Emprego de tecnologias terciárias de tratamento de efluente de indústria de papel e celulose pré-tratado biologicamente

Abstract

In the production of cellulose and paper, high volumes of water, wood and various amounts of chemicals are used, generating effluents with different characteristics in quantity and quality in the different production processes of the industry. The color and phenol present in the effluent from the Kraft process are due to the presence of lignin-derived molecules that are hardly biodegradable. The aim of the present work is to evaluate the removal of color and residual phenol from the effluent from a biologically pretreated pulp and paper industry, using coagulation and adsorption onto granular and powdered activated carbon. The work was carried out in three stages: (I) investigation of the ideal operating conditions for the coagulation process, having been tested: coagulant dosage and sedimentation time; (II) evaluation of the efficiency of the coagulation treatment under ideal conditions (optimized) and filtration tests in granular activated carbon, both the raw effluent (from the secondary biological treatment of the industry) and the filtrate coagulated effluent, thus verifying the efficiency of both treatments; and (III) adsorption tests on powdered activated carbon for the raw effluent, investigating the minimum time required to obtain the equilibrium time, the mass of the adsorbent material, the adsorption isotherms, and the study of treatment efficiency. In Step I, the results obtained indicated the use of coagulant dosage of 225 mg/L with sedimentation time of 20 min. In Step II after filtration the removals of 45%, 62%, 38%, 47% were reached for the parameters color, turbidity, COD and phenol, respectively. With the effluent clarified and later filtered, 64% removal for the COD parameter and removals of more than 90% were achieved for the other parameters. In step III it was verified that the minimum time necessary to obtain equilibrium in the adsorption process was of 5 min and that the mass of 1 and 0,5 g were equal and superior to the mass of 0,1 g of powered activated carbon. When the adsorption isotherms were determined for the color parameter, the experimental data were adjusted to the Langmuir and Freundlich models, showing a better fit to the Langmuir model. Subsequently, the performance of the adsorption process on powdered activated carbon was evaluated for the removal of the parameters for the ideal conditions. The results allowed to evaluate the high potential of the process in the advanced treatment of paper and cellulose effluent, with removals of 77% and 71% for turbidity and COD, respectively and above 90% for color and phenol.