Impacts of Pre-Oxidation and Coagulation on the Formation Potential of Chlorinated Ketone/Aldehyde Disinfection By-Products from Different Precursors

Halogenated ketones (HKs) and aldehydes (HAs) are prevalent emerging disinfection by-products (DBPs) threatening drinking water safety. Although pre-oxidation and coagulation are widely applied in drinking water treatment, critical knowledge gaps remain regarding the precursor-specific effects of KMnO4 and O3 pre-oxidation on chlorinated ketone/aldehyde formation potential, as well as the interaction between coagulation optimization and DBP yields. This study systematically investigates the effects of KMnO4/O3 pre-oxidation and optimized coagulation on the formation potential (FP) of 1,1-dichloroacetone (1,1-DCP), 1,1,1-trichloroacetone (1,1,1-TCP), and chloral hydrate (CH) from four typical precursors (fulvic acid, citric acid, L-threonine, L-asparagine). Batch pre-oxidation and chlorination experiments were performed; three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy was used to characterize organic-precursor structural changes, while gas chromatography–mass spectrometry (GC-MS) was adopted to quantify target DBPs. Results show that KMnO4 and O3 pre-oxidation significantly promote (p < 0.05) DBP formation from fulvic acid but exert precursor-specific effects on small-molecule precursors: KMnO4 enhances CKs while inhibiting CH from amino acids, and O3 suppresses all three DBPs from small-molecule precursors. Coagulation pretreatment weakly inhibits DBP formation (reduction rate < 20%) by removing partial precursors. This study clarifies the mechanism of process-driven DBP modulation and provides a theoretical basis for optimizing water treatment processes to control chlorinated ketone/aldehyde DBPs.