Evaluation of the anaerobic biodegradability of sewage sludge stabilized by anaerobic reactors / Avaliação da biodegradabilidade anaerobia de lodos de esgoto provenientes de reatores anaerobios sequenciais

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The potential of applicability of an anaerobic process can be evaluated from the knowledge of some characteristics of the residues to be treated. A preliminary evaluation of these characteristics can assist in the choice of a more suitable treatment system, what allows to estimate the production of biological solids, requirements for nutrients, methane production, etc. The characterization of the residues, through biodegradability tests, is of fundamental importance, once that the residues present a great variability for the quality, amount, Chemical Oxygen Demand (COD) and the presence of refractory organics. There are other important characteristics for the anaerobic treatment of sewage sludge, like pH, alkalinity, inorganic nutrients, temperature and the presence or not of very toxic compounds. During this work, a methodology for the evaluation of the anaerobic biodegradability of sewage sludge, stabilized by anaerobic reactors was developed using simplified bench tests, aiming to know more about the kinetics of biodegradation of sludge. With the intention to add complementary information about the studied sludge, it was also achieved the morphologic identification of the different groups of microorganisms that are responsible for the anaerobic digestion process. The developed methodology considers the determination of the ?intrinsic anaerobic biodegradability? of sewage sludge through the monitoring of the production and of the composition of biogas (concentrations of CH4 and CO2). The tests had been carried out in bottles of 280mL filled with 50% of its volume with sludge and water ratios to guarantee a volatile solids concentration about 10mg.L-1; the other 50% constituted the ?headspace? that, after the bottles had been hinted, were filled with N2. The assays had been carried through in a shaker (150rpm), under controlled temperature (35°C) and had the duration of 15 days, monitoring the pressure inside the flask and the composition of the biogas in every 2 days. The evaluation of the ?intrinsic anaerobic biodegradability? of the sludge was quantified through the determination of the maximum specific tax of production of CH4 (KCH4) and of the maximum specific rate of CO2 production (KCO2), which represent the intrinsic biodegradability coefficients? and had been achieved through the application of mathematical models adjusted to the profiles of molar concentration of CH4 and CO2 in function of the time. The results obtained in the biodegradability tests had reflected, in a general way, the behavior of the sequential anaerobic reactors (System B) operated in real scale with HDTs (Hydraulic Detention Time) of 30, 20 and 10 days, indicating that the developed methodology allowed to estimate the ?intrinsic biodegradability coefficients? of sewage sludge through simplified bench tests with good reproducibility

ASSUNTO(S)

anaerobic digestion waste water biodegradação biodegradation microbiology sewage sludge lodo de esgoto digestão anaerobica aguas residuais - microbiologia

ACESSO AO ARTIGO

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