Análise do fluxo de massa de chumbo no tratamento esgoto sanitário em reator UASB

Abstract

The removal of organic load by anaerobic digestion in UASB reactors is a consolidated process in the sanitary sewage treatment. The operational and dimensional technical criteria of this type of reactor are well established in the literature and are widely known in environmental sanitation. However, the flow of potentially toxic metals in the process still requires further studies. The aim of this work was to evaluate the mass flow of Lead in a 830L UASB reactor, operated with affluent temperature of 36.03 °C and HRT of 12.88 hours. The reactor was fed with sewage plus Pb(NO3)2, in order to release the Pb2+ cation in solution. The operation of the pilot reactor occurred in a period of 16 weeks, divided in 4 steps: (1) preliminary operation without lead, for 4 weeks; (2) Verification of lead accumulation in the sludge (1mg Pb2+ /L affluent concentration), for 5 weeks; (3) Influence of different concentrations of lead (affluent concentration of 1mg Pb2+/L, 3mg Pb2+/L and 5mg Pb2+/L); for 3 weeks and (4) a new operation without lead addition for 6 weeks. During this period, the quality of the affluent and effluent, the characteristics of the anaerobic sludge including the accumulation of lead, as well as the volume and quality of the biogas produced were evaluated. The results point to an accumulation of Lead in the sludge reaching the concentration of lead of 1933.5 mg/kg, decreasing the lead removal capacity from 100% to 9%, including the possibility of adding lead at the effluent outlet. There was also a trend of decreasing biogas production related to the accumulation of lead in the sludge.