Abstract:
Disclosed herein is an electrochemical measurement system for analyzing heavy metals in organic compound-containing samples, comprising: a lower plate; a flow channel plate; an upper plate; an organic compound-decomposing electrode and a heavy metal analysis electrode; and a flow changeover portion. The disclosed system can continuously perform a pretreatment process for organic compound decomposition and a process for heavy metal analysis, thus making it possible to achieve the selective analysis and separation of heavy metals in wastewater. Also, it can substitute for expensive spectrophotometric analysis equipment and makes it possible to monitor trace heavy metals on-line in situ. In addition, it may include a small-sized battery as a power source, such that it is easy to carry and use.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of pending International Patent Application PCT/KR2008/002679 filed on May 14, 2008, which designates the United States and claims priority of Korean Patent Application No. 10-2008-0040403 filed on Apr. 30, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a system for analyzing heavy metals in wastewater, and more particularly to an economical and efficient electrochemical analysis system for analyzing heavy metals in organic compound-containing samples, which allows a pretreatment process for organic compound decomposition and a process for heavy metal analysis to be performed continuously in one system. 
       BACKGROUND OF THE INVENTION 
       [0003]    With the rapid development of industry and the urbanizing tendency of the population, the emission of large amounts of chemical hazardous substances becomes an important factor threatening the natural environment and ecosystem. Hazardous heavy metals, including arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), fluorine (F), selenium (Se) and mercury (Hg), adversely affect the human body, are not decomposed in water or converted into stable compounds and remain mixed and contaminate water and soil. If these hazardous heavy metals get into and accumulate in the body through various food routes such as via fish by proceeding up the food chain and are absorbed in vivo, they bind to biological substances to form non-biodegradable organic complexes, and thus are not quickly discharged out of the body and are accumulated in organs (e.g., liver or kidneys) or bone. Thus, these hazardous heavy metals can impair the health. Particularly, because heavy metals, once accumulated in the body, are not easily released, heavy metal pollution is a threatening factor and difficult to recover from. 
         [0004]    The world health organization (WHO) strictly regulates the concentrations of various heavy metals which are hazardous to human health in drinking water to specific concentrations or less, and in order to prevent heavy metal pollution, countermeasures, including the regulation of pollutant emission, the improvement of pollutant treatment facilities, the development and growth of clean technology, and environmental education for social members, are performed. 
         [0005]    However, in order to fundamentally prevent heavy metal pollution, a technology capable of accurately measuring the amounts of hazardous heavy metals emitted to the environment, must be ensured, and the strict regulation of environmental pollution must be performed using this technology. 
         [0006]    Accordingly, the importance of the development of a technology for environmental prediction, monitoring and assessment is receiving great attention, and in order to meet the demand for novel environmental measurement procedures, to effectively cope with complicated, diversified environmental problems and ensure the assaying and analytic ability for generating compliance with international standards, studies focused on improving the reliability and accuracy of environmental measurement technology must be conducted. 
         [0007]    In industrial plants causing industrial environmental wastewater, an effective process capable of reducing environmental pollution by monitoring environmental pollution through the accurate analysis of the content of heavy metals in wastewater can be ensured. 
         [0008]    Wastewater from chemical industries, including petrochemicals, pulp industries, oil and fat industries, paper-making industries, petroleum purification processes, plastic industries and adhesive processes, which account for more than 27% of Korean industry, contain non-biodegradable organic compounds, including nitrobenzene, chlorophenol, benzidine and phenol. Such aromatic organic compounds are introduced into the human living environment, so that they are absorbed and concentrated in organisms and cause serious ecological problems in organisms. In addition, when the analysis of heavy metals in industrial wastewater is carried out, the accuracy of analytic results is reduced due to a matrix effect caused by the formation of metal complexes between heavy metals and organic compounds. 
         [0009]    When hazardous heavy metal concentration in environmental wastewater containing such organic compounds is measured, it is difficult to measure accurate amounts due to the matrix effect, and for this reason, various studies focusing on increasing the accuracy of measurement have been conducted. Thus, in order to analyze hazardous heavy metals in wastewater containing organic compounds, the separation and treatment of the organic compounds must be performed before the analysis. 
         [0010]    However, aromatic organic compounds are not readily degraded through low-cost biological methods, and in most cases they are degraded through separation methods, such as a precipitation method and a solvent extraction method, and chemical methods employing acids, alkalis or the like. However, such methods are excessively time-consuming and can reduce the accuracy of analysis due to the loss of samples, which can occur in pretreatment processes, and, in addition, they can cause secondary environmental pollution. 
         [0011]    Thus, in order to develop a method for the analysis of heavy metals in industrial wastewater, studies on the effective pretreatment of non-biodegradable organic compounds and the selective separation and concentration of heavy metals after the pretreatment are required. Also, it is required to develop small-scale systems for conducting pretreatment, concentration and measurement, which can substitute for expensive spectrophotometric analytic instruments (e.g., UV-VIS spectrophotometers, atomic absorption spectrometers, ICP atomic emission spectrometers) and which can monitor trace heavy metals on-line in situ. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention has been made in order to solve the above-described problems occurring in the prior art, and it is an object of the present invention to provide an economical and efficient electrochemical measurement system for analyzing organic compound-containing samples, which allows a pretreatment process for organic compound decomposition and a process for heavy metal analysis to be performed continuously in one system. 
         [0013]    To achieve the above object, the present invention provides an electrochemical measurement system for decomposing organic compounds in wastewater and analyzing heavy metals in the wastewater, comprising: a lower plate having a channel plate-receiving portion formed in the upper side thereof; a flow channel plate, which is received in and coupled to the channel plate-receiving portion of the lower plate and includes, formed in the upper side thereof, an organic compound-decomposing channel, a heavy metal analysis channel and a discharge channel, and an organic compound decomposition electrode-receiving portion and a heavy metal analysis electrode-receiving portion, which communicate with the organic compound-decomposing channel and the heavy metal analysis channel, respectively; an upper plate, which is coupled to the lower plate and the upper side of the flow channel plate so as to seal the upper side of the channels; an organic compound decomposition electrode and a heavy metal analysis electrode, which are received in and coupled to the organic compound decomposition electrode-receiving portion and the heavy metal analysis electrode-receiving portion, respectively; and a flow changeover portion, comprising an on/off valve, which is provided at the upper side of the upper plate and coupled to one end of each of the organic compound-decomposition channel, the heavy metal analysis channel and the discharge channel so as to selectively open and close the wastewater outlet of each of the organic compound-decomposition channel and the heavy metal analysis channel, and an on/off switch for operating the on/off valve. 
         [0014]    In the measurement system of the present invention, the lower plate is preferably formed of an aluminum material having an oxide layer formed on the surface thereof. 
         [0015]    Also, the flow channel plate is formed of elastic synthetic resin, and preferably PDMS. 
         [0016]    Preferably, the wastewater inlet of each of the organic compound-decomposing channel and the heavy metal analysis channel is formed in a circular shape, the wastewater outlet thereof is connected with the on/off valve, and the portion between the wastewater inlet and the wastewater outlet is formed in a curved shape consisting of continuously connected U shapes. 
         [0017]    Moreover, preferably, the organic compound-decomposing electrode is received in and coupled to the organic compound decomposition-receiving portion, such that it comes in contact with wastewater introduced into the organic compound-decomposing channel, thus decomposing organic compounds in the wastewater. Particularly, the organic compound-decomposing electrode comprises: a body, which corresponds to the shape of the organic compound decomposition electrode-receiving portion and is coupled hermetically to the organic compound decomposition electrode-receiving portion; a decomposition electrode, which is provided at the lower end of the body so as to come in contact with wastewater; and a connector, which is electrically coupled to the decomposition electrode, extends through the upper side of the body and is connected with electrochemical measurement equipment. 
         [0018]    Herein, the decomposition electrode is preferably made of any one selected from among a BDD (boron doped diamond) electrode, a Pt/Ti electrode, a carbon/carbon, a carbon/SUS electrode, a carbon/platinum electrode and an Au/Fe electrode. 
         [0019]    Also, preferably, the heavy metal analysis electrode is received in and coupled to the heavy metal analysis electrode-receiving portion so as to come in contact with wastewater introduced into the heavy metal analysis channel, thus analyzing heavy metals in the wastewater. Particularly, the heavy metal analysis electrode preferably comprises: a body, which corresponds to the shape of the heavy metal analysis electrode-receiving portion and is coupled hermetically to the heavy metal analysis electrode-receiving portion; an analysis electrode, which is provided at the lower end of the body so as to come in contact with wastewater; and a connector, which is electrically coupled to the analysis electrode, extends through the upper side of the body and is connected with electrochemical measurement equipment. 
         [0020]    Herein, the analysis electrode preferably consists of a counter electrode made of Pt, a reference electrode of Ag/AgCl and a working electrode of BDDE or GCE. Also, preferably, the analysis electrode is formed in a shape corresponding to the shape of the lower end of the body, the length ratio of the counter electrode to the reference electrode is 2:1, and the working electrode having a circular shape is formed in the central portion of the counter electrode and the reference electrode. 
         [0021]    Also, a pump for supplying wastewater to each of the channels at a specific rate is preferably provided adjacent to the inlet of each of the organic compound-decomposing channel, the heavy metal analysis channel and the discharge channel in the upper side of the upper plate. 
         [0022]    In addition, a power source-receiving portion for receiving the on/off valve and the on/off switch and an on/off switch-receiving portion for receiving the on/off switch are preferably formed in the upper side of the lower plate. 
       ADVANTAGEOUS EFFECTS 
       [0023]    The electrochemical measurement system according to the present invention can continuously perform a pretreatment process for organic compound decomposition and a process for heavy metal analysis, thus making it possible to achieve the selective analysis and separation of heavy metals in wastewater. Also, it can substitute for expensive spectrophotometric analysis instruments JJV-VIS spectrophotometers, atomic absorption spectrometers and ICP atomic emission spectrometers, and makes it possible to monitor trace heavy metals on-line in situ. In addition, it may include a small-sized battery as a power source, such that it is easy to carry and use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a perspective view showing the disassembled state of the inventive electrochemical measurement system for analyzing heavy metals in organic compound-containing samples. 
           [0025]      FIG. 2  is a perspective view of an organic compound decomposition electrode in the inventive electrochemical measurement system for analyzing heavy metals in organic compound-containing samples. 
           [0026]      FIG. 3  is a perspective view of a heavy metal analysis electrode in the inventive electrochemical measurement system for analyzing heavy metals present in organic compound-containing samples. 
           [0027]      FIG. 4  is a perspective view of the inventive electrochemical measurement system for analyzing heavy metals present in organic compound-containing samples. 
       
    
    
     DESCRIPTION OF IMPORTANT REFERENCE NUMERALS USED IN THE DRAWINGS 
       [0000]    
       
         
           
               100 : lower plate 
               110 : channel plate-receiving portion 
               120 : power source-receiving portion 
               130 : on/off switch-receiving portion 
               200 : flow channel plate  210 : organic compound-decomposing channel 
               220 : heavy metal analysis channel 
               230 : discharge channel 
               300 : upper plate 
               310 : organic compound decomposition electrode-receiving portion 
               320 : heavy metal analysis electrode-receiving portion 
               400 : organic compound decomposition electrode 
               410 : body 
               420 : decomposition electrode 
               430 : connector 
               500 : heavy metal analysis electrode 
               510 : body 
               520 : analysis electrode 
               530 : connector 
               600 : flow crossover portion 
               610 : on/off valve 
               620 : on/off switch 
               700 : power source 
           
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    Hereinafter, a preferred embodiment of the present invention will be described in further detail with reference to the accompanying drawings. 
         [0051]      FIG. 1  is a perspective view showing the disassembled state of the inventive electrochemical measurement system for analyzing heavy metals in an organic compound-containing sample, and  FIG. 2  is a perspective view of an organic compound decomposition electrode in the inventive electrochemical measurement system for analyzing heavy metals in an organic compound-containing sample. 
         [0052]    As shown in  FIGS. 1 and 2 , the inventive electrochemical measurement system for analyzing heavy metals in an organic compound-containing sample is a system for decomposing organic compounds in wastewater and analyzing heavy metals in the wastewater and comprises a lower plate  100 , a flow channel plate  200 , an upper plate  300 , an organic compound-decomposing electrode  400 , a heavy metal analysis electrode  500  and a flow changeover portion  600 . 
         [0053]    The lower plate  100  will now be described. 
         [0054]    The lower plate  100  is formed either of Teflon, which is physically and chemically stable and has excellent mechanical durability, or of alumina having an oxide layer formed on the surface thereof, and is in the form of a flat rectangular block. On the upper surface of the lower plate  100  is formed a channel plate-receiving portion  110  in which a flow channel plate  200  to be described later is received. The channel plate-receiving portion  110  has a rectangular shape and is formed in a depressed shape on the lower plate  100 . 
         [0055]    Also, in the upper side of the lower plate  100  is further formed a power source portion-receiving portion  120  in which a power source portion  700  for supplying power to an on/off valve  610  and an on/off switch  620 . In addition, at the upper portion of the lower plate is formed an on/off switch-receiving portion  120  in which the on/off switch  620  is received. The power source portion-receiving portion  120  and the on/off switch-receiving portion  130  are formed in a concave shape in the lower plate  100 , such that the power source portion  700 , that is, a small-sized battery, is received in the power source portion-receiving portion  120  so as to supply power to the on/off valve  610  and the on/off switch. 
         [0056]    Herein, the power source portion-receiving portion  120  conforms to the shape of the power source portion  700  for supplying power. If a small-sized battery is received in the power source portion-receiving portion  120 , the measurement system of the present invention is used for portable applications, and if the measurement system of the present invention is not used for portable applications, an external power source can be used as the power source portion  700  to supply power. 
         [0057]    The flow channel plate  200  will now be described. 
         [0058]    The flow channel plate  200  is received in and coupled to the channel plate-receiving portion  110  of the lower plate  100 , and at the upper side of the flow channel plate  200 , flow channels, particularly an organic compound-decomposing channel  210 , a heavy metal analysis channel  220  and a discharge channel  230 , are formed. Each of the channels is formed by processing (e.g., etching) the flow channel plate  200 , such that they are depressed from the surface of the flow channel plate  200 . 
         [0059]    The flow channel plate  200  is formed of elastic synthetic resin, such that the upper portion of the flow channel plate  200  is easily sealed hermetically through contact between each of the flow channels and the upper plate  300  to be described later. Preferably, the flow channel plate  200  is formed of poljdimethylsiloxane (PDMS) having excellent processability and durability. 
         [0060]    The flow channel plate  200  is slightly higher than the channel plate-receiving portion  110 , such that the upper plate  3 ) 0  is pressed down and elastically coupled to the upper portion of the flow channel plate  200 , thus further increasing the sealing of each of the channels formed in the flow channel plate  200 . 
         [0061]    The organic compound-decomposing channel  210  and the heavy metal analysis channel  220  are formed in a circular shape at the wastewater inlet thereof, and the middle portions thereof are formed in curved shapes consisting of continuously connected U shapes, and the wastewater outlet is connected with an on/off valve  610  to be described later. 
         [0062]    Namely, wastewater introduced into the wastewater inlet comes in contact with and reacts with an organic compound-decomposing electrode  400  and a heavy metal analysis electrode  300 , and then organic compounds in the wastewater are decomposed and heavy metals in the wastewater are analyzed. Then, the wastewater, subjected to the organic compound decomposition and heavy metal analysis processes, flows to the wastewater outlet through the U-shaped channel and is discharged through a discharge channel  230 . 
         [0063]    Herein, the organic compound-decomposing channel  210  and the heavy metal analysis channel  220  are formed in a curved shape consisting of continuously connected U shapes, and this curved shape serves to delay the reaction between wastewater, introduced into the wastewater inlet, and the organic compound-decomposing electrode  400 /heavy metal analysis electrode  500 , such that wastewater is concentrated on and brought into contact with each of the electrodes, whereby the organic compound decomposition and heavy metal analysis processes are performed in an accurate manner. 
         [0064]    Also, the wastewater, having undergone organic compound decomposition in the organic composition-decomposing channel  210  and the heavy metal analysis channel  220 , is discharged through the discharge channel  230  to the outside. 
         [0065]    In the process for decomposing organic compounds in wastewater, the on/off valve  610  is operated so as to cause the organic compound-decomposing channel  210  and the discharge channel to communicate with each other and so as to close the wastewater inlet of the heavy metal analysis channel  220 . In the process for analyzing heavy metals in wastewater, subjected to organic compound decomposition, the on/off valve  610  is operated so as to cause the heavy metal analysis channel  220  to communicate only with the discharge channel  220 . Each of the organic compound-decomposing process and the analysis process can also be repeated several times, and particularly, the organic compound-decomposing process is carried out such that wastewater is circulated several times through the organic compound-decomposing channel  210  and the discharge channel, such that organic compounds in the wastewater can be completely decomposed. 
         [0066]    Preferably, a pump is further provided adjacent to the inlet of each of the organic compound-degrading channel  210 , the heavy metal analysis channel  220  and the discharge channel, such that wastewater is supplied to each of the channels at a given flow rate. The pump is operated such that wastewater is supplied at a flow rate of about 0.02-12.3 m̂/min. 
         [0067]    Then, the upper plate  3 ) 0  is formed in a rectangular shape and is coupled to the lower plate  100  and the upper side of the flow channel plate  200  to seal the upper side of the channels. The upper plate  3 ) 0  is screwed to the upper side of the lower plate  100 , such that the separation of the flow channel plate  200  is easily performed. On the upper side of the upper plate  3 ) 0  is provided a pump (not shown; only an inlet “p”, which is connected with the pump, is shown in  FIG. 1 ) for supplying wastewater to the wastewater inlet of the channels, and on the upper side of the upper plate  3 ) 0  are formed the on/off valve  610  and on/off switch  620  to be described later. 
         [0068]    Also, at the wastewater inlet sides of the organic compound-decomposing channel  220  and the heavy metal analysis channel  220 , an organic compound decomposition electrode-receiving portion  310  and a heavy metal analysis electrode-receiving portion are formed which communicate with the channels and receive an organic compound decomposition electrode  400  and a heavy metal analysis electrode  300 . 
         [0069]    Now, the organic compound decomposition electrode  400  will be described. 
         [0070]    The organic compound decomposition electrode  400  is received in and coupled to the organic compound decomposition-receiving electrode  310 , such that it comes in contact with wastewater introduced into the wastewater inlet of the organic compound-decomposing channel  210 , thus providing for decomposition of organic compounds in the wastewater. 
         [0071]    As shown in  FIG. 2 , the organic compound decomposition electrode  400  comprises: a body  400 , which corresponds to the shape of the organic compound decomposition-receiving portion  310  and is hermetically coupled to the organic compound decomposition-receiving portion  310 ; a decomposition electrode  420 , which is formed on the lower end of the body  410  and comes in contact with wastewater; and a connector  430 , which is electrically connected with the decomposition electrode  420 , extends through the upper side of the body  410  and is connected with electrochemical measurement equipment. 
         [0072]    The body  410  of the organic compound decomposition electrode  400  is formed in the shape of the organic compound decomposition electrode-receiving portion  310 , that is, a cylindrical shape, and has a rubber O-ring provided at the middle portion thereof, such that it is coupled hermetically to the organic compound decomposition electrode-receiving portion  310 . 
         [0073]    Also, the electrode  420  is provided at the lower end of the body  410 , such that it comes in contact with wastewater to decompose organic compounds present in the wastewater. The electrode  420  consists of a positive (+) electrode and a negative (−) electrode. The (+) electrode and the (−) electrode are made of any one selected from among a BDD (boron doped diamond) electrode, a Pt/Ti electrode (an electrode consisting of platinum deposited on titanium), a carbon (glassy carbon) electrode and an Au/Fe electrode (an electrode consisting of gold deposited on iron). Preferably, the (+) electrode is made of carbon, and the (−) electrode is made of SUS or platinum. The electrode  420  electrolyzes organic compounds in wastewater to convert them into inorganic compounds (CO). 
         [0074]    In a conventional process for analyzing heavy metals in wastewater, a pretreatment process for decomposing the organic compounds must be carried out before the analysis process in order to accurately analyze the heavy metals. However, in the present invention, a pretreatment process involving organic compound decomposition and a heavy metal analysis process are continuously performed in one system. 
         [0075]    Furthermore, the connector  430  is electrically coupled to the decomposition electrode  420 , and extends through the upper side of the body  410  and is connected with electrochemical measurement equipment, such that the degree of decomposition of organic compounds can be measured by checking either the total amount of carbon remaining after electrolysis in the decomposition electrode  420  or the concentration of produced carbon dioxide. Until the decomposition of organic compounds reaches a given level, wastewater is circulated through the organic composition-decomposing channel  210  and the discharge channel  230 , such that the decomposition of the organic compounds is continuously performed. 
         [0076]    Moreover, the heavy-metal analysis electrode  300  is received in and coupled to the heavy metal analysis electrode-receiving portion  320 , such that it comes in contact with wastewater introduced into the heavy metal analysis channel  220 , thus analyzing heavy metals in the wastewater. 
         [0077]    As shown in  FIG. 3 , the heavy metal analysis electrode  300  comprises: a body  510 , which corresponds to the shape of the heavy metal analysis electrode-receiving portion  320  and is coupled hermetically to the heavy metal analysis electrode-receiving portion  320 ; an analysis electrode  520 , which is formed at the lower end of the body  510  and comes in contact with wastewater; and a connector  530 , which is electrically coupled to the analysis electrode  520 , extends through the upper side of the body  510  and is connected with electrochemical measurement equipment. 
         [0078]    The body  510  of the heavy metal analysis electrode  500  is formed in the shape of the heavy metal analysis electrode-receiving portion  320 , that is, a circular shape, and has a rubber O-ring formed at the middle portion thereof, such that it is coupled hermetically to the heavy metal analysis electrode-receiving portion  320 . 
         [0079]    Also, the analysis electrode  520  is formed at the lower end of the body  510  and comes in contact with wastewater to analyze the amount of heavy metals in the wastewater. It consists of a counter electrode “a” made of a Pt plate or a spiral platinum wire, a reference electrode “c” made of an AgCl/Ag electrode (an electrode consisting of silver chloride deposited on silver), and a working electrode “b” made of BDDE or GCE. Also, it serves to measure the amount of heavy metals contained in wastewater. 
         [0080]    Generally, the counter electrode must generally have a reaction area larger than that of the working electrode or the reference electrode. In consideration of this, the counter electrode, the working electrode and the reference electrode must be included in the heavy metal analysis electrode. The heavy metal analysis electrode  500  in  FIG. 3  is designed in consideration of the area of the lower area of the circular body, such that each of the electrodes can perform heavy metal analysis in an efficient manner. Also, the heavy metal analysis electrode  500  is generally formed in a circular form corresponding to the shape of the lower end of the body. 
         [0081]    Specifically, the counter electrode “a” is received in the lower end of the body  510  in order to efficiently analyze heavy metals, in a manner such that it is formed in a curved shape corresponding to the shape of the lower end of the body  510 , the length ratio of the counter electrode “a” to the reference electrode “b” is 2:1, and the working electrode “c” having a diameter of 5 mm is formed in the central portion of the counter electrode. 
         [0082]    Moreover, the connector  530  is electrically coupled to the analysis electrode  520 , and extends through the upper side of the body  510  and is connected to electrochemical measurement equipment, such that the amount of heavy metals can be measured by checking the concentration of metal ions from the analysis electrode  520 . 
         [0083]    Then, the flow changeover portion  600  is provided at the upper side of the upper plate  3 ) 0  and comprises: the on/off valve  610 , which is connected to one end of each of the organic compound-decomposing channel  210 , the heavy metal analysis channel  220  and the discharge valve  230  and selectively opens and closes the wastewater outlet of the channels; and the on/off switch  620  which operates the on/off valve  610 . The on/off valve  610  and the on/off switch  620  receive power from the power source  700 . 
         [0084]    The on/off valve  610  consists of a known electronic valve and selectively opens and closes the wastewater outlet of each of the organic compound-degrading channel  210  and the heavy metal analysis channel  220  according to the operation of the on/off switch. In the process of decomposing organic compounds in wastewater, the on/off valve  610  closes the wastewater outlet of the heavy metal analysis channel  220  and opens the organic compound-decomposing channel  210  and the discharge channel so as to communicate with each other. In the process of analyzing heavy metals in wastewater, the on/off valve  610  closes the wastewater outlet of the organic compound-decomposing channel  210  and opens the heavy metal analysis channel  220  and the discharge channel  230  so as to communicate with each other. 
       INDUSTRIAL APPLICABILITY 
       [0085]    As described above, according to the present invention, the pretreatment process for organic compound decomposition and the process for heavy metal analysis can be continuously performed in one system. Thus, the present invention can be applied in places or plants which require an efficient and economical process for analyzing organic wastewater.