Caracteriza??o de produtos microbianos sol?veis (SMPs) em reatores aer?bio e anaer?bio de bancada em diferentes condi??es operacionais.

O tratamento biol?gico ? caracterizado pela utiliza??o de bact?rias, aer?bias e/ou anaer?bias, para a degrada??o da mat?ria org?nica poluente. A an?lise da demanda qu?mica de oxig?nio (DQO) ? frequentemente utilizada para quantificar a mat?ria org?nica nos efluentes e medir a efici?ncia do tratamento biol?gico. A DQO efluente de reatores biol?gicos ? compreendida n?o apenas por compostos afluentes que n?o foram degradados, mas tamb?m por compostos produzidos pelos microrganismos durante o tratamento, denominados na literatura internacional de SMPs (Soluble Microbial Products). Acreditase que a minimiza??o da DQO residual de sistemas biol?gicos operados na aus?ncia de estresse e alimentados com esgoto tipicamente biodegrad?vel pode estar diretamente relacionada ? minimiza??o da produ??o de SMPs e, muito embora a import?ncia dos SMPs j? tenha sido reconhecida, a revis?o da literatura mostra que poucas pesquisas tentaram identificar sua estrutura qu?mica bem como relacionar sua produ??o a par?metros de opera??o dos reatores. Portanto, o principal objetivo desta pesquisa foi caracterizar, do ponto de vista quantitativo e qualitativo, os compostos microbianos presentes na fra??o centrifugada do efluente de reatores aer?bio e anaer?bio de mistura completa operados em escala de bancada e alimentados com glicose e acetato. Conforme esperado, a produ??o de SMPs no reator aer?bio foi superior ? do anaer?bio (a produ??o normalizada em rela??o ? DQO afluente para as diferentes condi??es operacionais ? SMP/So - variou de 2 a 68% no reator aer?bio e de 9 a 27% no reator anaer?bio). No reator anaer?bio, a carga org?nica aplicada n?o apresentou interfer?ncia significativa na convers?o da DQO afluente a SMPs sugerindo que os SMPs acumulados podem ter origem principal no decaimento da biomassa ao inv?s da utiliza??o do substrato. J? no reator aer?bio parece ter ocorrido o contr?rio. Considerando o tipo de substrato, a utiliza??o de acetato contribuiu para uma maior produ??o normalizada de SMPs em ambos os reatores, comparativamente ? glicose (no reator aer?bio, SMP/So de 41,9% para o acetato versus 14,1% para a glicose; no reator anaer?bio, 21,9% e 16,6% para o uso de acetato e de glicose, respectivamente). J? a temperatura parece n?o ter interferido significativamente na rela??o SMP/So no reator anaer?bio (18,1% a 15oC e 18,3% a 25oC). Por outro lado, no reator aer?bio, a produ??o normalizada de SMPs foi superior ? temperatura de 15oC (33,8% contra 18,7% a 25oC). No reator aer?bio, a DQO relacionada ao teor de prote?nas representou de 5 a 34% da DQO residual e o teor de carboidratos (tamb?m em termos de DQO) n?o ultrapassou 16%; j? para o reator anaer?bio, o teor de prote?nas atingiu seu m?ximo em 17% da DQO residual, o que confirma que a maior parte da DQO residual n?o foi proveniente de prote?nas e carboidratos. Em rela??o aos resultados de espectrometria de massas, os SMPs produzidos em cada fase operacional n?o pareceram provenientes de lise celular ou de EPS. A ocorr?ncia predominante de SMPs de baixas massas molares indicou produtos associados ? utiliza??o do substrato ou provenientes da degrada??o e/ou hidr?lise de SMPs de alta massa molar.Biological wastewater treatment is characterized by aerobic and/or anaerobic bacteria that degrade pollutant organic matter and parameters such as chemical oxygen demand (COD) are usually used to assess these treatments efficiency. Biological reactors effluent COD is comprised not only of influent compounds that have not been degraded, but also of some compounds produced by microorganisms during treatment, known as SMPs (Soluble Microbial Products) in the literature. It is believed that the decrease of effluent COD in non-stressed conditions biological systems fed with typically biodegradable sewage can be straightly connected to minimizing SMP production and, even though SMP importance had already been recognized, literature review shows that only few researches were dedicated to identifying their chemical structure, as well as to relating their production to reactors operational parameters. Therefore, the main goal of this research was to characterize, through quantitative and qualitative approaches, the microbial products present in the supernatant of aerobic and anaerobic bench scale CSTR fed with glucose and acetate. As expected, SMP production in the aerobic CSTR was higher than in the anaerobic one (normalized production of SMP concerning influent COD in different operational conditions ? SMP/So ? varied from 2 to 68% in the aerobic reactor and from 9 to 27% in the anaerobic reactor). In the anaerobic CSTR, the organic load did not seem to have interfered to the conversion from influent COD to SMP (SMP/So ratio), what suggests that accumulated SMP can have come mainly from biomass decay, rather than from substrate use. However, in the aerobic CSTR the opposite seems to have happened. Concerning substrate kind, acetate use contributed to a higher normalized production of SMP in both reactors, compared to glucose (in the aerobic reactor, SMP/So was 41,9% for acetate versus 14,1% for glucose; in the anaerobic reactor, 21,9% and 16,6% for acetate and glucose, respectively). Temperature did not seem to have significantly interfered to SMP/So rate in the anaerobic reactor (18,1% at 15oC and 18,3% at 25oC). On the other hand, in the aerobic CSTR, normalized SMP production was higher at 15oC (33,8% against 18,7% at 25oC). In the aerobic reactor, COD related to protein amount represented 5 to 34% of effluent COD and carbohydrates COD was not higher than 16%; in the anaerobic CSTR, protein amount achieved its maximum at 17% of effluent COD, what confirms that the majority of effluent COD had not come from proteins and carbohydrates. As far as mass spectrometry results are concerned, SMP produced by each operational phase did not seem to have come from cell lysis or EPS. The predominance of low molecular weight SMP indicated products related to substrate use or to degrading/ hydrolysis of high molecular weight SMP