1 DESCRIPTION METHOD FOR TREATING WASTE WATER CONTAINING ORGANIC COMPOUND 5 TECHNICAL FIELD [0001] The present invention relates to a method for treating waste water containing an organic compound and 10 particularly relates to a method for treating waste water containing an organic compound, by which an organic compound in organic-compound-containing waste water can be decomposed with high efficiency by using hydrogen peroxide as an oxidant in the presence of a catalyst. 15 BACKGOUND ART [0002] As a method for treating organic-compound containing waste water containing a variety of solvents, 20 organic chloride compounds and TOC in a further broader range discharged from oil plants, chemical plants and power plants, etc., for example, as a treatment method of waste water containing an organic compound, an activated carbon adsorption method and biotreatment method are 25 typical. However, in the activated carbon adsorption 2 method, although an organic compound is adsorbed to activated carbon, there are disadvantages such that the activated carbon after reaching adsorption equilibration has to be regenerated, highly condensed regenerated waste 5 liquid is generated with the regeneration, and a treatment thereof becomes necessary. Also, in a biotreatment method, a large capacity bio-reaction tank is necessary due to slow reaction speed and, furthermore, sludge is generated, which are disadvantageous. 10 [0003] Therefore, to overcome those disadvantages, methods of oxidative decomposition of organic-compound-containing waste water by using a catalyst have been attempted. For example, as a method for treating waste water containing 15 an imidazolidinone-based compound, the patent document 1 discloses a waste water treatment method, wherein an imidazolidinone-based compound is added with hydrogen peroxide and, under a heating condition of 100 to 180'C, the water is fed through a reaction column filled with a 20 catalyst carrying noble metals on a porous carrier so as to bring the waste water to contact with the catalyst, so that oxidative decomposition of an imidazolidinone-based compound is performed. [0004] 25 In the patent document 1, a plurality of columns 3 filled with a catalyst carrying a noble metal are connected in series and, waste water passed through a catalyst-filled column on the first stage is introduced to another catalyst-filled column on the second stage and 5 still another on the third stage successively so as to perform a multiple-stage catalyst treatment, consequently oxidative decomposition of an organic compound can be performed. 10 [Prior Art Documents] [Patent Article] [0005] [Patent Article 1] Japanese Patent No. 3457143 Publication 15 DISCLOSURE OF THE INVENTION [Object(s) to be Attained by the Invention] [0006] However, in the treatment method of waste water 20 containing an imidazolidinone-based compound described in the patent document 1 above, all of treatment water flowing through the catalyst-filled columns connected in series is fed to a catalyst-filled column on the subsequent stage. Here, when using hydrogen peroxide as 25 an oxidant in each catalyst-filled column, a gas is 4 generated from a catalyst reaction with the waste water. Then, the generated gas is also fed to a catalyst-filled column on the subsequent stage. Therefore, it was found out that an amount of gas to be fed to a catalyst-filled 5 column becomes larger on later stages and contact between a catalyst and waste water becomes less to deteriorate the reaction speed, consequently, oxidative decomposition does not proceed sufficiently in some cases. Also, when a gaseous component is large, an apparent linear velocity 10 of flowing waste water becomes faster and a catalyst in the catalyst columns is liable to be fluidized, which is disadvantageous. [0007] The present invention was made in consideration of 15 the circumstances above and has an object thereof to provide a method for treating waste water containing an organic compound, by which an organic compound in organic-compound-containing waste water can be decomposed with high efficiency by using hydrogen peroxide as an 20 oxidant in the presence of a catalyst. [Means to Attain the Object(s)] [0008] To attain the above objects, the present invention provides a method for treating waste water containing an 25 organic compound, for performing contact oxidative 5 decomposition on an organic compound by adding hydrogen peroxide to the waste water containing an organic compound and allowing the waste water to pass thorough an oxidation catalyst reaction column, wherein the oxidation 5 catalyst reaction column has a header tube on top thereof, a plurality of the oxidation catalyst reaction columns are arranged in series for the waste water to flow serially, and a gas is discharged from the header tube of each of the oxidation catalyst reaction columns. 10 (Invention 1) [0009] According to the invention (Invention 1), an organic compound can be decomposed by adding hydrogen peroxide to the organic-compound-containing waste water 15 and allowing the waste water to pass thorough an oxidation catalyst reaction column to perform a multiple step catalyst treatment on the organic-compound containing waste water. Here, a gas is generated due to oxidative decomposition of an organic compound by 20 hydrogen peroxide and oxidation catalyst, however, the gas generated in the oxidation catalyst reaction columns can be discharged by providing a header tube on top of each of the oxidation catalyst reaction columns. Thereby, it is possible to maintain contact between a catalyst and 25 organic-compound-containing waste water in each oxidation 6 catalyst reaction column, proceed oxidative decomposition sufficiently and decompose an organic compound sufficiently. [0010] 5 In the invention above (Invention 1), preferably the hydrogen peroxide is added at a stage prior to each of the plurality of oxidation catalyst reaction columns (Invention 2). [0011] 10 According to the invention (Invention 2), it is possible to maintain a preferable oxidative decomposition reaction in each of the oxidative catalyst reaction columns and to maintain an organic compound concentration sufficiently low in final treatment water. 15 [0012] According to the method for treating organic compound-containing waste water of the present invention, since hydrogen peroxide is added to waste water containing an organic compound, the water is allowed to 20 pass through a plurality of oxidation catalyst reaction columns, each having a header tube on top thereof, to perform a multiple-step catalyst treatment on organic compound-containing waste water, a gas generated by oxidative decomposition of an organic compound by 25 hydrogen peroxide and an oxidation catalyst in each 7 oxidation catalyst reaction column is discharged from the header tube on top of each oxidation catalyst reaction column. Therefore, it is possible to maintain preferable contact between a catalyst and waste water, proceed 5 oxidative composition sufficiently and decompose an organic compound sufficiently. BRIEF DESCRIPTION OF DRAWINGS [0013] 10 [FIG. 1] A systematic diagram showing a system capable of implementing a method for treating waste water containing an organic compound according to an embodiment of the present invention. [FIG. 2] A systematic diagram showing a system capable 15 of implementing a method for treating waste water containing an organic compound according to prior art. MODE FOR CARRYING OUT THE INVENTION [0014] 20 Below, a method for treating organic-compound containing waste water of the present embodiment will be explained with reference to FIG. 1. FIG. 1 is a systematic diagram showing a system capable of implementing a treatment method of waste water containing 25 an organic compound according to an embodiment of the 8 present invention. [0015] In FIG. 1, 1 indicates a storage tank for storing organic-compound-containing waste water W, the storage 5 tank 1 is connected in series with a first oxidation catalyst reaction column 2, second oxidation catalyst reaction column 3 and third oxidation catalyst reaction column 4, each filled with an oxidation catalyst C, through a first flow path 5, second flow path 6 and third 10 flow path 7, respectively, in a way that water can flow upward, and the third oxidation catalyst reaction column 4 is connected to a fourth flow path 8 at an upper portion. The first flow path 5 is provided with a pump P and a first hydrogen peroxide supply means 9, the second 15 flow path 6 is provided with a second hydrogen peroxide supply means 10, the third flow path 7 is provided with a third hydrogen peroxide supply means 11 and the fourth flow path 8 is provided with a cooling device 12 and a pressure adjusting valve 13. 20 [0016] Furthermore, on tops of the first oxidation catalyst reaction column 2, second oxidation catalyst reaction column 3 and third oxidation catalyst reaction column 4, header tubes 14A, 14B and 14C are provided, 25 respectively, and the header tubes 14A, 14B and 14C join 9 through a discharge tube 15. Note that 16 indicates a pressure adjusting valve provided on the downstream side of the discharge tube 15. [0017] 5 In the system explained above, the oxidation catalyst C to be filled in the oxidation catalyst reaction columns 2, 3 and 4 is not particularly limited as long as it can exhibit an oxidizing function in the presence of hydrogen peroxide. For example, platinum, 10 palladium, ruthenium, iridium, rhodium, gold, silver and osmium and other noble metal catalysts may be used. Those catalysts may be used alone by selecting one kind or in combination of two or more kinds. A carrier for carrying a catalyst is not particularly limited and, for example, 15 titania, silica, alumina, silica alumina, zeolite, activated carbon, polytetrafluoroethylene and other chemical proof resins, etc. may be used. A carrier for carrying a catalyst is preferably a porous carrier. A carrying amount of a noble metal catalyst is preferably 20 0.05 to 10 wt% and more preferably 0.1 to 5 wt%. [0018] Next, a method for treating waste water containing an organic compound of the present embodiment using a system configured as above will be explained. 25 [0019] 10 Organic-compound-containing waste water to be treated in the present invention is waste water containing an organic compound discharged from a chemical plant, paper factory, food/beverage manufacturing factory, 5 garbage incineration plant, night-soil treatment plant and sewerage treatment plant, etc. [0020] First, organic-compound-containing waste water W stored in the storage tank 1 is heated to 100 to 180'C as 10 needed, then, allowed to pass through the first flow path 5 by the pump P. Here, hydrogen peroxide is added from the first hydrogen peroxide supply means 9 to the organic-compound-containing waste water W. An adding amount of hydrogen peroxide here is 0.5 to 1 time a 15 hydrogen peroxide amount obtained from the formula (1) shown below by using an oxygen amount (0) obtained from a theoretical oxygen demand. Oxygen Amount (0) x 34/16 = Hydrogen Peroxide Amount ... (1) 20 Also, hydrogen peroxide adding amounts at the second hydrogen peroxide supply means 10 and third hydrogen peroxide supply means 11 are smaller than that added from the hydrogen peroxide supply means 9. [0021] 25 This organic-compound-containing waste water W is 11 supplied to flow upward to the first oxidation catalyst reaction column 2 to bring the organic-compound containing waste water W to contact with the oxidation catalyst C. Here, an SV of the organic-compound 5 containing waste water W is preferably 0.5 to 10h' and particularly preferably 0.5 to 5h . Reaction time necessary for decomposing an organic compound is affected by a concentration and kind of an organic compound in the organic-compound-containing waste water W, water quality, 10 such as other compounds, and water temperature, etc., so that the SV may be selected suitably considering these conditions. [0022] The hydrogen peroxide becomes an active oxygen due 15 to the catalyst and decomposed by an oxidative decomposition reaction of an organic compound. During this, elements C and N included in an organic compound become a CO 2 gas and N 2 gas. Since unreacted hydrogen peroxide becomes a gaseous component, such as an oxygen 20 gas, on the surface of the oxidation catalyst C and the organic-compound-containing waste water W flows upward to the first oxidation catalyst reaction column 2, the gaseous component is collected at an upper portion of the first oxidation catalyst reaction column 2. If the 25 gaseous component is left as it is, it is fed to the 12 second oxidation catalyst reaction column 3 and further to the third oxidation catalyst reaction column 4, which results in deterioration of efficiency of contact between the organic-compound-containing waste water W and the 5 oxidation catalyst C to hinder the oxidation catalyst from working effectively to decompose an organic compound. However, in the present embodiment, since the header tube 14A is provided at the top of the first oxidation catalyst reaction column 2, the gaseous component is fed 10 through the header tube 14A to the discharge tube 15, a pressure thereof is adjusted to a predetermined pressure by the pressure adjusting valve 16 and discharged. As a result, not only an oxidation reaction at the first oxidation catalyst reaction column 2 is performed 15 effectively, but only the organic-compound-containing waste water W after subjected to the catalyst oxidation treatment on the first stage is discharged from the first oxidation catalyst reaction column 2 to the second flow path 6. 20 [0023] Then, on the subsequent stage of the first oxidation catalyst reaction column 2, the second oxidation catalyst reaction column 3 through the second flow path 6, then, the third oxidation catalyst reaction 25 column 4 through the third flow path 7 are connected in 13 series in this order to perform contact catalyst oxidative decomposition on multiple (three) stages while discharging gas to be generated in the same way, so that an organic compound can be decomposed. During this, a 5 hydrogen peroxide solution is preferably added to each oxidation catalyst reaction column by providing the second hydrogen peroxide supply means 10 to the second flow path 6 and third hydrogen peroxide supply means 11 to the third flow path 7. By configuring the contact 10 oxidative decomposition process to have multiple stages and adding hydrogen peroxide at each stage, it is possible to attain a state that an active oxygen is always present in each oxidation catalyst reaction column, and decomposition of an organic compound can proceed 15 effectively. [0024] After performing a three-stage contact oxidative decomposition process in this way, treatment water from the fourth flow path 8 may be cooled to be close to the 20 normal temperature by the cooling device 12 and discharged from the fourth flow path 8 with a predetermined pressure by the pressure adjusting valve 13. Then, after going through other necessary treatment properly, it may be released to the external environment 25 or collected for reuse.
14 [0025] Note that the oxidation catalyst C may be used for a long period of time, but when deteriorated, it may be activated with acid for reuse or collected as a material 5 for catalyst manufacture for reuse, etc. [0026] Explanations were made on a method for treating organic-compound-containing waste water W of the present embodiment, however, the present invention is not limited 10 to the embodiment and may be modified in various ways. [0027] For example, three oxidation catalyst reaction columns are arranged in series for water to pass serially in the present embodiment, but it may be configured to 15 have two stages or four or more stages as long as it is multiple. [EXAMPLES] [0028] Below, the present invention will be explained 20 further in detail with specific examples. [0029] [Example 1] Three oxidation catalyst reaction columns 2, 3 and 4 were connected in series, each of them was filled with 25 approximately 500ml of a catalyst, wherein 100 parts by 15 weight of titania balls carry 0.5 part by weight of platinum, and header tubes 14A, 14B and 14C for releasing a gas were respectively connected thereto, so that the system shown in FIG. 1 was configured. Organic-compound 5 containing waste water W having pH4 containing TOC at a concentration of 526mg/L was allowed to flow though at a flow amount of 1.5L/hr at 160'C with an operation pressure of 8kg/cm2 at an SV of 3h , and a three-stage oxidative decomposition treatment was performed while 10 discharging a gas generated in the respective oxidation catalyst reaction columns 2, 3 and 4 from the discharge tube 15 through the header tubes 14A, 14B and 14C. Hydrogen peroxide was added in an amount of 2500mg/L on the first stage and 1000mg/L on the second and third 15 stages. A TOC concentration of treatment water at an outlet of each of the oxidation catalyst reaction columns 2, 3 and 4 was measured and the results are shown in Table 1. [0030] 20 [Comparative Example 1] Other than connecting the oxidation catalyst reaction columns 2, 3, 4 in series without connecting the header tubes 14A, 14B and 14C for releasing a gas and providing a gas/liquid separator 17 at an end of the 25 fourth flow path 8 to discharge treatment water and a 16 gaseous component separately through the fourth flow path 8 from the third oxidation catalyst reaction column 4, the system shown in FIG. 2 was configured in the same way as in example 1. Note that same reference numbers as in 5 FIG. 1 are added to the same components in FIG. 2 for convenience and detailed explanations thereon will be omitted. The same organic-compound-containing waste water W as in example 1 was allowed to pass through this system under the same condition and hydrogen peroxide was added 10 under the same condition to perform a three-stage oxidative decomposition treatment. A TOC concentration of treatment water at an outlet of each of the oxidation catalyst reaction columns 2, 3 and 4 was measured and the results are also shown in Table 1. 15 [0031] [Table 1] TOC Concentration (mg/L) First- Second- Third Example No. Initial Stage Stage Stage TOC Treatment Treatment Treatment Water Water Water Example 1 526 215 66 18 Comparative 526 315 130 65 Example 1 [0032] As is clear from Table 1, the TOC concentration was 20 reduced to 5% or lower in example 1, wherein oxidation 17 catalyst columns 2, 3, 4 were connected in series, each of them is connected to header tubes 14A, 14B and 14C for gas release and a three-stage oxidative decomposition treatment was performed while discharging a gas generated 5 in the respective oxidation catalyst reaction columns from the discharge tube 15. On the other hand, in comparative example 1, wherein the treatment was performed without discharging a gas generated in the respective oxidation catalyst reaction columns, the TOC 10 concentration was not reduced to 10%. Particularly, a large difference was observed in the TOC concentration in the first oxidation catalyst reaction column 2 on the first stage between the two. It is considered that this was because of difference in efficiency of contact 15 between an oxidation catalyst and the organic-compound containing waste water W caused by an existence/absence of a gaseous component. [Explanation of Reference Numbers] 20 [0033] 1... storage tank 2... first oxidation catalyst reaction column 3... second oxidation catalyst reaction column 4... third oxidation catalyst reaction column 25 9... first hydrogen peroxide supply means 18 10... second hydrogen peroxide supply means 11... third hydrogen peroxide supply means 14A, 14B and 14C... header tube 15... discharge tube 5 C... oxidation catalyst