Aplicabilidade do Activated Sludge Model No. 1 (ASM 1) para simulação do cotratamento de esgoto sanitário e lixiviado de aterro sanitário em lagoas aeradas / Activated Sludge Model No. 1 (ASM1) applicability for simulation of sanitary sewage and landfill leachate co-treatment in aerated lagoons

RESUMO A necessidade crescente de alternativas para o tratamento e a disposição de lixiviados de aterros sanitários é uma realidade no Brasil, principalmente com os avanços estabelecidos pela Política Nacional de Resíduos Sólidos a partir de 2010 e consequentes metas de substituição de lixões por aterros sanitários. Uma alternativa empregada, devido à facilidade de implantação, é o cotratamento com esgoto sanitário, por meio do recebimento do lixiviado em estações de tratamento de esgoto (ETE). Este estudo avaliou a aplicabilidade do Activated Sludge Model No. 1 (ASM1) para lagoas aeradas promovendo o cotratamento de esgoto e lixiviado. Os cenários simulados consistiram em proporções crescentes de adição de lixiviado ao sistema - que variaram de 0 a 10% - e, para cada um deles, foi avaliado o desenvolvimento de biomassa heterotrófica e autotrófica, o consumo de demanda química de oxigênio (DQO) em diferentes frações, a nitrificação, o consumo de oxigênio e a alcalinidade. Os resultados das simulações geradas indicaram que o modelo foi otimista em relação ao período de partida do sistema e à adaptação das comunidades microbianas consideradas frente aos cenários progressivamente agressivos oferecidos pela maior presença de lixiviado. Porém, representou adequadamente o prejuízo à qualidade do efluente devido à matéria orgânica recalcitrante e aos problemas relacionados à manutenção da nitrificação, frente ao aumento da capacidade de aeração e da demanda de alcalinidade. O ASM1 teve boa aplicabilidade, portanto, como ferramenta para avaliar qualitativamente o comportamento de ETE ao receber lixiviado para cotratamento e corroborar os riscos associados a essa alternativa, necessitando, porém, de modificações e detalhamentos adicionais para otimização de sistemas reais.

ABSTRACT The growing necessity for alternative landfill leachate treatment and disposal is a reality in Brazil, mainly when the advancements of the National Policy on Solid Wastes (2010) established goals for replacing dumping grounds with landfills. Due to its simplicity, a usual alternative is to perform co-treatment of municipal sewage and landfill leachate in wastewater treatment plants (WWTPs). This study assessed the applicability of the Activated Sludge Model No 1 (ASM1) to aerated lagoons promoting sewage and leachate co-treating. The simulated scenarios consisted of increasing proportions of leachate addition to the system, ranging from 0 to 10%, and for each of them the development of heterotrophic and autotrophic biomass, COD consumption in different fractions, nitrification, oxygen consumption and alkalinity were evaluated. The simulation results showed that the model was optimistic regarding the treatment system startup and microbial communities adaptation when exposed to increasingly aggressive conditions due to leachate addition. However, it correctly represented the detrimental effects on effluent quality due to recalcitrant organic matter and the issues with maintaining proper nitrification regarding aeration capacity and alkalinity demands. ASM1 has good applicability, therefore, as a tool to qualitatively assess the behavior of WWTP when receiving leachate for co-treatment and corroborates the risks associated with this alternative, however, requiring further modifications and details to optimize real systems.

Aerobic removal of stigmasterol contained in kraft mill effluents

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 percent, whereas the Biological Oxygen Demand (BOD5) was around 95 percent. The removal efficiency of stigmasterol removal was 96 percent when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR.