Water quality improvements during riverbank filtration: Fate of disinfection by-product precursors, pathogens, and potential surrogates

Riverbank filtration (RBF) is a process by which river water is subjected to ground passage prior to its extraction and use as a drinking water source. Research was conducted to evaluate the benefits of RBF in regard to control of disinfection by-product (DBP) precursor material and microorganisms at three mid-western United States drinking water utilities that currently use RBF (the Indiana-American Water facilities at Jeffersonville and Terre Haute, IN and the Missouri-American Water facility at Parkville, MO). Two wells at each site were chosen for study. At the Indiana-American Water study site, located along the Ohio River at Jeffersonville, IN, Well #9 (580 ft (177 m) from the river) and Well #2 (100 ft (30 m) from the river) were sampled for this study. At the Indiana-American Water study site, along the Wabash River at Terre Haute, IN, the Collector Well (located 90 ft (27 m) from the Wabash River, with horizontal arms extending out from the center at a depth of approximately 80 ft (24 m) below the river bottom) and Well #3 (400 ft (122 m) from the river) were sampled for this study. Finally, at the Missouri-American Water facility, located along the Missouri River at Parkville, MO, Well #4 and Well #5 (both wells located approximately 120 ft (37 m) from the river) were sampled for this study.; Reductions in concentrations of total organic carbon (TOC), dissolved organic carbon (DOC), and DBP precursors upon bank filtration at the three study sites were similar to or greater than those achieved by subjecting the river waters to a bench-scale conventional treatment train consisting of coagulation, flocculation, sedimentation, ozonation, and glass-fiber filtration. TOC and DOC reductions at the closer wells at the three sites ranged from 35% to 67%; trihalomethane (THM) and haloacetic acid (HAA) precursor concentrations were reduced by 50% to 80%. Reductions in precursors for haloacetonitriles, haloketones, chloral hydrate, and chloropicrin ranged from 30% to 100% following bank filtration. Reductions in TOC and DOC upon bench-scale conventional treatment of river waters (coagulation, flocculation, sedimentation, ozonation, and glass-fiber filtration) ranged from 20 to 50%; reductions in DBP precursor concentrations following bench-scale conventional treatment were between 40 and 80%. XAD-8 characterization of the natural organic matter (NOM) of river and well waters indicated no significant or consistent preferential removal of either "hydrophobic" or "hydrophilic" fractions upon ground passage. However, reductions in DBP precursors upon RBF were generally higher than the reductions in TOC and DOC, indicating a preferential reduction in the chlorine-reactive portion of the NOM. (Abstract shortened by UMI.)...