Evaluating surrogates for disinfection by‐products

Abstract

Data analysis suggests that UV‐254 absorbance is a better indicator than TOC concentration for chlorination by‐product formation in SDS tests—and is substantially easier, faster, and less costly to measure.Each of four low‐bromide waters was coagulated at three pH values (5.5, 7.0, and 8.0), and then simulated distribution system (SDS) chlorination tests were performed. The object of the study was to determine whether total organic carbon (TOC) or UV‐254 absorbance can be employed as an indicator of the trihalomethane (THM) and haloacetic acid (HAA) concentrations formed upon chlorination. Results showed that removal of TOC and UV‐254 always increased with decreasing coagulation pH, but the extent of removal varied with the different waters. Maximum reduction of SDSTHM and SDSHAA5 formation was achieved after coagulation at pH 5.5. UV‐254 proved to be a better surrogate for chlorinated by‐product formation than TOC. The applicability of the correlations to waters with higher bromide levels and different chlorination pH values should be evaluated.