Patent Publication Number: US-7914677-B2

Title: Water treatment apparatus and water treatment method

Description:
TECHNICAL FIELD 
     The present invention relates to a water treatment apparatus including a membrane device that carries out water treatment using a membrane and a pretreatment device that carries out pretreatment of water to be introduced into the membrane device and a water treatment method. 
     BACKGROUND ART 
     In the treatment apparatus and treatment method of water treatment, there have conventionally been several pretreatment devices and pretreatment methods as general pretreatment devices and pretreatment methods. As one example, a pretreatment device of a biological treatment device in waste water treatment includes settling, filtering, pH adjustment, ozone oxidation, adsorption and so on. 
     The purpose of the pretreatment device is to reduce the biological, chemical or physical load on the waste water treatment apparatus in the subsequent step, and a reduction in the scale of the waste water treatment apparatus, a reduction in the running cost, an improvement in the water quality of the water to be treated from the waste water treatment apparatus and so on are expected. 
     However, the conventional pretreatment does not have the function of maintaining a high dissolved oxygen concentration to the subsequent step for a long time by markedly raising the dissolved oxygen concentration in the water to be treated to carry out the treatment with improved activities of microorganisms. Furthermore, the conventional pretreatment does not have the function of improving the functions of the microorganisms by markedly raising the dissolved oxygen concentration in the water to be treated and markedly raising the treatment efficiency of the membrane device in the subsequent stage. 
     Moreover, the conventional pretreatment, which has general aeration with a blower, does not have a treatment function with micro-nano bubbles that contain both micro bubbles of a diameter of not greater than 50 microns and not smaller than one micron and nano bubbles of a diameter of not greater than one micron. It is noted that, in the case of the pretreatment with the micro-nano bubbles described above, there is the function of maintaining the dissolved oxygen to the subsequent step for a long time. 
     There have conventionally been nano bubble utilizing method and apparatus disclosed in JP 2004-121962 A. The nano bubble utilizing method and apparatus utilize the characteristics of surface-activating operation, sterilizing operation and so on by the achievement of a reduction in buoyancy, an increase in surface area, an increase in surface activity, generation of a local high-pressure field and electrostatic polarization, which are owned by nano bubbles. More concretely, it is disclosed that the characteristics are correlated to allow a variety of objects to be cleaned with a high function and a low environmental load by a dirt component adsorption function, an object surface high-speed cleaning function and a sterilizing function and to allow the contaminated water to be cleaned. 
     However, 
     (1) There is no disclosure of introducing and treating the water that contains the micro-nano-bubbles in a water tank which is filled with a charcoal or a synthetic charcoal and has an agitating device and thereafter introducing and treating the water in a membrane device. 
     (2) There is also no disclosure of newly generating water that contains the micro-nano bubbles in a micro-nano bubble generation tank, introducing the water that contains the micro-nano bubbles into a charcoal water tank which is filled with a charcoal or a synthetic charcoal and has an agitating device therein, carrying out treatment with raised activity of the microorganisms propagating in the charcoal or synthetic charcoal by the micro-nano bubbles and reducing the organic loads and so on of the membrane device. 
     Furthermore, there is a nano bubble generating method disclosed in JP 2003-334548 A. The nano bubble generating method, for use in a liquid, is constituted of (a) a step of decomposing and gasifying part of the liquid, (b) a step of applying ultrasonic waves in the liquid or (c) a step of decomposing and gasifying part of the liquid and applying ultrasonic waves. 
     However, 
     (3) There is also no disclosure of introducing and treating the water that contains the micro-nano bubbles in a water tank which is filled with a charcoal or a synthetic charcoal and has an agitating device and thereafter introducing and treating the water in a membrane device. 
     (4) There is also no disclosure of newly generating water that contains the micro-nano bubbles in a micro-nano bubble generation tank, introducing the water that contains the micro-nano bubbles into a charcoal water tank which is filled with a charcoal or a synthetic charcoal and has an agitating device in the water tank, carrying out treatment with raised activity of the microorganisms propagating in the charcoal or synthetic charcoal by the micro-nano bubbles and reducing the organic loads and so on of the membrane device. 
     As described above, there have conventionally been apparatuses of various systems as the pretreatment device of the membrane device, there is existing no pretreatment device capable of markedly preventing the clogging phenomenon of the membrane device and improving the ability of the membrane device by utilizing a simple apparatus that is low cost and ensures easy maintenance and energy saving. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a water treatment apparatus and a water treatment method capable of carrying out treatment by raising the activity of the microorganisms propagating in a charcoal or a synthetic charcoal and reducing the organic loads and so on of a membrane device in a subsequent step. 
     In order to solve the above problems, a water treatment apparatus of the present invention comprises: 
     a membrane device that treats introduced water by means of a membrane; and 
     a pretreatment device that carries out pretreatment of water to be introduced into the membrane device; wherein 
     the pretreatment device comprises: 
     a raw water tank which is filled with polyvinylidene chloride filler and into which water is introduced from outside; 
     a micro-nano bubble generation tank which has a micro-nano bubble generator that generates micro-nano bubbles including both of micro bubbles and nano bubbles and makes the water introduced from the raw water tank contain the micro-nano bubbles; 
     a water returning device that sends part of the water in the micro-nano bubble generation tank back to the raw water tank; and 
     a charcoal water tank which has agitating devices and is filled with a charcoal or a synthetic charcoal to treat the water introduced from the micro-nano bubble generation tank. 
     According to the above construction, part of the water in the micro-nano bubble generation tank is sent back to the raw water tank by the water returning device. Therefore, microorganisms propagating in the polyvinylidene chloride filler loaded in the raw water tank are activated by the micro-nano bubbles. Further, water is introduced from the micro-nano bubble generation tank into the charcoal water tank. Therefore, microorganisms propagating in the charcoal or the synthetic charcoal loaded in the charcoal water tank are also activated. As a result, organic matters in the water to be treated are effectively decomposed and treated by the activated microorganisms, and clogging of the membrane in the membrane device in the subsequent stage can be prevented. 
     That is, according to the present invention, the running cost can be reduced by reducing the frequency of replacement of the membrane in the membrane device. 
     One embodiment comprises a micro-nano bubble generation aid tank in which a micro-nano bubble generation aid to be added to the micro-nano bubble generation tank is reserved. 
     According to the embodiment, the micro-nano bubble generation aid reserved in the micro-nano bubble generation aid tank is added to the micro-nano bubble generation tank. Therefore, the micro-nano bubbles can be generated effectively and efficiently in the micro-nano bubble generation tank. 
     In one embodiment, the micro-nano bubble generation aid is alcohols or salts. 
     According to the embodiment, the alcohols or salts are used as the micro-nano bubble generation aid, and therefore, the micro-nano bubble generation aid can be procured inexpensively. Furthermore, by adding the alcohols or salts to the water to be treated, the incidence rate of the micro-nano bubbles can be improved up to about 100%. Furthermore, the alcohols and salts, which are simply decomposed in the charcoal water tank and easily removed by the membrane device in the subsequent stage, therefore exert no bad influence on the membrane device. 
     One embodiment comprises an activated carbon adsorption device in a stage subsequent to the charcoal water tank of the pretreatment device. 
     According to the embodiment, the activated carbon adsorption device is provided in the stage subsequent to the charcoal water tank filled with the charcoal or the synthetic charcoal, and therefore, two-stage treatment by charcoal becomes possible in the pretreatment device. Therefore, the organic matters in the water to be treated can be reliably treated, and the clogging of the membrane of the membrane device can be prevented more reliably. In particular, the microorganisms of which the microbial activity is increased by the micro-nano bubbles are propagating in the charcoal or the synthetic charcoal and the activated carbon, and the organic matter adsorbing treatment by charcoals (charcoal, synthetic charcoal, activated carbon) and the decomposition of the adsorbed organic matters by the microorganisms are linked together to markedly increase the organic matter decomposing ability. 
     Moreover, in the water treatment apparatus of one embodiment, the membrane device placed in the stage subsequent to the charcoal water tank includes any one of the ultrafiltration membrane device, the microfiltration membrane device and the reverse osmosis membrane device. 
     According to the embodiment, the organic matters in the water to be introduced into the ultrafiltration membrane device, the microfiltration membrane device, the reverse osmosis membrane device or the like are effectively decomposed. Therefore, the clogging of the membrane in the ultrafiltration membrane device, the microfiltration membrane device, the reverse osmosis membrane device or the like can be prevented. Furthermore, the micro-nano bubbles have the characteristic that they continuously stay in the water. Therefore, the cleaning effect on the membranes of the various membrane devices is improved by the micro-nano bubbles staying in the water to be treated, and the clogging of the membranes can further be effectively prevented. 
     In one embodiment, the membrane device placed in the stage subsequent to the activated carbon adsorption device includes any one of the ultrafiltration membrane device, the microfiltration membrane device and the reverse osmosis membrane device. 
     According to the embodiment, the organic matters in the water to be introduced into the ultrafiltration membrane device, the microfiltration membrane device, the reverse osmosis membrane device or the like are reliably decomposed by the two-stage treatment by the charcoals. Therefore, the clogging of the membrane in the ultrafiltration membrane device, the microfiltration membrane device, the reverse osmosis membrane device or the like can be prevented more reliably. Furthermore, the micro-nano bubbles have the characteristic that they continuously stay in the water. Therefore, the cleaning effect on the membranes of the various membrane devices is improved by the micro-nano bubbles staying in the water to be treated, and the clogging of the membranes can further be effectively prevented. 
     One embodiment constitutes part of an ultrapure water producing device or a waste water recycling device. 
     According to the embodiment, in the water used for manufacturing ultrapure water or for recycling the waste water in the ultrapure water producing device or the waste water recycling device, the organic matters are effectively treated through decomposition by the pretreatment device and the membrane device. Therefore, an ultrapure water of a good water quality or a recycle water of a good water quality can be obtained. 
     Moreover, the water treatment method of the present invention comprises the steps of: 
     introducing and treating water that contains micro-nano bubbles including both of micro bubbles and nano bubbles into a water tank which has agitating devices and is filled with a charcoal or a synthetic charcoal; and 
     introducing the water treated by the water tank into a membrane device and carrying out treatment by means of a membrane by the membrane device. 
     According to the above constitution, microorganisms propagating in the charcoal or the synthetic charcoal are activated by the micro-nano bubbles in the water tank filled with the charcoal or the synthetic charcoal. Therefore, organic matters in the water to be treated are effectively treated through decomposition by the activated microorganisms, and clogging of the membrane in the membrane device in the subsequent stage can be prevented. 
     In one embodiment, the membrane device is any one of an ultrafiltration membrane device, a microfiltration membrane device and a reverse osmosis membrane device. 
     According to the embodiment, the organic matters in the water to be introduced into the ultrafiltration membrane device, the microfiltration membrane device, the reverse osmosis membrane device or the like are effectively decomposed. Therefore, the clogging of the membrane in the ultrafiltration membrane device, the microfiltration membrane device, the reverse osmosis membrane device or the like can be prevented. Furthermore, the micro-nano bubbles have the characteristic that they continuously stay in the water. Therefore, the cleaning effect on the membranes of the various membrane devices is improved by the micro-nano bubbles staying in the water to be treated, and the clogging of the membranes can further be effectively prevented. 
     In one embodiment, the charcoal loaded in the water tank is bincho charcoal, and 
     the water treated by the membrane device is treated by a photocatalyst tank. 
     According to the embodiment, both the microorganisms propagating in the bincho charcoal loaded in the water tank and the photocatalyst tank placed in the stage subsequent to the membrane device have the functions of treating the organic matters. Therefore, the organic matter concentration in the water to be treated can be reduced as far as possible. 
     In one embodiment, any one of waste water, recycle water and service water before undergoing various treatments is used as the water. 
     According to the embodiment, the water to be subjected to treatment is any one of the waste water, the recycle water and the service water before undergoing various treatments. Therefore, all sorts of water can be treated. 
     In one embodiment, the charcoal loaded in the water tank is bincho charcoal, and 
     the water treated by the membrane device is treated by an ultraviolet irradiation tank or an ultraviolet irradiation device. 
     According to the embodiment, both the microorganisms propagating in the bincho charcoal loaded in the water tank and the photocatalyst tank or the ultraviolet irradiation device placed in the stage subsequent to the ultraviolet irradiation tank have the functions of treating the organic matters. Therefore, the organic matter concentration in the water to be treated can be reduced as far as possible. 
     One embodiment constitutes part of an ultrapure water manufacturing method or a waste water recycling method. 
     According to the embodiment, in the water used for manufacturing ultrapure water or for recycling the waste water, the organic matters are effectively treated through decomposition by the water tank and the membrane device. Therefore, an ultrapure water of a good water quality or a recycle water of a good water quality can be obtained. 
     As is apparent from the above, the water treatment apparatus of the present invention introduces the water in the micro-nano bubble generation tank into the charcoal water tank filled with the charcoal or the synthetic charcoal and sends part of the water in the micro-nano bubble generation tank back to the raw water tank by the water returning device. Therefore, the microorganisms propagating in the charcoal or the synthetic charcoal loaded in the charcoal water tank are activated by the micro-nano bubbles. Furthermore, the microorganisms propagating in the polyvinylidene chloride filler loaded in the raw water tank are also activated. Therefore, the organic matters in the water to be treated are effectively treated through decomposition by the activated microorganisms, and the clogging of the membrane of the membrane device in the subsequent stage can be prevented. 
     That is, according to the present invention, the running cost can be reduced by reducing the frequency of replacement of the membrane in the membrane device. 
     Moreover, the water treatment method of the present invention, which activates the microorganisms propagating in the charcoal or the synthetic charcoal by the micro-nano bubbles in the water tank filled with the charcoal or the synthetic charcoal, is therefore able to effectively treat by decomposition the organic matters in the water to be treated by the activated microorganisms and to prevent the clogging of the membrane in the membrane device in the subsequent stage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing construction of a water treatment apparatus of the present invention; 
         FIG. 2  is a view showing construction of a water treatment apparatus different from that of  FIG. 1 ; 
         FIG. 3  is a view showing construction of a water treatment apparatus different from those of  FIGS. 1 and 2 ; 
         FIG. 4  is a view showing construction of a water treatment apparatus different from those of  FIGS. 1 through 3 ; 
         FIG. 5  is a view showing construction of a water treatment apparatus different from those of  FIGS. 1 through 4 ; 
         FIG. 6  is a view showing construction of a water treatment apparatus different from those of  FIGS. 1 through 5 ; 
         FIG. 7  is a view showing construction of a water treatment apparatus different from those of  FIGS. 1 through 6 ; 
         FIG. 8  is a view showing construction of a water treatment apparatus different from those of  FIGS. 1 through 7 . 
     
    
    
     REFERENCE NUMERALS 
     
         
           1 : raw water tank 
           2 ,  17 ,  37 : pump 
           3 : polyvinylidene chloride filler 
           4 ,  5 ,  9 : valve 
           6 : micro-nano bubble generation tank 
           7 : micro-nano bubble generator 
           8 : circulating pump 
           10 : air suction pipe 
           11 : charcoal water tank 
           12 : air diffusing pipe 
           13 : blower 
           15 : charcoal 
           16 ,  36 : pit 
           19 : micro-nano bubble generation aid tank 
           20 : proportioning pump 
           21 : membrane device 
           22 : wire net 
           25 : ultrafiltration membrane device 
           26 : photocatalyst tank 
           27 : ultrapure water producing device 
           29 : microfiltration membrane device 
           31 : reverse osmosis membrane device 
           33 : cooling tower 
           35 : activated carbon adsorption device 
           40 : ultraviolet irradiation tank 
       
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in detail by embodiments shown in the drawings. 
     First Embodiment 
       FIG. 1  shows the schematic construction of a water treatment apparatus of the present embodiment. In  FIG. 1 , a reference numeral  1  denotes a raw water tank of a liquid, and a pump  2  that pumps up the liquid is provided. It is herein noted that the liquid in the present embodiment is defined widely as “water”  23 . It is noted that the “water”  23 , of course, includes “service water” and “waste water”. 
     The raw water tank  1  is internally filled with a polyvinylidene chloride filler  3 . Then, the water  23  introduced into the raw water tank  1  is discharged by the pump  2  with its discharge rate adjusted by a valve  4  and is introduced into a micro-nano bubble generation tank  6 . 
     A micro-nano bubble generator  7  is placed in the micro-nano bubble generation tank  6 , and micro-nano bubbles are generated by the micro-nano bubble generator  7 , generating micro-nano bubble streams  18  in the micro-nano bubble generation tank  6 . 
     A circulating pump  8  is placed outside the micro-nano bubble generation tank  6 , and the water in the micro-nano bubble generation tank  6  is forcefully fed to the micro-nano bubble generator  7 . As a result, the micro-nano bubble generator  7  generates micro-nano bubbles while taking in air supplied from an air suction pipe  10  connected to the micro-nano bubble generator  7 . It is noted that a valve  9  is interposedly provided for the air suction pipe  10 , and the air quantity is adjusted so that optimum micro-nano bubbles are easily generated. 
     Moreover, a micro-nano bubble generation aid from a micro-nano bubble generation aid tank  19  is quantitatively added to the micro-nano bubble generation tank  6  by a proportioning pump  20 . In this case, a very small amount of alcohols or salts of common salt or the like are added in concrete as the micro-nano bubble generation aid in consideration of the influence of a membrane device  21  in the subsequent stage. Then, part of the water in the micro-nano bubble generation tank  6  is sent back to the raw water tank  1  by opening a valve  5 . 
     Microorganisms propagate in the polyvinylidene chloride filler  3  loaded in the raw water tank  1  with a lapse of time. In the case, a greater number of active microorganisms propagate in the polyvinylidene chloride filler  3  by sending back the water that contains micro-nano bubbles from the micro-nano bubble generation tank  6 , and pretreatment of the water is to be carried out by the greater number of active microorganisms. 
     The water  23  that contains the micro-nano bubbles generated in the micro-nano bubble generation tank  6  as described above is subsequently introduced into a charcoal water tank  11 . The charcoal water tank  11  has a wire net  22  therein and the wire net  22  is filled with numbers of charcoal pieces  15 . Then, an air diffusing pipe  12  is placed in a lower position inside the charcoal water tank  11  so that the water  23  that contains the micro-nano bubbles and the charcoal pieces  15  are efficiently brought in contact with each other by streams of water. By discharging air from a blower  13  through the air diffusing pipe  12 , the inside of the tank is aerated. Thus, streams of water  14  are generated by the aeration of the inside of the charcoal water tank  11 , so that the water  23  containing the micro-nano bubbles and the charcoal pieces  15  can efficiently be brought in contact with each other. 
     The charcoal  15  have various kinds, and bincho charcoal that has an appropriate hardness and a specific gravity larger than “1” without being damaged by aeration are used. A state in which the charcoal  15  is sunk inside the wire net  22  can be maintained when the charcoal  15  have a specific gravity of not smaller than one, and this is therefore convenient. Since the charcoal  15  as a natural material has pores, the microorganisms propagate in the pores. Further, the microorganisms also propagate on the surface of the charcoal  15 . Then, the organic matters in the water  23  that contains the micro-nano bubbles are treated through decomposition by the microorganisms. In the case, due to the existence of the micro-nano bubbles in the water  23 , the activities of the microorganisms propagating on the surface and in the pores of the charcoal  15  increase, and the ability to treat the organic matters in the water  23  through decomposition is markedly increased. 
     Moreover, the charcoal  15  also has an ability to adsorb the organic matters. Then, the charcoals  15  repeat the adsorption and decomposition of the organic matters since the adsorbed organic matters are treated through decomposition by the microorganisms propagating in the pores, and the adsorbing ability of the charcoal  15  becomes apparently not deteriorated. Thereafter, the water (water to be treated)  23  of which the organic matters have been treated through decomposition is introduced into a pit  16 . The water  23  to be treated in the pit  16  is subsequently introduced into the membrane device  21  by a pump  17 . 
     There is (1) a microfiltration membrane device, (2) an ultrafiltration membrane device or (3) a reverse osmosis membrane device as a concrete example of the membrane device  21 . It is proper to select a device among the devices (1) through (3) according to the purpose and adopt the same as the membrane device  21 . 
     As described above, in the present embodiment, the water  23  that contains the micro-nano bubbles generated in the micro-nano bubble generation tank  6  is treated by being introduced into the charcoal water tank  11  which is internally filled with the charcoal pieces  15  and in which the agitating device constituted of the blower  13  and the air diffusing pipe  12  is placed and thereafter treated by being introduced into the membrane device  21 . Therefore, the micro-nano bubbles increase the activities of the microorganisms propagating in the charcoal  15 , so that the ability to treat the organic matters in the water through decomposition can be markedly increased. As a result, the clogging phenomenon due to the organic matters in the membrane device  21  of the microfiltration membrane device, the ultrafiltration membrane device or the reverse osmosis membrane device can be prevented. 
     Moreover, a very small amount of alcohols and salts are added as the micro-nano bubble generation aid to the micro-nano bubble generation tank  6 . Therefore, the incidence rate of the micro-nano bubbles with respect to the quantity of air supplied from the air suction pipe  10  can be improved up to about 100%. Furthermore, since the alcohols and salts are simply decomposed in the charcoal water tank  11  and easily removed by the membrane device  21  in the subsequent stage, no bad influence is exerted on the membrane device  21 . 
     Second Embodiment 
       FIG. 2  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to industrial water  24  in the present embodiment. Moreover, an ultrafiltration membrane device  25  is specifically employed as the membrane device  21  of the first embodiment. Furthermore, a photocatalyst tank  26  and an ultrapure water producing device  27  are arranged in this order following the ultrafiltration membrane device  25 . 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the industrial water  24 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of the industrial water  24 . Furthermore, the ultrafiltration membrane device  25  is specifically employed as the membrane device  21  of the first embodiment, and the photocatalyst tank  26  and the ultrapure water producing device  27  are arranged in this order following the ultrafiltration membrane device  25 . Therefore, the water  24  to be treated from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced in order of the ultrafiltration membrane device  25 →the photocatalyst tank  26 →the ultrapure water producing device  27 . 
     That is, according to the present embodiment, the water quality is improved by carrying out the pretreatment of the industrial water  24  by using the micro-nano bubble technique, and the water  24  to be treated is introduced sequentially into the ultrafiltration membrane device  25 , the photocatalyst tank  26  and the ultrapure water producing device  27 . 
     With the above arrangement, by virtue of the feature that the micro-nano bubbles are maintained for a long time in the water  24  to be treated and the feature that the detergency for the membrane is maintained, the water  24  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the ultrafiltration membrane device  25  and the ultrapure water producing device  27  but also improve the throughput capacities of the ultrafiltration membrane device  25  and the ultrapure water producing device  27 . 
     Third Embodiment 
       FIG. 3  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to waste water  28  in the present embodiment. Moreover, a microfiltration membrane device  29  is specifically employed as the membrane device  21  of the first embodiment. Furthermore, the photocatalyst tank  26  and the ultrapure water producing device  27  are arranged in this order following the microfiltration membrane device  29 . 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the waste water  28 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of a recycling device of the waste water  28 . Furthermore, the microfiltration membrane device  29  is specifically employed as the membrane device  21  of the first embodiment, and the photocatalyst tank  26  and the ultrapure water producing device  27  are arranged in this order following the microfiltration membrane device  29 . Therefore, the water  28  to be treated from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced in order of the microfiltration membrane device  29 →the photocatalyst tank  26 →the ultrapure water producing device  27 . 
     That is, according to the present embodiment, the water quality is improved by carrying out the pretreatment of the recycling device of the waste water  28  by using the micro-nano bubble technique, and the water  28  to be treated is introduced sequentially into the microfiltration membrane device  29 , the photocatalyst tank  26  and the ultrapure water producing device  27 . 
     With the above arrangement, by virtue of the feature that the micro-nano bubbles are maintained for a long time in the water  28  to be treated and the feature that the detergency for the membrane is maintained, the water  28  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the microfiltration membrane device  29  and the ultrapure water producing device  27  but also improve the throughput capacities of the microfiltration membrane device  29  and the ultrapure water producing device  27 . 
     Fourth Embodiment 
       FIG. 4  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to low-concentration organic waste water  30  in the present embodiment. Moreover, a reverse osmosis membrane device  31  is specifically employed as the membrane device  21  of the first embodiment. Furthermore, the ultrapure water producing device  27  is arranged following the reverse osmosis membrane device  31 . 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the low-concentration organic waste water  30 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of a recycling device of the low-concentration organic waste water  30 . Furthermore, the reverse osmosis membrane device  31  is specifically employed as the membrane device  21  of the first embodiment, and the ultrapure water producing device  27  is arranged following the reverse osmosis membrane device  31 . Therefore, the water  30  to be treated from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced in order of the reverse osmosis membrane device  31 →the ultrapure water producing device  27 . 
     That is, according to the present embodiment, the water quality is improved by carrying out the pretreatment of the recycling device of the low-concentration organic waste water  30  by using the micro-nano bubble technique, and the water  30  to be treated is introduced sequentially into the reverse osmosis membrane device  31  and the ultrapure water producing device  27 . 
     With the above arrangement, by virtue of the feature that the micro-nano bubbles are maintained for a long time in the water  30  to be treated and the feature that the detergency for the membrane is maintained, the water  30  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the reverse osmosis membrane device  31  and the ultrapure water producing device  27  but also improve the throughput capacities of the reverse osmosis membrane device  31  and the ultrapure water producing device  27 . 
     Fifth Embodiment 
       FIG. 5  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to neutral waste water  32  in the present embodiment. Moreover, the water  32  to be treated after being treated by the membrane device  21  of the first embodiment is recycled as a makeup water of a cooling tower  33 . 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the neutral waste water  32 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of a recycling device of the neutral waste water  32 . Furthermore, the cooling tower  33  is arranged following the membrane device  21  of the first embodiment. Therefore, the water  32  to be treated from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced from the membrane device  21  to the cooling tower  33 . 
     That is, according to the present embodiment, the water quality is improved by carrying out the pretreatment of the recycling device of the neutral waste water  32  by using the micro-nano bubble technique, and the water  32  to be treated is introduced sequentially into the membrane device  21  and the cooling tower  33 . 
     With the above arrangement, by virtue of the feature that the micro-nano bubbles are maintained for a long time in the water  32  to be treated and the feature that the detergency for the membrane is maintained, the water  32  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the membrane device  21  but also improve the throughput capacity of the membrane device  21 . Furthermore, the micro-nano bubbles are maintained for a long time in the water  32  to be treated that has undergone the pretreatment by the micro-nano bubbles. Therefore, the water to be treated  32  in the cooling tower  33  is maintained in a state in which the water quality is stable. 
     Sixth Embodiment 
       FIG. 6  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to a tap water  34  in the present embodiment. Moreover, an activated carbon absorption device  35  is arranged in a stage subsequent to the pit  16  of the first embodiment, and the water  34  to be treated that has undergone activated carbon absorption treatment in the activated carbon absorption device  35  is once introduced into the pit  36 . Then, the water  34  to be treated in the pit  36  is introduced into the membrane device  21  by a pump  37 . 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the tap water  34 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of the tap water  34 . Furthermore, the activated carbon absorption device  35  and the pit  36  are arranged in between the pit  16  and the membrane device  21  of the first embodiment. Therefore, the water  34  to be treated from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced in order of the activated carbon absorption device  35 →the membrane device  21 . 
     The tap water  34  is a water of a comparatively good water quality. However, when the water quality is severely demanded, the grade of the water quality of the water  34  to be treated can be improved by arranging the activated carbon absorption device  35  in a stage subsequent to the charcoal water tank  11  as described above. 
     That is, according to the present embodiment, the water quality is further improved by carrying out the pretreatment of the tap water  34  by using the micro-nano bubble technique, the charcoal and the activated carbon. 
     With the above arrangement, the micro-nano bubbles are maintained for a long time in the water  34  to be treated that has undergone the pretreatment by the micro-nano bubbles, and therefore, the microorganisms propagating particularly in the activated carbon inside the activated carbon absorption device  35  are further activated. Therefore, the organic matters adsorbed by the activated carbon in the activated carbon absorption device  35  are decomposed by the activated microorganisms, and the activated carbon enters a state as if it were regenerated. Therefore, the activated carbon in the activated carbon absorption device  35  can be regarded as a biological activated carbon that does not need the so-called regeneration. 
     Moreover, by virtue of the detergency maintained by the micro-nano bubbles for the membrane, the water  34  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the membrane device  21  but also improve the throughput capacity of the membrane device  21 . 
     Seventh Embodiment 
       FIG. 7  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to waste water  38  in the present embodiment. Moreover, the activated carbon absorption device  35  is placed as in the case of the sixth embodiment, and the water  34  to be treated that has undergone the activated carbon absorption treatment in the activated carbon absorption device  35  is introduced into the membrane device  21  by the pump  37 . 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the waste water  38 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of the waste water  38 . Furthermore, the activated carbon absorption device  35  and the pit  36  are arranged in between the pit  16  and the membrane device  21  as in the case of the sixth embodiment. Therefore, the waste water  38  from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced in order of the activated carbon absorption device  35 →the membrane device  21 . 
     The water quality of the waste water  38  is not better than that of the tap water  34 . Therefore, it is necessary to ensure the pretreatment for the waste water  38 . Accordingly, as described above, the activated carbon absorption device  35  is arranged in a stage subsequent to the charcoal water tank  11 , so that the pretreatment is more reliably carried out by the charcoal  15  and the activated carbon. 
     That is, according to the present embodiment, the water quality is further improved by carrying out the pretreatment of the waste water  38  by using the micro-nano bubble technique, the charcoal and the activated carbon. 
     With the above arrangement, the micro-nano bubbles are maintained for a long time in the water  38  to be treated that has undergone the pretreatment by the micro-nano bubbles, and therefore, the microorganisms propagating particularly in the activated carbon inside the activated carbon absorption device  35  are further activated. Therefore, the organic matters adsorbed by the activated carbon in the activated carbon absorption device  35  are decomposed by the activated microorganisms, and the activated carbon enters a state as if it were regenerated. Therefore, the activated carbon in the activated carbon absorption device  35  can be regarded as a biological activated carbon that does not need the so-called regeneration. 
     Moreover, by virtue of the detergency maintained by the micro-nano bubbles for the membrane, the water  38  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the membrane device  21  but also improve the throughput capacity of the membrane device  21 . 
     Eighth Embodiment 
       FIG. 8  shows the schematic construction of a water treatment apparatus of the present embodiment. 
     In contrast to the fact that the liquid supplied to the raw water tank  1  has been defined widely as the water  23  in the first embodiment, the liquid is limited to industrial water  39  in the present embodiment. Moreover, an ultraviolet irradiation tank  40  and the ultrapure water producing device  27  are arranged in this order following the membrane device  21  of the first embodiment. 
     The components other than the above are the same as in the first embodiment and denoted by the same reference numerals as in the first embodiment with no detailed description provided therefor. 
     As described above, in the present embodiment, the liquid supplied to the raw water tank  1  is limited to the industrial water  39 . Therefore, the present embodiment is a water treatment apparatus for the pretreatment of the industrial water  39 . Further, the ultraviolet irradiation tank  40  and the ultrapure water producing device  27  are arranged in this order following the membrane device  21  of the first embodiment. Therefore, the water  39  to be treated from the charcoal water tank  11  where the organic matters have been treated through decomposition is introduced in order of the membrane device  21 →the ultraviolet irradiation tank  40 →the ultrapure water producing device  27 . 
     That is, according to the present embodiment, the water quality is improved by carrying out the pretreatment of the industrial water  39  by using the micro-nano bubble technique, and the water  39  to be treated is introduced sequentially into the membrane device  21 , the ultraviolet irradiation tank  40  and the ultrapure water producing device  27 . 
     With the above arrangement, by virtue of the feature that the micro-nano bubbles are maintained for a long time in the water  39  to be treated and the feature that the detergency for the membrane is maintained, the water  39  to be treated that has undergone the pretreatment by the micro-nano bubbles is able to not only prevent the clogging phenomenon of the membrane in the membrane device  21  and the ultrapure water producing device  27  but also improve the throughput capacities of the membrane device  21  and the ultrapure water producing device  27 . 
     Experimental Example 
     An experimental example of the first embodiment is described below. That is, an experimental apparatus was produced on the basis of  FIG. 1 . The capacity of the raw water tank  1  of the present experimental device is 300 liters, the capacity of the micro-nano bubble generation tank  6  is 50 liters, and the capacity of the charcoal water tank  11  is 500 liters. Industrial water was introduced as the water  23  into the raw water tank  1 , and an ultrafiltration membrane was used as the membrane of the membrane device  21 . Further, a micro-nano bubble generation aid obtained by dissolving common salt was introduced into the micro-nano bubble generation aid tank  19  and added to the micro-nano bubble generation tank  6 . 
     The experimental apparatus was operated for about two days, and thereafter, the throughput capacity of the ultrafiltration membrane in the membrane device  21  was measured. As a result, the penetration rate was improved by 20% in comparison with the capacity of the conventional ultrafiltration membrane. 
     In each of the above embodiments, bincho charcoal is loaded as the charcoal  15  in the charcoal water tank  11 . However, since bincho charcoal is recently insufficient, it is acceptable to load a synthetic charcoal that produces the same effect.