4 - Primary treatment of oily wastewaters by floating and settling down separation methods

Abstract

Oily effluents can contaminate water and soil, harming the environment. Settling down processes can initially break emulsion bonds into water and oil phases, but a minor part of oil is solubilized into the water. Thus flotation is a tool capable of treating these effluents in order to make them suitable for disposal. In this sense, initially, this chapter addresses settling down processes and some types of flotation such as Dissolved Air Flotation, Induced Air Flotation, and Electroflotation, explaining which operational parameters are used, such as liquid and air flows, pH, and surfactants. Through these parameters, it is possible to measure the microbubbles—through the Sauter’s Diameter—that collide against the dispersed oil droplets and heavy metal ions, reducing the effluent concentration. This chapter then presents a step-by-step approach to building floaters for removing oil from effluents and emphasizes the use of biological surfactants as sustainable collecting agents in the flotation process to replace the toxic chemical surfactants used.