The control of tastes and odors in drinking waters obtained from surface water sources is a major problem in water purification. Tastes and odors in surface waters may come from aquatic plants such as algae natural land drainage, and the discharge of domestic sewage and industrial wastes. The odor bearing materials, largely organic, may undergo physical and chemical changes as a result of sedimentation, vaporization, oxidation, temperature and light effects, and biochemical action. The study was undertaken to determine the types and quantities of materials present in petroleum refinery gravity oil separator effluents that contribute to taste and odor when discharged into surface waters used as drinking water sources. (Author)