purity test, as the presence of bacteria introduces organic carbon. Analyser field testing and reports A non-profit research and testing organization, the Instrumentation Testing Association (ITA) can provide results of field testing online TOC analysers in an industrial wastewater application. Gulf Coast Waste Disposal Authority (GCWDA), Bayport Industrial Wastewater Treatment Plant in Pasadena, Texas sponsored and conducted this test in 2011. The GCWDA Bayport facility treats approximately 30 mgd of industrial waste received from approximately 65 customers (primarily petrochemical). Field tests consisted of operating online TOC analysers at the influent of the Bayport facility in which TOC concentrations can range from 490 to 1020 mg/L with an average of 870 mg/L. GCWDA conducts approximately 102 TOC analyses in their laboratory per day at their Bayport treatment facility and use TOC measurements for process control and billing purposes. GCWDA plans to use online TOC analysers for process control, detecting influent slug loads from industries and to potentially use online TOC analysers to detect and monitor volatiles of the incoming stream. Field tests were conducted for a period of 90-days and used laboratory conformance measurements once per day to compare with analyser output to demonstrate the instrument's overall accuracy when subjected to many simultaneously changing parameters as experienced in real-time monitoring conditions. Field test results can provide information regarding instrument design, operation and maintenance requirements which influence the performance of the instruments in field applications. The field test report includes evaluations of online TOC analysers utilizing the following technologies: High temperature combustion (HTC), high temperature catalytic/combustion oxidation (HTCO), supercritical water oxidation (SCWO), and two-stage advanced oxidation (TSAO). Combustion In a combustion analyser, half of the sample is injected into a chamber where it is acidified, usually with phosphoric acid, to turn all of the inorganic carbon into carbon dioxide as per the following reaction: CO2 + H2O ⇌ H2CO3 ⇌H+ + HCO3− ⇌ 2H+ + CO32− This is then sent to a detector for measurement. The other half of the sample is injected into a combustion chamber which is raised to between 600–700 °C, some even up to 1200 °C. Here, all the carbon reacts with oxygen, forming carbon dioxide. It is then flushed into a cooling chamber, and finally into the detector. Usually, the detector used is a non-dispersive infrared spectrophotometer. By finding the total inorganic carbon and subtracting it from the total carbon content, the amount of organic carbon is