Avaliação do efeito de diferentes tempos de aeração em filtro biológico aerado submerso na remoção de matéria orgânica e nitrogenada

Abstract

The improper sludge disposal causes negative consequences for the environment, mainly affecting water bodies. Therefore, increasingly treatment systems with a high efficiency of removal of pollutants are required, such as, for example, Submerged Aerated Biological Filter (SABF), an aerobic reactor that requires the presence of O2, is provided mechanically with onus of energy cost. In this context, the aeration system of 6 BAF used in the post-treatment of 6 UASB-type anaerobic reactors from the effluent treatment plant of the Federal University of Lavras (ETE-UFLA) was studied. These reactors are of upward flow with support medium filled with pall rings and polypropylene grids that operate in a continuous aeration regime, which generates approximately a daily consumption of 298 kW. The objective of this study was to evaluate the operating conditions of the FBAS that provide high efficiency in the removal of organic matter and nitrogenous to lower energy demands. The investigations were carried out from the monitoring of dissolved oxygen (DO), and samples the FBAS affluent and effluent were collected to obtain data on the variables of COD, TKN, N-NH4 + NO3 -, NO2 -, pH and temperature that were analyzed according to the Standard Methods methodology, in order to verify the treatment efficiencies. Initially we studied the set of 6 FBAS arranged in series, in these were observed different concentrations of OD (p <0.05), th e 6 th reactor being the least oxygenated, with a lower OD average of 5 mg.L -¹. However, there was no significant difference (p> 0.05) in COD and NTK removal efficiencies, which presented mean values of 83 ± 7% and 69 ± 11%, respectively, and there was yet nitrate accumulation in the final effluent. From the 6 th reactor, four aeration times were tested: continuous aeration, CA (24h) and intermittent aeration, IA (12h), (6h) and cycle (2: 4h). The data showed good results for removal of COD, N-NH4 + and nitrification efficiency for both CA and IA with means above 81%, 65% and 60%, respectively, which differed significantly (p <0.05) only in IA (6h) that corresponded inefficiently to the removal of nitrogen. Among the times, the IA (12h) stands out as the most appropriate time to optimize the treatment in the FBAS, since it presented high COD removal around 92 ± 2%, and removal of the total nitrogen in 37 ± 9% due to simultaneous nitrification and denitrification (SND), can also generate energy savings of 50%.