WATER TREATMENT SYSTEM

Provided is a water treatment system which realizes reduction of the environmental load and energy saving. The system includes: an adsorption unit (10) provided with an adsorbent (11) of adsorbing a target in an aqueous solution which is supplied thereto; an separation tank (20) supplied with the target removed from the adsorbent (11) by a medium contacting thereto, water and the medium after contacting, and separating the medium from the mixture of the supplied water, medium and target; a circulation passage connecting the adsorption unit (10) with the separation tank (20), whereby a circulation unit circulates the medium between the adsorption unit (10) and the separation tank (20) via the passage; and an operation control unit 50 controlling a flow of the medium in accordance with a change in an amount of the water removed from the adsorbent (11) and supplied to the separation tank (20).

BACKGROUND ART

Waste water and treated water of oil sands from, for example, oil mines, petroleum chemistry plants, and industrial plants contain polluted substances, such as metal elements (for example, in a form of simple substance, compound or ion) and water-soluble organic substances. Therefore, from the viewpoint of reducing an environmental load, when such water (or waste water) is discharged to the outside (e.g., river and ocean), the metal elements and water-soluble organic substances, etc., in the waste water are removed and then discharge as purified water. Herein, the water-soluble organic substances include, for example, benzene, phenol, and naphthenic acid or the like.

A technique of removing the polluted substances includes, for example, a magnetic separation technique utilizing a magnetite. However, depending on a kind and a size of such polluted substances, there are some cases in which those polluted substances are not completely removed. In such a case, after the polluted substances are removed from the waste water to a certain degree through the magnetic separation technique, another treatment may be further performed for the waste water after the above mentioned treatment.

For example, after waste water is treated by the magnetic separation technique, the waste water thus treated may have contact with, for example, activated charcoal, zeolite, and aluminum oxide (hereinafter, simply referred to as “activated charcoal, etc.,”). Accordingly, the polluted substances remaining in the waste water thus treated come to be adsorbed by the activated charcoal, etc., allowing the concentration of the polluted substances in the water to be  reduced. Then, the water thus treated is discharged into the outside. Note another treatment is performed on the activated charcoal, etc., which adsorbs the polluted substances, etc., such that the adsorbed polluted substances are removed therefrom. Accordingly, the activated charcoal, etc., recovers a function for adsorbing polluted substances again. Such a treatment performed on the activated charcoal, etc., is referred to as “recycling” in this specification.

A recycling technique of the activated charcoal, etc., includes, for example, a method for exposing the activated charcoal, etc., with high-temperature steam, to have the adsorbed polluted substances vaporized so as to discharge the polluted substances thus vaporized. Alternatively, another exemplary technique includes a method for contacting the activated charcoal, etc., with an electrolyte solution containing, for example, sodium chloride to desorb the adsorbed polluted substances. Herein, the addition of the electrolyte to the polluted substances thus desorbed may decompose the water-soluble organic substances, that is, polluted substances. Further, the activated charcoal, etc., used for the above mentioned treatment may be replaced by new activated charcoal, etc.

Moreover, it is known that a different recycling technique of the activated charcoal, etc is described in Patent Literature 1. More specifically, Patent Literature 1 discloses a technique for removing water from a solid material containing water by using a liquefied substance. This technique comprises the steps of: contacting a solid material containing water with a liquefied substance that turns to gas at 25° C. and 1 atm. (hereinafter, referred to as a substance D); dissolving water contained in the solid material into the liquefied substance D; and obtaining the liquefied substance D with the high water content, thereby to remove the water contained in the solid material. Then, the technique further comprises the steps of: vaporizing the substance D in the obtained liquefied  substance D with the high water content; separating the vaporized substance D from the water; collecting the gas of the separated substance D; liquefying the substance D by pressurizing, cooling or performing the combination to, the collected gas, so as to obtain a liquid thereof; and reusing the liquid again for removing the water contained in the above mentioned solid material. Further, the patent document discloses a technique for recovering the energy generated at the external system during the vaporization process, and utilizing the energy thus recovered for the liquefying process as a part of the power used in the liquefying process.

PRIOR ART REFERENCE

Patent Literature

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, the above mentioned recycling techniques have a drawback from a viewpoint of zero emission and energy saving. That is, in order to generate high-temperature steam, electrical power or thermal power is required, resulting in a drawback from the standpoint of the energy saving. Further, when the technique has the step of letting the electrolyte solution flow, a large amount of the electrolyte solution is needed for the flow in order to remove the polluted substances. This step may produce an additional amount of the waste water containing polluted substances. Moreover, according to the above mentioned recycling techniques, there is no index clearly indicating the endpoint at which the recycling process is completed. This may force the recycling process to be excessively repeated in some cases. Furthermore, when the activated charcoal,  etc., is replaced by new one, the used activated charcoal, etc., may be removed to the external system, resulting in a drawback from the standpoint of a zero emission procedure.

Hence, the inventors of the present invention have investigated a method to be replaced by the conventional recycling techniques. As a result, the inventors of the present invention have found that in the adsorption treatment of polluted substances by the activated charcoal, etc., polluted substances in absence of water are hardly adsorbed by the activated charcoal, etc., while a waste liquid containing such polluted substances is likely to be adsorbed by the activated charcoal, etc. Further, the inventors of the present invention have found that in order to recycle the activated charcoal, etc., it is effective to remove water in the waste liquid that contains the polluted substances and has been adsorbed by the activated charcoal, etc. Those findings enable the polluted substances adsorbed by the activated charcoal, etc., to be removed together with water, resulting in the recycling of the activated charcoal, etc.

According to the technology disclosed in Patent Literature 1, coals containing water are dehydrated by using dimethyl ether. Herein, it should be noted that such coals are continuously dehydrated further even until the coals turn to contain no water. Accordingly, the above mentioned dehydration process may be continuously performed, regardless of the necessity of further performing the dehydration operation, for example, in a case that no further dehydration is needed because of the little water content in the treated coals. When the activated charcoal, etc., is recycled through the technology disclosed in Patent Literature 1, the technology disclosed in the patent document still has room for further improvement from a viewpoint of energy saving.

The present invention has been made in view of the above mentioned  drawbacks. Here, an object of the present invention is to provide a water treatment system that realizes higher energy saving while reducing an environmental load.

Means for Solving the Problems

The present inventors have significantly investigated a water treatment system so as to solve the above mentioned drawbacks. Accordingly, the present inventors have found that the above mentioned drawbacks are solved by a method for controlling a medium flow corresponding to a change in the water amount supplied to a separation tank (or separation unit). Herein, the method comprises the step of circulating the medium to successively contact with the adsorbent.

Effect of the Invention

According to the present invention, a water treatment system is provided, which realizes further energy saving while reducing an environmental load.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments for carrying out the present invention (or present embodiments) will be explained in detail referring to the accompanying drawings. Herein, it should be noted that the present embodiments are not limited to the following descriptions as described below.

1. First Embodiment

FIG. 1is a schematic diagram illustrating a water treatment system100in a first embodiment. The water treatment system100includes an adsorption tower10, a separation tank20, piping for interconnecting the adsorption tower10and the separation tank20together, and piping through which waste water, purified water and treated water flow (inFIG. 1, the piping is indicated by thick lines with arrows in order to simplify the illustration, and the direction of the arrow indicates the flow direction), valves1,2,3, and4provided at each piping, and an operation control unit50that controls respective units of the water treatment system100. The adsorption tower10has an adsorbent11filled therein to adsorb polluted substances contained in the waste water. Further,  dashed lines indicate electrical signal lines connected in a wired or wireless manner.

A liquid of dimethyl ether (or medium) is circulated between the adsorption tower10and the separation tank20, and thus a circulation passage of dimethyl ether is formed therebetween. Dimethyl ether is circulated by an unillustrated circulation pump, etc. That is, as illustrated inFIG. 1, the circulation passage of dimethyl ether (or circulation passage) connects the adsorption tower10(or adsorption unit) with the separation tank20(or separation unit). Herein, the dimethyl ether (or medium) to be in contact with the adsorbent11is circulated between the adsorption tower10(or adsorption unit) and the separation tank20(or separation unit) by the circulation pump (or circulation unit).

A liquid level sensor21is provided in the separation tank20, and thus the liquid level (or total height of an ether layer20aand a water layer20b) in the separation tank20is measurable. That is, the liquid level sensor21is to measure the liquid level of the liquid (or ether layer20aand water layer20b) reserved in the separation tank20. In the water treatment system100, recycling of the adsorbent11is performed based on this liquid level. This will be discussed later in detail together with an explanation for “recycling control of adsorbent11”.

The adsorption tower10adsorbs polluted substances contained in the waste water, and discharges the water to the outside as purified water. The adsorption tower10is filled with the adsorbent11(e.g., activated charcoal, aluminum oxide, or zeolite) that adsorbs polluted substances contained in the waste water. That is, waste water (or aqueous solution) is supplied to the adsorption tower10(or adsorption unit). Herein, the adsorption tower10is provided with the adsorbent11that adsorbs polluted substances (or targets) in  the waste water (or aqueous solution) thus supplied.

The waste water flows through the inside of the adsorption tower10from the lower part thereof with the valves1and3being opened and the valves2and4being closed. The waste water supplied to the adsorption tower10contacts the adsorbent11, and thus polluted substances contained in the waste water are adsorbed by the adsorbent11. Then, the waste water (i.e., purified water) of which impurities have been adsorbed and thus removed is discharged to the outside through the opened valve3.

Next, in the adsorption tower10, the dimethyl ether flows from the lower part of the tower10to recycle the adsorbent11. More specifically, dimethyl ether flowing through the inside of the adsorption tower10and contacting the adsorbent11removes polluted substances dissolved in water adsorbed by the adsorbent11together with water. Then, dimethyl ether, polluted substances and water, which have been released from the adsorbent11, are thus supplied to the separation tank20.

Next, the separation tank20(or separation unit) separates dimethyl ether, the polluted substances and water thus supplied from the adsorption tower10, into the ether layer20a(or upper layer) containing dimethyl ether, and the water layer20b(or lower layer) containing the polluted substances and water. A mixture thus supplied from the adsorption tower10is accumulated in the separation tank20. Accordingly, this allows the mixture to be separated into the ether layer20aand the water layer20b.That is, the polluted substances (or targets) and water both of which have been removed by having the adsorbent11contact with dimethyl ether (or medium), and dimethyl ether (or medium) which has contacted with the adsorbent11, are supplied to the separation tank20. Then, dimethyl ether (or medium) is selectively separated from the mixture of  the supplied water, dimethyl ether (or medium) and polluted substances (or targets).

Note that solid materials discharged from the adsorption tower10to be undissolved in both of water and dimethyl ether, are thus deposited on the bottom of the separation tank20as sludge20c.The sludge20cis periodically discharged to the outside.

Here, the ether layer20ain the separation tank20is to be returned to the adsorption tower10through the above-explained circulation passage of dimethyl ether. Next, the returned dimethyl ether is utilized for recycling the adsorbent11again. This recycle of dimethyl ether allows a total amount of dimethyl ether discharged to the outside to be decreased.

The water layer20bin the separation tank20contains polluted substances (that is, heavy metal ions, water-soluble organic substances, etc.) removed from the adsorbent11. Hence, the water layer20bis to be discharged as treated water through a valve6and a flow volume sensor8, thereby to be treated by an unillustrated treatment device. The water amount supplied from the adsorption tower10is generally little. Accordingly, the water amount layer20bis little, allowing the amount of the treated water supplied to the unillustrated treatment device to be reduced. That is, the polluted substances released from the adsorbent11are to be collected and treated in a condensed state.

The operation control unit50controls the circulation pump that circulates dimethyl ether based on the liquid level measured by the liquid level sensor21. In other words, the operation control unit50controls the flow of dimethyl ether (or medium) in accordance with a change in the water amount supplied to the separation tank20. Herein, the change in the water amount is caused by having  the dimethyl ether (or medium) circulate and successively contact with the adsorbent11. The detail of the control by the operation control unit50will be described hereinafter.

The operation control unit50also controls, for example, the valves1,2,3, and4, and a pump (unillustrated) that supplies the waste water to the adsorption tower10. Further, the operation control unit50adjusts the opening degree of the valve6in accordance with the flow volume measured by the flow volume sensor8.

The operation control unit50includes, for example, a CPU (or Central Processing Unit), a RAM (or Random Access Memory), a ROM (or Read Only Memory), an I/F (or interface), an HDD (or Hard Disk Drive), a sensor circuit and a control circuit (or both unillustrated). The above mentioned controlling operations are realized by the CPU executing a predetermined control program stored in the ROM.

[Recycling Control of Adsorbent11]

Next, a control method for recycling the adsorbent11in the water treatment system10will be described. The operation control unit50executes the following control operations.

As explained above, dimethyl ether is successively circulated between the adsorption tower10and the separation tank20. Here, dimethyl ether contacts with the adsorbent11thereby to recycle the adsorbent11.

In this circulation, when all the polluted substances adsorbed by the adsorbent11are released and transferred to the separation tank20, it becomes unnecessary to further recycling the adsorbent11. Accordingly, from a  viewpoint of energy saving, the recycling control operations are set to be terminated in the water treatment system100, after the polluted substances adsorbed by the adsorbent11have been released and transferred to the separation tank20,

Generally, waste water to be supplied to the adsorption tower10is filtrated by a filter, etc., in advance. Accordingly, such waste water to be treated hardly contains large sized polluted substances (or solid materials). Hereby, a major part of the polluted substances (more specifically, heavy metal ions and water-soluble organic substance, etc.) is dissolved in the waste water. Hence, the polluted substances are dissolved in water and then adsorbed by the adsorbent11. As a result, when the adsorbent11is recycled using dimethyl ether, the polluted substances are released and transferred (or collected) together with water. Therefore, the more the polluted substances adsorbed by the adsorbent11are collected in the separation tank20, the more the amount of the water layer20bin the separation tank20increases.

When the recycling process of the adsorbent11by dimethyl ether is completed, the adsorbent11turns to not adsorb any polluted substances. At that state, only dimethyl ether is circulated and the water amount layer20bin the separation tank20becomes unchanged. If the water amount layer20bbecomes unchanged, the liquid level in the separation tank20measured by the liquid level sensor21becomes also unchanged. As described above, the control operation is performed such that that recycling of the adsorbent11is terminated in the water treatment system100, when a change in the liquid level becomes substantially zero.

As explained above, in the water treatment system100, a change in the water amount supplied to the separation tank20is calculated based on the liquid  level measured by the liquid level sensor21. Herein, since the amount of dimethyl ether to be circulated is constant, the level of the ether layer20abecomes substantially constant. Accordingly, the liquid level measured by the liquid level sensor21changes in association with a change in the water amount supplied to the separation tank20. Note the change in the water amount is caused by the circulation of dimethyl ether (or medium) successively contacting with the adsorbent11. This allows the change in the water amount supplied to the separation tank20to be calculated based on the liquid level measured by the liquid level sensor21.

FIG. 2is a graphic diagram illustrating a change in the water amount supplied to the separation tank20per an elapsed time. The horizontal axis indicates an elapsed time after the start of recycling, and the vertical axis indicates the water amount supplied to the separation tank20at the time elapsed after the start of recycling (i.e., the water amount collected from the adsorption tower10).

The water amount collected from the adsorption tower10becomes maximum (V2) right after the recycling of the adsorbent11is started via the contact with dimethyl ether. Since water is continuously supplied at the flow volume of substantially V2for a while after the start of recycling, a change in the liquid level increases. Then, the amount of collected water as time passes gradually decreases, and a change in the liquid level gradually decreases along with the decrease in the collected water amount. In this embodiment, when a time t1elapses and the amount of supplied water becomes V1(or water amount at the recycling limit), circulation of dimethyl ether is terminated, whereby the recycling process is terminated. This terminated time is set at the time when the change in the liquid level becomes equal to or smaller than a predetermined value. Note the circulation process is continued for a while after the  termination of the circulation, thereby to completely remove the polluted substances together with water adsorbed by the adsorbent11.

In other words, when the valve6is closed, a change in the liquid level measured by the liquid level sensor21is relatively large right after the start of the recycling process. Thereafter, since the amount of collected water gradually decreases, a change in the liquid level becomes small. Then, when a change in the liquid level measured by the liquid level sensor21(or a change per a unit time) becomes smaller than a predetermined degree, the circulation of dimethyl ether is terminated, whereby the recycling process is also terminated. After that, as explained above, the circulation is continued for a while after the circulation has been terminated, thereby to completely remove the polluted substances. Note the allowable range of the change in the liquid level may be set via performing experiments or a test operation, etc. For example, if a change in the liquid level becomes equal to or smaller than the change level when the water amount supplied to the separation tank20is V1, the control operation may be terminated.

Next, the mixture of the polluted substances and water (or water layer20b) removed from the adsorbent11is discharged to the outside through the valve6. The flow volume sensor8measures the flow volume of the mixture (i.e., the water layer20b) of the water and the polluted substances (or liquid) discharged when the water and the polluted substances (or liquid) stored in the separation tank8are discharged to the outside. After that, the opening degree of the valve6is adjusted appropriately based on the discharging flow volume measured by the flow volume sensor8such that no ether layer20ain the separation tank20is discharged to the outside. Accordingly, the water layer20bis discharged to the outside as treated water.

Advantages

According to the water treatment system100of this embodiment, the recycling process of the adsorbent11is controlled based on the change in the liquid level (in other words, the change in the water amount) in the separation tank20. The execution of such recycling control suppresses unnecessary recycling regardless of the absence of the adsorbed substances on the adsorbent11, allowing the energy saving to be accomplished. Further, the recycling of the adsorbent11is controlled based on the change in the liquid level in the separation tank20, whereby the adsorbent11may be recycled based on a simple index.

Further, the circulation of dimethyl ether utilized for recycling the adsorbent11enables a discharging amount thereof to the outside to become extremely small. Accordingly, the water treatment system100of this embodiment is suitable for accomplishing zero emission which is desirable in recent years from the viewpoint of decrease in the environmental load.

Moreover, since the adsorbent11adsorbs heavy metal ions via a small amount of the ionic aqueous solution, the heavy metal ions are collected in the separation tank20in an aqueous solution state. Hence, the heavy metal ions collected from the adsorbent11are collected in the separation tank20in a condensed manner. Accordingly, the volume of the treated water subjected to a removal of heavy metals can be reduced, allowing the removal efficiency of heavy metals in the treated water by heavy metal removing equipment (not shown) to be improved. Furthermore, this also allows the removing equipment to be downsized.

Further, since heavy metal elements can be obtained in a condensed manner, according to the water treatment system100, so-called rare metals, such as  palladium, cobalt, and platinum, can be efficiently collected from waste water at a low cost. As explained above, the water treatment system100of this embodiment is suitable for not only purification of waste water but also the application for, for example, collecting metal elements.

2. Second Embodiment

Next, with reference toFIG. 3, an explanation will be given of a water treatment system200in a second embodiment. Note the same component as that of the water treatment system100will be denoted by the same reference numeral, and the detailed explanation thereof will be omitted. The water treatment system200has the same basic structure as that of the water treatment system100. Therefore, in the following explanation, different features from the above-explained water treatment system100will be mainly explained.

FIG. 3is a schematic diagram illustrating the water treatment system200in the second embodiment. The water treatment system100inFIG. 1is provided with the separation tank20and the liquid level sensor21, but instead of those components, a scattering valve5, another separation tank22, and a compressor30, etc., are provided.

The scattering valve5(or vaporization unit) is provided in the halfway of the circulation passage of dimethyl ether (or circulation passage) from the adsorption tower10(adsorption unit) to the separation tank20, and vaporizes flowing dimethyl ether (or medium). Further, the separation tank22(or separation unit) is a three-layer separation tank that separates the target into three layers: an unillustrated layer (gas layer) containing dimethyl ether; the water layer20b(or liquid layer); and a sludge20c(solid layer). The compressor30(or liquefying unit) is provided in the halfway of the circulation passage of dimethyl ether (or circulation passage) from the separation tank20to  the adsorption tower10(or adsorption unit), and liquefies flowing dimethyl ether (or medium).

As different from the water treatment system100illustrated inFIG. 1, there is no ether layer20athat is a layer of liquid. This is because the circulating dimethyl ether is transformed into gas in the separation tank22according to the water treatment system200, which will be discussed in detail hereinafter.

Dimethyl ether circulates the circulation passage of dimethyl ether, whereby the adsorbent11is to be recycled. Hereby, polluted substances adsorbed by the adsorbent11are supplied to the separation tank22together with dimethyl ether and water. A mixture of the polluted substances, water and dimethyl ether to be supplied to the separation tank22is scattered by the scattering valve5(including orifices, etc.) provided between the adsorption tower10and the separation tank22, and then supplied to the separation tank22.

When the mixture of the polluted substances, water, and dimethyl ether is scattered, dimethyl ether is firstly vaporized due to the difference of the boiling points. Accordingly, by scattering the mixture of those substances before supplied to the separation tank22, such a mixture can be separated into vapor of dimethyl ether, a liquid of polluted substances and water. Then, dimethyl ether changed to vapor is discharged to the external system through the upper portion of the separation tank22, compressed by the compressor30to be liquefied again, and returned to the adsorption tower10.

On the other hand, the liquid of the polluted substances and water are accumulated in the separation tank22having a partition wall23. Solid substances are deposited as the sludge20c,and a supernatant liquid (or water layer20b) is discharged to the outside as treated water. Further, the sludge20cis collected in a centrifugal apparatus9through a valve7. Next, the sludge20cis separated into treated water and dehydrated sludge by the centrifugal apparatus9, and discharged to the outside.

The recycling control of the adsorbent11is basically consistent with that of the above-explained water treatment system100in the first embodiment. According to the water treatment system200in the second embodiment, however, no liquid level sensor is provided in the separation tank22. Therefore, as different from the water treatment system100, the valve6is opened right after the recycling control of the adsorbent11starts, a time of the termination of the recycling control is set based on a change in the discharging flow volume of the water layer20bmeasured by the flow volume sensor8. That is, when the change in the flow volume based on the measured flow volume by the flow volume sensor8is equal to or smaller than a predetermined value, it is determined that removal of water and polluted substances from the adsorbent11is completed, and thus the recycling control is terminated. Accordingly, such a simple structure may realize the recycling with saving energy.

As explained above, according to the water treatment system200, the operation control unit50calculates a change in water supplied to the separation tank22using the flow volume measured by the flow volume sensor8. That is, in the water treatment system200, since the valve6is fully opened right after the recycling control has been started, the discharging flow volume corresponds to the amount of supplied water. Further, the change in discharging flow volume corresponds to a change in supplied water.

By constructing the water treatment system200as explained above, dimethyl ether, water and the polluted substances can be further surely divided well in the separation tank22. Hence, it becomes possible to more surely prevent dimethyl ether from being discharged to the outside through the valve6.

Next, with reference toFIG. 4, an explanation will be given of a water treatment system300in a third embodiment. The same component as that of the water treatment system100will be denoted by the same reference numeral, and the detailed explanation thereof will be omitted. The water treatment system300uses the same basic structure as that of the water treatment system100, and thus the differences from the above-explained water treatment system100will be mainly explained in the following explanation.

FIG. 4is a schematic diagram illustrating the water treatment system300in the third embodiment. In the water treatment system100inFIG. 1, only one adsorption tower10is connected, while in the water treatment system300, two adsorption towers10aand10busing the same structure as that of the adsorption tower10are connected in parallel with the separation tank20. The adsorption towers10aand10binclude the same adsorbents11aand11b,respectively. In accordance with such a structure, valves1a,2a,3a,4a,1b,2b,3b,and4bare provided so as to connect those towers each other like the water treatment system100. Those valves are controlled by the operation control unit50.

In the water treatment system300, the adsorption towers10aand10bare connected and provided in a parallel manner. Accordingly, waste water flows through the adsorption tower10bto allow the adsorbent11bto adsorb the polluted substances, while at the same time, dimethyl ether flows through the adsorption tower10aalready adsorbing the polluted substances, thereby recycling the adsorbent11a.

That is, in such a case, for example, the valves1aand3aare controlled to be closed and the valves2aand4aare controlled to be opened, as the flow  control of dimethyl ether to the adsorption tower10a.Accordingly, no waste water is supplied to the adsorption tower10a,while only dimethyl ether is supplied thereto. Further, the valves2band4bare controlled to be closed and the valves1band3bare controlled to be opened as the flow control of waste water to the adsorption tower10b.Hence, no dimethyl ether is supplied to the adsorption tower10b,while only waste water is supplied thereto. Next, after the recycling of the adsorbent11aof the adsorption tower10ais completed, the opening/closing of the valves are changed. Subsequently, waste water is supplied to the adsorption tower10a,while at the same time, recycling of the adsorbent11bof the adsorption tower10bis performed.

As explained above, adsorption and recycling operations both performed simultaneously may reduce a time necessary for water treatment. This allows the water treatment to be conducted in a highly efficient manner. Further, even when, for example, the adsorption tower10abecomes defective, the water treatment can be continuously conducted using the adsorption tower10b.Accordingly, stable water treatment is enabled.

Next, an explanation will be given of a water treatment system400in a fourth embodiment with reference toFIG. 5. The same component as those of the water treatment system200illustrated inFIG. 3and the water treatment system300illustrated inFIG. 4will be denoted by the same reference numeral, and the detailed explanation thereof will be omitted. Further, the water treatment system400uses the same basic structure as those of the water treatment systems200and300, and the differences from the water treatment systems200and300will be mainly explained in the following explanation.

In the water treatment system400, the separation tank22, etc., illustrated inFIG. 3are provided, and the adsorption towers10aand10bare connected in a parallel manner. Hence, dimethyl ether, water and polluted substances can be further surely separated from each other in the separation tank22. Accordingly, it becomes possible to further surely prevent dimethyl ether from being discharged to the outside through the valve6. Moreover, both adsorption and recycling operations conducted simultaneously enables a time necessary for the water treatment to be reduced. Hence, the water treatment can be conducted in a highly efficient manner. Furthermore, even when, for example, the adsorption tower10abecomes defective, the water treatment can be continuously conducted using the adsorption tower10b.Accordingly, this realizes a stable water treatment.

Next, an explanation will be given of a water treatment system500in a fifth embodiment with reference toFIG. 6. The same component as that of the water treatment system100will be denoted by the same reference numeral, and the detailed explanation thereof will be omitted. Further, since the water treatment system500uses the same basic structure as that of the water treatment system100, the differences from the water treatment system100will be mainly explained in the following explanation.

FIG. 6is a schematic diagram illustrating the water treatment system500in the fifth embodiment. The water treatment system500has two adsorption towers10cand10dconnected in series. An adsorbent11cis filled in the adsorption tower10c,and an adsorbent11dis filled in the adsorption tower10d.According to the water treatment system500, the adsorbent11cis, for example, an activated charcoal, while the adsorbent11dis, for example, aluminum oxide. The adsorbent11cmainly adsorbs water-soluble organic substances, while aluminum oxide mainly adsorbs heavy metal ions.

Depending on the elements contained in waste water, it is unable to completely carry out a removal through a single adsorption unit (e.g., an activated charcoal, aluminum oxide or zeolite) in some cases. Hence, in order to surely remove the elements contained in waste water, according to the water treatment system500, two kinds of adsorbents11cand11dare utilized. By utilizing multiple kinds of adsorbents in accordance with the elements contained in waste water as explained above, elements in waste water can be further surely adsorbed and removed.

Next, an explanation will be given of a water purification system600using the water treatment system100in the first embodiment with reference toFIG. 7. The same component as that of the water treatment system100illustrated inFIG. 1will be denoted by the same reference numeral, and the detailed explanation thereof will be omitted. The operation control unit50also controls, in addition to the water treatment system100, the operation of a magnetic separation system800.

FIG. 7is a schematic diagram of the water purification system600using the water treatment system100in the first embodiment. According to the water purification system600, waste water supplied to the water treatment system100is pretreated by the magnetic separation system800. That is, the magnetic separation system800removes the polluted substances from waste water to some degree to purify the waste water, and the water treatment system100further purifies that waste water to which the removal operation has been performed.

In the magnetic separation system800, first, a flocculant tank30supplies a  flocculant (e.g., poly-aluminum chloride) to waste water. Next, a magnetite tank supplies magnetite (e.g., iron) to the waste water. Furthermore, the mixture of those substances is sufficiently stirred and mixed in a stirring tank33by stirring blades33a.Accordingly, microflocs containing polluted substances in waste water and magnetite, etc., are formed in the stirring tank33.

To the aqueous solution containing the microflocs thus formed, is added a polymer (e.g., polyglutamic acid or polyalginic acid) from a polymer tank32. Then, the aqueous solution is sufficiently stirred and mixed in a stirring tank34by stirring blades34a.Accordingly, the microflocs are grown, thereby to form large flocs. Next, the aqueous solution containing the large flocs is supplied to a floc removing tank35.

The floc removing tank35is provided with a hollow magnetic drum36with a meshed surface. The surface of the magnetic drum36is magnetized, and the lower portion of the magnetic drum36is arranged so as to be soaked in a liquid in the floc removing tank35. Next, as the magnetic drum36rotates, the flocs in the liquid containing magnetite are adsorbed on the surface of the magnetic drum36. The adsorbed flocks are transferred to the upper space of the magnetic drum36associated with the rotation of the magnetic drum36, thereby to contact with a brush roller37rotating in the opposite direction to the magnetic drum36. This allows the flocs to be forcibly scraped from the surface of the magnetic drum36by the brush roller37. Then, the flocks thus scraped are stored in a flock collecting apparatus39through a scraper38.

The waste water from which the polluted substances have been removed as flocks as mentioned hereinbefore is purified to a certain degree. However, some flocks may be left since the floc removing tank35is unable to completely remove the flocs in some cases. Further, in other cases, no flocs or no  microflocs are formed, letting polluted substances remained in the waste water. In such a case, the water discharged from the magnetic separation system800is supplied to the water treatment system100, enabling the discharged water to be purified more surely and in highly efficient.

The flocs remained as an insufficient removal in the floc removing tank35can not be adsorbed by the adsorbent11or pass through the pores, thereby to stack in some cases. Here, in such a case, when the adsorbent11is recycled by dimethyl ether, such flocs thus remained come to be dissolved in dimethyl ether flowing through the flocs. This allows the stacking flocs not adsorbed or not passing through the pores to be dissolved and removed.

As explained above, according to the purification system600, the waste water (or aqueous solution) is discharged from the magnetic separation system (or oil/water separation system). Then, the discharged water is to be supplied to the adsorption tower10(or adsorption unit) of the water treatment system100. By carrying out the separation twice in this manner, the polluted substances are more surely removed from the waste water.

Next, an explanation will be given of a water purification system700including the water treatment system200in the second embodiment with reference toFIG. 8. The same component as those of the water treatment system200illustrated inFIG. 3and the magnetic separation system800illustrated inFIG. 7will be denoted by the same reference numeral. The detailed explanation thereof will be omitted.

FIG. 8is a schematic diagram of the water purification system800including the water treatment system200in the second embodiment. The  water treatment system200uses the same basic structure as that of the water purification system600as explained with reference toFIG. 7. However, in the water purification system700, the water treatment system200is provided instead of the water treatment system100of the water purification system600. Even though the water purification system is constructed as mentioned above, heavy metals, etc., in waste water are surely and efficiently removed.

8. Modified Examples

Hereinbefore, the respective embodiments have been explained with reference to the drawings. Herein, it should be noted that the embodiments of the present invention are not limited to the illustrated examples. Hence, any unit may be, for example, added, deleted, or replaced arbitrary with respect to the illustrated examples without departing from the scope and spirit of the present invention.

Some of the structures of the respective embodiments may be combined together. More specifically, for example, the water treatment system100may be provided with the scattering valve5of the water treatment system200. Further, for example, the water treatment system200may be provided with the liquid level sensor21of the water treatment system100. Moreover, the separation tank22(three-layer separation tank) of the water treatment system200may be applied to the water treatment system100. Furthermore, a flow volume sensor may be provided in the halfway of the circulation passage of dimethyl ether between the adsorption tower10and the separation tank20to measure a change in the flow volume.

The separation unit is not limited to the illustrated examples, and any arbitrary units are applicable. For example, a three-phase separation tank (or separator) may be utilized as the separation tank22with the partition wall23in  the example illustrated inFIG. 3. However, any unit is applicable as far as such a unit can separate vaporized dimethyl ether. Further, in order to facilitate dimethyl ether to be vaporized, a heater may be equipped with the separation tank22so as to heat a supplied liquid. That is, the vaporizing unit for vaporizing dimethyl ether is not limited to the scattering valve. Moreover, the liquefying unit that liquefies dimethyl ether is not limited to the compressor, and may be, for example, a cooler.

Further, the two adsorption towers are provided in the cases of, for example,FIG. 4andFIG. 6, while three or more adsorption towers may be provided. Moreover, in the illustrated examples, a single separation tank is provided, while multiple separation tanks may be provided for the separation process.

Furthermore, in the respective embodiments as explained above, for example, dimethyl ether is utilized as a medium for removing the polluted substances. However, it should be noted that such a medium is not limited to dimethyl ether. That is, any media are applicable as far as the media enable the polluted substances adsorbed by the adsorbent11to be, for example, dissolved or mixed therein to remove the polluted substances, and the media are separable in the separation tanks20and22. More specifically, such media applicable include, in addition to dimethyl ether, ethers such as diethyl ether, and methyl ethyl ether; ketones such as acetone, and methyl ethyl ketone; alcohols such as methanol, ethanol, propanol, butanol, pentanol, and hexanol; and aldehydes such as formaldehyde, and acetaldehyde, and chloroform or the like. Those media may be used in a mixed manner as needed. Moreover, when, for example, ketones or alcohols are utilized as media, waste water and the media are separable based on the difference in the boiling points.

However, among those media, in the first embodiment illustrated inFIG. 1,  for example, it is preferable to use a medium that separates into two layers in the separation tank20. More specifically, application of ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether, is preferable. On the other hand, in the second embodiment illustrated inFIG. 3, for example, it is preferable to apply a medium that turns to gas at 25° C. and 101 kPa. More specifically, application of ethers such as dimethyl ether, diethyl ether, and methyl-ethyl ether, is preferable.

The kind and filled amount of the adsorbent11can be set arbitrary in accordance with the kind and amount of polluted substances. Exemplary adsorbents11include an activated charcoal, aluminum oxide, and zeolite, and can be used in a combined manner as needed. Note the structure of the adsorption unit is not limited to an adsorption tower, and an arbitrary structure can be used. Further, the oil/water separation system that separates an oil and water from each other is not limited to the magnetic separation system. Hereby, oil and water can be separated through any arbitrary techniques.

In the above mentioned examples, substances adsorbed by the adsorbent include water soluble organic substances and heavy metal ions. However, such substances are not limited to those examples. Although the target to be adsorbed by the adsorbent is not limited, it is preferable that such a target should be at least one of water soluble organic substances and metal elements. A form of metal element is not limited to the exemplified heavy metal ion, and may include a simple substance, a compound and a complex thereof, etc. Further, such a metal may be a metal other than a heavy metal. Herein, a form of the metal may also include an elemental substance, a compound and a complex thereof, etc.

EXPLANATION OF REFERENCES