Reator anaeróbio-aeróbio de leito fixo aplicado ao tratamento de esgoto doméstico utilizando conchas de sururu como material suporte principal

Abstract

This work evaluated the performance of an upflow and fixed bed aerobic-anaerobic reactor (RAALF), continuously operated, on a bench scale, filled with expanded clay and sururu shells as a support material for biomass immobilization, used for domestic sewage treatment. The use of the sururu shell as the main supporting material was due to the importance of testing reactor performance using low cost and easily available material. Furthermore, Oliveira Netto (2007) obtained good results in removal of organic matter and nitrogen having the polyurethane foam as main support material while operating a reactor with similar configuration. In a first step, the performance of the combined system was evaluated without recirculation of the liquid phase in total hydraulic detention time (TDH) near 11 hours, being 8 hours for the anaerobic phase and approximately 3 hours for the aerobic phase, where the efficiency of removal of organic matter and nitrification were, respectively, 75% and 100%. The nitrification occurred after the 11th operational day of the combined system and was stable at the end of this stage. Even with complete nitrification, there was no limitation of inorganic carbon, demonstrating that the support material fulfilled the role of expected buffer effect, without the need for alkalinity supplementation. In the second stage of operation, with the recirculation of the treated effluent inserted in a recirculation ratio of 1.5, gains were obtained in relation to the removal of organic matter, with an average efficiency of 85%, however, the total nitrogen removal observed was order of 36%, indicating denitrification impairment. The reactor showed an effective response to nitrification when compared to polyurethane foam, with the sururu shells allowing the maintenance of alkalinity in the substrate. However, the sururu shells may also not have contributed to the denitrification, since the increase in pH of the effluent may have reduced the speed of the process. Another factor that may also have impaired the nitrogen removal process was the excess aeration in the system. The hydrodynamic test performed in the RAALF showed behavior tending to the complete mixing and showed deviations of ideality as dead zones and long tail effect, indicating that the support material may have influenced the hydrodynamics of the reactor. The results showed that the reactor provided an effluent with reduced organic matter and that the sururu shell favored the conversion of nitrogen, proving the feasibility of using the material as main support in a combined fixed bed reactor applied to the domestic sewage treatment.