Disinfection by-products (DBPs) discharged into surface waters from upstream wastewater treatment plants (WWTPs) may result in occurrence of DBPs in downstream drinking water treatment plants (DWTPs). This article evaluates the effects of five biogeochemical mechanisms (biodegradation, photolysis, hydrolysis, volatilization, and adsorption) on the fate of several types of DBPs in surface waters that receive disinfected wastewater discharges. Pseudo-first order rate constants of the five mechanisms were obtained from literature reviews, laboratory experiments and/or quantitative structure-activity relationships. The dominant removal mechanism for each DBP class is: 1) volatilization for trihalomethanes (THMs), 2) biodegradation for dihalogenated haloacetic acids (HAAs), 3) hydrolysis for haloacetonitriles (HANs), and 4) photolysis for nitrosoamines (NAs), while adsorption of DBPs onto suspended solids is not important for all classes. The receiving waterbody geometry (width, depth), flowrate, and meteorological conditions are also important factors affecting the fate of DBPs.