ABSTRACT
The metal-mechanical industry is responsible for the synthesis of one of the most complex oily effluents, which are difficult to treat and reuse. These effluents constitute, among other pollutants, cutting fluids, which are used to cool and lubricate metal parts in the machining system. For the treatment of effluents with these characteristics, it is important to integrate physical, chemical and biological treatments, in order to ensure all quality parameters are in accordance with current legislation. Among these treatments is the chemical precipitation, whose main objective is to reduce metallic ions that are highly toxic to living beings. In addition, another generally effective alternative for the treatment of oily effluents is the advanced oxidative processes (AOPs), which use hydroxyl radical (•OH) as the main oxidizing agent, mainly for the recalcitrant compounds removal, that is, persistent to conventional treatments typologies, such as the activated side and settling ponds. However, biological treatments are of major importance in several treatment plants, because they are effective in the removal of several organic compounds and are of relatively low cost, being aerobic or anaerobic, depending on the treatment purpose and the pollutants in the effluent. This type of treatment has a greater efficacy when using autochthonous microorganisms from the effluent itself, since they are already adapted to the pre-existing pollutants in the matrix. It is worth mentioning that AOPs can be used before biological treatments to remove pollutants that are toxic to the microorganisms and, consequently, to increase the effluent biodegradability, or afterwards, to reduce compounds that persist after biological treatment. Thus, this chapter reiterates the importance of using treatment methods in an integrated way for a significant process efficacy.
