Air flotation techniques for oily wastewater treatment

Oil/water emulsions pose a major threat to the environment and aquatic health and its occurrence at many phases in the production and treatment of crude oil make its treatment a critical step to enhancing water security. Oil can be found as free oil, unstable oil/water emulsion and as a highly stable oil/water emulsion. One of the common methods of generating microbubbles in oily wastewater treatment in the oil and gas industry is dissolved air flotation. It is a proven and effective technology and is regularly used in this industry. The influence of key parameters on the removal efficiency using induced gas flotation and dissolved gas flotation was examined, including oil concentration, pH values, and the effects of salinity. The effect of bubble size and interfacial tensions on the performance of the separation process and its impact on removal efficiency was also discussed. The general fundamentals of the air flotation process have also been covered and the pretreatment systems used were highlighted because the performance of the gas flotation process can be dramatically improved by adding effective pretreatment processes. The use of various types of coagulants for effective oily wastewater treatment is also discussed. One of the key processes highlighted in this chapter is the hybridized coagulant/flocculant system that uses ferric chloride as the chosen coagulant and chitosan as a biodegradable flocculant added to a dissolved air flotation process. An understanding of the effects of various physicochemical parameters of the influent on the dissolved air flotation process performance will improve its efficiency.