Total Organic Carbon (TOC) and Dissolved Organic Carbon (DOC)

TOC concentrations are regulated by the Safe Drinking Water Act through the Long-Term 2 Enhanced Surface Water Treatment Rule and the Stage 2 Disinfectant Byproduct Rule. Both Rules identify removal requirements based on source water characteristics such as alkalinity and source water TOC levels.

Generally, TOC is removed through the addition of coagulants during the flocculation and sedimentation processes and through the filtration process. Dissolved organic carbon (DOC) measures the total amount of organic matter that can pass through a filter no larger than 0.45 µm. Since high levels of DOC may interfere with disinfection efficiency, DOC concentrations are monitored for removal before the disinfection stage of the water treatment process.