Characterization of Disinfection Byproduct Precursors Based on Hydrophobicity and Molecular Size

Abstract

Natural organic matter (NOM) from five water sources was fractionated using XAD resins and ultrafiltration membranes into different groups based on hydrophobicity and molecular weight (MW), respectively. The disinfection byproduct formation from each fraction during chlorination and chloramination was studied. In tests using chlorination, hydrophobic and high MW (e.g., >0.5 kDa) precursors produced more unknown total organic halogen (UTOX) than corresponding hydrophilic and low MW (e.g., <0.5 kDa) precursors. Trihaloacetic acid (THAA) precursors were more hydrophobic than trihalomethane (THM) precursors. The formation of THM and THAA was similar among different fractions for a water with low humic content. Hydrophilic and low MW (<0.5 kDa) NOM fractions gave the highest dihaloacetic acid (DHAA) yields. No significant difference was found for DHAA formation among different NOM fractions during chloramination. Increasing pH from 6 to 9 led to lower TOX formation for hydrophobic and high MW NOM fractions but had little impact on TOX yields from hydrophilic and low MW fractions. Bromine and iodine were more reactive with hydrophilic and low MW precursors as measured by THM or HAA formation than their corresponding hydrophobic and high MW precursors. However, hydrophobic and high MW precursors produced more UTOX when reacting with bromine and iodine.

The formation and control of emerging disinfection by-products of health concern

“…In other research, it was found that a significant portion of the TOX produced during chlorination or chloramination was of a high molecular weight (Khiari et al 1997;Hua & Reckhow 2007). An analytical constraint in further identification of TOX components has been that GC/MS, a principal measurement tool, can only typically be used to identify DBPs with molecular weights of up to approximately 650 Da.…”

Role of Aluminum Speciation in the Removal of Disinfection Byproduct Precursors by a Coagulation Process

“…However, the role of aluminum speciation in THM and HAA precursor removal was different. Some investigations indicated that THM and HAA had different precursors (23,24). In their results, aliphatic structures played a more important role in THM formation than HAA formation, while HAAs had more aromatic structures as their precursors than THMs.…”

Disinfection byproduct precursor removal by enhanced coagulation and their distribution in chemical fractions

“…This method separates NOM into several components according to their chemical properties (hydrophilicityhydrophobicity). Based on this method, the behaviors of different NOM fractions have been investigated (Chow et al, 2005;Hua and Reckhow, 2007;Kitis et al, 2002;Krasner et al, 1996;Liang and Singer, 2003;Matilainen et al, 2011;Panyapinyopol et al, 2005). The results showed that the hydrophilic fractions of NOM are composed mostly of aliphatic carbon and nitrogen compounds (such as carbohydrates, sugars, and amino acids), while hydrophobic NOM primarily consists of humic and fulvic acids and is rich in aromatic carbon, phenolic structures and conjugated double bonds (Krasner et al, 1996).…”