram which shows the water treatment system used for the water treatment method which concerns on Embodiment 2. FIG. In the water treatment system used for the water treatment method which concerns on Embodiment 2, the schematic diagram which shows the accelerated oxidation treatment tank provided with the multistage The schematic diagram which shows the water treatment system used for the water treatment method which concerns on Embodiment 3. FIG.

Explanation of symbols

1a Ozone treatment tank 1b, 1b1, 1b2, 1b3 Accelerated oxidation treatment tank 2 Biological treatment tank 3 Sand filter 4a1, 4b1 Dissolved ozone concentration measurement unit 4a2, 4b2 Waste ozone gas concentration measurement unit

Claims (7)

A water treatment method for performing at least ozone treatment (1A) for supplying ozone to a water to be treated and biological treatment (2) for decomposing organic matter by microorganisms,
The treated water is treated water having a chemical oxygen demand (COD _Mn ) exceeding 20 mg / L,
In the ozone treatment (1A), the ozone injection rate is controlled so that the dissolved ozone concentration in the treated water is within the determined range by measuring the dissolved ozone concentration in the treated water, and the ozone The injection rate is controlled to be 1 to 3 times (weight ratio) the chemical oxygen demand in the water to be treated,
After the ozone treatment (1A), the biological treatment (2) is performed with a plastic carrier-holding biofilm,
By using the biologically treated water from the biological treatment (2) for the ozone treatment (1A), the water treatment is carried out between the ozone treatment (1A) and the biological treatment (2). Processing method. The water treatment method according to claim 1 , wherein the ozone injection rate is controlled so that the dissolved ozone concentration is 10 mg / L or less. The water treatment method according to claim 1 or 2 , wherein an accelerated oxidation treatment (1B) for supplying ozone and hydrogen peroxide is performed instead of the ozone treatment (1A). The water treatment method according to claim 3 , wherein the accelerated oxidation treatment (1B) is performed in multiple stages. A water treatment system comprising at least an ozone treatment tank for ozone treatment (1A) and a biological treatment tank for biological treatment (2),
Used to treat water to be treated with chemical oxygen demand (COD _Mn ) exceeding 20 mg / L,
The ozone treatment tank includes a dissolved ozone concentration measurement unit, and controls the ozone injection rate so that the dissolved ozone concentration measured by the dissolved ozone concentration measurement unit falls within the determined range. but has a structure capable of controlling so that the a 1-3 times the chemical oxygen demand of the water to be treated (weight ratio),
Subsequent to the ozone treatment tank, the biological treatment tank having a plastic carrier holding biofilm is provided,
The water treatment system used for the water treatment method according to claim 1, wherein a circulation structure is provided between the ozone treatment tank and the biological treatment tank. The water treatment system of Claim 5 provided with the accelerated oxidation treatment tank for accelerated oxidation treatment (1B) instead of the ozone treatment tank. The water treatment system according to claim 6 , wherein the accelerated oxidation treatment tank is provided in multiple stages.

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