Wastewater treatment equipment

Abstract

To provide a wastewater treatment apparatus capable of treating a hardly decomposable substance such as an organic halogen compound or 1,4-dioxane at a high removal rate.SOLUTION: There is provided a wastewater treatment apparatus, including: a treatment tank 1 for treating wastewater containing a hardly decomposable substance; a microbubble generator 2 installed in the treatment tank 1; and a circulation pump 3 for circulating wastewater in the tank to the treatment tank 1 and the microbubble generator 2, and configured to treat the hardly decomposable substance by generating microbubbles in a waste liquid in the treatment tank 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wastewater treatment device using microbubbles. [Background technology]

[0002] Depending on the solvents and raw materials used in manufacturing, wastewater discharged from factories may contain persistent substances such as trihalomethanes, organohalogen compounds such as dioxins, and 1,4-dioxane. Environmental regulations for these persistent substances have become stricter in recent years, with a limit of 0.5 mg / L for 1,4-dioxane in particular being set as an industrial wastewater discharge limit in 2012. Factory wastewater treatment typically involves methods such as activated sludge, activated carbon adsorption, and distillation. However, 1,4-dioxane is difficult to decompose through biological treatment. Furthermore, separation by adsorption and distillation is also difficult. Therefore, treating wastewater containing 1,4-dioxane using conventional treatment methods is extremely difficult.

[0003] One method for treating wastewater containing persistent substances is the oxidative decomposition of organic matter using highly oxidizing hydroxyl radicals. As described in Non-Patent Documents 1 and 2, microbubbles, which have been refined to a diameter of 50 μm or less, self-collapse in water, generating hydroxyl radicals. This behavior has led to the application of microbubbles in wastewater treatment. Patent Document 1 proposes treating wastewater with microbubbles containing ozone gas using a swirling flow microbubble generator to decompose persistent substances. However, ozone gas reacts with organic matter in the wastewater, making it difficult to fully decompose the persistent substances. Microbubble treatment has proven particularly difficult when treating wastewater with a high organic content, i.e., wastewater with a high chemical oxygen demand (CODMn) in the acidic high-temperature permanganate process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-172892 [Non-patent literature]

[0005] [Non-Patent Document 1] Masayoshi Takahashi et al., "The Latest Technology of Fine Bubbles - From the Generation and Characteristics of Microbubbles and Nanobubbles to Applications in Food, Agriculture, Environmental Purification, and Medicine," NTS Publishing Co., Ltd., 308-312 (2006) [Non-patent document 2] Masayoshi Takahashi, Journal of the Society of Seawater Science of Japan, Vol. 64, No. 1, 19-23 (2010) Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a wastewater treatment device that has a high removal rate of persistent substances. [Means for solving the problem]

[0007] The first aspect of the present invention is a wastewater treatment device comprising a treatment tank for treating wastewater containing a persistent substance selected from toluene and 1,4-dioxane, a microbubble generator, a circulation pump for circulating wastewater between the treatment tank and the microbubble generator, and a silent discharge ozone generator, wherein a gas containing ozone gas is supplied to the microbubble generator, and the concentration of ozone gas contained in the gas supplied to the microbubble generator is 50 to 5000 g / m 3 The flow rate of the gas supplied to the microbubble generator is in the range of 0.02 to 0.3 with respect to the flow rate of the circulating wastewater. the law of nature, ■ The microbubble generator is an ejector type and supplies gas from the outside. The nozzle is provided with an air inlet communicating with the flow path. The present invention relates to a wastewater treatment device. 。 [Effects of the Invention]

[0008] The wastewater treatment device of the present invention can effectively reduce persistent substances contained in wastewater, and can also reduce persistent substances contained in wastewater even if the wastewater has a high CODMn content. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] The treatment tank 1 used in the present invention is preferably made of a material that is ozone-resistant to an ozone concentration of about 100 ppm, such as SUS316, SUS304, fluororesin, polyvinyl chloride resin, acrylic resin, concrete, etc. The shape of the treatment tank is not important, but it is preferably sized so that the microbubble generator 2 can be installed at least 10 cm below the water surface, and more preferably so that it can be installed at least 20 cm below the water surface.

[0012] The microbubble generator 2 used in the present invention is preferably an ejector-type nozzle. The nozzle is preferably made of a material resistant to ozone concentrations of approximately 1000 ppm, such as SUS316, SUS304, fluororesin, polyvinyl chloride resin, or acrylic resin. Microbubble generation methods include various methods, such as ejector, cavitation, swirl flow, pressurized dissolution, and ultrasonic. While microbubble generation typically requires a small amount of gas to be supplied to the microbubble generator, ejector-type nozzles have a high vacuum flow path, allowing microbubbles to be generated even with a larger gas supply than other methods. In other words, the use of an ejector-type nozzle allows for the generation of large volumes of microbubbles, enabling the efficient decomposition of persistent substances. Furthermore, because the flow path of the ejector-type nozzle is a high vacuum, gas is self-supplied to the nozzle through the air inlet 6 shown in Figure 1. The gas flow rate can be controlled by adjusting the valve 5 or the amount of ozone gas generated by the ozone generator 4.

[0013] The circulation pump 3 used in the present invention may be either a submersible pump or a land-based pump. The number of times that the circulation pump 3 circulates the wastewater between the treatment tank 1 and the microbubble generator 2 is preferably 0.08 to 2 times per minute, more preferably 0.1 to 1 time per minute. By setting the number of times to 0.08 or more, the wastewater can be made uniform within the treatment tank 1. Furthermore, 2 times or less reduces the energy consumption of the circulation pump 3, which is preferable from the standpoint of cost-effectiveness.

[0014] The gas supplied to the microbubble generator 2 may be ozone gas, oxygen, air, or a mixture thereof, and is preferably a gas containing ozone gas. Microbubbles containing ozone gas are preferred because they generate a significantly greater amount of hydroxyl radicals than microbubbles containing oxygen or air. An ozone generator is preferably used as a means for supplying ozone gas. Using an ozone generator allows for efficient supply of ozone. Ozone generation methods include silent discharge, ultraviolet lamp, corona discharge, and plasma, but it is more preferable to use a silent discharge ozone generator, which can stably supply high-concentration ozone gas.

[0015] The flow rate of the gas supplied to the microbubble generator 2 is preferably in the range of 0.02 to 0.3 relative to the flow rate of the circulating wastewater. By setting it in this range, the supplied gas efficiently becomes microbubbles with a diameter of 50 μm or less, and persistent substances can be effectively reduced.

[0016] The ozone gas supplied from the ozone generator 4 contains oxygen, and the ozone gas concentration in the gas is 50 to 5000 g / m 3 It is preferable that the concentration of ozone gas is in the range of 50 g / m 3 At or above this level, the amount of hydroxyl radicals generated increases significantly, which is preferable in that it increases the effect of reducing persistent substances. Also, if the ozone concentration is too high, not only is there a risk of corrosion of the equipment, but the waste ozone gas is discharged unreacted at a high concentration, so that the concentration is less than 5000 g / m. 3 It is preferable to do the following:

[0017] The rate of ozone gas generated by the ozone generator 4 is determined from the ozone gas concentration and the flow rate of the gas containing ozone gas, and is preferably in the range of 0.1 to 1 g / h per 1 L of wastewater present in the treatment tank 1. An ozone gas generation rate of 0.1 g / h or more per 1 L of wastewater is preferable because the wastewater contains a high concentration of organic matter, and sufficient hydroxyl radicals are generated even when the organic matter reacts with ozone, allowing for effective reduction of persistent substances. Furthermore, because a large-capacity ozone generator is required to increase the rate of ozone gas generation, a rate of 1 g / h or less is preferable from the standpoint of cost-effectiveness.

[0018] The wastewater to be treated includes wastewater containing dioxins, environmental hormones, polycyclic aromatic hydrocarbons (PAHs), polyvinyl alcohol (PVA), organic solvents, and surfactants, regardless of the CODMn value of the wastewater. Furthermore, the persistent substances targeted by the present invention include organic mercury compounds, organic arsenic compounds, trichloroethylene, tetrachloroethylene, carbon tetrachloride, dichloromethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,3-dichloropropene (agricultural chemical), thiuram (agricultural chemical), simazine (agricultural chemical), thiobencarb (benthiocarb) (agricultural chemical), benzene, chloroform, trans-1,2-dichloroethylene, 1,2-dichloropropane, p-dichlorobenzene, isoxathion, diazinon, fenitrothion (MEP), isoprothiolane, oxine copper (organic copper), chlorothalonil (TPN), propyzamide, EPN, dichlorvos (DDVP), fenobucarb (BPMC), iprobe Nphos (IBP), chlornitrofen (CNP), toluene, xylene, diethylhexyl phthalate, phenols, organophosphates, anionic surfactants, nonionic surfactants, phthalates, hexachlorocyclohexane (HCH), 2-methylisoborneol, geosmin, formaldehyde, dichloroacetic acid, trichloroacetic acid, dichloroacetonitrile, chloral hydrate, humus (humic substances), 1,4-dioxane, dioxins, polychlorinated biphenyls, polybrominated biphenyls, hexachlorobenzene, pentachlorophenol, 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, amitrole, atrazine, alachlor, simazine, hexachlorocyclohexane (HCH), carbaryl, chlordane, oxychlordane, trans-nonachlor, 1,2-Dibromo-3-chloropropane (DBCP), DDT, DDE and DDD, Kelthane (Dicofol), Aldrin, Endrin, Dieldrin, Endosulfan (Benzoepin), Heptachlor, Heptachlor Epoxide, Malathion (Malanthion), Methomyl (Lannat), Methoxychlor, Mirex, Nitrofen, Toxaphene (Camphechlor), Tributyltin (TBT), Triphenyltin (TPT), Trifluralin, Alkylphenols, Bisphenol A, Phthalates, Di-2-ethylhexyl phthalate, Butyl Benzyl phthalate These include benzo[a]pyrene, di-n-butyl phthalate, dicyclohexyl phthalate, diethyl phthalate, benzo[a]pyrene, 2,4-dichlorophenol, di-2-ethylhexyl adipate, benzophenone, 4-nitrotoluene, octachlorostyrene, aldicarb, benomyl (benlate), keypon (chlordecone), mancozeb (mancozeb), maneb, metiram, metribuzin, cypermethrin, esfenvalerate, fenvalerate, permethrin, vinclozolin, zineb, ziram, dipentyl phthalate, dihexyl phthalate, and dipropyl phthalate. [Example]

[0019] The present invention will be described below with reference to examples, but the present invention is not limited thereto in any way.

[0020] [Example 1] Using the wastewater treatment device shown in Figure 1, an experiment was conducted under the following conditions. Wastewater: Organic solvent-containing wastewater containing 2.6 mg / L of 1,4-dioxane (CODMn: 2000.0 mg / L) Treatment tank 1: Acrylic resin tank (width 900 x depth 450 x height 450 mm) Microbubble generator 2: Ejector type nozzle Circulation pump 3: Land circulation pump Volume of wastewater to be treated: 150L Flow rate circulated by circulating pump 3: 114 L / min The wastewater was treated using air as the gas supplied to the microbubble generator 2. The opening of the valve 5 was adjusted to set the flow rate A of the gas supplied to the microbubble generator 2 to 15 L / min. 150 L of wastewater was placed in treatment tank 1, and the wastewater was circulated using circulation pump 3 while air was supplied to microbubble generator 2. The wastewater was treated with microbubbles for 146 hours. The concentration of 1,4-dioxane before and after treatment with microbubbles was measured in accordance with JIS K0125, and the removal rate of 1,4-dioxane was calculated.

[0021] [Example 2] The same treatment as in Example 1 was carried out except that the opening of the valve 5 was adjusted and the flow rate A of the gas supplied to the microbubble generator 2 was changed to 32 L / min.

[0022] [Example 3] The opening of the valve 5 was adjusted to allow the ozone gas generated by the ozone generator 4 to have a concentration of 56 g / m 3 in addition to the air. 3 The treatment was carried out in the same manner as in Example 1 except that the gas containing ozone was taken in (the flow rate of air was 15 L / min, and the flow rate X of the gas containing ozone gas was 5 L / min).

[0023] [Example 4] The same treatment as in Example 1 was carried out except that the gas supplied to the microbubble generator 2 was changed to oxygen and the flow rate A of the gas supplied to the microbubble generator 2 was changed to 5 L / min.

[0024] The results of Examples 1 to 4 are shown in Table 1. The number of times that wastewater is circulated through the treatment tank 1 and the microbubble generator 2 is calculated in W / V [1 / min].

[0025] [Table 1]

[0026] In Examples 1 to 4, in which the gases supplied were air, ozone-containing gas, and oxygen, it was revealed that 1,4-dioxane was effectively reduced by using the wastewater treatment device of the present invention.

[0027] [Example 5] Using the wastewater treatment device shown in Figure 1, an experiment was conducted under the following conditions. Wastewater: organic solvent-containing wastewater containing 1,4-dioxane at 100.0 mg / L (CODMn: 310.0 mg / L) Treatment tank 1: Acrylic resin tank (width 900 x depth 450 x height 450 mm) Microbubble generator 2: Ejector type nozzle Circulation pump 3: Land circulation pump Volume of wastewater treated: 125L Flow rate circulated by circulation pump 3: W: 80 L / min Flow rate of gas containing ozone gas generated from ozone gas generator 4: 5 L / min Amount of ozone gas generated from ozone gas generator 4: 16.8 g / h Flow rate A of gas supplied to microbubble generator 2: 5 L / min 125 L of wastewater was placed in the treatment tank 1, and the wastewater was circulated by the circulation pump 3, while the ozone gas concentration was 56 g / m 3 The gas was supplied to the microbubble generator 2, and the wastewater was treated with microbubbles for 13.5 hours. The concentration of 1,4-dioxane before and after treatment with microbubbles was measured in accordance with JIS K0125, and the removal rate of 1,4-dioxane was calculated.

[0028] [Example 6] The same treatment as in Example 5 was carried out except that the flow rate X of the gas containing ozone gas was changed to 1.5 L / min, the amount of ozone generated O was changed to 10.8 g / h, and the flow rate A of the gas to be supplied was changed to 1.5 L / min. The ozone gas concentration at this time was 120 g / m 3 It was.

[0029] [Example 7] The same treatment as in Example 5 was carried out except that the flow rate A of the gas supplied to the microbubble generator 2 was changed to 20 L / min by adjusting the opening of the valve 5 to take in air at 15 L / min in addition to the gas containing ozone gas into the microbubble generator. The ozone gas concentration at this time was 14 g / m 3 It was.

[0030] [Example 8] The same treatment as in Example 5 was carried out except that the flow rate A of the gas supplied to the microbubble generator 2 was changed to 40 L / min by adjusting the opening of the valve 5 to take in air at 35 L / min in addition to the gas containing ozone gas into the microbubble generator. The ozone gas concentration at this time was 7 g / m 3 It was.

[0031] [Example 9] The same treatment as in Example 5 was carried out except that the wastewater volume V was changed to 90 L, the circulating flow rate W was changed to 6 L / min, the flow rate X of the ozone-containing gas was changed to 1 L / min, the ozone generation rate O was changed to 9.0 g / h, and the flow rate A of the supplied gas was changed to 1 L / min. The ozone gas concentration at this time was changed to 150 g / m 3 It was.

[0032] [ Comparative Example 2 ] The same treatment as in Example 5 was carried out except that the gas supplied to the microbubble generator 2 was oxygen.

[0033] [Example 11] Treatment tank 1: Acrylic resin tank (width 300 x depth 250 x height 450 mm) Volume of wastewater treated: 24L Circulating flow rate W: 12L / min Flow rate of gas containing ozone gas: 2.4 L / min Ozone gas generation rate: 14.4 g / h Flow rate A of gas supplied to microbubble generator 2: 2.4 L / min The treatment was carried out in the same manner as in Example 5, except that the conditions were changed to those described above. The ozone gas concentration was 100 g / m 3It was.

[0034] [ Comparative Example 3 ] The same treatment as in Example 11 was carried out except that a swirl flow type nozzle was used for the microbubble generator 2, the flow rate X of the gas containing ozone gas was changed to 1 L / min, the amount of ozone generated O was changed to 9.0 g / h, and the flow rate A of the gas to be supplied was changed to 1 L / min. The ozone gas concentration at this time was 150 g / m 3 It was.

[0035] [Example 13] The same treatment as in Example 5 was carried out except that the wastewater to be treated was organic solvent and surfactant-containing wastewater containing 23.4 mg / L of 1,4-dioxane (CODMn: 23,000.0 mg / L) and the treatment time was changed to 40 hours.

[0036] [Comparative Example 1] As a comparative example of the present invention, an air diffuser was installed instead of the microbubble generator 2. Other than that, the same treatment as in Example 5 was carried out.

[0037] Example 5 9. Example 11. Example 13. Comparative Example 1 ~3 The results are shown in Table 2.

[0038] [Table 2]

[0039] Example 5 - Using wastewater with CODMn of 310.0 mg / L 9. Example 11 , Comparative Example 1 ~3 It can be seen that the Example using the wastewater treatment device of the present invention reduces 1,4-dioxane more effectively than the Comparative Example. Furthermore, it was revealed that the use of the device of the present invention can reduce 1,4-dioxane even in the wastewater of Example 13, which contains a high concentration of organic matter and has a CODMn of 23,000.0 mg / L. [Explanation of symbols]

[0040] 1 Treatment tank 2 Microbubble generator 3 Circulation Pump 4. Ozone Generator 5 valves 6 Air supply port 7~11 Transfer Line

Claims

1. In a wastewater treatment device, a treatment tank for treating wastewater containing a persistent substance selected from toluene and 1,4-dioxane; A microbubble generator, a circulation pump that circulates wastewater through the treatment tank and the microbubble generator; Equipped with a silent discharge ozone generator, A gas containing ozone gas is supplied to the microbubble generator, The concentration of ozone gas contained in the gas supplied to the microbubble generator is 50 to 5000 g / m 3 is in the range of The flow rate of the gas supplied to the microbubble generator is in the range of 0.02 to 0.3 with respect to the flow rate of the circulating wastewater, The wastewater treatment device is characterized in that the microbubble generator is an ejector type, and is a nozzle having an air inlet for supplying gas from the outside and connected to a flow path.

2. 2. The wastewater treatment device according to claim 1, wherein the number of times that the wastewater is circulated between the treatment tank and the microbubble generator by the circulation pump is in the range of 0.08 to 2 times per minute.

3. 3. The wastewater treatment apparatus according to claim 1, wherein the amount of ozone gas generated by the ozone generator is in the range of 0.1 to 1 g / h per 1 L of wastewater present in the treatment tank.

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