Avaliação do tratamento de efluente Kraft por processos Fenton e Foto-fenton isolados ou associados a pré-tratamento em reator MBBR

Abstract

Despite its economic importance, the industries of pulp and paper should also be noted for its high potential to generate environmental impacts due mainly to the great generation of effluents containing lignin and its derivatives, organic matter, wood fibers and components of the cooking liquor. The presence of these components contributes with a high recalcitrance, COD, BOD, color, toxicity and high pH to this wastewater. The conventional wastewater treatment systems used in these industries are based typically on biological degradation processes, however, they are less effective in the presence of toxic substances and molecules are difficult to degrade. An alternative treatment that has been highlighted is the Advanced Oxidation Processes (AOP) because they have shown good results of degradation for many micropollutants and recalcitrant compounds. The AOP methods are based on in-situ generation of highly oxidizing species, especially the hydroxyl radical ( OH). However, the exclusive treatment by this route can be quite costly. This study seeks to analyze the efficiency of Fenton (Fe2+/H2O2) and photo - Fenton (UV/Fe2+/H2O2) processes applied exclusively to treat Kraft effluents or associated with a pre-treatment step performed in a moving bed biological reactor (MBBR). However, the exclusive treatment by this route can be quite costly. This study seeks to analyze the efficiency of Fenton (Fe2+/H2O2) and photo - Fenton (UV/Fe2+/H2O2) processes applied exclusively to treat Kraft effluents or associated with a pre-treatment step performed in a moving bed biological reactor (MBBR). The initial characterization of the effluents showed that the pretreated has a COD of about half of the raw, however, for other analytical parameters assessed, for example, ligninic, aromatic and phenolic compounds the pre -treated effluent showed similar values to those of raw. It was observed that with the pretreated effluent MBBR was possible to perform Fenton and the photo-Fenton process with lower concentrations of reagents and reaction times and still achieve a higher degradation compared to the raw wastewater. Regarding ligninics compounds in raw wastewater the removal by Fenton was 30% at 240 min of reaction compared to 66 % in 45 minutes by photo - Fenton . For the same parameter in the pretreated samples the removals were 80 % after 60 minutes in Fenton and 84 % after 15 minutes in the photo-Fenton . The results confirmed the negative interference of COD in the performance of AOP and the advantage of employing a biological pre-treatment step.