Page 71 - Application Handbook - TOC
P. 71
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.
