Pós-tratamento de esgoto sanitário de reator anaeróbio de manta de lodo: por processos de coagulação/floculação/sedimentação e por filtração biológica aeróbia

Abstract

The aim of this study was to investigate two different types of post-treatment for sanitary sewage from anaerobic sludge blanket reactors (UASB), by coagulation/flocculation/sedimentation processes and by aerobic biological filtration. For the coagulation/flocculation/sedimentation process, tannin-based coagulants (APS5T, AP Plus and AP C1) and polyaluminium chloride (PAC) were evaluated at concentrations of 15 and 30 mg/L. Jar tests were performed using a speed of 120 rpm and a time of 1 minute for rapid mixing and 40 rpm and 15 minutes for slow mixing with sedimentation times of 45, 60 and 90 minutes. The tannin-based coagulants were superior to PAC for the removal of chemical oxygen demand (COD), turbidity and total solids (ST). For total phosphorus removal, the PAC was superior to the others and for the removal of ammonia nitrogen (N-NH4+) none of the coagulants had satisfactory performance, being above 20 mg/L. However, tannin-based coagulants were promising and competitive with PAC for post-treatment of anaerobic sludge blanket reactors. Biological filtration was monitored in full scale in order to investigate the efficiency of the system for the removal of carbonaceous organic matter, solids and nitrogen. The best removal results were 87 % for COD, 91 % for BOD and 100 % for sedimentable solids, with mean effluent concentrations of 48 mg/L, 22 mg/L and 0 mL/L, respectively. However, nitrogen removal in the system was discrete.