Remoção simultânea de matéria orgânica e nitrogênio em sistema combinado de MBBR de alta carga e biofiltro

Abstract

The present study aimed to evaluate the removal of organic matter and nitrogen from a synthetic wastewater, simulating domestic sewage, in biological systems combining the moving bed biofilm reactor (MBBR) and trickling filters, subjected to high organic and nitrogen loads. Under these conditions, the maximum load that allowed complete removal of the soluble components of the synthetic wastewater in the MBBR was determined, leaving the particulate material (generated solids) to be removed in the biofilters. For this purpose, two systems, operated in parallel, were evaluated, and the difference between them was only the support used in the biofilter (Kaldnes K3 in one and Aqua Porous Gel (APG) in the other). The load variation was obtained by decreasing the hydraulic retention time (HRT), which varied from 3 to 1.5 h. In general, the MBBRs showed high efficiency of removal of organic matter, evaluated in terms of soluble chemical demand for oxygen (COD) (above 90%) and total nitrogen (above 85%), under volumetric organic loads (VOC) of 4.8 and 7.2 kgDQO.m-3 .d-1 , respectively. When higher loads were applied (notably 8.3 and 9.6 kgDQO.m-3 .d-1 ), total nitrogen removal decreased to around 60% in MBBRs due to the reduction in nitrification efficiency. Although the MBBRs were subjected to high concentrations of dissolved oxygen, simultaneous nitrification and denitrification was observed in all operating conditions, leading to the reduction of nitrate/nitrite generated by nitrification. The filter filled with APG support showed better retention of particulate solids throughout the experiment, which ranged from 76 to 100%.