Avaliação do processo de tratamento biológico de águas residuárias sanitária e industrial em sistema combinado com reator biológico de contato seguido de filtro aerado submerso

Abstract

This study presents the operational results of a pilot wastewater treatment plant. The assays were carried out in two phases: Phase 1 involved the operation of a rotating biological contactor (RBC), while Phase 2 involved a combined system operation of a submerged aerated biofilter (SAB) downstream from the RBC. The RBC and SAB units were assayed in the treatment of sanitary sewage. The average feeding rate was 82.9 L.h-1 and the active sludge recirculation rate when operated only with the RBC was 60% of the former. Despite being a rotating reactor, the RBC under investigation did not have biodiscs because it was used as a microbial bed, consisting of corrugated high-density polyethylene (HDPE) tubes fixed on a metal structure in the shape of a rotating reel submerged in the aeration cell at about 90% of its diameter, providing subtracting contact between tubes a 41-m2 surface area for biofilm fixation. On the other hand, the SAB, which was comprised of corrugated HDPE rings that provided a 55-m2 contact area, was employed to polish the RBC effluent only in Phase 2 when sludge recycling was interrupted at the beginning of the process. This operation, which is typical of activated sludge systems, was carried out in Phase 1 (211 days). Substrate characterization showed maximum chemical oxygen demand (COD) concentrations of 3820.8 mgL-1 (average of 1004.5 mgL-1), an indication of contamination by liquid industrial effluents. In the first stage of testing (with the RBC), the treated effluent after secondary sedimentation tank were achieved in this study, biochemical oxygen demand (BOD) removal averages of 71.3% and the COD removals of 79.6%, respectively. Among the forms of nitrogen analysis, the concentration of organic nitrogen showed the greatest reductions reaching an average maximum of 51.2% and 91.5%. In the second stage of tests (RBC followed by SAB) efficiency BOD removal achieved was 78.2%, while the COD efficiency removal was 71.6%. The removal of volatile suspended solids after BAS achieved 39.2%, whereas RBC achieved volatile suspended solids removal of 65.3%. The pilot plant also showed that the concentration of SAB in the downstream of RBC minimized the variations in concentrations of all measured parameters, related to partially or fully treated wastewater, bringing benefits not linked to removal of carbonaceous organic matter.