Avaliação do desempenho da eletrocoagulação no tratamento de uma indústria de papel e celulose

Abstract

Pulp and paper industries, despite their economic importance, are among the largest water consumers in the industrial sector, using it in virtually all stages of the production process. As a result, they generate large volumes of liquid effluents with complex composition, characterized by high organic load, the presence of lignin, phenolic compounds, dyes, intense color, and suspended solids, many of which are difficult to degrade by conventional biological treatments. The inadequate disposal of these effluents poses a significant environmental risk, which makes it essential, from environmental, economic, and legal standpoints, to adopt technologies capable of bringing the effluent into compliance with discharge standards. In this context, electrocoagulation stands out as an electrochemical treatment alternative, in which the coagulating agent is generated within the reactor itself from the dissolution of the electrodes, eliminating the need to add chemical coagulants. This study aimed to evaluate the application of electrocoagulation in the treatment of effluent from the emergency lagoon of a pulp and paper industry, analyzing the influence of operating conditions on the efficiency of the process. To this end, the effluent was first characterized through physicochemical analyses and then subjected to treatment tests carried out in stages, in which electrolysis time, initial pH, conductivity adjustment by the addition of sodium chloride, and electrode material, using aluminum and iron electrodes, were evaluated. In each test, the removal of COD, BOD, solids, turbidity, and color, as well as the variation in conductivity and pH, was monitored. The best results were obtained with aluminum electrodes, in an acidic medium, with conductivity adjustment and 5 hours of electrolysis, a condition in which COD removal of up to 79.9%, BOD reduction of 62.0%, and color removal of 99.3% were achieved, along with a significant reduction in turbidity. It was observed that contaminant removal occurred predominantly through electroflotation, with the generation of scum and sludge, whose proper disposal must be considered, although the residue has reuse potential. It is concluded that electrocoagulation is efficient in treating this type of effluent, especially in removing color and organic matter, proving to be a promising alternative to complement conventional methods and to contribute to compliance with current environmental legislation and to reducing the impacts generated by the sector.