RESUMO
Biofiltration consists of a filter-bed of organic matter serving both as carrier for the active biomass and as nutrient supply, through which the polluted gas passes. The selection of a suitable medium material is of major importance to ensure optimum biofilter efficiency. Peanut shells are an agricultural byproduct locally available in large quantities at a low price in most tropical and sub-tropical countries. A previous study showed that peanut shells are physically and chemically suitable for biofiltration. This paper presents the results obtained during a six month biofiltration experiment using peanut shells as medium and methanol as air pollutant. It is shown that peanut shells are potentially suitable as biofiltration medium, since degradation rates of up to 30 kg MeOH/m(3)d with an empty bed residence time of 19s was obtained. The biofilter showed a good resistance to shock load and no operational problems were observed.
Assuntos
Arachis/química , Metanol/química , Metanol/isolamento & purificação , Nozes/química , Ultrafiltração/métodos , AbsorçãoRESUMO
We studied Cr fractionation in three semi-arid soils (cultivated, under-the-canopy, and outside-the-canopy soils). The soils were amended with: Cr3+, Cr6+, tannery sludge, Cr3++tannery sludge, and Cr6++tannery sludge and all soils were incubated for 30 and 120 days at 25 degrees C. The Cr in three semi-arid soils was fractionated using sequential extraction (Tessier scheme). Data of Cr fractionation were used to find the correlations with microbial activities determined in previous work. The microbial activities: CO2-C evolved, dehydrogenase activity and nitrification were determined in the same soils amended with the same treatments. Tannery sludge was added at 0.0125 g g(-1) soil and Cr3+ or Cr6+ at 250 microg g(-1) soils. After 120 days of incubation, higher values of concentration of Cr were found in the residual fraction in the three soils amended with all the treatments, except cultivated and outside-the-canopy soils amended with Cr6++tannery. The non-residual fraction tended to decrease with time except in cultivated and outside-the-canopy soils amended with Cr6++tannery sludge. CO2-C evolved was significantly correlated (p<0.05 and p<0.001) with fractions bound to: Mn oxides, Fe oxides organic matter at 30 and 120 days of incubation (from r=0.827 to 0.979). Dehydrogenase activity was correlated with fractions bound to Fe oxides and bound to organic matter, and nitrification with fraction bound to organic matter at 30 days of incubation (r=0.874, 0.959, and 0.803, respectively). These results suggest that even in a sparingly available Cr fraction in semi-arid soils has effect on microbial activities.
Assuntos
Cromo/análise , Resíduos Industriais , Microbiologia do Solo , Poluentes do Solo/análise , Curtume , Dióxido de Carbono/metabolismo , Nitratos/metabolismo , Oxirredutases/metabolismo , Esgotos , SoloRESUMO
Biofiltration is the most commonly used biological gas treatment technology and is extensively used for the treatment of polluted air with gas flow rates of up to 2 x 10(5) m(3)/h. It involves a filter bed of organic matter serving both as carrier for microorganisms and as nutrient supplier. Polluted gas passes through the filter bed and is cleaned by biological activity. Biofiltration is not being developed in Latin America as in the USA, Canada or Europe; the main reason probably being the absence of specific technology and of potential organic carriers locally available. Five different agriculture by-products available in Latin America: peanut shells, rice husk, coconut shells, cane bagasse and maize stubble, were chemically, physically and structurally characterized for their potential use as biofilter carrier. It was found that peanut shells could be used as biofilter carrier and therefore would have potential biological application.