Aplicação de diferentes metodologias de descarte controlado para melhoria das propriedades do lodo granular aeróbio

Abstract

The stabilization of aerobic granular sludge (AGS) reactors is still a challenge as several operational strategies are not fully understood. Recent studies indicate that the sludge discharge in AGS reactors can be applied aiming stabilizing and controlling the biomass present in the reactor. The main objective of this work was to evaluate different strategies of sludge discharge in the operational characteristics of AGS reactors and in the removal efficiencies of C, N and P. In reactor R1, sludge was discharged in order to maintain the sludge age between 10 and 20 days; In R2, sludge discharge was performed to control the F/M ratio between 0.2 to 0.4 gCOD/gSS.day; In R3 a fixed weekly discharge of 10% of the system sludge was applied. The use of sludge discharge has been found to cause initial system instability and solids washout as well as decrease organic matter and nutrient removal capacity, taking about 12 days for the system to achieve operational stability. The use of selective discharge by controlling the sludge age allowed the system to have a stable operation throughout the experiment period, obtaining good removal efficiencies of organic matter, ammonia nitrogen and phosphorus and good retention of solids in the reactor. Sludge disposal based on the F/M ratio also showed promising results, with operational stability with respect to solids and good removal efficiencies. However, it was considered a less effective strategy compared to the first methodology. The fixed discharge performed during the aerobic phase did not prove to be a good methodology for sludge disposal, obtaining the lowest COD, nitrogen and phosphorus removal efficiencies, and higher operational instability such as solids loss.