Otimização da técnica de eletrofloculação via análise de superfície de resposta aplicada ao efluente de uma indústria cosmética

Abstract

The generation of effluents in the most varied industrial sectors has contributed to the environmental degradation, especially when not treated and disposed in the soil or water sources. In this context, there is the cosmetic industry, which is responsible for the generation of effluents, which need adequate treatment due to its characteristics, such as: fragrances, dyes, oils and detergents. The objective of this research was to characterize the effluent of the cosmetic industry and to evaluate the efficiency of the treatment of Electroflocculation (EF) with the use of aluminum electrode, in the removal of Chemical Oxygen Demand (COD), turbidity, apparent color and absorbance. The effluent used was provided by a cosmetic industry located in the state of Rio Grande do Sul, and the same originated from the cleaning of floors and equipment for the production of shampoos, deodorants, sunscreens, makeup, among others. Characterization parameters were: temperature, apparent color, turbidity, hydrogenation potential (pH), conductivity, dissolved oxygen (DO), COD, Sedimentable Solids (SedS), Total Suspended Solids (TSS), Fixed Suspended Solids (FSS) Volatile Suspended Solids (VSS) and Oils and Grease Content (OGC). The physico-chemical analyzes were carried out at the Water and Ecotoxicology Laboratory of the Federal University of the South Frontier, Cerro Largo / RS. The application of EF occurred by means of a pilot system, where a volume of effluent of 500 mL was used at a stirring of 600 RPM and a pair of aluminum electrodes with submerged area in the effluent of 25 cm 2 , isolated electrically the distance of 1 cm. In order to verify the efficiency of EF applied to the effluent of the cosmetic industry, the experimental design employed was the Rotational Central Composite Design (RCCD) composed of 12 tests. The electrical current and the treatment time were used as independent variables, obtaining, as dependent variables, the percentage of removal of COD, turbidity, apparent color and absorbance at wavelength 350 nm. In the characterization of the cosmetic industry effluent the following values were obtained: temperature 25.90 ± 0.08 °C, apparent color 8989.25 ± 7.83 u.C, turbidity 818.77 ± 0.94 NTU, pH 5.38 ± 0.02, conductivity 2.92 ± 0.01 mS cm -1 , DO 1.78 ± 0.22 mgO 2 L -1 , COD 1042.19 ± 43.70 mgO 2 L -1 , SedS 0.09 ± 0.01 mLL -1 h -1 , TSS 21.67 ± 2.36 mgL -1 , FSS 13.33 ± 2.36 mgL -1 , VSS 8.33 ± 2.36 mgL -1 , OGC 57.00 ± 3.00 mgL -1 . It was verified that the use of RCCD was feasible, being possible to identify the current values of 4.18 A and time of 18.98 optimized minutes, in the process of removal of the dependent variables. The treatment by EF was efficient, with removal of 66.12 % COD, 90.96 % turbidity, 97.07 % apparent color and 97.83 % absorbance. Of the analyzed parameters the color and the SedS did not reach the values stipulated by the legislation, temperature, pH, DO and COD (flow up to 100 m 3 d -1 ) were within the limit allowed for effluent releases in water bodies according to Resolutions CONAMA 357/2005 and 430/2011 and CONSEMA 128/2006, the OGC served only the value of vegetable and animal oils from CONAMA 430/2011.