Pós-tratamento de efluente de UASB em reator de leito empacotado com aeração intermitente em escala piloto

Abstract

Most Brazilian Wastewater Treatment Plants do not promote nitrogen removal. Conventional nitrogen removal processes use two physically separate steps for nitrification and denitrification, which increases reactor building and operating costs. Researchers have shown that some models of reactors with polyurethane foam (PU) support are efficient for the concomitant removal of Chemical Oxygen Demand (COD) and total nitrogen (TN) in a single unit. However, there is no experimental data from pilot scale reactors treating an influent combination of raw sewage with effluent from the Upflow Anaerobic Sludge Blanket Reactor (UASB). For this reason, the objective of this work was to evaluate the influence of aeration time for the post treatment of sanitary sewage in a reactor with a volume of 5.65 m3, packed bed with Biobob®, intermittent aeration and recirculation. The reactor was operated for 565 days with a Hydraulic Detention Time (TDH) of 10 hours and a recirculation flow (Qr) equal to 2 times the inlet flow. Aeration was done under three different conditions, in 180-minute cycles: continuous aeration, 120 min aerating followed by 60 min with no aeration and 60 min aerating followed by 120 min with no aeration. The influent levels of COD, TKN and N-NH4+ varied from 562 to 512 mg L-1, 55.8 to 51.0 mg L-1 and 52.1 to 45.6 mg L-1, respectively. The results of effluent COD varied from 67 to 133 mg L-1. The concentration of Total Kjeldahl Nitrogen (TKN) effluent ranged from 8.1 to 18.7 mg L-1. The effluent values of N-NO3- and N-NO2- vary from 1.5 to 0.7 mg L-1 and 0.6 to 1.0 mg L-1. After 465 days of operation with 10-hour TDH, the excess sludge was removed and characterized. Hydrodynamic tests were carried out before and after removing the sludge. It was observed a reduction in the dead volume in the pre-disposal and post-disposal conditions from 974 to 719 L, respectively. It was possible to verify that the packed bed reactor with Biobob® with intermittent aeration and recirculation is efficient for the post treatment of sanitary sewage, promoting the removal of COD and NT in a single unit.