The reverss osmosis process, which employs a cellulose acetate membrane, offers a means of producing water low in inorganic and organic substances from single solute aqueous systems, multi-solute aqueous systems, and secondary-treated sewage effluents. Compounds when in an aqueous system having significantly higher vapor pressure than water may appear in significant quantities in the reclaimed water. This process can also serve as a means of concentrating weak waste water to a point where the waste water can be more economically treated. The permeation of 55 chemical species singly in an aqueous solution and dispersion, and/or in multi-component systems were investigated. The degree of permeation of radioactive nuclei and of some enteric microorganisms are also reported on. (Author)