Lagoas de polimento: influência do regime de operação, tempo de permanência e profundidade.

Abstract

Polishing Lagoons (LP) are post-treatment units treated with effluents previously treated anaerobically. As LP depends on some factors so that it can perform well, such as the hydrodynamic regime to be operated (continuous flow or sequential batches), the depth and the residence time. In this sense, this work had as objective to reach the objective of the LP hydraulic regime, regarding the removal of organic matter, thermotolerant coliforms (CTT), ammonia and phosphate from UASB reactor effluents. In addition, an interference of dwell times and depth in the performance of LP systems in series was evaluated. The LP were applied in the post-treatment of the effluent from a UASB reactor, which treated municipal sewage in Campina Grande. The lagoons were operated in sequential batches (LPBS) and in continuous flow (LPFC). In the latter regime, two distinct configurations were used: unitary lagoons and series lagoons. Laboratory analyzes of the following parameters were performed: OD, pH, COD, SST, ammonia, phosphate and temperature. LPBS were monitored daily, while LPFCs were only monitored three times a week. For a comparison between the series lagoon systems composed of 0.20 and 0.40 meters deep lagoons, a statistical analysis was applied, with the aid of the Past software (2020). The harmful results that, in relation to the hydrodynamic regime, as LPBS have the better performance than LPFC, requiring a shorter residence time. However, the application of that operating regime requires additional costs for the automation of the system. As for the analysis between a single LPFC and two units in series, it is corrected that, for a good performance, about 16 days were estimated. A statistical analysis, that there was no difference between the results obtained for the depths investigated. Thus, the use of ponds with a depth of 0.40 meters becomes lower, as it allows the reduction of the pond area and presents good results in terms of total system performance.