Abstract: The presence of disinfection by-products (DBPs) or their precursors can impair the safety of potable water sources when indirect potable wastewater reuse occurs. The primary purpose of this dissertation is therefore to address the impacts of DBPs formation on indirect potable wastewater reuse, specifically focusing on the occurrence, fate, and treatment of DBP precursors & DBPs in WWTPs, receiving waterbodies, and downstream DWTPs. As part of an AWWARF (American Water Works Association Research Foundation) project with Metropolitan Water District of South California, a US-wide survey was conducted at 24 WWTPs along with investigations of effluent-dominant rivers and laboratory systems. This project observed that the trihalomethane (THM) precursors were ranged from 0.95 to 3.5 μM, haloacetic acid (HAA) precursors were ranged from 0.70 to 6.8 μM; haloacetonitrile (HAN) precursors were ranged from 0.05 to 0.54 μM, and nitrosodimethylamine (NDMA) precursors were present up to 28.4 nM. This study thus detected abundant DBP precursors in WWTP effluents, and the range of DBP precursors were related to the types of wastewater treatment processes. This dissertation modeled the fate of DBPs & DBP precursors in receiving surface waters. DBPs preformed at WWTPs were removed by >50% by several biogeochemical processes, including adsorption, biodegradation, hydrolysis, photolysis, and/or volatilization. The dominant mechanism contributing to loss of THMs was volatilization (kinetics contribution >80%), dihaloacetic acids was biodegradation (>60%), HANs was hydrolysis (>50%), and nitrosoamines was photolysis (>80%). The impacts of preformed DBPs on drinking water were therefore significantly diminished, and the major risks of wastewater-derived DBPs in DWTP were more likely derived from DBP precursors. This project also evaluated the removals of DBP precursors and other effluent organic matter, as measured by dissolved organic carbon (DOC) and nitrogen (DON). Results indicated that typical water treatment processes (i.e., coagulation, softening, and PAC adsorption) may supplement WWTP processes and enable indirect potable wastewater reuse. Overall, the findings can be used to better understanding the wastewater effluent quality in WWTPs, knowing the removals of preformed DBPs and DBP precursors in conveying watersheds, and selecting treatment processes in DWTPs. These efforts may assist minimization of DBPs.