EFFECTS OF ALUM COAGULATION ON SPECIATIONAND DISTRIBUTION OF DISINFECTION BY PRODUCTS

摘要

The impacts of alum coagulation on the distribution of disinfection by-products (DBPs),rntrihalomethanes (THMs) and haloacetic acids (HAAs), were evaluated under controlledrnchlorination conditions using four surface waters. Among the nine HAAs found inrnwaters, dihaloacetic acids (X2AAs) have been found to be the dominant species in all ofrnthe raw and alum treated waters. Alum coagulation tends to remove morernmonohaloacetic acids (XAAs) and trihaloacetic acids (X3AAs) precursors than that ofrndihaloacetic acids (X2AAs). Alum coagulation treated water had a lower HAA9/TTHMrnratio compared with that of the raw water. The increase of THM bromine incorporationrnfactors (BIFa) value of alum treated water was statistically significant in comparison withrnthe raw water. On average, BIFa increased by 54% after the alum coagulation process inrnthese four different waters. This indicated that THM speciations shifted in favor of thernmore brominated compounds. However, alum coagulation treatment process had lessrneffect on HAA bromine incorporation factors (BIFb) than it did on BIFa. BrominernIncorporation Factor (BIF) values decreased with time in the THM and HAA formationrnprocesses, especially within the first 10 hours of the reaction time. This suggested thatrnbrominated THMs or HAAs formed faster than the chlorinated species in the initialrnperiod.