Page 3 - 6_TOC in daily practice
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Sum parameter – Total Organic Carbon



                                         Continuous TOC/TN determination in

                                         wastewater treatment plants
                    SCA-130-601


            A uniform definition of  wastewater does not        ■ TOC determination in wastewater
            yet  exist.  Wastewater  is  often  used  as  a     Two oxidation techniques are now commonly
            generic term for sludge, industrial wastewater      used in TOC analysis:
            and  infiltration  water.  The  contents  of              catalytic combustion, where carbon
            wastewater can vary  widely depending on                   compounds  are  converted  into  CO 2
            their origin, and a distinction is made between            using    a    catalyst  under     high
            oxygen consuming compounds, nutrients,                     temperatures      with    subsequent
            harmful substances and contaminants [1].                   detection of the resulting CO 2 using
                                                                       an NDIR detector
            Wastewater treatment is  carried out to                   wet chemical oxidation, which applies
            eliminate wastewater contents and to restore               a  combination  of  UV  irradiation  and
            the natural water quality.                                 persulfate for oxidation. The resulting

                                                                       CO 2 is either detected via an NDIR
                                                                       detector or using a conductivity
                                                                       detector.
                                                                For  TOC  determination  in  wastewater,
                                                                catalytic combustion has become the method
                                                                of  choice  based  on  its  higher  oxidation
                                                                potential,  especially  for  particles.  Regarding
                                                                TOC methods, the  German Wastewater
                                                                Ordinance states the following: “A TOC
                                                                system with thermal-catalytic combustion
                                                                                                o
                                                                (minimum  temperature  of  670  C)  must  be
                                                                used.”

            In  municipal  wastewater  treatment  plants,       ■ TOC-4200
            biological processes are used in aerobic and        The  TOC-4200  is  a  high-performance
            anaerobic  wastewater treatment for the             analyzer with catalytic combustion at 680 °C.
            degradation  of  organically  highly  polluted      Depending on the sample characteristics,
            wastewater. These plants use microbiological        three TOC analysis methods can be selected
            degradation processes. A stable nutrient ratio      (direct  method,  difference  method,  addition
            (carbon : nitrogen : phosphorus) is a               method). The automatic dilution function
            precondition for  an optimal  degradation           enables TOC analyses up to 20,000 mg/L. In
            capacity of the microorganisms. Therefore, it       addition, the TOC-4200 can be extended with
            is important to continuously monitor the inflow     a module  for measuring the total bound
            to the sewage plant. The treated effluent           nitrogen (TN). An automatic dilution function
            leaving the sewage plant must also be               and the self-calibration option allow a virtually
            monitored continuously. Only when the limit         independent  operation  of  the  measuring
            levels of the German Wastewater Ordinance           system.
            are reached, the water may flow back.
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