Treatment of a nano-ceramic coating bearing effluent integrating adsorption and a coagulation/flocculation process

In the metal mechanics industry, the surface treatment by nano-ceramic coating results in the generation of a hard-to-treat industrial effluent. The treatment process by coagulation/flocculation/ sedimentation usually presents non-conformities regarding the emission standard in terms of organic load. The objective of this work was to improve the removal of chemical oxygen demand (COD) with the use of powdered activated carbon (PAC) prior to the coagulation/flocculation process. The procedure applied consisted of dispersion of the PAC particles in the raw effluent for adsorption of soluble contaminants, followed by hetero-aggregation of PAC and the suspended pollutants with the use of polyaluminum chloride and polyacrylamide. The addition of PAC, at a concentration of 0.5 g L-1, resulted in a reduction of more than 50% in the residual concentration of organic load compared to the conventional treatment. The integration of adsorption with the coagulation/flocculation process met all effluent emission conditions established by the environmental agency, as well as significant gains in reducing toxicity. This technique ensured greater operational stability in the removal of COD observed through statistical capability analysis (Cp). The addition of PAC to the process increased the weight amount of sludge, but this was not an impediment in operational and cost terms.