AbstractThe re m oval or elimination of organic residues from aqueous waste streams represents a major need in the chemical industry. We have developed a new class of membrane called “supported polymeric liquid membranes” that are capable of removing and concentrating low molecular weight organic compounds from dilute aqueous solutions, especially those that also contain high concentrations of inorganic salts. Attractive features of this membrane process include the ability to recover the contaminants in concentrated form for either recycle or more economical disposal, low pressure (ambient) operation, simple scale‐up using commercial hollow fiber modules, and ease of in‐situ regeneration of the polymeric liquid. The process has shown treatment feasibility for several types of aqueous waste streams. This paper describes the laboratory development activities for treating a waste stream containing a dilute mixture of C2–C6 carboxylic acids and nitric acid.