This research focuses on the factors affecting successful multistage pilot-scale operation of Integrated Membrane Systems (IMS) to treat a highly organic surface water. Fifteen months of pilot-scale nanofiltration of the Hillsborough River in Tampa, Florida, have yielded important operational and design considerations. This paper presents water quality and fouling results for various IMS process trains. In addition, fouling mechanisms are explored and crucial design criteria for sustained operation are presented. Includes 4 references, tables, figures.