JPH09117796A - How to remove persistent organic substances - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To improve ozone utilization efficiency without requiring a complicated ozone contact tower, and to effectively remove persistent organic substances. SOLUTION: The raw water is sequentially introduced into an ozone contact tower 3 and a biological filter bed 4, and when the hardly decomposable organic matter in the raw water is decomposed by an ozone oxidation treatment and a biological oxidation treatment, the biological treatment outflowed from the biological filter bed 4 Water is diverted and returned to the inflow section of the ozone contact tower 3 to be repeatedly subjected to ozone oxidation treatment and biological oxidation treatment. Thereby, the OH radical generated by the reaction between ozone and the radical-inducing substance in the raw water can be maximally utilized for the oxidation of the hardly decomposable organic substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing hardly decomposable organic substances contained in wastewater and the like.

[0002]

2. Description of the Related Art Wastewater containing hardly-decomposable organic substances such as COD is treated by successively introducing it into an ozone contact tower 1 and a biological filter bed 2 as shown in FIG. That is, the raw water is introduced into the ozone contact tower 1, and the hardly-decomposable organic matter in the raw water is subjected to ozone oxidation treatment with ozonized gas to produce biodegradable organic matter and nitrate nitrogen, and the ozone-treated water flowing out from the ozone contact tower 1 Is introduced into the biological filter bed 2 to decompose and remove biodegradable organic substances and nitrate nitrogen in the ozone-treated water by biooxidation treatment under anaerobic or aerobic conditions.

Further, as shown in FIG. 9, a treatment method is also performed in which a plurality of ozone contact towers 1 and biological filter beds 2 are provided and raw water is sequentially introduced into these ozone contact towers 1 and biological filter beds 2. There is.

[0004]

In the ozone oxidation treatment, ozone molecules dissolved in water directly oxidize an oxidizable substance (direct oxidation) and react with a radical inducing substance to form OH radicals. Oxidizes oxidizing substances (radical oxidation). In the case of direct oxidation, not all persistent organic substances can be oxidized because the reaction is selective. On the other hand, radical oxidation is not only useful for the oxidation of hardly decomposable organic substances because the OH radical has an extremely strong oxidizing power and small substance selectivity, but the reaction time can be shortened and the volume of the reaction tower can be reduced. Have advantages.

However, the wastewater containing persistent organic matter is
In addition to the radical inducer, a large amount of scavenger substances that decompose OH radicals are present. Therefore, the radical oxidation reaction is a competitive reaction between the hardly decomposable organic substance to be treated and the scavenger substance. Therefore, if there are many scavenger substances in the raw water, the proportion of ozone used for the oxidation of the hardly decomposable substance will be small.

Here, the conventional method is a method of passing the ozone contact tower 1 and the biological filter bed 2 in a transient manner as described with reference to FIG. 8, or a plurality of stages as described with reference to FIG. This is a method in which the ozone contact tower 1 and the biological filter bed 2 are provided in a transient manner. Therefore, even if dissolved ozone reacts with a radical inducer contained in raw water to generate OH radicals,
Since the generated OH radicals have almost no substance selectivity as described above, the OH radicals to be treated are hard-to-decompose organic substances,
It reacts with easily biodegradable organic substances generated by the oxidation and scavenger substances. As a result, the rate at which ozone is used to oxidize persistent organic substances becomes smaller. Therefore, as shown by the white squares in the graph of FIG. 10, it is necessary to increase the ozone reaction amount (g / m ³ ) in order to reduce the COD (index of the persistent organic matter amount) in the treated water. As indicated by the black squares in the graph, the ozone utilization efficiency (reaction amount of ozone ΔO ₃ / removable amount of persistent organic compounds ΔCOD) becomes worse as the ozone reaction progresses.

In order to increase the oxidation efficiency of the hardly decomposable organic matter, conditions are set such that the concentration of ozone and OH radicals is high and the concentration of easily biodegradable organic matter and scavenger substance is low in the ozone contact tower. Must. However, in the method shown in FIG. 8, the ozone and OH radicals are used for the reaction with the scavenger substance and the biodegradable organic substance in the ozone contact tower because of their large concentrations. Even in the method shown in FIG. 9, in the first step, the proportion of OH radicals decomposed by the scavenger substance is large, and in the second step, the radical inducer substances contained in the raw water are reduced by biooxidation to generate OH radicals. Since it becomes difficult, the radical oxidation necessary for the oxidation of the hardly decomposable organic substance becomes difficult to occur. Therefore, the reaction takes time, and the generated OH radicals are highly likely to be decomposed by the scavenger substance which reacts quickly.

The present invention solves the above-mentioned problems, and it is possible to improve the ozone utilization efficiency without the need for a complicated ozone contact tower and to effectively remove the persistent organic substances. To aim.

Specifically, the present invention keeps the concentrations of the scavenger substance and the biodegradable organic substance in the ozone contact column low, minimizes the influence thereof, and produces OH generated by the reaction between ozone and the radical-inducing substance. The purpose is to maximize the use of radicals for the oxidation of persistent organic substances.

[0010]

The method for removing persistent organic substances according to the present invention comprises introducing raw water into an ozone contact tower and a biological filter in order, and subjecting the persistent organic substances in the raw water to ozone oxidation treatment and biological oxidation. A method for removing persistent organic matter that decomposes by treatment, in which the biologically treated water that has flowed out of the biological filter is diverted and returned to the inlet of the ozone contact tower for repeated ozone oxidation and biological oxidation treatment. Is.

In addition, the method for removing persistent organic substances according to the present invention comprises introducing raw water into an ozone UV contact tower equipped with a UV irradiator and a biological filter in order, and subjecting the persistent organic substances in raw water to an ozone UV oxidation treatment. In the method for removing hardly decomposable organic matter that is decomposed by oxidization and bio-oxidation treatment, the bio-treated water that has flowed out of the biological filter is diverted and returned to the inflow part of the ozone UV contact tower to repeatedly perform ozone UV oxidation treatment and bio-oxidation It is designed to be processed.

Further, the method of removing the persistent organic substance of the present invention is to introduce the raw water into the ozone catalyst contact tower filled with the ozone radical generating catalyst and the biological filter in order to oxidize the persistent organic substance in the raw water by the ozone catalytic oxidation. In the method of removing persistent organic substances that decompose by treatment and biological oxidation treatment, the biological treated water that has flowed out of the biological filter is split and returned to the inflow part of the ozone catalyst contact tower to repeatedly perform ozone catalytic oxidation treatment and biological treatment. It is designed to be oxidized.

As the ozone contact tower, it is possible to use one having a structure in which the ozonized gas is diffused from a diffuser arranged at the bottom, or a U-tube type ozone contact tower equipped with an ejector type ozone injection device.

The biological filter bed can be removed under the aerobic condition or under the anaerobic condition by adding methanol as a hydrogen donor as necessary to remove not only organic compounds but also nitrogen compounds. it can. Therefore, an aerobic filter, an anaerobic filter, and a biological filter having an aerobic region and an anaerobic region in a single tank can be used.

According to the above-mentioned first construction, the raw water sequentially flows into the ozone contact tower and the biological filter bed, and the treated water is circulated and again flows into the ozone contact tower and the biological filter bed. Repeated. As a result, the hardly-decomposable organic matter is effectively removed in the single ozone contact tower and the biological filter bed. The reaction and behavior of organic substances by this treatment method are as follows.

1) Ozone-decomposable organic substances having multiple unsaturated bonds or benzene ring bonds contained in raw water are decomposed at the same time as they flow in, and converted into bio-degradable organic substances. Therefore, the concentration of easily decomposable organic substances in the ozone contact tower is reduced.

2) Organic substances which are hardly biodegradable such as humic acid and humic substances in raw water are converted into easily biodegradable organic substances by ozone and OH radicals. In this respect, these organics are radical scavengers, while at low concentrations these organics are radical inducers.

In the above-described circulation type ozone oxidation treatment method of the first structure, since humic acid and water from which humic substances have been removed by the biological oxidation treatment in the latter stage are circulated, humic acid and humin in the ozone contact tower are circulated. The quality of the substance becomes low, and these substances act as radical inducers that efficiently generate radicals, and act less as radical scavengers.

Therefore, the concentration of OH radicals in the ozone contact tower increases, and the OH radicals efficiently react with the hardly decomposable organic substance. Therefore, as in the conventional transient ozone oxidation treatment method, since the concentration of humic acid and humic substances in the ozone contact tower is high, these act as scavenger substances, and the reaction between these scavenger substances and ozone is difficult to decompose. It is prevented that the reaction between organic substances and ozone is superior.

3) Substances that are extremely difficult to decompose ozone and difficult to biodegrade, in other words, non-decomposable organic substances, cannot be removed by this system, so they flow out simply by circulating in the system.
That is, according to the first configuration described above, it is possible to efficiently decompose the moderately ozone-decomposable organic substance as shown in 1) and the moderately ozone-decomposable organic substance as shown in 2). Therefore, the ozone utilization efficiency in the decomposition of ozone hardly-decomposable organic substances becomes higher than before.

According to the above-mentioned second or third structure, OH is generated by the UV or ozone radical generating catalyst.
The amount of radicals generated can be increased, which allows
Substances that are extremely difficult to decompose ozone and difficult to biodegrade, in other words, non-decomposable organic substances, can be decomposed in the ozone contact tower or converted into easily biodegradable substances.

In other words, both the easily decomposable ozone organic matter and the hardly-decomposable ozone organic matter are efficiently decomposed inside the ozone contact tower, and the ozone utilization efficiency in the decomposition of the hardly-decomposable ozone organic matter is further improved. growing.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration of a water treatment device in which a method for removing a persistent organic substance according to an embodiment of the present invention is performed. In FIG. 1, 3 is an ozone contact tower constructed so that the water to be treated and ozone are efficiently contacted in the tower, and 4 is a living organism in which a tank is filled with a filter medium layer 5 to which microorganisms such as biological activated carbon are attached. It is a filter bed.

A raw water supply pipe 6 and a circulating water supply pipe 7 for circulating and returning circulating water from the latter stage are connected to the upper part of the ozone contact tower 3, and an ozone supply pipe 8 led from an ozone generator outside the tower.
And a liquid sending pipe 9 for sending the ozone-treated water subjected to the ozone oxidation treatment in the tower to the biological filter bed 4, and a diffuser pipe 10 communicating with the ozone supply pipe 8 is provided in the tower.

A liquid feed pipe 9 led from the ozone contact tower 3 is connected to the upper part of the biological filter bed 4, and a biological treated water pipe 11 for sending the biologically treated water which has been subjected to the biological oxidation treatment in the tank to the subsequent stage is connected to the bottom portion. doing.

The biologically treated water pipe 11 is guided to the water storage tank 12 to store the biologically treated water inside the water storage tank 12. In addition, the circulating water pump 13 is interposed, and a part of the biologically treated water in the water storage tank 12 is returned to the ozone contact tower 3 as circulating water at an arbitrary flow rate. 14 is a water tank 1
It is a treated water pipe that allows the remaining biological treated water in 2 to flow out as treated water.

The operation of the above configuration will be described. The raw water is supplied from the raw water supply pipe 6 into the ozone contact tower 3,
The circulating water is circulated and returned from the circulating water supply pipe 7, and the ozonized gas is introduced from the ozone supply pipe 8 through the diffuser pipe 10.

As a result, the water to be treated consisting of the raw water and the circulating water and the ozonized gas come into contact with each other, the ozone molecules are dissolved in the water to be treated, and the dissolved ozone directly oxidizes the ozone-decomposable organic substances in the water to be treated. To reduce the concentration of ozone-decomposable organic substances. At the same time, the dissolved ozone reacts with the radical inducer in the water to be treated to generate OH radicals,
The generated OH radicals radically oxidize the hardly-decomposable organic substance in the water to be treated, thereby reducing the concentration of the hardly-decomposable organic substance.

Then, the ozone-treated water containing the easily-biodegradable organic matter produced by the oxidation of the easily-decomposable ozone organic matter and the hardly-decomposable organic matter flows into the biological filter bed 4, and the easily-biodegradable organic matter in the ozone-treated water is Under aerobic conditions in which dissolved oxygen in which ozonized gas is dissolved is present, the microorganisms attached to the filter medium layer 5 ingest and oxidize it, and a part thereof is decomposed into carbon dioxide gas. The biologically treated water in the biological filter 4 is the biologically treated water pipe 1
1 is sent to the water tank 12.

The above operation will be described in more detail. As mentioned above, raw water contains various substances,
The concentrations of ozone-decomposable organic substances, biodegradable organic substances, radical scavengers, and radical-inducing substances are also high. On the other hand, the concentrations of these substances are extremely low in the circulating water that is circulated and returned to the ozone contact tower 3 after undergoing ozone oxidation in the ozone contact tower 3 and biological oxidation in the biological filter bed 4.
The proportion of ozone-decomposable organic substances in the organic substances contained in the circulating water is high.

Since such raw water and circulating water are mixed in the ozone contact tower 3, even when the concentration of substances such as humic acid and humic substances is high in the raw water, the concentration is reduced, and its function as a radical scavenger. It will be suppressed and the effect as a radical inducer will be exerted,
The concentration of OH radicals generated from dissolved ozone molecules increases. As a result, efficient direct oxidation of ozone and radical oxidation are performed, and ozone-decomposable organic substances are also effectively oxidized.

Therefore, in the above-mentioned method, it is difficult to efficiently generate OH radicals by the conventional ozone oxidation / biological oxidation multi-step treatment, and even when OH radicals are generated, radical scavenger is generated. Therefore, the disadvantage that it is not easy to effectively generate radical oxidation can be solved. Therefore, the ozone utilization efficiency in the decomposition of the ozone hardly decomposable organic matter becomes higher than ever.

FIG. 2 is a graph showing the amounts of easily decomposable organic substances, hardly decomposable organic substances and non-decomposable organic substances contained in water in each treatment process, in comparison with the conventional method. (Raw water + circulating water)
Has a mixing ratio of raw water and circulating water of 1: 9. In the circulation method of the present invention, the efficiency of removing hardly decomposable organic substances is improved as compared with the conventional transient method.

FIG. 3 is a graph showing the level of ozone consuming substances in the ozone contact tower in comparison with the conventional method. The level means an ozone equivalent ratio (mgO / mgO). In the circulation method of the present invention, compared to the conventional transient method,
The level of scavenger and easily decomposed COD is low, and the level of hardly decomposed COD is high.

In the ozone contact tower 3 described above, the ozonized gas is diffused from the diffuser pipe 10 provided at the bottom, and the water flow is directed downward, but the raw water supply pipe 6 and the circulating water supply pipe are used. 7 may be connected to the lower part of the ozone contact tower 3 so that the direction of the water flow is upward.

Alternatively, as shown in FIG. 4, by using a double tube type (U-tube type) ozone contact tower 16 equipped with ejector type ozone injection means 15, the dissolution efficiency of ozone can be enhanced. Reference numerals 9a and 9b are an ozone-treated water circulation pipe and an ozone-treated water circulation pump, respectively, which circulate the ozone-treated water. The raw water supply pipe 6 and the circulating water supply pipe 7 may be connected to the upper part of the ozone contact tower 16 as shown, or may be connected to the lower part of the ozone contact tower 16.

Further, although FIG. 1 shows the biological filter bed 4 in which the direction of the water flow is downward, the liquid feed pipe 9 is connected to the biological filter bed 4.
The biological treatment water pipe 11 may be connected to the upper part of the biological filter bed 4 so that the direction of the water flow is upward.

Alternatively, as shown in FIG. 5, an aeration device 19 is provided between the two filter medium layers 17 and 18, and a biological filter bed 20 having an anaerobic region and an aerobic region in one tower is provided. Can also be used. Thus, if the anaerobic condition is achieved together with the aerobic condition, the nitrogen compound can be removed in addition to the organic matter.

FIG. 6 shows the overall structure of a water treatment apparatus in which the method for removing hardly decomposable organic substances according to another embodiment of the present invention is carried out. This water treatment apparatus has a UV irradiation device 21 inside the ozone contact tower 3. 1 has the same configuration as that shown in FIG.

When the UV irradiation device 21 irradiates UV while introducing ozonized gas into the ozone contact tower 3,
O from ozone dissolved in treated water from ozonized gas
Generation of H radicals is promoted, and the concentration of OH radicals increases. As a result, even extremely difficult ozone-decomposable organic substances can be decomposed, and the ozone utilization efficiency in the decomposition of the hardly-decomposable organic substances is significantly increased.

FIG. 7 shows an overall structure of a water treatment apparatus in which the method for removing hardly decomposable organic substances according to still another embodiment of the present invention is carried out. This water treatment apparatus has a radical generating catalyst inside the ozone contact tower 3. The structure is the same as that shown in FIG. 1 except that 22 is filled.

When the ozonized gas is introduced into the ozone contact tower 3 filled with the radical generating catalyst 22, the ozone dissolved in the water to be treated from the ozonized gas is adsorbed on the surface of the radical generating catalyst 22, and the ozone is locally generated. As the concentration increases, the generation of OH radicals is promoted by the action of the active sites existing on the surface of the radical generation catalyst 22,
The concentration of radicals increases. As a result, an efficient radical oxidation reaction occurs on the surface of the radical generating catalyst 22, and the ozone utilization efficiency in the decomposition of the hardly decomposable organic substance is significantly increased.

[0043]

As described above, according to the present invention, the treated water that has undergone the ozone oxidation treatment and the biological oxidation treatment is returned to the ozone contact tower, so that OH radicals can be efficiently generated. At the same time, the adverse effect of the radical scavenger can be reduced, and thus the generated OH radical can be utilized for the radical oxidation reaction of the ozone hardly decomposable organic substance. As a result, it is possible to improve the ozone utilization efficiency in the decomposition of the hardly decomposable organic matter.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a water treatment device in which a method for removing a persistent organic substance according to an embodiment of the present invention is performed.

FIG. 2 shows the amount of easily decomposable organic substances, hardly decomposable organic substances and non-decomposable organic substances contained in water in each treatment step in the same method for removing hardly decomposable organic substances as compared with the conventional method for removing hardly decomposable organic substances. It is the graph shown in the comparison.

FIG. 3 is a graph showing the level of ozone-consuming substances in the ozone contact tower in the method for removing the hardly decomposable organic matter in comparison with the conventional method for removing the hardly decomposable organic matter.

FIG. 4 is an explanatory diagram showing a configuration of another ozone contact tower arranged in a water treatment device in which the method for removing hardly decomposable organic matter is performed.

FIG. 5 is an explanatory view showing a configuration of another biological filter bed arranged in a water treatment device in which the method for removing hardly decomposable organic matter is performed.

FIG. 6 is an explanatory diagram showing an overall configuration of a water treatment device in which a method of removing a persistent organic substance according to another embodiment of the present invention is performed.

FIG. 7 is an explanatory diagram showing an overall configuration of a water treatment device in which a method for removing a persistent organic substance according to still another embodiment of the present invention is performed.

FIG. 8 is an explanatory diagram showing the overall configuration of a water treatment device in which a conventional method for removing persistent organic substances is performed.

FIG. 9 is an explanatory diagram showing an overall configuration of another water treatment device in which a conventional method for removing hardly decomposable organic substances is performed.

FIG. 10 is a graph showing a relationship between an ozone reaction amount and COD of treated water and ozone utilization efficiency in a conventional method for removing a persistent organic substance.

[Explanation of symbols]

 3 Ozone contact tower 4 Biological filter bed 6 Raw water supply pipe 8 Ozone supply pipe 7 Circulating water supply pipe 21 UV irradiation device 22 Ozone radical generating catalyst

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirokazu Minami, Inou Kubota Co., Ltd. 1-47 Shikazu Higashi, Naniwa-ku, Osaka City, Osaka (72) Inventor Kodai Yoshizaki Shikazu-higashi, Naniwa-ku, Osaka, Osaka 1-chome 2-47 Kubota Co., Ltd.

Claims (3)

[Claims] 1. A method for removing a persistent organic substance, which comprises sequentially introducing raw water into an ozone contact tower and a biological filter bed to decompose the persistent organic substance in the raw water by ozone oxidation treatment and biological oxidation treatment. Divide the biologically treated water flowing out from the floor,
A method for removing hardly decomposable organic matter, which comprises returning to the inflow part of an ozone contact tower and repeatedly performing ozone oxidation treatment and biological oxidation treatment. 2. Ozone UV equipped with a UV irradiation device for raw water
In the method for removing hardly decomposable organic matter, which is sequentially introduced into the contact tower and the biological filter bed to decompose the hardly decomposable organic matter in the raw water by ozone UV oxidation treatment and biological oxidation treatment, the biologically treated water flowing out from the biological filter bed A method for removing hardly decomposable organic substances, characterized in that the ozone is subjected to ozone UV oxidation treatment and biological oxidation treatment repeatedly by returning the ozone to the inflow part of the ozone UV contact tower. 3. A hardly decomposable substance in which raw water is sequentially introduced into an ozone catalyst contact tower filled with an ozone radical generating catalyst and a biological filter bed to decompose hardly decomposable organic substances in the raw water by an ozone catalytic oxidation treatment and a biological oxidation treatment. In the method of removing volatile organic substances,
A method for removing hardly decomposable organic matter, characterized in that biologically treated water that has flowed out of a biological filter is divided and returned to the inflow section of an ozone catalyst contact tower, and repeatedly subjected to ozone catalytic oxidation treatment and biological oxidation treatment.