The separation of oil and produced water mixtures from oil and gas producing wells has traditionally been accomplished by gravity settlers (e.g., multi‐phase separators, skimmers, and flotation cells). However, current EPA regulations on the organic content of discharged produced water have reached the limits of these separation techniques. The industry is in need of new technologies to treat these waters. One such technology that we have found promissing is organics/water separation by nanofiltration membranes. Copyright © 1990 American Institute of Chemical Engineers