Dissolved Organic Carbon or DOC is a measurement of the amount of organic matter in water that can be passed through a filter, commonly 0.45 µm.
WHY IS IT IMPORTANT?
For drinking water, Dissolved Organic Carbon is an important water quality parameter measured for several purposes. Elevated levels of DOC may interfere with the effectiveness of disinfection processes such as UV, ozone and chlorination thus should be monitored for removal prior to disinfection. In plants that disinfect with chlorine, DOC concentrations are a primary concern due to the harmful by-products that form when chlorine reacts with organic matter. DOC in finished water can lead to aesthetic problems and increase the potential for bacterial regrowth in the distribution system. Regulations for DOC are specific to each country, with aesthetic objective in drinking water being approximately 5 mg/L. Additionally, DOC is used in the calculation of SUVA which determines the aromatic portion of DOC, a major precursor for THM formation.
A common method for Dissolved Organic Carbon analysis is Method 415.1. The procedure for analyzing DOC requires that the samples first be passed through a 0.45 µm filter. The test involves converting organic carbon to carbon dioxide (CO2) through oxidation (Combustion, UV promoted or Persulfate oxidation). The concentration of CO2 generated is measured using an infrared analyzer and reported as organic carbon (mg/L).