AU2013218880B2

AU2013218880B2 - Method for treating waste water containing organic compound

Info

Publication number: AU2013218880B2
Application number: AU2013218880A
Authority: AU
Inventors: Toshitsugu Nakahara
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2012-02-10
Filing date: 2013-02-05
Publication date: 2017-12-07
Anticipated expiration: 2033-02-05
Also published as: JP2013163150A; WO2013118702A1; AU2013218880A1

Abstract

Waste water (W) containing an organic compound (also referred to as "organic-compound-containing waste water (W)) is supplied into a first oxidation catalyst reaction column (2) while adding aqueous hydrogen peroxide to the organic-compound-containing waste water (W) from a first hydrogen peroxide supply means (9) to bring the organic-compound-containing waste water (W) into contact with an oxidation catalyst (C), thereby decomposing the organic compound by an oxidative decomposition reaction. Simultaneously, a gaseous component is generated. However, a header tube (14A) is provided at the top of the first oxidation catalyst reaction column (2) and therefore the gaseous component is discharged from a gas discharge tube (15) through the header tube (14A). The waste water (W) is then allowed to pass through a second oxidation catalyst reaction column (3) and a third oxidation catalyst reaction column (4) in this order while discharging a generated gas. In this manner, contact catalyst oxidative decomposition of the organic compound is carried out in three stages. Thus, the organic compound can be highly decomposed. According to this method for treating organic-compound-containing waste water, it becomes possible to decompose an organic compound in the organic-compound-containing waste water with high efficiency using hydrogen peroxide in the presence of a catalyst.

Description

METHOD FOR TREATING WASTE WATER CONTAINING ORGANIC COMPOUND

DEFINITION

In the present description and claims, the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises".

TECHNICAL FIELD

The present disclosure relates to a method for treating waste water containing an organic compound and 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.

BACKGOUND ART

The reference to prior art in this specification is not and should not be taken as an acknowledgment or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia or in any other country.

As a method for treating organic-compound-containing waste water containing a variety of solvents, 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 typical. However, in the activated carbon adsorption 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 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.

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 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 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.

In the patent document 1, a plurality of columns 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 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.

[Prior Art Documents] [Patent Article] [Patent Article 1] Japanese Patent No. 3457143 Publication

DISCLOSURE

However, in the treatment method of waste water 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 an oxidant in each catalyst-filled column, a gas is 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 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 of flowing waste water becomes faster and a catalyst in the catalyst columns is liable to be fluidized, which is disadvantageous.

The present disclosure was made in consideration of 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, in some aspects, with high efficiency by using hydrogen peroxide as an oxidant in the presence of a catalyst.

The present disclosure provides a method for treating waste water containing an organic compound, for performing contact oxidative 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 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. (Disclosure 1)

According to the disclosure an organic compound can be decomposed by adding hydrogen peroxide to the organic-compound-containing waste water 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 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 organic-compound-containing waste water in each oxidation catalyst reaction column, proceed oxidative decomposition sufficiently and decompose an organic compound sufficiently.

In accordance with a further disclosure, there is provided a method for treating waste water containing an organic compound, for performing contact oxidative 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 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, the header tube of each of the oxidation catalyst reaction columns join through a discharge tube, and a pressure adjusting valve is provided on the downstream side of the discharge tube.

In the disclosures above, preferably the hydrogen peroxide is added at a stage prior to each of the plurality of oxidation catalyst reaction columns

According to the disclosure, 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.

According to the method for treating organic-compound-containing waste water of the present disclosure, since hydrogen peroxide is added to waste water containing an organic compound, the water is allowed to 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 hydrogen peroxide and an oxidation catalyst in each 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 oxidative composition sufficiently and decompose an organic compound sufficiently.

BRIEF DESCRIPTION OF DRAWINGS

[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 disclosure.

[FIG. 2] A systematic diagram showing a system capable of implementing a method for treating waste water containing an organic compound according to prior art.

MODE FOR CARRYING OUT THE DISCLOSURE

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 an organic compound according to an embodiment of the present disclosure .

In FIG. 1, 1 indicates a storage tank for storing organic-compound-containing waste water W, the storage 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 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 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.

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, respectively, and the header tubes 14A, 14B and 14C join through a discharge tube 15. Note that 16 indicates a pressure adjusting valve provided on the downstream side of the discharge tube 15.

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, 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, 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 0.05 to 10 wt% and more preferably 0.1 to 5 wt%.

Next, a method for treating waste water containing an organic compound of the present embodiment using a system configured as above will be explained.

Organic-compound-containing waste water to be treated in the present disclosure is waste water containing an organic compound discharged from a chemical plant, paper factory, food/beverage manufacturing factory, garbage incineration plant, night-soil treatment plant and sewerage treatment plant, etc.

First, organic-compound-containing waste water W stored in the storage tank 1 is heated to 100 to 180°C as 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 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)

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.

This organic-compound-containing waste water W is 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-containing waste water W is preferably 0.5 to 10h_1 and particularly preferably 0.5 to 5h_1. 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, such as other compounds, and water temperature, etc., so that the SV may be selected suitably considering these conditions.

The hydrogen peroxide becomes an active oxygen due 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 CCt gas and N2 gas. Since unreacted hydrogen peroxide becomes a gaseous component, such as an oxygen 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 gaseous component is left as it is, it is fed to the 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 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 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 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.

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 column 4 through the third flow path 7 are connected in 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 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 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 effectively .

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 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 or collected for reuse.

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 for catalyst manufacture for reuse, etc.

Explanations were made on a method for treating organic-compound-containing waste water W of the present embodiment, however, the present disclosure is not limited to the embodiment and may be modified in various ways.

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 have two stages or four or more stages as long as it is multiple. [EXAMPLES]

Below, the present disclosure will be explained further in detail with specific examples.

[Example 1]

Three oxidation catalyst reaction columns 2, 3 and 4 were connected in series, each of them was filled with approximately 500ml of a catalyst, wherein 100 parts by 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-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-1, and a three-stage oxidative decomposition treatment was performed while 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 lOOOmg/L on the second and third 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.

[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 fourth flow path 8 to discharge treatment water and a 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 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 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.

[Table 1]

As is clear from Table 1, the TOC concentration was reduced to 5% or lower in example 1, wherein oxidation 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 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 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 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] I. . . storage tank 2.. . first oxidation catalyst reaction column 3.. . second oxidation catalyst reaction column 4.. . third oxidation catalyst reaction column 9.. . first hydrogen peroxide supply means 10.. . second hydrogen peroxide supply means II. .. third hydrogen peroxide supply means 14A, 14B and 14C... header tube 15... discharge tube C... oxidation catalyst

Claims

CLAIMS [Claim 1] A method for treating waste water containing an organic compound, for performing contact oxidative 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 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, the header tube of each of the oxidation catalyst reaction columns join through a discharge tube, and a pressure adjusting valve is provided on the downstream side of the discharge tube. [Claim
2] The method for treating waste water containing an organic compound according to claim 1, wherein the hydrogen peroxide is added at a stage prior to each of the plurality of oxidation catalyst reaction columns.