Resumo A indústria de celulose utiliza mais de 40 m3 de água por tonelada de celulose produzida, gerando grandes volumes de efluentes. Em geral, possui altas concentrações de matéria orgânica, cor e ecotoxicidade. Os sistemas de tratamento de efluentes mais amplamente utilizados na indústria de celulose são os biológicos, incluindo sistemas de reator de leito móvel que são eficientes na remoção de matéria orgânica biodegradável. O presente trabalho teve como objetivo avaliar a remoção de matéria orgânica, compostos fenólicos totais, cor e derivados de lignina no tratamento de efluente de celulose Kraft através do reator de leito móvel (MBBR), bem como avaliar o desenvolvimento de biofilme de meios de suporte por análise de sólidos e microscopia eletrônica de varredura. Os parâmetros avaliados durante o tratamento foram: DBO5, DQO, cor, compostos fenólicos totais, derivados de lignina e sólidos, com testes realizados em cargas orgânicas de 0,7 e 8,9 kgDQO m-3 d-1. A remoção de matéria orgânica permaneceu estável, sendo superior a 80% para DBO5 e acima de 42% para DQO. A cor e os compostos fenólicos totais foram removidos acima de 7 e 28%, respectivamente. Foi observado remoção de compostos derivados de lignina acima de 19% nas cargas avaliadas. O biofilme formado no MBBR foi observado e confere estabilidade ao sistema biológico no tratamento do efluente de celulose Kraft.

Abstract The pulp industry uses more than 40 m3 of water per ton of pulp produced, generating high effluent flows. In general, it presents high concentrations of organic matter, color and ecotoxicity. The most widely used effluent treatment systems in the pulp industry are biological, including moving bed biofilm systems that are efficient in removing biodegradable organic matter. This work evaluated the removal of organic matter, total phenolic compounds, color and lignin derivatives in the treatment of Kraft cellulose effluent using the moving bed biofilm reactor (MBBR), and also evaluated the support media biofilm development by solid analysis and scanning electron microscopy. The parameters evaluated during treatment were: BOD5, COD, color, total phenolic compounds, lignin derivatives, and solids, with tests performed on organic loads from 0.7 and 8.9 kgCOD m-3 d-1. Organic matter removal remained stable, being over 80% to BOD5 and over 42% to COD. The color and the total phenolic compounds were removed up to approximately 7 and 28%, respectively. Over 19% removal of derivatives of lignin compounds was observed in both organic load rates. In the MBBR, biofilm was confirmed and enabled this biological system to treat the cellulose effluent in a stable way.

RESUMEN La industria de celulosa genera grandes flujos de efluentes que contienen una alta demanda química de oxígeno (DQO), demanda bioquímica de oxígeno (DBO5), color y ecotoxicidad. Este estudio tuvo como objetivo evaluar el tratamiento del efluente de celulosa Kraft en lagunas aireadas con medios de soporte de esponja (APG). Fue evaluado el arreglo de los medios de soporte en carga orgánica volumétrica de 0,2 kgDQO m-3 d-1, después de esto se estudió una variación de carga de 0,2 a 1,2 kgDQO m-3 d-1. Se evaluaron los parámetros DBO5, DQO, color, derivados de lignina, compuestos fenólicos totales y ecotoxicidad en D. magna. Las remociones de DQO y DBO5 fueron de 32% y 88%, respectivamente, para los medios de soporte libres y confinados en 0,2 kgDQO m-3 d-1. No hubo remoción del color o compuestos fenólicos totales en estas condiciones. Considerando la variación de la carga orgánica volumétrica, el mejor desempeño fue para 1,2 kgDQO m-3 d-1, donde fueron eliminados 50% y 75% de la DQO y DBO5, respectivamente. La remoción del color, compuestos fenólicos totales y derivados de lignina fueron de cerca de 20%, 18% y 10%, respectivamente. La ecotoxicidad aguda se redujo a factor de toxicidad de 1 en todos los tratamientos. Comparando los sistemas de laguna aireada sin la presencia del APG, se sugiere aplicar un soporte esponjoso en carga orgánica más alta que aquellas típicas de lagunas aireadas.

ABSTRACT The pulp industry generates high effluent flows, which contain high chemical oxygen demand (COD), biochemical oxygen demand (BOD5), colour and ecotoxicity. This study aimed to evaluate the treatment of Kraft pulp effluent by aerated lagoon modified with sponge support media (APG). It was assessed the arrangement of the support media in the aerated lagoons in the organic load rate (OLR) of 0.2 kgCOD m-3 d-1, and after that, with OLR variation from 0.2 to 1.2 kgCOD m-3 d-1. The parameters evaluated were BOD5, COD, colour, lignin derivatives, total phenolic compounds and acute ecotoxicity in D. magna. COD and BOD5 removals were 32% and 88%, respectively, for free and confined support media in 0.2 kgCOD m-3 d-1. There was no colour or total phenolic compounds removal under these conditions. Considering the treatment in which there was a variation of the organic load rate, 1.2 kgCOD m-3 d-1 had the best performance. In this case, 50% and 75% of COD and BOD5 were removed, respectively. Removal of colour, total phenolic compounds and lignin derivatives were around 20%, 18% and 10%, respectively. The acute ecotoxicity was reduced to toxicity factor equal to 1 in all treatments. Comparing the aerated lagoon modified systems with those without the APG, it was suggested to apply spongy support in higher organic load rate than these typically used in aerated lagoons.

Kraft mill effluent, due to its organic matter content and acute toxicity, must be treated. A primary treatment followed by a secondary treatment is the most common system. Aerated lagoon is also considered an effective biological treatment, although this technology has some drawbacks related with operation parameters and land extension space. Moreover, the recovery efficiency for micropollutants contained in kraft mill effluent is questioned due to the anoxic zone in the system. The goal of this work is to evaluate the performance of the aerated lagoon to remove stigmasterol contained in kraft mill effluents. Kraft mill effluent was treated by an aerated lagoon (AL), which was operated with three different stigmasterol load rates (SLR = 0.2, 0.6 and 1.1 mg/L x d) and a hydraulic retention time of 1 day. The AL’s maximum Chemical Oxygen Demand (COD) removal was 65%, whereas the Biological Oxygen Demand (BOD5) was around 95%. The removal efficiency of stigmasterol removal was 96% when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR.