The objectives of this study are to understand the interactions of disinfection byproducts (DBPs) with natural organic matter (NOM) and flocs during conventional treatment, focusing on the solid / liquid phase formation of DBPs, and to characterize and quantify the extent of DBPs that form under chlorine and chlorine dioxide preoxidant application. A bench-scale jar testing apparatus was used to simulate the full-scale conventional treatment process. A modified jar with limited headspace was used in all experiments to minimize the loss of volatile DBPs. Tests were conducted at 20°C ± 1°C with aluminum sulfate (Al₂(SO₄)₃ · 14H₂O, alum) as the coagulant, and preliminary tests were performed to select the alum dose needed to meet US Environmental Protection Agency's (USEPA) enhanced coagulation total organic carbon (TOC) removal requirements. Jar tests were run to simulate rapid mix, tapered flocculation and sedimentation. This research plan utilized four waters. The source waters were selected from distinct geographical locations within the United States to encompass a spectrum of raw water quality, such as turbidity and NOM concentration as measured by total organic carbon (TOC). Alum was dosed from a stock concentration of 20 g/L prepared from Fisher Scientific certified grade aluminum sulfate. The oxidants that were used in the study were taken from the following stock solutions: chlorine 3675 mg/L; and, chlorine dioxide 2000 mg/L, generated on site at Colorado State University, Fort Collins, Colorado. Adsorbable organic halogens (AOX) measurements were conducted using a Mitsubishi model TOX-10 using a modified Standard Method 5320B. Trihalomethanes (THMs) and haloacetic acids (HAAs) were analyzed using a HP GC 6890 applying a modified USEPA Method 551.1 and a modified Standard Method 6251 B, respectively. The experimental approach included chlorine, natural organic matter, floc and disinfection byproduct interactions during coagulation. Includes 3 references, tables, figures.