Desempenho do biorreator anaeróbio de membrana dinâmica no tratamento de águas residuárias domésticas

Abstract

The activities that generate economic and social development have substantially increased the demand for drinking water, consequently increasing the volume of wastewater, which imposes the need to know, develop and adapt sewage treatment technologies. Therefore, the present study aimed to investigate the performance of the filtration process and the fouling mechanism present in an anaerobic dynamic membrane bioreactor (AnDMBR), on a pilot scale, treating domestic sewage from a vertical housing development. The dynamic membrane (DM) was developed on a polypropylene support material, with an average pore size of 90 µm and located in a module external to the bioreactor. The performance of the process was investigated using three different initial permeate flows (780, 1170 and 1755 L m^-2 h^-1), which were called phases I, II and III, respectively. Phase I was operated without backwashing (Cycle 1) and with backwashing (Cycle 2) on the membrane module after a 10% reduction in the permeate flow, while phases II and III were operated with backwashing. The hydraulic retention time (HRT) and the cell retention time (CRT) for Phase I were 18 h and 140 days, for Phase II they were 8 h and 84 days, and for Phase III they were 12 h and 76 days, respectively. To minimize energy costs, the AnDMBR system was operated under hydraulic pressure. The results showed that Phases I and III did not differ from each other, with higher performances in the average removal of total COD of 87 ± 1.4% and 86.4 ± 0.8%, true color of 73.1 ± 7.3% and 66.3 ± 10.3%, and mean TSS concentration in the effluent of 56.5 ± 20.6 mg L^-1 and 52.2 ± 17.8 mg L^-1, respectively. While Phase II differed from the others, I have had an inferior performance in the average removal of total COD of 78.6 ± 1.9%, soluble COD of 59.6 ± 3.8%, true color of 47.8 ± 9, 7%, and mean TSS concentration in the effluent of 89.1 ± 10.5 mg L^-1. However, although there is a difference between the phases, in general the system performed well in all monitored phases, achieving total COD removal of 84%, soluble COD of 69% and true color of 68%, being able to remove 94% suspended solids and produce an effluent with low turbidity (17 NTU), complying with the WHO recommendations regarding helminth eggs for irrigation of class B crops such as cereals, industrial crops, forage crops, pastures and trees. The predominant fouling mechanism in the formation of DM in all phases was cake filtration, the main cause of which was the high concentration of the inoculum sludge. This fact confirms the prominence of the formation of DM during filtration and the high solid-liquid separate.