The removal of oil from wastewater by air flotation: A review

Oil and grease are common industrial pollutants whose removal is normally effected by gravity separation followed by a chemically enhanced air separation process. In this review, the author discusses oil and grease, their sources, their analysis, and their removal. Although removal by chemical treatment, gravity separation, and ultrafiltration are discussed initially in the article, the major thrust of the review is removal of oil by air bubbles. Discussed are the theory of flotation and equipment involved (in generating the bubbles with the discussion based on the mechanism of bubble generation), i.e., dissolved, induced, or nozzle air flotation systems. In the review, many performance data are given for numerous types of industrial wastewaters in one of several air flotation systems. The final section of the review deals with air pollution aspects, handling of the recovered product, and costs.