AWWA WQTC60616

Aromatic carbon is considered one of the most reactive molecular moieties with respect to trihalomethanes (THM) formation during water chlorination. Studies have shown that ultraviolet absorbance at 254 nm (UVA254) is a good proxy for aromatic content in dissolved organic carbon (DOC). Thus, specific UVA254 (SUVA254), which is equal to carbon normalized UVA254, has been widely used as a measure for aromatic organic carbon content and trihalomethane formation potential. However, recent studies have questioned the reliability of using SUVA254 to predict THM formation because nitrate, bromide and non-reactive conjugated double bonds of organic carbon under chlorination also absorb UVA at 254 nm. The authors hypothesize that the difference in SUVA254 before and after chlorination (ΔSUVA254) should be proportional to the formation of THM if SUVA254 measures the amount of THM reactive sites in DOC. The authors examined DOC originating from agricultural soils in the Sacramento-San Joaquin Delta and from 35 river sites in the Sacramento-San Joaquin watershed. The relationships between SUVA254, ΔUVA254/DOC and ΔSUVA254 versus specific THM formation potential were evaluated. Results indicated that the correlation coefficients of ΔUVA254/DOC-STHMFP and ΔSUVA254-STHMFP are slightly better than SUVA- STHMFP. Also, all these parameters in terms of UVA at 272 nm provide slightly better correlation than UVA at 254 nm. Includes 13 references, table, figures.