Reduction of dissolved organic matter and trihalomethane formation potential during laboratory-scale soil-aquifer treatment

Dissolved organic matter (DOM) in recovered groundwater from soil-aquifer treatment (SAT) has the potential to generate harmful disinfection by-products. This study investigated the reduction of mass and trihalomethane formation potential (THMFP) of DOM fractions from secondary effluent during laboratory-scale SAT. Using XAD-8 and XAD-4 resins, DOM was fractionated into three fractions: hydrophobic acid (HPO-A), transphilic acid (TPI-A) and hydrophilic fraction (HPI). HPO-A was removed by 61.1%, TPI-A by 54.9% and HPI by 75.0% as dissolved organic carbon (DOC) during the laboratory-scale SAT, respectively. The reduction of THMFP from HPO-A, TPI-A and HPI was 27.24, 26.24 and 36.08%, respectively. Specific THMFP for each DOM fraction increased across the soil columns. HPO-A was found to be the major precursor of THMs. THMFP was strongly correlated to ultraviolet light at 254 nm (UV-254) for HPO-A and HPI, while the relationship between THMFP and UV-254 for TPI-A was significantly poor.