This study has investigated the biological nitrogen removal by simultaneous nitrification and denitrification (SND) processes in a system of continuous flow activated sludge (AS) process. The investigation had four stages and evaluated the system behavior under different solid retention times (SRT), food-to-mass (F/M) ratios and dissolved oxygen (DO) concentrations. The data showed that the concentration of DO 0.5±0.2 mgO/L did not affect the growth of heterotrophic bacteria (2.2-3.1 d at 20°C) and autotrophic nitrifying bacteria (0.16-1.94 d at 20°C), resulting in values very close to those obtained in conventional AS processes. The chemical oxygen demand (COD) removal was over 90% in all stages. The decrease in SRT from 37.2 to 27.8, 19.0 and 10.0 days had no significant influence on the development of SND. In the stage where the carbon/nitrogen (C/N) ratio was 4.3 mgCOD/mgN  L, SND efficiency was of 55%. In the following stages, the C/N ratio was increased and it was possible to achieve efficiencies higher than 98% SND. Overall, the data showed that appropriate controls of carbon and nitrogen input are required to achieve an efficient SND. An established SND technology can save operation time and energy, and might replace the traditional two stages: biological nitrification and denitrification process.

-A laboratory scale activated sludge sequencing batch reactor was operated in order to obtain total removal of influent ammonia (200; 300 and 500 mg NH 3 -N.L -1 ) with sustained nitrite accumulation at the end of the aerobic stages with phenol (1,000 mg C 6 H 5 OH.L -1 ) as the carbon source for denitrifying microorganisms during the anoxic stages. Ammonia removal above 95% and ratios of (NO

O presente artigo objetivou avaliar a aplicação da operação de stripping como pré-tratamento de um lixiviado de aterro sanitário visando à redução da carga de amônia afluente a um sistema biológico de tratamento, bem como, a utilização do processo de coagulação-floculação-sedimentação para a remoção da matéria orgânica recalcitrante de um lixiviado de aterro pré-tratado em um sistema de lodo ativado. As taxas de remoção de nitrogênio amoniacal variaram entre 3,5 e 3,6 mg N-NH3.L-1.h-1 para o sistema de stripping composto por um reator submetido à agitação mecânica e entre 3,2 e 3,3 mg N-NH3.L-1.h-1 para o reator submetido à aeração com bolhas grossas. Quanto ao pós-tratamento, os resultados obtidos indicaram que são requeridas dosagens acima de 400 mg Fe+3.L-1 e 400 mg Al+3.L-1, para a obtenção de eficiências de remoção de matéria orgânica recalcitrante superiores a 90%.

No abstract