DBP formation during chloramination

Abstract

Batch study results may help utilities select appropriate chloramination conditions to limit DBP formation. Batch experiments were conducted on three diverse water sources to study the formation of dissolved organic halogen (DOX), trihalomethanes (THMs), haloacetic acids (HAAs), and cyanogen halides (CNX) during chloramination. The authors used preformed chloramines to examine the effect of pH, mass ratio of chlorine to ammonia–nitrogen (Cl 2 to N), and bromide concentration on disinfection by‐product (DBP) formation. Formation of specific DBPs as well as the group parameter DOX was greatest at low pH and high Cl 2 ‐to‐N ratios and followed the general trend of decreasing with increasing pH and decreasing Cl 2 ‐to‐N ratio. Bromide addition increased the concentration of bromine‐substituted DBPs and DOX. These experiments demonstrated that because of dihaloacetic acid formation, HAA formation is more problematic during chloramination than THM formation. Because the specific DBPs measured in this research (THMs, six HAAs, and CNX) accounted for no more than 35 percent of the DOX concentration, utilities may want to consider both specific DBPs and DOX in selecting appropriate chloramination conditions.