Evaluating TOC analytical results

The Disinfectants/Disinfection By-products (D/DBP) Rule includes total orga nic carbon (TOC) as a regulatory compliance parameter with the idea that TO C concentration is a direct Indicator of the potential for DBP formation up on chlorination. a comprehensive study was conducted to evaluate the abilit y of the two most common methods-ultraviolet (UV)-persulfate oxidation and catalytic combustion-to measure the particulate fraction of the TOC in wate r and determine whether this fraction contributes to DBP formation. Results showed that particulate TOC fraction in a natural water was more accuratel y measured by the combustion method. Therefore, the method used by a water utility to evaluate TOC removal through a water treatment plant can signifi cantly affect the chemical dosages required for regulatory compliance and t reatment cost. Furthermore, chlorination testing results suggest that the D BP formation reactions may not be affected by particulate TOC, leading the authors to propose that dissolved organic carbon rather than TOC is a more appropriate indicator of DBP formation potential in water treatment.