Abstract:
An apparatus for recycling rinsing wastewater for electropainting is provided. The apparatus includes a pre-filtration unit, a primary treated-water tank, a micro filtration unit, a secondary treated-water tank, an ultrafiltration unit, an active carbon filtration unit, a final treated-water tank, and an ultrasonic sterilizing unit. Accordingly, sludge is reduced through physical treatment without using a coagulant. Advantageously, the apparatus is installed at facilities having a reduced scale and provides additional facility options available due to elimination of a chlorine disinfectant. Furthermore the apparatus reduces costs for purchasing a coagulant, purchasing a disinfectant, and treating sludge, suppresses corrosion of a filtering device, and increases filtration time by delaying fouling of a filtering device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2014-181948, filed on Dec. 17, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention provides an apparatus for recycling rinsing wastewater for electropainting, and more particularly, for electropainting which reduces sludge through physical treatment without using a coagulant. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a high-quality water source is difficult to secure due to contamination of rivers and eutrophication by reservoirs and dams and the cost for purifying water is increasing due to an increase in personnel expenses and raw material prices, therefore the cost of water has substantially increased. As a dry season and a rainy season are clearly distinguished due to unusual temperature and a deficit of water is expected in the dry season, it is necessary to secure new water sources. However, securing a new water source is challenging due to economic, social, and environmental constraints. Under these circumstances, purifying and recycling of wastewater produced manufacturing processes may be a plan capable of reducing the costs for purchasing water and treating wastewater and may function as a new water source. 
         [0006]    Electroplating used in the process of manufacturing vehicles specifically including a rinsing step in the painting pre-treatment process is water intensive. The electropainting process improves the anti-corrosive property and corrosion resistance of a vehicle body. During the process a paint coating is forcibly applied to a body of a vehicle using an electrical phenomenon by charging the vehicle body with a negative polarity and the paint with a positive polarity. The non-adhering paint on a vehicle body painted by electropainting is removed through ultrafiltration rinsing, including a three-stage rinsing process and final rinsing process utilizing pure water, thereby ensuring painting quality. The rinsing wastewater produced during the ultrafiltration rinsing is filtered and returned to an electropainting bath where the electropaint is filtered and separated through an ultrafiltration filter and then condensed. Finally, the filtered treated-water is reused as the rinsing water. 
         [0007]    Next, the rinsing water produced by the three-stage rinsing and final rinsing is discharged and transported for treatment at a sewage water treatment plant. Typically, the rinsing waste water contains pure water and electropaint, thereby making the rinsing water suitable for recycling through an appropriate purifying process. For example, a technique for recycling electropainting wastewater includes recycling electropainting wastewater producing high-quality recycled water however, the process is complicated and difficult to manage. Additionally, there is a need for a substantial facility due to a large wastewater collection tank and a sludge deposition tank, and significant operational expenses including purchasing chemicals, treating sludge, and the cost of electricity for operating a blower for aeration. 
         [0008]    An alternate method for treating rinsing wastewater includes a water tank-condensing tank, a film separation apparatus, an acid injection apparatus, and a pH measuring apparatus are included. The rinsing wastewater collected in the water tank-condensing tank is treated by the film separation apparatus, and the filtered treated-water is supplied to other processes. The condensed water then flows to the water tank-condensing tank. Further, acid is automatically injected by the pH measuring apparatus and the acid injection apparatus, therefore the pH of the treated-water is maintained within a predetermined range. 
         [0009]    Beneficially, the above mentioned technique provides simplified maintenance and requires a relatively small facility, but condensed water is continuously returned back to the water tank-condensing tank from the film separation apparatus, therefore a substantially sized tank is required. Further, the concentration of the electropaint in the rinsing wastewater to be treated increases and there is not pre-treatment apparatus before the rinsing wastewater flows into the film separation apparatus. Consequently, fouling is generated on the separation film and the duration of the filtration limited. 
         [0010]    Another method for treating rinsing wastewater includes a purifying apparatus for securing drinkable water using a self-power source that utilizes a power generator when the power supply is limited for instance, in circumstances related to natural disasters. The purifying apparatus is divided into a power supply portion and a purifying portion, in which the purifying portion includes a water supply pump, a pre-filter, a switch valve, a micro membrane filter, a reverse osmosis filter, an active carbon filter, a chlorine tank, and a chlorine agent injection pump. 
         [0011]    Raw water supplied by the water supply pump is pre-treated by the pre-filter, and then transported to the micro membrane filter or the reverse osmosis filter by the switch valve, and then filtered. The treated-water filtered by the micro membrane filter is treated by the active carbon filter to remove impurities including odor impurities. The treated-water that has been subjected to the micro membrane filter and the active carbon filter or the reverse osmosis filter is disinfected with chlorine which then produces drinkable water. However, the technique has been designed to produce drinkable water for emergencies. For example, the process treats raw water having limited amounts of contamination. However, the process is not effective in treating electropainting wastewater contaminated that may contain substantial quantities of recycle treated-water from painting. 
         [0012]    In particular, the processes utilizes the pre-filter, micro membrane filter, active carbon filter, and disinfecting with chlorine. Typically, removal of the contaminants contained in electropainting wastewater with the micro membrane filter involves a substantial level of difficulty. Consequently, a substantial amount of contaminants are removed by the active carbon filter, resulting in frequent replacement of the active carbon filter. For example, active carbon filters are typically installed in two lines and the two lines are alternately operated. Alternate operation of a plurality of filters results in an increased expense attributed to purchasing new active carbon and treat wasted active carbon. Further, when treated-water is discharged containing contaminants resulting from inappropriate maintenance of the active carbon filter, excessive quantities of chlorine are used in the chlorine disinfection process, THMs Tri-halomethanes (THMs), a carcinogenic substance is produced as a byproduct in the disinfection, and the remaining chlorine may cause corrosion of facilities and products. 
         [0013]    In the processes by the pre-filter, reverse osmosis filter, and disinfecting with chlorine, the reverse osmosis filter operating at a high pressure requires frequent backwash since fouling may be generated by electropaint. However, backwashing may be difficult due to the adhesion of the electropainting and the high-pressure operation, such that the productivity of treated-water may be reduced. Therefore, the inventor(s) has attempted to develop an apparatus for recycling rinsing wastewater for electropainting which can solve the problems requiring a substantial facility, economical efficiency, maintenance, wastewater treatment, and quality. 
         [0014]    The above information disclosed in this Background section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0015]    The exemplary embodiment provides an apparatus for recycling rinsing wastewater produced during electropainting which may reduce sludge through physical treatment without requiring a coagulant by including a pre-filtration unit, a micro filtration unit, an ultrafiltration unit, an active carbon filtration unit, and an ultrasonic sterilizing unit. 
         [0016]    An exemplary embodiment provides an apparatus for recycling rinsing wastewater for electropainting which may include a pre-filtration unit that may include having a pre-filter configured to filter and remove floats and electropaint flux in rinsing wastewater transported through an inlet; a primary treated-water tank that may be connected with the pre-filter unit and may maintain primary treated-water filtered by the pre-filter unit. A micro filtration unit may be connected with the primary treatment tank and may include a micro filtration separator configured to filter and remove electropaint particles in the primary treated-water. A secondary treated-water tank may be connected with the micro filtration unit and may maintain secondary treated-water filtered by the micro filtration unit. Further, an ultrafiltration unit may be connected with the secondary treated-water tank and may include an ultrafiltration separator configured to filter and remove the remaining contaminants in the secondary treated-water and an active carbon filtration unit may be connected with the ultrafiltration unit and may have an active carbon for adsorbing and removing ions, a odor, and a minimal amount of remaining contaminants in the secondary treated-water filtered by the ultrafiltration unit. A final treatment tank may be connected to the active carbon filtration unit and may filter final treated-water via the active carbon filtration unit and an ultrasonic sterilizing unit may be attached to the final treatment tank to remove microorganisms disposed in the final treated-water. 
         [0017]    In another aspect, a portion of the secondary treated-water disposed in the secondary treated-water tank may be used as backwashing water for backwashing the micro filtration unit. For example, the backwashing water may be transported to the backwashing water inlet of the micro filtration unit and discharged through the backwashing water outlet by the backwashing water supply pump. The backwashing water may remove electropaint on the micro filtration separator of the micro filtration unit. 
         [0018]    In some exemplary embodiments, the final treated-water in the final treated-water tank may be used as backwashing water for backwashing the ultrafiltration unit. The backwashing water may be transported to the backwashing water inlet of the ultrafiltration unit and discharged through the backwashing outlet by the backwashing water supply pump. Additionally, the backwashing water may remove remaining contaminants on the ultrafiltration separator of the ultrafiltration unit. In another embodiment, the final treated-water in the final treated-water tank may be used as backwashing water for backwashing the active carbon filtration unit. The backwashing water may be transported to the backwashing water inlet of the active carbon filtration unit and discharged through the backwashing outlet by the backwashing water supply pump. Additionally, the backwashing water may remove ions, an odor, and a minimal amount of contaminants adsorbed on the active carbons in the active carbon filtration unit. 
         [0019]    The ultrasonic sterilizing unit may include an ultrasonic wave generator may be configured to generate ultrasonic waves; and an ultrasonic oscillator that may be vibrated by the ultrasonic waves generated by the ultrasonic generator. In other exemplary embodiments, the backwashing water that may be discharged through the backwashing water outlet of the micro filtration unit may be kept in a condensed water tank. The backwashing water discharged through the backwashing water outlet of the ultrafiltration unit may be maintained in the secondary treated-water tank. The backwashing water discharged through the backwashing water outlet of the active carbon filtration unit may be maintained in the secondary treated-water tank. 
         [0020]    The apparatus according exemplary embodiments may reduce sludge through physical treatment without utilizing a coagulant. Additionally, the apparatus may be installed at facilities having a limited scale, and may reduce expenses associated with purchasing a coagulant, purchasing a disinfectant, and treating sludge. The apparatus may be maintained by automatic operation, may be readily available for various facilities due to elimination of the use of a chlorine disinfectant, may suppress corrosion of a filtering device, and may increase filtration time by delaying fouling of a filtering device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is an exemplary embodiment of a diagram illustrating the configuration of an apparatus for recycling rinsing wastewater for electropainting according to an exemplary embodiment of the present invention; and 
           [0022]      FIG. 2  is an exemplary embodiment of an enlarge view schematically illustrating an ultrasonic sterilizer according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
         [0024]    The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the terms to describe most appropriately the best method he or she knows for carrying out the invention. 
         [0025]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. For example, In order to make the description of the present invention clear, unrelated parts are not shown and, the thicknesses of layers and regions are exaggerated for clarity. Further, when it is stated that a layer is “on” another layer or substrate, the layer may be directly on another layer or substrate or a third layer may be disposed therebetween. 
         [0026]    Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.” 
         [0027]    It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
         [0028]    Hereinafter, an exemplary embodiment will be described in detail. The present invention provides an apparatus for recycling rinsing wastewater for electropainting which may recycle rinsing wastewater produced in electropainting, through physical treatment without utilizing a coagulant. An apparatus for recycling rinsing wastewater for electropainting according to an exemplary embodiment of the present invention may include as illustrated in  FIG. 1 , a pre-filtration unit  100  having a pre-filter  135  configured to filter and remove floats and electropaint flux in rinsing wastewater transported through an inlet  110 ; a primary treated-water tank  200  may be connected with the pre-filter unit  100  and may store primary treated-water filtered by the pre-filter unit  100 . 
         [0029]    Further a micro filtration unit  300  may be connected with the primary treatment tank  200  and may include a micro filtration separator  335  for that may filter and remove electropaint particles disposed in the primary treated-water. A secondary treated-water tank  400  may be connected with the micro filtration unit  300  and may store secondary treated-water filtered by the micro filtration unit  300 . An ultrafiltration unit  500  may be connected with the secondary treated-water tank  400  and may include an ultrafiltration separator  535  that may filter and remove the remaining contaminants in the secondary treated-water. An active carbon filtration unit  600  may be connected with the ultrafiltration unit  500  and may have an active carbon  635  that may adsorb and remove ions, an odor, and a minimal amount of remaining contaminants in the secondary treated-water filtered by the ultrafiltration unit  500 . A final treatment tank  700  may connect the active carbon filtration unit  600  and may store the final treated-water  710  filtered by the active carbon filtration unit  600  and an ultrasonic sterilizing unit  800  may be attached to the final treatment tank  700  to remove microorganisms disposed in the final treated-water  710 . 
         [0030]    In particular, the pre-filtration unit  100  may include the pre-filter  135  and a pre-filter case  130  that may fix the pre-filter  135  and may provide a treatment space for wastewater, and the pre-filter case  130  may have the inlet  110  through which electropainting wastewater may flow to the interior, a fixing rail  133  that may fix the pre-filter, and an outlet  120  through which the primary treated-water may be discharged. The micro filtration unit  300  may include the micro filtration separator  335 , a micro filtration unit case  330  that may fix the micro filtration separator  335  and may provide a treatment space for wastewater, a manometer  340 , and a backwashing water supply pump  350 . The micro filtration unit case  330  may have an inlet  310  through which the primary treated-water may flow within, an outlet  320  through which the secondary treated-water may be discharged, a backwashing water inlet  351 , and backwashing water outlet  353 . 
         [0031]    The ultrafiltration unit  500  may include the ultrafiltration separator  535 , an ultrafiltration unit case  530  that may fix the ultrafiltration separator  535  and may provide a treatment space for wastewater, a manometer  540 , and a backwashing water supply pump  550 . The ultrafiltration unit case  530  may have an inlet  510  through which the secondary treated-water may flow within, a third treated-water outlet  520 , a backwashing water inlet  551 , and backwashing water outlet  553 . The active carbon filtration unit  600  may include an active carbon filtration unit case  630  forming an active carbon filtration layer and may provide a treatment space for wastewater, active carbons  635 , a flowmeter  640 , and a backwashing water supply pump  650 . The active carbon filtration unit case  630  may have an inlet  610  through which third treated-water may flow within, an outlet  620  through which final treated-water may be discharged, an active carbon support  637 , a backwashing water inlet  651 , and a backwashing water outlet  653 . 
         [0032]    Moreover, some of the secondary treated-water disposed the secondary treated-water tank  400  may be used as backwashing water for backwashing the micro filtration unit  300 . The backwashing water may be transported to the backwashing water inlet  351  of the micro filtration unit  300  and may be discharged through the backwashing water outlet  353  by the backwashing water supply pump  350  connected with the secondary treated-water tank  400 . The backwashing water may flow in the opposite direction for filtration and may flow to the exterior from the interior of the micro filtration separator  335  thereby removing the electropaint particles condensed on the micro filtration separator  335 . In other words, since the micro filtration unit  300  may be configured to filter electropainting particles from the treated-water flowing to the interior from the exterior of the micro filtration separator  335 , as the filtration time elapses, the electropainting particles may be condensed on the exterior side of the micro filtration separator  335 , thereby reducing the transmission efficiency. For example, backwashing to remove the electropainting particles condensed on the micro filtration separator  335  may improve the method. 
         [0033]    In particular, the backwashing water including the electropainting particles removed by backwashing may be transported to the condensing tank  360  through the backwashing outlet  353  of the micro filtration unit  300 . When required, the backwashing water may be returned to the micro filtration unit  300  and reused or may be transported to a sewage water treatment plant for further treatment. The backwashing for the micro filtration separator  335  may be performed with aeration and may be performed after completion of the filtration by the micro filtration unit  300  and filtration by the micro filtration unit  300  may be performed after the backwashing is completed. 
         [0034]    Similarly, a portion of the final treated-water  710  disposed in the final treated-water tank  700  may be used as backwashing water for backwashing the ultrafiltration unit  600  and the backwashing water may be transported to the backwashing water inlet  551  of the ultrafiltration unit  500  and may be discharged through the backwashing outlet  553  by the backwashing water supply pump  550 . The backwashing water may flow in the opposite direction to that of the filtration which flows from the exterior to the interior of the ultrafiltration separator  535 . Additionally, the remaining contaminants condensed and accumulated on the ultrafiltration separator  535  may be removed. 
         [0035]    Furthermore, the ultrafiltration separator  535  of the ultrafiltration unit  500  may be configured to filter remaining contaminants such as low-molecular resin, non-reacting substances, and organic substances from the treated-water flowing to the interior from the exterior of the ultrafiltration separator  530 . As the filtration time elapses, the remaining contaminants may form a contaminant cake layer by being condensed and accumulated on the exterior side of the micro filtration separator  535 . For example, the transmission efficiency of the ultrafiltration separator  535  may be reduced. Backwashing for removing the cake layer of contaminants condensed and accumulated on the ultrafiltration separator  535  may be required. The backwashing water including contaminants removed by the backwashing may be transported to the secondary treated-water tank  400  through the backwashing water outlet  553  of the ultrafiltration unit  500  and reused. Additionally, the backwashing water may be transported to a sewage water treatment plant and further treated. The backwashing for the ultrafiltration separator  535  may be performed with aeration and may be performed after filtration by the ultrafiltration unit  500  is completed, and filtration by the ultrafiltration unit  500  may be performed after the backwashing is completed. 
         [0036]    Further, a portion of the final treated-water  710  disposed in the final treated-water tank  700  may be used as backwashing water for backwashing the active carbon filtration unit  600 . The backwashing water may be transported to the backwashing water inlet  651  of the active carbon filtration unit  600  and may be discharged through the backwashing outlet  653  by the backwashing water supply pump  650 . The backwashing water flowing upward opposite to that for filtration may remove ions, an odor, and a minimal amount of remaining contaminants adsorbed on the active carbons  635 . The active carbons  635  in the active carbon filtration unit  600  may adsorb ions, an odor, and a minimal amount of remaining contaminants from the treated-water, the adsorption efficiency of the surfaces of the active carbons  635  decreases as the filtration time elapses. Additionally, backwashing for removing the ions, odor, and remaining contaminants on the active carbons  635  may be required. 
         [0037]    The backwashing water including the ions, the odor, and the minimal amount of remaining contaminants removed by the backwashing may be transported to the secondary treated-water tank  400  through the backwashing water outlet  653  of the active carbon filtration unit  600  and reused. Additionally, when necessary, the backwashing water may be transported to a sewage water treatment plant and further treated. The backwashing for the active carbon filtration unit  600  may be performed with aeration and may performed after filtration by active carbon filtration unit  600  is completed, and filtration by the active carbon filtration unit  600  may be performed after the backwashing is completed. Furthermore, when the quality of the final treated-water is not improved even after the active carbon filtration unit is backwashed, the active carbons  635  may be replaced. 
         [0038]    Alternatively, as illustrated in  FIG. 2 , the ultrasonic sterilizing unit  800  may include an ultrasonic wave generator  810  that may be configured to generate ultrasonic waves; and an ultrasonic oscillator  830  that may be configured to generate a vibration using the ultrasonic waves generated by the ultrasonic generator  810 . The ultrasonic oscillator  830  of the ultrasonic sterilizing unit  800  may be installed exterior to the final treated-water tank  700 , enabling prevention of deterioration of the sterilizing efficiency due to contamination on the ultrasonic oscillator  830 . Further, the ultrasonic oscillator  830  may be three-dimensionally installed on various sides, in addition to a side of the final treated-water tank, thereby eliminating a dead zone and maximizing the sterilizing effect of the final treated-water  710 . 
         [0039]    The backwashing water discharged through the backwashing water outlet  353  of the micro filtration unit  300  may be maintained in the condensed water tank  360 , the backwashing water discharged through the backwashing water outlet  553  of the ultrafiltration unit  500  may be maintained in the secondary treated-water tank  400 . The backwashing water discharged through the backwashing water outlet of the active carbon filtration unit  600  may be maintained in the secondary treated-water tank  400 . Further, the primary treated-water disposed in the primary treated-water tank  200  may be supplied to the micro filtration unit by the primary treated-water supply pump  210  and the secondary treated-water in the secondary treated-water tank  400  may be supplied to the ultrafiltration unit by the secondary treated-water supply pump  410 . 
         [0040]    The apparatus for recycling rinsing wastewater for electropainting according to an exemplary embodiment of the present invention may be used for recycling wastewater produced in a rinsing process of removing foreign substances on an object painted in electropainting. 
       Example 
       [0041]    The exemplary embodiment described herein provides an apparatus for recycling rinsing wastewater for electropainting and a comparative example of a chemical treatment apparatus. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Exemplary Embodiment 
                 Comparative example 
               
             
          
           
               
                   
                 Raw 
                 Treated- 
                 Treatment 
                 Raw 
                 Treated- 
                 Treatment 
               
               
                 Item 
                 wastewater 
                 water 
                 efficiency 
                 wastewater 
                 water 
                 efficiency 
               
               
                   
               
               
                 Organic 
                 1,276 mg/l 
                 7.7 mg/l 
                 99.4%  
                  978 mg/l 
                 6.8 mg/l 
                 99.3%  
               
               
                 substances 
               
               
                 Floats 
                  58.7 mg/l 
                   0 mg/l 
                 100% 
                 87.3 mg/l 
                   0 mg/l 
                 100% 
               
               
                 Common 
                 10,000 
                 0 
                 100% 
                 10,000 
                 0 
                 100% 
               
               
                 bacteria 
                 cfu/100 ml 
                 cfu/100 ml 
                   
                 cfu/100 ml 
                 cfu/100 ml 
               
               
                   
               
             
          
         
       
     
         [0042]    Table 1 compares the efficiencies of treating rising wastewater for electropainting by an exemplary embodiment of the apparatus for recycling rinsing wastewater for electropainting according to an exemplary embodiment and a comparative example of a chemical treatment apparatus. 
         [0043]    In the exemplary embodiment, a hollow fiber type (ID 0.65 mm, OD 1.0 mm) was used for a micro filtration separator of a micro filtration unit, the size of apertures of the separator was 0.2 μm or less, flux was 45 l/m 2 -Hr or less, and operation pressure was 1.0 kgf/cm 2  or less. In the embodiment, a hollow fiber type (ID 1.2 mm, OD 1.8 mm) was used for an ultrafiltration separator of an ultrafiltration unit, the size of apertures of the separator was 0.0.1 μm or less, flux was 65 to 75 l/m 2 -Hr, and operation pressure was 2.0 kgf/cm 2  or less. 
         [0044]    Alternatively, the chemical treatment apparatus in the comparative example includes a cohering unit, a float separating unit, a sand filtration unit, an active carbon filtration unit, an ozone oxidizing unit, a micro filtration unit, and an ultrafiltration unit. The chemical treatment apparatus of the comparative example required injecting a coagulant of about 375 ml/m 3 , a pH conditioner of about 275 ml/m 3 , and a cohering agent of about 75 ml/m 3 . As the result of the test on the embodiment and the comparative example, the embodiment treated organic substances by 99.4% and floats and common bacteria by 100%. The comparative example also treated organic substances by 99.3% and floats and common bacteria by 100%. 
         [0045]    However, it could be found from the test that the exemplary embodiment physically treated the substances without using a chemical such as a coagulant, thereby reducing environmental contamination due to use of a chemical and it did not produce sludge unlike that the comparative example which produced a sludge of about 125 l/m 3 . Therefore, the apparatus for recycling rinsing wastewater for electropainting according to the exemplary embodiment did not produce sludge without using a chemical while being equal in treatment efficiency to the chemical treatment apparatus of the related art. 
         [0046]    The invention was described in connection with what is presently considered to be exemplary embodiments, but on the contrary, is intended to cover various modifications and equivalents arrangements included within the sprit and scope of the appended claims. In addition it is to be considered that all of these modifications and alterations fall within the scope of the present invention and the claims to be described below.