Microbial interactions and nitrogen removal performance in an intermittently rotating biological contactor treating mature landfill leachate.

Developing efficient landfill leachate treatment is still necessary to reduce environmental risks. However, nitrogen removal in biological treatment systems is often poor or costly. Studying biofilms in anoxic/aerobic zones of rotating biological contactors (RBC) can elucidate how microbial interactions confer resistance to shock loads and toxic substances in leachate treatment. This study assessed the nitritation-anammox performance in an intermittent-rotating bench-scale RBC treating mature leachate (diluted). Despite the leachate toxicity, the system achieved nitritation with an efficiency of up to 34 % under DO values between 0.8 and 1.8 mg.L-1. The highest average ammoniacal nitrogen removal was 45.3 % with 10 h of HRT. The 16S rRNA sequencing confirmed the presence of Nitrosonomas, Aquamicrobium, Gemmata, and Plantomyces. The coexistence of these bacteria corroborated the selective pressure exerted by leachate in the community structure. The microbial interactions found here highlight the potential application of RBC to remove nitrogen in landfill leachate treatment.

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.

Fast start-up of the single-stage nitrogen removal using anammox and partial nitritation (SNAP) from conventional activated sludge in a membrane-aerated biofilm reactor.

The single-stage nitrogen removal using anammox and partial nitritation (SNAP) is a promising alternative for low-cost ammonium removal from wastewaters. This study aimed to evaluate the anammox biomass enrichment and SNAP process start-up in a laboratory-scale membrane-aerated biofilm reactor (MABR) at nitrogen loading rates of 50 g N.m-3.d-1 (period 1) and 100 g N.m-3.d-1 (period 2). Anammox activity was observed after 48 days, and the SNAP process was stable after 80 days. In period 1, the average total nitrogen (TN) removal was 78 ±â€¯6%, and the maximum removal was 84%. In period 2, the average TN removal was 61 ±â€¯5%, and the maximum was 69%. Higher dissolved oxygen levels may have caused imbalances in the microbial community in period 2, decreasing the reactor performance. These results demonstrated the potential of the MABR for the fast implementation of the single-stage partial nitritation and anammox processes.