JP2012187443A - Water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus capable of achieving the complete decomposition of biodegradable organic matter and the decomposition of hardly decomposable matter with an appropriate combination of chemical oxidation and biological oxidative decomposition.SOLUTION: A part or the most part of second treated water subjected to oxidation treatment in an ultraviolet oxidation tower 5 is returned to a filtration tank 3 through a fourth water supply pipe 51, a valve 54 and a fifth water supply pipe 52 (a first circulating path). This circulation has an effect of decomposing organic matter partially oxidized in the ultraviolet oxidation tower 5, by microorganisms living in the filtration tank 3. A part or the most part of final treated water in an activated carbon tower 6 is returned to a first water tank 4 through a seventh water supply pipe 56, a valve 59 and an eighth water supply pipe 57 (a second circulating path). In this case, decomposition is effective when the concentration of the remaining hardly decomposable matter is comparatively low.

Description

  The present invention relates to a water treatment apparatus, and more particularly to a technique for treating organic substances contained in water and organic substances that are difficult to biodegrade.

  Conventionally, various components are contained in wastewater discharged from production processes in factories and the like, and in recent years, various treatment technologies have been developed and applied to help reduce the burden on the environment. However, certain substances, especially organic chemical substances that are difficult to biodegrade (hereinafter referred to as “hard-degradable substances”) are not sufficiently decomposed even in normal biological treatment processes, so they are released into public waters as they are. Often done. Most of these persistent substances are synthesized, and when released into the environment, they are ingested by animals and plants and concentrated in the body, and as a result of the food chain, they can accumulate in the human body and cause health damage. There is sex. Therefore, for example, as described in Patent Document 1, a water treatment apparatus using “biodegradation” and “oxidation by ultraviolet rays” has been proposed.

In addition, conventionally known technologies for separating and decomposing impurities contained in water include “precipitation / flotation”, “biodegradation”, “activated carbon adsorption”, “chemical oxidation”, and “promoted oxidation”. Yes. In “precipitation / floating”, relatively large particles that can settle or float can be separated, but soluble organic substances cannot be separated. In “biodegradation”, aerobic decomposition and anaerobic decomposition are performed to decompose organic compounds. In the “activated carbon adsorption”, residual organic substances are adsorbed by activated carbon. “Chemical oxidation” is oxidative decomposition by ozone, chlorine, hydrogen peroxide, etc., and partial oxidation of organic matter occurs, but decomposition to water (H ₂ O) and carbon dioxide (CO ₂ ) Have difficulty. “Promoted oxidation” is a method of decomposing organic matter by generating OH radicals by combining ozone and hydrogen peroxide, or by combining ultraviolet rays and the above oxidizing agents, and can decompose to H ₂ O and CO ₂ . It has a stronger oxidizing power than ordinary chemical oxidation.

JP 2010-221173 A

  However, among the above-mentioned technologies, “active carbon adsorption”, “chemical oxidation”, and “promoted oxidation” are performed on organic substances that remain after biological treatment and are difficult to decompose. However, equipment costs and maintenance costs increase. Therefore, it is desired to reduce the size of the water treatment device and reduce the running cost.

  The present invention has been made in order to solve the above-mentioned problems, and is capable of completely decomposing a biodegradable organic substance and appropriately decomposing a hardly decomposable substance between chemical oxidation and biological oxidative decomposition. It aims at providing the water treatment apparatus which can perform combination.

  A water treatment apparatus according to an aspect of the present invention includes a raw water tank for storing treated water, a filtration tank for biodegrading and filtering the treated water supplied from the raw water tank to obtain first treated water, A first water tank for storing the first treated water filtered in the filtration tank; and an ultraviolet oxidation unit for obtaining a second treated water by oxidizing the first treated water supplied from the first water tank with ultraviolet rays, An activated carbon filtration unit that obtains a final treated water by filtering the second treated water oxidized in the ultraviolet oxidation unit with activated carbon, and a part of the second treated water oxidized in the ultraviolet oxidation unit is returned to the filtration tank. And a first circulation path.

  In this water treatment device, there is an effect that organic matter that has been partially oxidized in the ultraviolet oxidation section is decomposed into microorganisms that live in the filtration tank by circulation in the first circulation path.

  Moreover, in the said water treatment apparatus, you may provide the 2nd circulation path which returns a part of final treated water filtered with the said activated carbon filtration part to said 1st water tank. In this case, it is effective when the remaining hardly decomposable substance has a relatively low concentration due to the circulation of the second circulation path. The effect by this is as follows. (1) The organic matter adsorbed on the activated carbon in the activated carbon filtration part is decomposed by microorganisms grown in the activated carbon. (2) The organic matter adsorbed on the activated carbon is further subjected to oxidative decomposition by OH radicals generated by oxidation of the ultraviolet oxidation portion. By circulating the second circulation path, the effects of (1) and (2) are repeated, and the decomposition of the organic matter is promoted.

  The water treatment apparatus may further include an oxidant supply unit that inputs an oxidant to the first treated water supplied to the ultraviolet oxidation unit. In this case, the organic matter adsorbed on the activated carbon by the OH radical generated by the oxidizing agent and the ultraviolet rays in the ultraviolet oxidation portion can be further subjected to oxidative decomposition.

  In the water treatment apparatus, the ultraviolet oxidation unit includes a reaction tank into which the first treated water is injected, a cylindrical quartz jacket is provided in the reaction tank, and a low-pressure mercury lamp and an external device are provided in the quartz jacket. An air supply pipe for supplying air; and ozone that releases ozone containing ozone generated from contact between the low-pressure mercury lamp and the air in the quartz jacket from the lower part of the reaction tank to the first treated water A chemical air tube may be provided. The main ultraviolet ray emitted from the low-pressure mercury lamp is 254 nm, and in this case, it further reacts with an oxidizing agent to generate OH radicals (the OH radicals decompose organic substances). The low-pressure mercury lamp also emits 185 nm ultraviolet light, which can generate ozone by contact with oxygen (air).

2 is a flow sheet showing the configuration of the water treatment apparatus 1. 2 is a longitudinal sectional view showing a structure of an ultraviolet oxidation tower 5. FIG.

  Hereinafter, the water treatment apparatus 1 which is one Embodiment of the water treatment apparatus of this invention is demonstrated based on drawing. First, the configuration of the water treatment apparatus 1 will be described with reference to FIG. The water treatment apparatus 1 includes a raw water tank 2 in which treated water is stored, a filtration tank 3 that biodegrades and filters the treated water supplied from the raw water tank 2 to obtain first treated water, and a filtration tank 3. The first water tank 4 in which the filtered first treated water is stored, the ultraviolet oxidation tower 5 that oxidizes the first treated water supplied from the first water tank 4 with ultraviolet light, and the first oxidized water in the ultraviolet oxidation tower 5. Activated carbon tower 6 (corresponding to the activated carbon filtration section) for filtering the two treated water with activated carbon, treated water tank 7 for storing the final treated water filtered by the activated carbon tower 6, and an oxidizer supply section 62 for supplying an oxidizer I have.

  Moreover, the raw | natural water tank 2 and the filtration tank 3 are connected by the 1st water supply pipe 21, and the 1st pump 22 which sends to-be-processed water from the raw | natural water tank 2 to the filtration tank 3 is provided in the 1st water supply pipe 21. . The filtration tank 3 and the first water tank 4 are connected by a second water supply pipe 33, and the second water supply pipe 33 is provided with a second pump 34. The first water tank 4 and the ultraviolet oxidation tower 5 are connected by a third water supply pipe 41, and the third water supply pipe 41 is provided with a third pump 42.

  A fourth water supply pipe 51 is connected to the ultraviolet oxidation tower 5, and the fourth water supply pipe 51 branches into a fifth water supply pipe 52 and a sixth water supply pipe 53 from the middle, and the tip of the fifth water supply pipe 52 is filtered. Connected to the tank 3, the tip of the sixth water supply pipe 53 is connected to the activated carbon tower 6. The fifth water supply pipe 52 is provided with a valve 54, and the sixth water supply pipe 53 is also provided with a valve 55. The fourth water supply pipe 51, the fifth water supply pipe 52, and the valve 54 constitute a first circulation path.

  A seventh water supply pipe 56 is connected to the activated carbon tower 6, and the seventh water supply pipe 56 branches from the middle into an eighth water supply pipe 57 and a ninth water supply pipe 58, and the tip of the eighth water supply pipe 57 is the first one. Connected to the water tank 4, the tip of the ninth water supply pipe 58 is connected to the treated water tank 7. The eighth water supply pipe 57 is provided with a valve 59, and the ninth water supply pipe 58 is also provided with a valve 60. The seventh water supply pipe 56, the eighth water supply pipe 57 and the valve 59 constitute a second circulation path. Further, an oxidant supply pipe 63 is connected to the oxidant supply part 62, and the oxidant built in the oxidant supply part 62 is supplied to the third water supply pipe 41 and sent to the ultraviolet oxidation tower 5. Yes.

  Next, details of each of the above-described configurations will be described. The raw water tank 2 is connected to a supply source (not shown) of raw water that is treated water, and stores the raw water. The raw water stored in the raw water tank 2 is sent to the filtration tank 3 via the first water supply pipe 21 by the first pump 22.

  The filtration tank 3 is connected to the downstream side of the raw water tank 2 through the first water supply pipe 21. The filtration tank 3 performs biological treatment, which is a pretreatment for performing chemical oxidation treatment on raw water such as factory waste water. Specifically, in order to treat a hardly decomposable substance contained in raw water that is to be treated, it is first necessary to efficiently decompose biologically degradable components. In order to decompose organic substances efficiently and at low cost, it is important to first decompose biodegradable organic substances almost completely in a biodegradation reaction. This is because the biodegradation method has the lowest running cost compared to other decomposition methods.

  As shown in FIG. 1, an air diffuser 32 is provided at the bottom of the filtration tank 3, and the air diffuser 32 discharges air supplied from an air pump (not shown) to agitate the inside of the filter tank 3. Further, a filtration membrane unit 31 is provided in the filtration tank 3, and the first treated water filtered by the filtration membrane unit 31 is sent to the first water tank 4 by the second pump 34 through the second water supply pipe 33. . The filtration membrane unit 31 performs biological treatment by a membrane separation activated sludge method (MBR; membrane bioreactor). Therefore, the filtration tank 3 serves as a biological reaction tank and a filtration tank. In the filtration tank 3, the fully decomposed waste water is filtered by the filtration membrane unit 31 immersed in the filtration tank 3. The filtration membrane of the filtration membrane unit 31 has a pore size of 1 μm or less, and completely separates biological sludge and suspended matter generated in the filtration tank 3. For this reason, high concentration sludge is accumulated in the filtration tank 3, and high concentration microorganisms are retained in proportion thereto. Perhaps the biodegradation reaction is promoted to obtain highly biodegraded transparent filtered water. In addition, since the suspended solids are completely separated in the filtration membrane unit 31, no precipitation treatment is required as in the normal activated sludge method. Further, a fifth water supply pipe 52 is connected to the filtration tank 3, and a part of the second treated water oxidized by the ultraviolet oxidation tower 5 is refluxed.

  The first water tank 4 stores the first treated water biologically treated in the filtration tank 3 and a part of the final treated water filtered by the activated carbon tower 6 is refluxed. In the ultraviolet oxidation tower 5, chemical oxidation is performed on the first treated water biologically treated in the filtration tank 3.

An example of the oxidation treatment in the ultraviolet oxidation tower 5 will be described below. Chemical oxidation is necessary to decompose hardly decomposable substances, but when these substances are oxidized, molecular cleavage occurs from oxidation in the molecular shape, and finally H ₂ O and CO _2. Is broken down by. This will be described by taking ethylene glycol, which is one of the hardly decomposable substances, as an example. The oxidative decomposition of ethylene glycol is decomposed into H ₂ O and CO ₂ in the following order.
OHCH ₂ —CH ₂ OH + O ₂ → 2HCOOH + O ₂ → 2H ₂ O + 2CO ₂

However, a large amount of oxidant and energy are required to decompose to H ₂ O and CO ₂ by chemical oxidation. As can be seen from the above reaction formula, the oxidation of the organic substance undergoes intramolecular oxidation to generate a carboxylic acid having a —COOH group, that is, an organic acid. Considering that ordinary organic acids can be easily decomposed in vivo, chemical oxidation does not completely oxidize H ₂ O and CO ₂ , but also oxidizes the intermediate and then biodegrades. Obviously, running can reduce running costs. Therefore, an appropriate combination of chemical oxidation and biological oxidative decomposition is important for the decomposition of a hardly decomposable substance.

  The first treated water stored in the first water tank 4 is sucked by the third pump 42, added with the oxidant sent from the oxidant supply unit 62 through the oxidant supply pipe 63, and sent to the ultraviolet oxidation tower 5. It is done. Examples of the oxidizing agent added at this time include ozone, hydrogen peroxide, and sodium hypochlorite. About the addition method of an oxidizing agent, it changes with kinds of oxidizing agent as follows.

  In the case of ozone, since ozone is a gas body, an ejector (not shown) is provided in the third water supply pipe 41 after the third pump 42, and suction is performed using the negative pressure generated thereby, or ultraviolet oxidation A method of supplying a diffuser tube in the tower 5 and supplying ozone into the ultraviolet oxidation tower 5 can be considered. Since these methods are gas supply, the stirring effect can be sufficiently obtained by gas-liquid mixing in the ultraviolet oxidation tower 5.

  On the other hand, since hydrogen peroxide and sodium hypochlorite are liquids, there is a possibility that sufficient mixing is not performed in the ultraviolet oxidation tower 5. The following two methods can be considered as means for solving this problem. As a first method, a method in which an air diffusion tube is provided at the bottom of the ultraviolet oxidation tower 5 and air is supplied from this to stir the inside of the tank can be considered.

  The following method can be considered as the second method. As shown in FIG. 2, the ultraviolet oxidation tower 5 has a third water supply pipe 41 connected to the upper part of a cylindrical sealed reaction cylinder 70 (corresponding to a reaction tank), and the first treated water is injected into the reaction cylinder 70. A fourth water supply pipe 51 through which the oxidized second treated water is discharged is connected to the lower part of the pipe. Further, a cylindrical quartz jacket 71 is provided in the ultraviolet oxidation tower 5, a discharge tube 73 and an air supply tube 72 are provided in the quartz jacket 71, a power supply 76 is connected to the discharge tube 73, and an air supply tube 72 is supplied with air from the upper part 72 </ b> A and discharges air from below the discharge tube 73. Air containing ozone generated in contact with the discharge tube 73 (arrow shown in FIG. 2) is discharged into the reaction tube 70 from the diffuser tube 75 provided at the lower portion of the ultraviolet oxidation tower 5 by the ozonized air tube 74. Spread. This method is particularly effective when a low-pressure mercury lamp that emits ultraviolet rays of 185 nm is used.

  As an example of the discharge tube 73, a low-pressure mercury lamp is used. The main ultraviolet rays emitted from this low-pressure mercury lamp are 254 nm, and this wavelength has a bactericidal effect, and further reacts with an oxidizing agent to generate OH radicals (the OH radicals decompose organic substances). The low-pressure mercury lamp also emits ultraviolet rays of 185 nm, and the ultraviolet rays generate ozone by contact with oxygen (air). Accordingly, the ozonized air in the quartz jacket 71 is taken out by the ozonized air tube 74 and blown into the reaction cylinder 70 of the ultraviolet oxidation tower 5 to give a stirring effect, and generate OH radicals to help the oxidation. be able to.

  Next, the activated carbon tower 6 will be described. The activated carbon tower 6 is filled with activated carbon that filters the second treated water into final treated water. Further, the activated carbon tower 6 is connected to a sixth water supply pipe 53 into which the second treated water flows and a seventh water supply pipe 56 from which the final treated water flows out. Normally, as shown in FIG. A sixth water supply pipe 53 is connected to the upper part of the activated carbon tower 6 and a seventh water supply pipe 56 is connected to the lower part of the activated carbon tower 6 so that the second treated water flows from the top to the bottom of the activated carbon tower 6. In this case, the gas remaining in contact with ozone or air in the UV oxidation tower 5 in the previous stage is accumulated in the activated carbon. Regular backwashing is performed to remove this. On the other hand, the sixth water supply pipe 53 may be connected to the lower part of the activated carbon tower 6, and the seventh water supply pipe 56 may be connected to the upper part, so that the second treated water flows from the bottom to the upper side of the activated carbon tower 6. In this case, since the activated carbon layer in the activated carbon tower 6 is in a fluidized state, no gas is accumulated in the activated carbon layer, so there is no need for backflow cleaning.

Next, the points of the present invention will be described. The method of oxidizing treatment with an oxidant and ultraviolet rays in the ultraviolet oxidation tower 5 can decompose most of organic substances into H ₂ O and CO ₂ by increasing the amount of oxidant and the number of ultraviolet lamps and increasing the residence time. Practical application is difficult due to increased running costs. As means for solving this problem, the water treatment apparatus 1 of the present embodiment employs the following method. First, as shown in FIG. 1, a part or most of the second treated water oxidized by the ultraviolet oxidation tower 5 is filtered through the fourth water supply pipe 51, the valve 54 and the fifth water supply pipe 52 (first circulation path). Return to tank 3. By this circulation, there is an effect that the organic matter partially oxidized in the ultraviolet oxidation tower 5 is decomposed into microorganisms that live in the filtration tank 3. This method is effective when the remaining hardly decomposable substance has a relatively high concentration. Since the biodegradability is improved when the hardly decomposable substance is subjected to partial oxidation by ultraviolet oxidation, it is returned to the filtration tank 3 having a large amount of microorganisms for decomposition.

Further, as shown in FIG. 1, part or most of the final treated water discharged from the activated carbon tower 6 is returned to the first water tank 4 by the seventh water supply pipe 56, the valve 59 and the eighth water supply pipe 57. (Second circuit). In this case, it is effective when the remaining hardly decomposable substance has a relatively low concentration. The effect by this is as follows.
(1) The organic matter adsorbed on the activated carbon is decomposed by microorganisms grown in the activated carbon.
(2) The organic matter adsorbed on the activated carbon by the OH radical generated by the oxidizing agent and ultraviolet rays is further subjected to oxidative decomposition.
(3) By performing the circulation, the effects of (1) and (2) are repeated, and the decomposition of the organic matter is promoted. Because of these effects, the activated carbon itself is regenerated along with the decomposition of organic matter, so that the adsorption capacity is increased and the life of the activated carbon is remarkably extended.

  In the above two types of circulation, it is necessary to increase the circulation ratio with respect to the raw water inflow as the amount of residual organic matter increases, but a range of 1: 1 to 1:10 is usually preferable. However, there is no need to circulate when the organic concentration of the influent water is very low. The circulation ratio is adjusted by circulating the second treated water to the filtration tank 3 by changing the opening ratio of the valve 54 and the valve 55. Further, the circulation of the final treated water to the first water tank 4 is performed by changing the ratio of the opening degree of the valve 59 and the valve 60. The flow rate to the fifth water supply pipe 52 by adjusting the opening of the valve 54 and the valve 55: The flow ratio to the sixth water supply pipe 53 is, for example, the amount of residual organic matter in the range of 9: 1 to 0:10. It may be adjusted accordingly. Further, the flow rate ratio to the eighth water supply pipe 57 by adjusting the opening degree of the valve 59 and the valve 60: the flow ratio ratio to the ninth water supply pipe 58 is, for example, a range of about 5: 1 to 0: 5 of residual organic matter. What is necessary is just to adjust according to quantity.

Next, the experimental result using the said water treatment apparatus 1 is demonstrated as Table 1. FIG. Diethylene glycol was used as the hardly decomposable substance.
(1) Treatment conditions and raw water composition: 200 ppm diethylene glycol aqueous solution, pH of about 6, TOC (Total Organic Carbon) 45 ppm
・ Water flow conditions: 10L / h
-Filtration tank 3: 250 L, activated sludge is kept at about 5000 ppm. Filtration area 0.5m ²
・ UV oxidation tower 5: Capacity 5L, 40W low-pressure mercury lamp ・ Activated carbon tower 6: Activated carbon filling 10L
・ Oxidizing agent: ozone, injection amount 100ppm

上記表１に示すように、酸化剤を加えず、第一循環路（循環（１））、第二循環路（循環（２））とも循環水量無しの場合（ＲＵＮ−１）は、ジエチレングリコールの除去率が３３％と低いが、酸化剤を加えて、第一循環路（循環（１））、第二循環路（循環（２））とも循環水量が４０Ｌ／ｈの場合（ＲＵＮ−３）は、ジエチレングリコールの除去率が９６％と高いことが分かる。また、酸化剤を加えて、第一循環路（循環（１））のみの場合（ＲＵＮ−２）でも、ジエチレングリコールの除去率が８２％と高く有効であることが分かる。 (2) Treatment results The results of comparison with and without oxidizing agent and with or without circulation are shown.
However, the amount of circulating water in both the first circulation path (circulation (1)) and the second circulation path (circulation (2)) was 40 L / h.

As shown in Table 1 above, when no oxidizer is added and the first circulation path (circulation (1)) and the second circulation path (circulation (2)) are not circulated (RUN-1), diethylene glycol Although the removal rate is as low as 33%, the amount of circulating water is 40 L / h for both the first circulation path (circulation (1)) and the second circulation path (circulation (2)) by adding an oxidizing agent (RUN-3). It can be seen that the removal rate of diethylene glycol is as high as 96%. It can also be seen that the removal rate of diethylene glycol is as high as 82% and is effective even when only the first circulation path (circulation (1)) is added (RUN-2).

According to the water treatment apparatus 1 having the above configuration, the following effects are obtained. In other words, the treated water after UV oxidation is mostly in a state in which biodegradation is possible without being decomposed to H ₂ O and CO ₂ only by partial oxidation of the hardly decomposable organic matter. Therefore, there is a cost merit in returning this to the filtration tank 3 (activated sludge tank) and biodegrading. On the other hand, when decomposing with the activated carbon tower 6, there is a limit to the amount of microorganisms living in the activated carbon, so it is suitable for drainage with as low a concentration as possible. Since decomposition by microorganisms requires dissolved oxygen, the dissolved oxygen at room temperature is about 10 ppm. Therefore, the organic substance concentration within the range in which this concentration of oxygen is consumed is appropriate.

  In addition, it cannot be overemphasized that the water treatment apparatus of this invention is not restricted to the said embodiment, Various deformation | transformation are possible. For example, the pH may be adjusted as follows. The pH changes as the decomposition of organic matter proceeds. When carbohydrates are oxidized, organic substances are produced, which lowers the pH. On the other hand, since amines liberate ammonia, the pH rises. Therefore, in the filtration tank 3 and the activated carbon tower 6, since the biodegradation is proceeding, the pH is adjusted to near neutral.

  Further, gas-liquid separation may be performed after the ultraviolet oxidation tower 5. If a gas such as ozone is blown into the activated carbon tower 6 as it is, the activated carbon tower 6 may float and mix due to bubbles and flow out of the system. On the other hand, even in the case of a downward flow, bubbles may accumulate in the activated carbon tower 6 and a sudden increase in the filtration pressure differential pressure may occur. Therefore, a gas-liquid separation mechanism may be provided in the fourth water supply pipe 51 after the ultraviolet oxidation tower 5 so that only the liquid flows into the activated carbon tower 6. Further, the reaction tube 70 and the quartz jacket 71 are not necessarily limited to a cylindrical shape, and the reaction tube 70 and the quartz jacket 71 may be a square tube or the like.

DESCRIPTION OF SYMBOLS 1 Water treatment apparatus 2 Raw water tank 3 Filtration tank 4 1st water tank 5 UV oxidation tower (UV oxidation part)
6 Activated carbon tower (activated carbon filtration part)
7 treated water tank 21 first water supply pipe 22 first pump 31 filtration membrane unit 32 aeration pipe 33 second water supply pipe 34 second pump 41 third water supply pipe 42 third pump 51 fourth water supply pipe 52 fifth water supply pipe 53 sixth Water supply pipe 54 Valve 55 Valve 56 Seventh water supply pipe 57 Eighth water supply pipe 58 Ninth water supply pipe 59 Valve 60 Valve 62 Oxidant supply part 63 Oxidant supply pipe 70 Reaction cylinder 71 Quartz jacket 73 Discharge pipe 74 Ozonated air pipe 75 Diffuser

Claims (4)

A raw water tank for storing treated water;
A filtration tank for biodegrading and filtering the treated water supplied from the raw water tank to obtain first treated water;
A first water tank for storing the first treated water filtered in the filtration tank;
An ultraviolet oxidation unit that obtains second treated water by subjecting the first treated water supplied from the first water tank to oxidation treatment with ultraviolet rays;
An activated carbon filtration unit that obtains a final treated water by filtering the second treated water oxidized by the ultraviolet oxidation unit with activated carbon;
A water treatment apparatus comprising: a first circulation path for returning a part of the second treated water oxidized in the ultraviolet oxidation unit to the filtration tank.   The water treatment apparatus according to claim 1, further comprising a second circulation path for returning a part of the final treated water filtered by the activated carbon filtration unit to the first water tank.   The water treatment apparatus according to claim 1, further comprising an oxidant supply unit that introduces an oxidant into the first treated water supplied to the ultraviolet oxidation unit. The ultraviolet oxidation part is
Comprising a reaction tank into which the first treated water is injected;
A cylindrical quartz jacket is provided in the reaction vessel,
A low-pressure mercury lamp and an air supply pipe for supplying air from the outside are provided in the quartz jacket,
Furthermore, an ozonized air pipe is provided that discharges air containing ozone generated by contact between the low-pressure mercury lamp and the air in the quartz jacket from the lower part of the reaction tank to the first treated water. The water treatment apparatus in any one of Claims 1-3.

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