Tratamentos de efluente industrial com elevada carga orgânica

Abstract

Water is an essencial natural resource used in industrial production on a large scale, resulting in effluents with polluting potencial. An exemple of industry that uses water in several stages is the one that produces medium density fiberboard (MDF), which generates effluent with high chemical oxygen demand (COD) in the debarking of logs, wood preparation and treatment/cooking. To reduce the pollutant capacity of the effluent, treatments are applied, which may be chemical, physical, physicochemical or biological. As an example of physical-chemical treatment there is the conventional coagulation/flocculation by the addition of coagulants agents, that has as purpose the desestabilization of particles of the liquid by the addition of chemicals, allowing the agglomeration and subsequent separation of pollutant particles. As an alternative to conventional treatment, coagulating agentes may be replaced by the application of an electric current. In order to obtain better results, the biosorption process can be combined with the coagulation/flocculation treatment, improving the staining and reducing the COD of the efluente by the sorption of pollutants by a dead biomass - such as residual meal of chia seeds or malt bagasse. In the present study, the efficiency of the conventional treatment (by the addiction of coagulating agents aluminum sulfate and ferric chloride in different concentrations) and the electrochemical treatment of coagulation and flocculation by the application of electric current of 10 V and 20 V were evaluated based on percentage reduction of COD of the effluent from an MDF industry. After being individually applied, the treatments that presented the bests results were combined and then allied to the biosorption process with the residual meal of chia seeds or malt bagasse, resulting in a serie of treatment processes consisting of the electrochemical, conventional and biosorption stages. The main challenge was dealing with an industrial effluent with COD in the 130,000 mg/L scale, reaching between 45% and 80% removal in the applied treatments.