To fulfill the Information Collection Rule (ICR) treatment study requirements for the Kansas City Missouri Water Services Department (KCMWSD) and Water District No. 1 of Johnson County (WDNo1JC), candidate nanofiltration (NF) membranes were prescreened to determine suitability for subsequent ICR testing. Suitable membranes were required to have a total organic carbon and atrazine rejection of 60% and 80% respectively. This level of rejection was deemed appropriate based on historical and published data. The objective for this study was to isolate the mechanism(s) responsible for atrazine rejection from NF membranes. This is important information necessary to determine what impact membrane selection may have on synthetic organic compound (SOC) removal or even system operation. Mechanisms effecting atrazine removal that were studied included: steric rejection, which is related to membrane pore size; adsorption of atrazine to the membrane; mass transfer of atrazine through the membrane; electrostatic repulsion by the membrane surface charge; and, binding with source water natural organic matter. WDNo1JC and KCMWSD are two neighboring water utilities treating Missouri River water using a lime softening process. These two utilities were granted an ICR common source designation so that both studies could be conducted at the same site. Testing was performed at the KCMWSD and feed water was drawn prior to filtration. A schematic of full scale and pilot scale treatment processes is presented. It should be noted that the ICR required NF be evaluated as a polishing treatment for existing unit processes. For the KCMWSD and WDNo1JC this resulted in redundant softening processes in series (lime softening followed by NF). The rational for this ICR requirement was that the majority (280 of 304) of surface water plants required to conduct an ICR treatment study, use a treatment process other than softening. Includes 17 references, tables, figures.