TOC Analyzer for Wastewater

The appropriate TOC analyzers – that is total organic carbon analyzers, or meters – can help in determining the number of carbon-containing compounds within the wastewater. The quantity of carbon in a freshwater stream is an indicator of the organics present in it. Amount of carbon content is directly proportional to the amount of oxygen that is consumed by the stream. High amount of organics results in an increase in microbial growth, which contributes to the decrease in the amount of oxygen. Monitoring of both the plant effluent and the stream for organics levels must be done through the use of an appropriate TOC analyzer. Liquid waste discharged from a factory may contain carbon-based compounds with various levels of toxicity. Drop in oxygen levels and toxic substances can create unhealthy conditions for aquatic organisms.  One method that TOC analyzers use to analyze wastewater is the use of High Temperature Catalytic Oxidation (HTCO).

TOC Analyzers that use High Temperature Catalytic Oxidation (HTCO)

For many TOC analyzers that use HTCO, oxidation occurs at 680o C in combination with a platinum catalyst in an oxygen-rich environment. Carbon dioxide concentration is measured by non-dispersive infrared (NDIR) method within the TOC analyzer chamber.
The sample becomes oxidized upon injection into the TOC analyzer’s furnace; the oxidizable material within the sample is converted into gaseous form. This gas is transported by a carbon-free carrier gas, which passes the gas through a moisture trap and halide scrubbers so that the water vapor and halides are removed from it before it is detected by the detector. It’s important to get rid of these substances because they can affect the carbon dioxide gas detection. The utility of this method of oxidation lies in the fact that it provides complete oxidation of organic material including solid matter and particulates which can be injected into the furnace.

A main issue with TOC analyzers that use HTCO is the unstable baseline of this method, which originates from the gradual build-up of non-volatile residues in the combustion tube within the TOC analyzer. Background correction is required on a continuous basis as the residues continuously change TOC background levels.  In HTCO, the aqueous samples are injected directly into a furnace with high temperature; therefore, only sample aliquots that are small in size (less than two milliliters and normally less than 400 micro-liters) can be used. This makes the process less sensitive than chemical oxidation processes, which handle as much as 10 times more sample. General data and peaks can be re-calculated using the NPOC (non-purgable organic carbon) method by the TOC analyzer.