Lagoas de transbordo aplicadas ao melhoramento de efluentes destinados a lagoas de polimento de batelada sequencial.

Abstract

Recent research shows that the combination of a UASB reactor + a polishing pond in a sequential batch regime (LPBS) for sewage treatment produces a much better effluent quality than a conventional stabilization pond system in a smaller area. To operate the polishing pond with sequential batches, it may be convenient to have an overflow pond that receives effluent from the UASB reactor with continuous flow and feeds the batch polishing ponds, as these can facilitate the operation of the system, as well as improve the quality of the system effluent. In the present work, three transhipment lagoons were operated on a pilot scale, with different depths and in residence times between 1.5 and 3 days, analyzing their performance in terms of physical-chemical parameters. The removal efficiency of the evaluated variables varied according to depth and HRT. The COD removal ranged from 51% to 14%, decreasing from the highest HRT to the lowest. For solids optimal removals were observed, with similar final concentrations in relation to TDH. As for helminth eggs, good removal efficiencies were also found, with more than 90% for all ponds and HRT analyzed. For chlorophyll the highest concentrations were observed in the LT1 lagoon between 160 to 322 µg / L. Similarly, the sulfide removal efficiency was higher in the LT1 lagoon, with performances ranging from 64% to 95%, the other lagoons (LT2 and LT3) had partial removal between 23% to 60%. The OD concentrations, although low, were also higher in the LT1 lagoon (between 1 and 0.4 mg / L). Finally, the CO2 concentrations demonstrated efficient desorption, between 40% to 80% removal, causing a reduction in acidity and consequently decreasing the time to increase the pH in the subsequent polishing pond. It’s concluded, therefore, that the lagoons, in addition to functioning as an equalization tank, perform other tasks efficiently. In which, it is emphasized that the most important task observed was the retention of the sludge particles discharged from the UASB together with its effluent. As well as it can be proved that the overflow ponds can be considered a good treatment alternative in order to better effluents destined for polishing ponds.