JP4641131B2 - Water treatment apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water treatment apparatus and method, and more particularly to a water treatment apparatus and method suitable for treating raw water containing a hardly decomposable organic substance such as dioxins.
[0002]
[Prior art]
Conventionally, in order to decompose difficult-to-decompose organic substances such as dioxins contained in wastewater, ozone is dissolved in the wastewater, and this is irradiated with ultraviolet rays to generate OH radicals, which promotes oxidative decomposition of the organic matter. (Japanese Patent Laid-Open No. 2001-70962, etc.).
[0003]
For example, ozone gas generated by an ozone generator using PSA is dissolved in raw water treated through a sand filtration tower, an activated carbon tower, or a biological activated carbon tower, and is contained in the raw water by irradiating ultraviolet rays with an ultraviolet irradiation device. Refractory organic substances can be oxidatively decomposed. At this time, the ozone addition pressure is limited by the ozone gas supply pressure (about 0.1 MPa at the maximum) of the ozone generator, and the ozone addition is performed at a pressure lower than this or using an apparatus such as an ejector.
[0004]
Here, since the raw water to be treated usually contains a radical scavenger that is a reaction inhibitor in the oxidative decomposition of organic matter by ozone / ultraviolet rays, ozone is added to the raw water in advance before the accelerated oxidation treatment to remove the radical scavenger. The pre-ozone treatment to remove is often performed.
[0005]
In order to further reduce the concentration of organic substances in the water, these devices may be provided in the circulation line and a back pressure valve may be provided at a predetermined position in the flow path to repeatedly perform the accelerated oxidation treatment.
[0006]
[Problems to be solved by the invention]
By the way, in the above-described accelerated oxidation treatment, the total amount of ozone gas supplied to the raw water does not change to OH radicals by ultraviolet irradiation, and the amount of supplied ozone is usually used for the waste ozone / treated water mixed fluid after ultraviolet irradiation. About 10 to 20% of unreacted ozone remains. This unreacted ozone is normally released into the atmosphere at atmospheric pressure or slightly negative pressure. However, for the purpose of cost reduction, there is an attempt to collect unreacted ozone and reuse it for accelerated oxidation treatment or pre-ozone treatment. Has been made.
[0007]
However, in order to recycle the recovered ozone for the accelerated oxidation treatment or the pre-ozone treatment, the ozone must be in a pressurized state, so that a sufficient cost reduction effect cannot be achieved. That is, as a means for pressurizing ozone, a pressure fan is generally used. However, because of the chemical nature of ozone, it is necessary to take an explosion-proof measure on the pressure fan, which increases costs. In addition, a method of providing a blower in the exhaust ozone gas line or supplying an ejector at a destination where ozone is reused and supplying it with a pump can be considered, but these methods all require power for pressurization, and power means The cost increases due to the installation and supply of energy to the device.
[0008]
Further, in the conventional method, the processing conditions in the accelerated oxidation treatment tend to become unstable. In particular, when the accelerated oxidation treatment is repeatedly performed in the circulation line, the raw water and the treated water circulate in the circulation path with the pressure gradually changing. Therefore, it becomes very difficult to perform the accelerated oxidation treatment stably.
[0009]
The present invention has been made in view of the above-mentioned problems of the prior art, and stable decomposition of the accelerated oxidation treatment in decomposing the hardly decomposable organic matter in water by the accelerated oxidation treatment using ozone / ultraviolet rays. Another object of the present invention is to provide a water treatment apparatus and method that enables efficient and inexpensive reuse of unreacted ozone after treatment.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the water treatment device of the present invention is:
Ozone adding means for adding ozone to raw water containing hardly decomposable organic matter to obtain an ozone / raw water mixed fluid;
An ultraviolet irradiation means for irradiating the ozone / raw water mixed fluid with ultraviolet rays to obtain a waste ozone / treated water mixed fluid;
Having pressure adjusting means and liquid level adjusting means, separating the waste ozone / treated water mixed fluid into a gas containing unreacted ozone and treated water, and adjusting the gas pressure and the treated water level A gas-liquid separation tank that stabilizes the pressure of the ozone / raw water mixed fluid in the ultraviolet irradiation means,
It is characterized by providing.
[0011]
Moreover, the water treatment method of the present invention comprises:
An ozone addition step of adding ozone in a pressurized state to raw water containing a hardly decomposable organic substance to obtain an ozone / raw water mixed fluid;
An ultraviolet irradiation process of irradiating the ozone raw water mixed fluid with ultraviolet rays to obtain a waste ozone / treated water mixed fluid;
The waste ozone / treated water mixed fluid is separated into a gas containing unreacted ozone and treated water, and the pressure of the ozone / raw water mixed fluid in the ultraviolet irradiation process is adjusted by adjusting the pressure of the gas and the level of the treated water. A gas-liquid separation process that stabilizes
It is characterized by including.
[0012]
In the present invention, ozone is added to raw water containing a hardly decomposable organic substance, and when the organic substance is decomposed by irradiating it with ultraviolet rays, the gas separated from the waste ozone / treated water mixed fluid after the ultraviolet irradiation is used. By adjusting the pressure and the level of the treated water to stabilize the pressure of the ozone / raw water mixed fluid during UV irradiation, the treatment conditions in the ozone / ultraviolet treatment are sufficiently stabilized, and the ozone dissolution rate in the raw water Is maintained at a high level, it is possible to efficiently and reliably oxidatively decompose the hardly decomposable organic substances contained in the raw water.
[0013]
In addition, since the unreacted ozone separated from the waste ozone / treated water mixed fluid in this way has a sufficiently high pressure, it can be used in a pressurized state without using a pressure fan or the like that is provided with an explosion-proof measure. It can be reused and a sufficient cost reduction is achieved.
[0014]
Therefore, according to the present invention, a water treatment apparatus and method that enable stable implementation of accelerated oxidation treatment using ozone / ultraviolet light and efficient and inexpensive reuse of unreacted ozone after treatment are realized. .
[0015]
The water treatment apparatus of the present invention further includes a pre-ozone treatment means for removing radical scavengers contained in the raw water by adding unreacted ozone from the gas-liquid separation tank to the raw water before being supplied to the ozone addition means. It is good also as providing.
[0016]
Further, the water treatment method of the present invention further includes a pre-ozone treatment step of adding unreacted ozone from the gas-liquid separation step to the raw water before being supplied to the ozone addition step to remove radical scavengers contained in the raw water. It may be characterized by including.
[0017]
By performing pre-ozone treatment using unreacted ozone separated from the treated water obtained by the accelerated oxidation treatment in this way, radical scavengers, which are reaction inhibitors in the oxidative degradation of persistent organic substances by ozone / ultraviolet rays, are removed. Therefore, the decomposition efficiency of the organic matter in the accelerated oxidation treatment can be further increased. In addition, the required amount of fresh ozone (ozone produced by the ozone supply means) required for the entire apparatus can be sufficiently reduced compared to the conventional system, so the ozone generation means can be reduced in size and the amount of power used can be reduced. Is realized.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.
[0019]
FIG. 1 is a schematic configuration diagram showing a preferred embodiment of the water treatment apparatus of the present invention. In FIG. 1, a pre-ozone treatment apparatus 11 adds ozone to raw water containing a hardly decomposable organic substance, and converts radical scavengers (COD, BOD, Ca ions, Fe ions, Mn ions, Al ions, etc.) contained in the raw water. The raw water that has been subjected to the pre-ozone treatment is sent to the treated raw water tank 1 and stored. In the present embodiment, ozone used in the pre-ozone treatment apparatus 11 is supplied from a gas-liquid separation tank 5 described later.
[0020]
A circulation line 10 is connected to the treated raw water tank 1, and the raw water in the treated raw water tank 1 is drawn to the circulation line 10 by the circulation pump 2 and returned to the treated raw water tank 1 again. In the circulation line 10, an ejector 3, an ultraviolet irradiation device 4, and a gas-liquid separation tank 5 are arranged in this order along the flow of raw water.
[0021]
The ejector 3 is connected with an ozone generator 8 having a built-in ozone generation power source (not shown), and the amount of ozone generation can be increased or decreased according to the voltage of the power source. Thereby, in the ejector 3, after a predetermined amount of ozone is added to the raw water drawn from the treated raw water tank 1, the ozone / raw water mixed fluid is sent to the ultraviolet irradiation device 4.
[0022]
The ultraviolet irradiation device 4 includes an ultraviolet irradiation tank 4a and an ultraviolet lamp 4b, and the ozone / raw water mixed fluid staying in the ultraviolet irradiation tank 4a is irradiated with ultraviolet rays from the ultraviolet lamp 4b. As a result, OH radicals are generated in the mixed fluid, so that the hardly decomposable organic substance is oxidized and decomposed by the OH radicals. In addition, although the number of the ultraviolet lamps 4b in FIG. 1 is three, it is not limited to this, One or two may be sufficient and four or more may be sufficient.
[0023]
The mixed fluid that has passed through the ultraviolet irradiation device 4 is accommodated in a gas-liquid separation tank 5 and separated into a liquid phase and a gas phase. A pressure adjusting device 6 is provided in the upper part of the gas-liquid separation tank 5, and a liquid level adjusting device 7 is provided in the lower part. Connected to the pressure adjusting device 6 is a pressure measuring device (differential piezoelectric transmitter or the like), a PIC (pressure indicating control system) including an indicating controller and a control valve. By applying a suitable output from the indicating controller to the control valve automatically and continuously (PID control), the pressure can be controlled to be constant. Also connected to the liquid level adjusting device 7 is a liquid level measuring device (such as a differential piezoelectric transmitter capable of converting pressure into a liquid level), an LIC (liquid level indicating and adjusting system) comprising an indicating controller and a control valve. By applying an output that corresponds to the liquid level (converted value from pressure) measured by the liquid level measuring device automatically and continuously from the indicating controller to the control valve (PID control), a constant liquid Can be controlled. Thus, the region from the gas phase portion of the gas-liquid separation tank 5 to the ultraviolet irradiation device 4 is sealed with a liquid phase by the pressure adjusting device 6 and the liquid level adjusting device 7, and the gas-liquid separation is performed by the pressure adjusting device 6. The pressure of the gas phase in the tank 5 can be adjusted and the liquid level of the liquid phase can be adjusted by the liquid level adjusting device 7. As a result, the pressure of the ozone / raw water mixed fluid in the ultraviolet irradiation device 4 can be set to a desired value. Can be adjusted.
[0024]
The gas containing unreacted ozone separated in the gas-liquid separation tank 5 is supplied to the pre-ozone treatment device 11 while being pressurized to a predetermined pressure by the pressure adjusting device 6. On the other hand, the treated water is returned from the gas-liquid separation tank 5 to the treated raw water tank 1 and circulated through the circulation line 10 again or discharged from the treated water pump 9 to the outside of the apparatus.
[0025]
Next, a method for treating raw water containing a hardly decomposable organic substance using the water treatment apparatus having the above-described configuration will be described.
[0026]
The raw water to be treated in the present invention contains a hardly decomposable organic substance as described above. Specific examples of the hardly decomposable organic substance include dioxins, organic halogen compounds such as trichlorethylene, TOC (total organic Carbon; all-organic carbon material).
[0027]
Such raw water usually contains a radical scavenger which is a reaction inhibitor of oxidative decomposition of a hardly decomposable organic substance in the accelerated oxidation treatment by ozone / ultraviolet rays. Therefore, in the pre-ozone treatment apparatus 11, ozone is added to the raw water in advance. Thus, it is preferable to perform a pre-ozone treatment for removing the radical scavenger. Thereby, the decomposition | disassembly efficiency of the organic substance in an accelerated oxidation process can be improved more. In addition, the use of unreacted ozone obtained in the gas-liquid separation step, which will be described later, in the pre-ozone treatment requires a conventional amount of fresh ozone (ozone produced by the ozone supply means) required for the entire apparatus. This is preferable in that it is sufficiently reduced. The raw water from which the radical scavenger has been removed is sent to the treated raw water tank 1 and stored.
[0028]
The raw water in the treated raw water tank 1 is drawn out to the circulation line 10 by the circulation pump 2 and mixed with ozone from the ozone generator 8 in the ejector 3 to become an ozone / raw water mixed fluid (ozone adding step). The ozone supply pressure from the ozone generator 8 is usually lower than the pressure of the raw water drawn out by the circulation pump 2, but by using the ejector 3, both of the raw water are higher than ozone. Can be mixed. For example, when the supply pressure of ozone is 0.1 MPa and the pressure of raw water is 0.3 to 0.4 MPa, an ozone / raw water mixed fluid pressurized to 0.2 to 0.3 MPa can be obtained. The ozone dissolution rate in the mixed fluid can be 80 to 90%. In addition, when the pressure of raw | natural water exceeds the said upper limit, it exists in the tendency for the difference with an ozone supply pressure to be too large and to fully mix both.
[0029]
Next, the ozone / raw water mixed fluid is sent to the ultraviolet irradiation device 4, and the mixed fluid staying in the ultraviolet irradiation tank 4a is irradiated with ultraviolet rays from the ultraviolet lamp 4b (ultraviolet irradiation step). As a result, OH radicals are generated from ozone in the mixed fluid, and the hardly decomposable organic matter is oxidatively decomposed by the oxidizing power of the OH radicals.
[0030]
The mixed fluid after the ultraviolet irradiation process is a mixed fluid (exhaust ozone / treated water) of treated water purified by oxidative decomposition of organic matter and a gas containing unreacted ozone that has not been consumed by the ultraviolet irradiation device 4 (exhaust ozone gas). These are accommodated in the gas-liquid separation tank 5 and separated into a liquid phase and a gas phase (gas-liquid separation step).
[0031]
At this time, the region from the gas phase portion of the gas-liquid separation tank 5 to the ultraviolet irradiation device 4 is sealed with the liquid phase (treated water), and the gas phase in the gas-liquid separation tank 5 by the pressure adjusting device 6. The liquid level is adjusted by the pressure of the (exhaust ozone gas) and the liquid level adjusting device 7. Thereby, the pressure of the ozone / raw water mixed fluid in the ultraviolet irradiation device 4 can be adjusted to a desired value (preferably 0.2 to 0.3 MPa), and the processing conditions can be stabilized.
[0032]
The gas containing unreacted ozone separated in the gas-liquid separation tank 5 is pressurized to a predetermined pressure by the pressure adjusting device 6 and supplied to the pre-ozone treatment device 11 in a pressurized state. Thereby, unreacted ozone can be efficiently and inexpensively reused in the pre-ozone treatment. On the other hand, the treated water is returned from the gas-liquid separation tank 5 to the treated raw water tank 1 and circulated through the circulation line 10 again or discharged from the treated water pump 9 to the outside of the apparatus.
[0033]
As described above, in the present embodiment, ozone is added to raw water containing a hardly decomposable organic substance, and when the organic substance is decomposed by irradiating it with ultraviolet rays, it is separated from the waste ozone / treated water mixed fluid after the ultraviolet irradiation. By adjusting the pressure of the gas and the level of the treated water to stabilize the pressure of the ozone / raw water mixed fluid during UV irradiation, the treatment conditions are sufficiently stabilized and the ozone dissolution rate is maintained at a high level. Therefore, the hardly decomposable organic substance contained in the raw water can be efficiently and reliably oxidatively decomposed.
[0034]
In addition, since the unreacted ozone separated from the waste ozone / treated water mixed fluid in this way has a sufficiently high pressure, it can be used in a pressurized state without using a pressure fan or the like that has been subjected to explosion-proof measures. It can be reused and a sufficient cost reduction is achieved.
[0035]
Furthermore, by performing pre-ozone treatment using unreacted ozone separated from treated water obtained by accelerated oxidation treatment, radical scavengers, which are reaction inhibitors in the oxidative degradation of persistent organic substances by ozone / ultraviolet rays, are removed. In addition to improving the decomposition efficiency of the organic matter, the required amount of fresh ozone (ozone produced by the ozone supply means) required for the entire apparatus can be sufficiently reduced compared to the conventional case. In addition, the ozone generating means can be reduced in size and the amount of power used can be reduced.
[0036]
The present invention is not limited to the above embodiment. For example, in the apparatus shown in FIG. 1, unreacted ozone separated in the gas-liquid separation tank 5 is supplied to the pre-ozone treatment apparatus 11 and reused. However, the unreacted ozone is supplied to the ejector 3 to promote oxidation. It may be reused as ozone for treatment, or it may be reused as ozone used for pre-stage ozone treatment, sludge ozone treatment, and the like. The pre-stage ozone treatment here refers to a treatment for decomposing dioxins adsorbed on SS with ozone as a pre-process for removing COD, BOD and SS (suspended solids) contained in raw water. The sludge ozone treatment refers to a treatment for decomposing dioxins concentrated in the sludge with ozone.
[0037]
【The invention's effect】
As described above, in the present invention, ozone is added to raw water containing a hardly decomposable organic substance, and when the organic substance is decomposed by irradiating it with ultraviolet light, the waste ozone / treated water mixed fluid after ultraviolet irradiation is used. By adjusting the pressure of the separated gas and the liquid level of the treated water to stabilize the pressure of the ozone / raw water mixed fluid during UV irradiation, the treatment conditions in the accelerated oxidation treatment are sufficiently stabilized, and ozone dissolution Since the rate is maintained at a high level, it is possible to efficiently and reliably oxidatively decompose the hardly decomposable organic substances contained in the raw water.
[0038]
Further, since the unreacted ozone separated from the waste ozone / treated water mixed fluid in this way has a sufficiently high pressure, this unreacted ozone uses a pressurized fan or the like that has been subjected to explosion-proof measures. At least, it can be reused in a pressurized state, and a sufficient cost reduction is achieved.
[0039]
Therefore, according to the present invention, a water treatment apparatus and method that enable stable execution of accelerated oxidation treatment and efficient and inexpensive reuse of unreacted ozone after treatment are realized.
[Brief description of the drawings]
FIG. 1 is a flowchart schematically showing a preferred embodiment of a water treatment apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Treatment raw water tank, 2 ... Circulation pump, 3 ... Ejector, 4 ... Ultraviolet irradiation apparatus, 4a ... Ultraviolet irradiation tank, 4b ... Ultraviolet lamp, 5 ... Gas-liquid separation tank, 6 ... Pressure adjustment apparatus, 7 ... Liquid level adjustment Device: 8 ... Ozone generator, 9 ... Treated water pump, 10 ... Circulation line, 11 ... Pre-ozone treatment device.

Claims (4)

Ozone adding means for adding ozone to raw water containing hardly decomposable organic matter to obtain an ozone / raw water mixed fluid;
UV irradiation means for irradiating the ozone / raw water mixed fluid with ultraviolet rays to obtain a waste ozone / treated water mixed fluid;
A pressure adjusting means and a liquid level adjusting means, separating the waste ozone / treated water mixed fluid into a gas containing unreacted ozone and treated water, and adjusting the pressure of the gas and the liquid level of the treated water. A gas-liquid separation tank that stabilizes the pressure of the ozone / raw water mixed fluid in the ultraviolet irradiation means by adjusting;
A water treatment apparatus comprising:   The apparatus further comprises pre-ozone treatment means for adding unreacted ozone from the gas-liquid separation tank to the raw water before being supplied to the ozone addition means to remove radical scavengers contained in the raw water. The water treatment apparatus according to claim 1. An ozone addition step of adding ozone in a pressurized state to raw water containing a hardly decomposable organic substance to obtain an ozone / raw water mixed fluid;
An ultraviolet irradiation step of irradiating the ozone raw water mixed fluid with ultraviolet rays to obtain a waste ozone / treated water mixed fluid;
The waste ozone / treated water mixed fluid is separated into a gas containing unreacted ozone and treated water, and the ozone / treated water in the ultraviolet irradiation step is adjusted by adjusting the pressure of the gas and the liquid level of the treated water. A gas-liquid separation process that stabilizes the pressure of the raw water mixed fluid;
A water treatment method comprising: The method further comprises a pre-ozone treatment step of adding unreacted ozone from the gas-liquid separation step to the raw water before being supplied to the ozone addition step to remove radical scavengers contained in the raw water. The water treatment method according to claim 3.

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