USING THE SYSTEM
22
TOC reduction and monitoring
Total organic carbon (TOC) describes level of organic contaminants in pure water. High concentration
of organic contaminants may affect results of several analytical methods, e.g. high-performance liquid
chromatography. Therefore, for some applications TOC level should be controlled and kept minimal.
Grade II water, coming to the storage tank, generally has low TOC level, if proper deionization resins
are used. However, TOC level may rise during storage, therefore water recirculation through
photooxidation module and polishing cartridge is necessary to keep TOC level low.
Unfortunately, organic contaminants may not have effect on conductivity of water, so conductivity
sensors cannot be used for TOC monitoring. A special TOC monitoring module is needed to measure
TOC level. The monitoring module consists of a TOC photooxidation module, valve and a conductivity
sensor.
TOC monitoring module (optional) operation principle
This section does not refer to Trace configuration.
During recirculation stage a water sample is introduced into the TOC photooxidation module where it
is oxidized for several minutes. During this phase water conductivity rises because of oxidation of
organic molecules. The rise of conductivity is proportional to TOC level of water.
After the oxidation phase is finished, water is released from the TOC photooxidation module and its
conductivity is measured by the conductivity sensor. TOC level is calculated from the rise of
conductivity.
Note: As TOC measurement is made during the recirculation stage, the TOC value is shown on the
display only after the system has partially filled the storage tank with water and completed at least one
recirculation cycle.
Diagnostic screen
If the “Mode” has been pressed two times, the Diagnostic screen is shown. The diagnostic screen
displays status of all the sensors and components as well as tank level.
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