A 40-million gallon per day membrane softening process is currently in designfor the City of Boca Raton, Florida and will be the largest nanofiltration plantin the world. In recent years, the City of Boca Raton, Florida, has experienced agradual, but steady increase in the levels of color in the raw and finished waterat its Glades Road Water Treatment Plant. In addition, increasing levels ofdissolved organics in the raw water have made compliance with more stringentregulations for disinfection byproducts (DBPs) more difficult with the existingconventional lime softening process. While the lime process does remove somecolor, DBP precursors, and associated constituents, it is not capable of meetingboth DBP and color standards simultaneously. In addition, the utility isreceiving increasing customer complaints about high color levels in the finishedwater. With the passage of more stringent regulations for DBPs under the UnitedStates Environmental Protection Agency (USEPA) and State of Florida Safe DrinkingWater Acts (SDWAs), the City has recognized the need to pursue other treatmentprocess alternatives to provide continued compliance with drinking water qualityregulations. This paper discusses the results of pilot-scale and bench-scaletesting and how the information gathered was used to design Boca Raton's newnanofiltration plant. Includes tables, figures.