Analytical methods and equipment were developed to correlate membrane fouling with feedwater quality parameters under controlled operating conditions. A self-contained, portable bench-scale reverse osmosis (RO) test unit was fabricated and installed at locations with source waters including surface water, lime-clarified and microfiltered secondary treated wastewater, tertiary treated wastewater, brackish groundwater and agricultural drainage water. Four commercially available membranes were tested: three polyamide membranes and one cellulose acetate membrane. Membranes were operated in a single-pass configuration, each at a constant flux of 10 gfd and 4 percent recovery. Typical duration of each run was 10 to 12 weeks or until the feed pressure to any polyamide membrane exceeded 200 psi. Membrane operating parameters (transmembrane pressure, water flux and solute rejection) were measured daily and water quality grab samples were collected weekly. Water quality analyses included general minerals, microbial analysis by heterotrophic plate counts and epifluorescence microscopy, community analysis by 16S rRNA and particle size analysis. At the end of each test, membranes were autopsied to determine both the physiochemical properties (ATR/FTIR spectrometry, zeta potential, particle size analysis and scanning electron microscopy) of the membrane and the nature of the biological material accumulated on the membrane surface (protein, carbohydrate, microbiological analysis by heterotrophic plate counts and epifluorescence microscopy, community analysis by 16S rRNA). Collected data were compiled in a database. Chemical, physical, and biological characteristics of the source waters, membranes and fouling layers were measured and used to develop relationships between source water quality, membrane composition, and membrane fouling using conventional multivariate analysis and artificial neural net analysis. Includes abstract only.