Tratamento de águas oleosas com alto grau de emulsificação e presença de sólidos de baixa densidade utilizando fad

Abstract

A methodology was developed for the treatment of an effluent from the metalworking industry composed of water, cutting fluid and graphite. The recovery of components from an effluent from the machining process becomes complex due to the coexistence of solids such as graphite, mixed with a water-oil emulsion. Due to the use of graphite in very small particles and emulsified in water with the aid of an emulsifier, distributing in both phases (aqueous and organic), making the treatment process difficult. In general, treating such an effluent requires, in the preliminary step, the breaking of the emulsion so that the graphite dispersed in the liquid medium is recovered. The treatment was initially performed in a prototype phase separation in laboratory scale, counting on recirculation tanks, pumps, hydrocyclones and continuous decanter. In an initial stage the effluent was acidified by the addition of sulfuric acid PA as a way of breaking the solid-liquid emulsion. Subsequently, the solid phase was reered with the aid of a hydrocyclone, resulting in an overflow of the equipment of a mixture of water and residual oil. The mixture of part of the water and the water-cutting fluid, after acid destabilization of the emulsion, was separated into the continuous decanter, giving rise to a stream of cutting fluid and an aqueous phase containing residual oil, contaminated by about 130 ppm Of organic phase. The aqueous phase was then subjected to a dissolved air flotation (FAD) process, aided by a demulsifying biosurfactant in a FAD prototype, also on a laboratory scale. In order to define adequate conditions to obtain an aqueous phase with contamination level that allowed its return to the process, the operational conditions of application of the FAD technique were determined with the aid of an experimental design of the type rotational central compost (CDCR). At the end of the aqueous phase recovery process, a residual oil content of 12% was obtained, below that required by the Brazilian environmental regulatory agency (CONAMA) for discharge in water bodies, which is 20 ppm. The recoveries of graphite and cutting fluid are suggested studies for the next works.