Development of a membrane-based process for the treatment of oily waste waters. Annual report, March 4, 1993--March 5, 1995

Abstract

The goal of this program was to develop an economical oily-water treatment system based on reverse-osmosis (RO) membrane technology. The RO system would be used to: (1) reduce oil-production costs by reducing the volume of waste water for which disposal is required; (2) form the basis of a generic waste-water treatment system that can easily be integrated into oil-field operations, especially at production facilities that are small or in remote locations: and (3) produce water clean enough to meet current and anticipated environmental regulations. The specific focus of this program was to develop a hollow-fiber membrane module capable of treating oily waste waters. Typically, the organics in oily waste water swell or dissolve the materials used in conventional polymeric membranes and modules. Our goal was to develop hollow-fiber membranes and modules that were more solvent-resistant than conventional membrane modules. We successfully achieved this goal. During the course of this program. we developed thin-film-composite (TFC) membranes, which consisted of a solvent-resistant selective coating placed on a solvent-resistant hollow-fiber support. These TFC membranes were used in low-cost, hollow-fiber modules, which were made using solvent-resistant components. The modules were tube-side-feed modules, in which the oily waste water travels down the inside (lumen) of the hollow fiber. The selective coating allows water to pass freely through the wall of the fiber, but restricts the transport of oil and grease and some of the dissolved organics and salts in the feed. Using these modules, more than 90% of the oily waste water can be recovered as clean permeate (suitable for discharge), while the remaining 10% is removed as oily-water concentrate (which can be recycled for recovery of the oil or disposed of in an environmentally acceptable manner).