Total organic carbon (TOC) measures the total amount of carbon bound in organic compounds in a water sample. It indicates the level of organic contamination and the potential for disinfection byproduct formation.
Total organic carbon (TOC) is an analytical measurement of the total carbon present in organic molecules dissolved and suspended in water. TOC analysis involves oxidizing all organic carbon to carbon dioxide (CO2) through combustion, UV-persulfate oxidation, or wet chemical oxidation, then measuring the CO2 produced. TOC is reported as the sum of dissolved organic carbon (DOC) and particulate organic carbon (POC), though in many water samples, DOC dominates. TOC is a critical parameter in drinking water treatment because natural organic matter reacts with chlorine and other disinfectants to form disinfection byproducts (DBPs) such as trihalomethanes and haloacetic acids, which are regulated carcinogens. The EPA's Stage 2 Disinfectants and Disinfection Byproducts Rule requires many water systems to reduce TOC through enhanced coagulation or softening. Typical TOC concentrations range from 1-20 mg/L in surface waters and 0.2-2 mg/L in groundwater. TOC monitoring is also used in wastewater treatment to assess organic loading and treatment effectiveness, and in ultrapure water systems for pharmaceutical and semiconductor manufacturing where TOC must be maintained below parts-per-billion levels.