RESUMO
Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions. The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0. The objective was to remove Cr(VI) and total Cr from the effluent, this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(VI) in a bioreactor with neodymium magnets that applied a magnetic field (intensity 85.4 mT) to the mixed culture. The removal of Cr(VI) was approximately 100.0% for the bioreactor with a magnetic field and 93.3% for the bioreactor without a magnetic field for 9 hr of recirculation of the synthetic effluent by the bioreactor. The removal of total Cr was 61.6% and 48.4%, with and without a magnetic field, respectively, for 24 hr. The desorption of Cr(VI) in the synthetic effluent was 0.05 mg/L, which is below the limit established by Brazilian legislation (0.1 mg/L) for the discharge of effluent containing Cr(VI) into bodies of water. The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture. The desorption of Cr(VI) in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.
Assuntos
Cromo/análise , Poluentes Químicos da Água/análise , Biomassa , Reatores Biológicos , Brasil , Campos MagnéticosRESUMO
In the present study, the bioremoval of Cr(VI) and the removal of total organic carbon (TOC) were achieved with a system composed by an anaerobic filter and a submerged biofilter with intermittent aeration using a mixed culture of microorganisms originating from contaminated sludge. In the aforementioned biofilters, the concentrations of chromium, carbon, and nitrogen were optimized according to response surface methodology. The initial concentration of Cr(VI) was 137.35 mg l(-1), and a bioremoval of 85.23% was attained. The optimal conditions for the removal of TOC were 4 to 8 g l(-1) of sodium acetate, >0.8 g l(-1) of ammonium chloride and 60 to 100 mg l(-1) of Cr(VI). The results revealed that ammonium chloride had the strongest effect on the TOC removal, and 120 mg l(-1) of Cr(VI) could be removed after 156 h of operation. Moreover, 100% of the Cr(VI) and the total chromium content of the aerobic reactor output were removed, and TOC removals of 80 and 87% were attained after operating the anaerobic and aerobic reactors for 130 and 142 h, respectively. The concentrations of cells in both reactors remained nearly constant over time. The residence time distribution was obtained to evaluate the flow through the bioreactors.