JP2017000994A - Water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in a water treatment system for treating organic substances in water, an apparatus which can continuously treat the organic substances at low cost without changing an adsorbent.SOLUTION: A water treatment system comprising: a wet oxidation decomposition apparatus 100 which oxidatively decomposes in water an organic substance contained in water to be treated to discharge a primary treated water; and water treatment equipment 200 which includes adsorption elements 211 and 221 that adsorb the organic substance and desorb the organic substance absorbed when brought into contact with steam, and which alternately carries out an adsorption step where the primary treated water is supplied to the adsorption elements 211 and 221 to have the organic substance contained in the primary treated water adsorbed by the adsorption elements 211 and 221 and secondary treated water is discharged and a desorption step where steam is supplied to the adsorption elements 211 and 221 to desorb the organic substance therefrom, the vapor is liquefied and condensed, and water having a higher concentration of organic substance than that in the primary treated water is discharged as concentrated water. The concentrated water discharged from the water treatment equipment 200 is supplied to the wet oxidation decomposition apparatus 100.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a water treatment system for purifying water to be treated by removing the organic substance from the water to be treated containing the organic substance, and in particular, an industry containing the organic substance discharged from various factories or research facilities. The present invention relates to a water treatment system that purifies industrial treated water by efficiently removing organic substances from the treated water.

  Conventionally, a wet oxidative decomposition apparatus is widely known as a method for treating an organic substance in water. This treatment method includes the Fenton method using hydrogen peroxide and iron, the accelerated oxidation method using ozone and ultraviolet rays or hydrogen peroxide together, the electrolysis method for forcibly applying voltage to water, etc. Organic substances in water are oxidatively decomposed by the generated radicals.

  As an example, FIG. 1 shows an example of the tendency of the ozone addition amount and organic substance concentration to be reduced by the accelerated oxidation method. As shown in FIG. 1, the reduction amount of the organic substance is large at the beginning of the treatment, but thereafter, the reduction amount tends to be small. FIG. 2 shows an example of the relationship between the processing efficiency (decomposition rate) and the required power based on FIG. In response to the trend shown in FIG. 1, there is a problem that a large amount of power is applied in accordance with high-efficiency processing.

  Further, an exchangeable adsorption device is generally known as a backup device for a wet oxidative decomposition apparatus. That is, it is a simple processing device that allows water containing an organic substance to flow through a tank filled with an adsorbent such as activated carbon and removes the organic substance in the water using the adsorbent.

  However, the exchangeable adsorption device continues to adsorb organic substances for a certain period of time, and if the adsorption capacity of the adsorbent reaches saturation, it is necessary to replace it with a new one, or to remove the adsorbent from the device once and regenerate it for continuous purification. In addition, the purification of water, unlike the purification of air, is unavoidable for the growth of microorganisms, and the life of the adsorbent may be shortened.

  On the other hand, water treatment devices that can be removed efficiently and stably by alternately performing the removal of organic substances by adsorption (adsorption process) and the regeneration of the adsorbent (desorption process) using an adsorbent ( For example, Patent Document 1). This water treatment apparatus realizes continuous purification of water, basically does not require replacement of the adsorbent, and can stably remove organic substances with high efficiency.

  When activated carbon fiber is used as an adsorbent, it is known that activated carbon fiber has a property of removing organic substances with high efficiency because of its high adsorption rate. In the water treatment device, the adsorbed and removed organic substance is desorbed from the adsorbent during regeneration and discharged as a gas containing the organic substance (desorption gas). When water vapor is used as the desorption medium, the desorption gas is liquefied. By condensing, it can be recovered as concentrated water containing an organic substance at a high concentration, and thus has a function as a concentrating device (for example, Patent Document 2).

JP 2006-055712 A JP 2014-217833 A

  The present invention has been made in the background of the above-described technical problems. In a water treatment system for treating an organic substance in water by using a wet oxidative decomposition apparatus, there is basically no replacement of the adsorbent, It is an object of the present invention to provide a low-cost backup device that can treat organic substances.

As a result of intensive studies in order to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is as follows.
(1) A water treatment system for purifying treated water by removing the organic substance from the treated water containing the organic substance,
A wet oxidative decomposition apparatus that oxidizes and decomposes organic substances in water to be treated and discharges primary treated water;
It includes an adsorbing element that adsorbs an organic substance by bringing water containing the organic substance into contact with it, and desorbs the adsorbed organic substance by bringing water vapor into contact therewith, and supplies the primary treatment water to the adsorbing element to perform a primary treatment. An adsorption step of adsorbing an organic substance contained in water to the adsorption element and discharging it as secondary treated water; and desorbing the organic substance from the adsorption element by supplying water vapor to the adsorption element; A water treatment device that alternately performs a desorption step of discharging water containing an organic substance having a concentration higher than the concentration of the organic substance in the primary treated water as concentrated water;
The water treatment system is configured such that the concentrated water discharged from the water treatment device is supplied to the wet oxidative decomposition device and subjected to water treatment.
(2) The water treatment system according to (1), wherein the wet oxidative decomposition apparatus is a wet oxidative decomposition apparatus using any one of a Fenton method, an accelerated oxidation method, and an electrolysis method.
(3) The water treatment system according to (1) or (2), wherein the water treatment device removes water adhering to the adsorption element and discharges it as removed water.
(4) The water treatment system according to (3), wherein water vapor is used to remove water adhering to the adsorption element.
(5) The water treatment system according to (3) or (4), wherein the removed water discharged from the water treatment device is configured to be supplied again to the water treatment device.
(6) The water treatment system according to any one of (1) to (5), wherein the adsorption element includes at least one member selected from the group consisting of activated carbon, activated carbon fiber, and zeolite.

  The water treatment system according to the present invention treats organic substances in water to be treated with high efficiency by performing secondary treatment with an adsorption / desorption type water treatment device as a backup of a wet oxidative decomposition device, and is discharged from the water treatment device. There is an advantage that water treatment can be performed at low cost by reprocessing the concentrated water with a wet oxidative decomposition apparatus.

It is an example of the decreasing tendency of the ozone addition amount and organic substance concentration by an accelerated oxidation method. It is an example of the relationship between the processing efficiency (decomposition rate) and required power of the accelerated oxidation method. It is an example of the form for implementing this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments shown in the drawings, the same or corresponding parts are omitted as appropriate, and the description thereof will not be repeated.

  FIG. 3 is one of the system configuration diagrams of the water treatment system according to the embodiment of the present invention. As shown in FIG. 3, the water treatment system in the present embodiment mainly includes a wet oxidative decomposition apparatus 100 and a water treatment apparatus 200.

  The wet oxidative decomposition apparatus 100 is an apparatus that oxidizes and decomposes an organic substance from water to be treated containing the organic substance. There are equipment using methods such as the Fenton method using hydrogen peroxide and iron, the accelerated oxidation method using ozone and ultraviolet light or hydrogen peroxide in combination, and the electrolysis method for forcibly applying voltage to water. As long as the organic substance in water is oxidatively decomposed by radicals generated by the above, there is no particular limitation.

  Water to be treated containing an organic substance is treated by the wet oxidative decomposition apparatus 100 and then discharged as primary treated water.

  The water treatment device 200 is a backup device for secondary treatment of the primary treated water discharged from the wet oxidative decomposition apparatus 100. It has the 1st processing tank 210 and the 2nd processing tank 220 which each accommodated the adsorbents 211 and 221 as an adsorption element. The adsorbents 211 and 221 adsorb slight organic substances contained in the primary treated water by bringing the primary treated water into contact therewith. Therefore, in the water treatment apparatus 200, the organic material is adsorbed by the adsorbents 211 and 221 by supplying the primary treated water to the adsorbents 211 and 221. Thereby, the organic substances in the water to be treated are almost completely removed. It will be discharged as secondary treated water. The adsorbents 211 and 221 are desorbed of the adsorbed organic substances by bringing a smaller amount of water vapor into contact with the supplied primary treated water. The water vapor discharged from the first treatment tank 210 and the second treatment tank 220 and the desorbed organic substance are cooled and condensed by the condenser 230 and discharged from the water treatment apparatus 200 as concentrated water.

  The first treatment tank 210 and the second treatment tank 220 are connected to a primary treatment water supply line, a secondary treatment water discharge line, a water vapor supply line, and a concentrated water discharge line. Has a configuration in which a flow path switching means that is switched to a connected / disconnected state is connected to each processing tank using a valve or the like. The 1st processing tank 210 and the 2nd processing tank 220 function as an adsorption tank and a desorption tank alternately by operating opening and closing of the valve mentioned above. When the 1st processing tank 210 is functioning as an adsorption tank, the 2nd processing tank 220 functions as a desorption tank. Specifically, when the primary treatment water is supplied to the first treatment tank 210 and a flow path is secured so that the treatment water is discharged from the first treatment tank 210, the second treatment tank 220 is supplied with water vapor. The concentrated water is discharged from the second treatment tank 220. The water treatment apparatus 200 in the present embodiment is configured such that the adsorption tank and the desorption tank are alternately switched over time.

  The concentrated water discharged from the water treatment apparatus 200 is configured to be supplied as treated water of the wet oxidative decomposition apparatus 100. This is because it is not necessary to treat the concentrated water separately. Also, as described above with reference to FIGS. 1 and 2, when the wet oxidative decomposition apparatus treats an organic substance with high efficiency (for example, removal efficiency of 99% or more), the wet oxidative decomposition apparatus 100 is enlarged to have a processing capacity. This is because it is more efficient to concentrate a small amount of organic substances discharged in the wet oxidative decomposition apparatus 100 in the water treatment apparatus 200 and reprocess in the wet oxidative decomposition apparatus 100 rather than to increase the water content. .

  Although not shown, the water treatment apparatus 200 removes (dehydrates) water adhering to the adsorbents 211 and 221 and discharges it as removed water when the adsorption tank is switched to the desorption tank, and then desorbs by supplying water vapor. An apparatus that initiates is preferred. This is because when the water adsorbed on the adsorbents 221 and 221 is removed in advance and then steam desorption is performed, the amount of concentrated water can be reduced and the concentration rate can be increased. As the means for removing adhering water, means such as self-weight removal, high-speed purge with a high-pressure gas such as compressed air, nitrogen, and water vapor, and suction using a vacuum pump can be used, but high-speed purge with water vapor is preferred. This is because there is no need to separately add a means for removing the adhering water, the adhering water can be removed with high efficiency, and the adsorption tank is heated, so that the concentration ratio and desorption efficiency are increased. The water vapor used for dehydration is liquefied and condensed when it comes into contact with the adhering water and becomes part of the removed water.

  Although not shown, it is preferable that the removed water is configured to be supplied to the water treatment apparatus 200 again. This is because it is not necessary to separately process the removed water with another water treatment apparatus.

  The adsorbents 211 and 221 preferably include at least one member selected from the group consisting of activated carbon, activated carbon fiber, and zeolite. As the adsorbents 211 and 221, activated carbon or zeolite having a granular shape, a granular shape, or a honeycomb shape is used, but it is more preferable to use activated carbon fibers. Since the activated carbon fiber has a fibrous structure with micropores on the surface, the contact efficiency with water is high, and the adsorption rate of organic substances in water is particularly high, which is extremely high compared to other adsorbents. It is a member that can realize adsorption efficiency.

  The physical properties and raw materials of activated carbon fibers that can be used as the adsorbents 211 and 221 are not particularly limited. What is necessary is just to select suitably according to the organic substance which is a removal object.

  The vapor pressure, temperature, and the like of water vapor that is a desorption medium of the water treatment apparatus 200 are not particularly limited, but may be set as appropriate according to the heat-resistant temperature and physical properties of the adsorbent used. However, it is necessary to desorb with water vapor having a mass smaller than that of the water to be treated supplied to the water treatment apparatus 200. When the mass of water vapor is larger, the organic substance is not concentrated, and concentrated water containing an organic substance having a higher concentration than the organic substance concentration in the water to be treated cannot be obtained.

  Although the embodiment of the present invention has been described using two adsorbents and a processing tank, the apparatus may be configured using two or more processing tanks. Moreover, although not shown in figure, the apparatus structure using one adsorbent and a processing tank may be sufficient. For example, when one processing tank consisting of the adsorbent 211 and the processing tank 210 is used, when the processing tank 210 functions as a desorption tank, the raw water is temporarily stored and the adsorption process is completed after the desorption process is completed. A switching cycle functioning as a tank may be used.

  The organic substance contained in the water to be treated of the present invention is not particularly limited, but aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, acrolein, ketones such as methyl ethyl ketone, diacetyl, methyl isobutyl ketone, and acetone, 1,4-dioxane , 2-methyl-1,3-dioxolane, 1,3-dioxolane, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and other esters, ethanol, n-propyl alcohol, isopropyl alcohol, butanol and other alcohols , Glycols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, organic acids such as acetic acid and propionic acid, phenols, toluene, xylene, cyclohexane Any aromatic organic compound, ethers such as diethyl ether and allyl glycidyl ether, nitriles such as acrylonitrile, chlorinated organic compounds such as dichloromethane, 1,2-dichloroethane, trichloroethylene, epichlorohydrin, N-methyl-2- Examples include pyrrolidone, dimethylacetamide, N, N-dimethylformamide organic compounds, and the like.

  With the water treatment system shown in FIG. 3 described above, the wet oxidative decomposition apparatus 100 and the water treatment apparatus 200 are processed in this order to treat organic substances in the water to be treated with high efficiency. 100 functions as an apparatus for concentrating to an organic substance concentration that can be efficiently oxidatively decomposed at 100, so that the wet oxidatively decomposed apparatus 100 can be prevented from increasing in size and running cost, and there is no need to replace the adsorbent. It can be set as the water treatment system which can perform water treatment.

  The characteristic configurations of the embodiment of the present invention described above with reference to FIG. 3 can be combined with each other.

  Further, in the embodiments of the present invention described above, the description has been made without particularly showing the constituent elements such as the fluid conveying means such as the pump and the fan and the fluid storing means such as the storage tank. What is necessary is just to arrange | position to an appropriate position as needed.

  Thus, the above-described embodiments disclosed herein are illustrative in all respects and are not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Evaluation was performed by the following method.
(BET specific surface area)
The BET specific surface area was measured by measuring the amount of nitrogen adsorbed on the sample when the relative pressure was raised in the range of 0.0 to 0.15 in the atmosphere of the boiling point of liquid nitrogen (-195.8 ° C), and a BET plot. Was used to determine the surface area (m ² / g) per unit mass of the sample.
(Pore volume)
The pore volume was measured by a nitrogen gas adsorption method at a relative pressure of 0.95.
(Average pore diameter)
The average pore diameter was determined by the following formula.
dp = 40000 Vp / S (where dp: average pore diameter (径))
Vp: pore volume (cc / g)
S: BET specific surface area (m ² / g)
(Organic substance removal effect)
The water to be treated (raw water) was 1,4-dioxane 5 mg / L. The removal effect was confirmed by measuring the concentration of 1,4-dioxane in and out of the accelerated oxidation (hereinafter referred to as “AOP”) apparatus and the water treatment apparatus 200 as the wet oxidative decomposition apparatus 100 after 500 hours of operation.
(Organic substance concentration evaluation)
Each water was analyzed and measured by gas chromatography.

<Example 1>
As the system, the embodiment shown in FIG. 3 was used.
Under the conditions of ozone concentration 50 mg / L and hydrogen peroxide concentration 100 mg / L, the water to be treated was introduced into the AOP apparatus so that the amount of treated water was 4000 L / h to obtain primary treated water. The outlet concentration at that time was 1,4-dioxane 0.5 mg / L or less. The power used at that time was 6 kw or less as shown in Table 1.

Next, two adsorbing elements with a weight of 4 kg using activated carbon fibers having an average pore diameter of 17.2 mm, a BET specific surface area of 2050 m ² / g, and a total pore volume of 0.87 m ³ / g as an adsorbent for the water treatment apparatus are prepared. And it installed in the water treatment apparatus of FIG. 3, the primary treated water was introduce | transduced so that the amount of treated water might be 4000 L / h, and the secondary treated water was obtained. The 1,4-dioxane concentration in the secondary treated water at that time was 0.01 mg / L or less.

  Next, the adsorbent adhering water was removed (dehydrated) by removing its own weight, and the removed water was returned to the water treatment device. Next, water vapor of 0.1 MPa and 120 ° C. was supplied to the adsorbent and desorbed. The water vapor used for desorption and 1,4-dioxane desorbed from the adsorbent were recovered as concentrated water. The water to be treated was concentrated about 200 times at 20 L / h of concentrated water and returned to the AOP device.

  The water purified by the water treatment system of this example was able to treat 1,4-dioxane even after 500 hours with the performance of the secondary treated water having a concentration of 0.01 mg / L or less.

<Comparative Example 1>
The water to be treated of Example 1 was introduced into an AOP apparatus under the conditions of ozone concentration 400 mg / L and hydrogen peroxide concentration 100 mg / L to obtain AOP treated water. The outlet concentration at that time was 1,4-dioxane 0.01 mg / L or less. The power used was 50 kW as shown in Table 1, and required 8 times or more of the power required in the example.

<Comparative example 2>
The primary treated water of Example 1 was secondarily treated by an exchangeable adsorption apparatus using crushed coal having an average pore diameter of 14.5 mm, a BET specific surface area of 1300 m ² / g, and a total pore volume of 0.54 m ³ / g. . At that time, the amount of activated carbon required to adsorb the 1,4-dioxane concentration in the secondary treated water to 0.01 mg / L or less for 500 hours was 20 t or more, and it was necessary to be 2250 times or more of the example.

  The water treatment system of the present invention treats organic substances in water to be treated with high efficiency by performing secondary treatment with an adsorption / desorption type water treatment device as a backup of a wet oxidative decomposition device, and is discharged from the water treatment device. Reprocessing concentrated water with a wet oxidative decomposition apparatus has the advantage of being able to perform water treatment at a low cost, which greatly contributes to the industry.

100: wet oxidative decomposition apparatus 200: water treatment apparatus 210: first treatment tank 211: adsorbent 220: second treatment tank 221: adsorbent 230: condenser

Claims (6)

A water treatment system for purifying treated water by removing the organic substance from the treated water containing the organic substance,
A wet oxidative decomposition apparatus that oxidizes and decomposes organic substances in water to be treated and discharges primary treated water;
It includes an adsorbing element that adsorbs an organic substance by bringing water containing the organic substance into contact with it, and desorbs the adsorbed organic substance by bringing water vapor into contact therewith, and supplies the primary treatment water to the adsorbing element to perform a primary treatment. An adsorption step of adsorbing an organic substance contained in water to the adsorption element and discharging it as secondary treated water; and desorbing the organic substance from the adsorption element by supplying water vapor to the adsorption element; A water treatment device that alternately performs a desorption step of discharging water containing an organic substance having a concentration higher than the concentration of the organic substance in the primary treated water as concentrated water;
The water treatment system is configured such that the concentrated water discharged from the water treatment device is supplied to the wet oxidative decomposition device and subjected to water treatment.   The water treatment system according to claim 1, wherein the wet oxidative decomposition apparatus is a wet oxidative decomposition apparatus using any one of a Fenton method, an accelerated oxidation method, and an electrolysis method.   The said water treatment apparatus is a water treatment system of Claim 1 or 2 which removes the water adhering to the said adsorption | suction element, and discharges this as removal water.   The water treatment system according to claim 3, wherein water vapor is used to remove water adhering to the adsorption element.   The water treatment system of Claim 3 or 4 comprised so that the removal water discharged | emitted from the said water treatment apparatus may be supplied to the said water treatment apparatus again.   The water treatment system according to claim 1, wherein the adsorption element includes at least one member selected from the group consisting of activated carbon, activated carbon fiber, and zeolite.