Application of Foam Fractionation Technology for the Removal of Disinfection Byproduct Precursors: Challenges and Opportunities

Abstract

Foam fractionation is a cost-effective physicochemical process that concentrates surface-active compounds at the air-water interface and is recognized for its effectiveness in removing per- and polyfluoroalkyl substances (PFAS) from different aqueous matrices. To this date, evaluation of simultaneous control of disinfection byproduct (DBP) formation in drinking water and potable reuse systems through foam fractionation had not been investigated. This thesis evaluated the removal of DBP precursors using a bench-scale foam fractionation system assisted by cetyltrimethylammonium bromide (CTAB), analyzing surrogate solutions and water samples from the Occoquan Reservoir, an indirect potable reuse source, at pH levels between 6.5-8.5. Foam fractionation experiments demonstrated high removal efficiencies for the carbonaceous surrogate (humic acid; 80-96%, average 88.7%) and the nitrogenous surrogate (L-tryptophan; 80-99%, average 92.4%). In the real water matrix, post-fractionation decreased dissolved organic carbon by 35%, UV absorbance and specific UV absorbance at 254 nm by 78% and 65%, respectively, indicating effective removal of aromatic and hydrophobic natural organic matter. Following chlorination, regulated trihalomethane formation fell 88-97% and haloacetic acids by 60-82% at pH 6.5-7.0; haloketones, haloacetaldehydes, and trichloronitromethane were near-completely suppressed in the post-treatment. In the treated water, toxicity-weighted responses increased by 58-110% across all pH levels, attributed to a shift towards brominated species incorporation from CTAB-derived bromide. At the lowest CTAB dosing tested, toxicity-weighted response declined to approximately 1%, whereas the bromine substitution factor plateaued at 30-40% of untreated levels. Bromine substitution therefore persisted at bromide concentrations well below those associated with the full CTAB dose, indicating that reducing bromide loading alone did not remove it under the tested CTAB removal conditions. These findings show that foam fractionation can effectively reduce the downstream DBP formation potential, while emphasizing the importance of careful surfactant selection and further optimization in engineering design for achieving public health goals in drinking water treatment context.