Relationship between Brominated THMs, HAAs, and Total Organic Bromine during Drinking Water Chlorination

Abstract

Naturally occurring bromide present in drinking water can be quickly oxidized by chlorine to bromine, which can react with natural organic matter to form brominated disinfection byproducts (DBPs). This study investigated the relationship between known specific brominated DBPs and total organic bromine (TOBr) formed during chlorination of NOM isolates and natural waters in the presence of various levels of bromide. Unknown TOBr (UTOBr) is determined as the difference between TOBr and bromine incorporated into measured specific DBPs. The unknown TOBr fraction, as represented by the ratio of UTOBr to TOBr increased with increasing initial bromide concentrations during chlorination. The majority of organic bromine was incorporated into known specific DBPs during chlorination of low bromide containing waters. Hydrophilic and low molecular weight (MW) NOM was more reactive with bromine as measured by the formation of trihalomethanes and haloacetic acids than corresponding hydrophobic and high MW NOM. However, hydrophobic and high MW NOM formed more TOBr than hydrophilic and low MW NOM. Water utilities should work to remove both hydrophobic and hydrophilic NOM in the water sources to reduce the formation of chlorinated and brominated DBPs.