Wang, LK and Wang, MHS (2022). Hazardous wastewater treatment in petroleum refining industry using best available flotation and filtration technologies. In: “Evolutionary Progress in Science, Technology, Engineering, Arts and Mathematics (STEAM)”, Wang, LK and Tsao, HP (eds.), 4 (7G), STEAM-VOL4-NUM7G-JULY2022. ISBN 978-0-9890870-3-2. pp.75-136 pages. July 2022., Lenox Institute Press, Massachusetts, USA. ———-ABSTRACT: This publication introduces the interrelationships among the different processes and a specific effluent flow model for predicting current industrial flow on a refinery by refinery basis. The wastewaters generated by the industry are diverse and complex, representing a full range of hazardous organic and inorganic substances, such as volatile organics, semi-volatile organics, pesticides, cyanides, arsenic, and many heavy metals. Wastewater characteristics of refinery effluents from the oil-water separator are researched and compiled. Special emphasis is placed on the introduction of in-plant control technologies for reduction of wastewater volume and pollutant loading, preliminary treatment of sour water, primary treatment for oil-water separation and the best available end-of-pipe treatment processes, such as high rate dissolved air flotation (DAF) and flotation-filtration (DAFF), and many others. This publication also covers: (a) The effectiveness of treatment technologies for hazardous substances; (b) The concept and practice of zero discharge in the industry; (c) The method for determination of toxic substances effluent limitation; (d) The case histories involving the use of DAF and DAFF for waste treatment in the petroleum refining industry; (e) Recommendation of the Best Practicable Control Technology Currently Achievable (BPT) for developing countries; and (f) Recommendation of the Best Available Technology Economically Achievable (BAT) to all industrial countries.