Biomedical subjects

R Auria

Publications and source records attributed to R Auria.

10 recordsLinked to original sources

PubMed2003

Effects of packing material on the biofiltration of benzene, toluene and xylene vapours.

Biofiltration was used to eliminate volatile organic compounds from air streams in bench-scale reactors inoculated with an adapted consortium. Organic and inert supports were tested on 100 days of operation. The supports were: peat, vermiculite, a mixture of vermiculite and activated carbon, tree bark and, porous glass Rashig rings. A mixture of benzene, toluene and xylene vapors with a load of 200 gC m(-3) h(-1) was fed to the biofilters with an empty bed residence time of 60 s. Removal efficiencies higher than 95% were obtained with the mixture of vermiculite and activated carbon, 85% for peat and bark, 80% for vermiculite and 65% for the Rashig rings. In all cases, drying problems in beds were observed after several days of operation. Water addition with or without nutrients was required to maintain and increase the performance of biofilters. In steady state operation, experiments at loads ranging from 50 to 400 gC m(-3) h(-1) were carried out and a maximum elimination capacity of 260 gC m(-3) h(-1) was obtained for vermiculite-activated carbon support. The three xylene isomers were degraded. Observations of the supports surface by scanning electronic microscopy at the end of the biofiltration experiment showed abundant growth of fungi, which were not in the inoculum, had colonized the biofilter.

Air Pollution↗

PubMed2002

Biofiltration of volatile ethanol using sugar cane bagasse inoculated with Candida utilis.

Candida utilis (C. utilis) growing on sugar cane bagasse complemented with a mineral salt solution was studied for gaseous ethanol removal in a biofilter. Ethanol loads from 93.7 to 511.9 g/h m(3) were used, by varying both inlet ethanol concentration (9.72 to 52.4 g/m(3)) and air flow rate (1.59 x 10(-3) to 2.86 x 10(-3) m(3)/h). At a loading rate of 93.7 g/h m(3), a steady-state was maintained for 300 h. Ethanol removal was complete, and 76.3% of the carbon consumed was found in carbon dioxide. At an higher aeration rate (ethanol load=153.8 g/h m(3)), the biofilter displayed an average removal efficiency (RE) of 70%, and an elimination capacity (EC) of 107.7 g/h m(3). Only 64.4% of the carbon consumed was used for CO(2) production. Acetaldehyde and ethyl acetate in the outlet gas attained 7.86 and 20.4% in terms of carbon balance, respectively. In both cases, the transient phase was less than one day. At a high inlet ethanol concentration (52.4 g/m(3)), no steady-state was observed and the process stopped during the third day. In the three cases, final biomass was poor, ranging from 10.5 to 14.8 mg/g dm. Final pH 4.0-4.6, indicated that acidifying non-volatile metabolites, such as acetate, accumulated in the reactor.

Agriculture↗

PubMed2001

Toluene biofiltration by the fungus Scedosporium apiospermum TB1.

The performance of biofilters inoculated with the fungus Scedosporium apiospermum was evaluated. This fungus was isolated from a biofilter which operated with toluene for more than 6 months. The experiments were performed in a 2.9 L reactor packed with vermiculite or with vermiculite-granular activated carbon as packing material. The initial moisture content of the support and the inlet concentration of toluene were 70% and 6 g/m3, respectively. As the pressure drop increased from 5-40 mm H2O a strong initial growth was observed. Stable operation was maintained for 20 days with a moisture content of 55% and a biomass of 33 mg biomass/g dry support. These conditions were achieved with intermittent addition of culture medium, which permitted a stable elimination capacity (EC) of 100 g/m3(reactor)h without clogging. Pressure drop across the bed and CO2 production were related to toluene elimination. Measurement of toluene, at different levels of the biofilter, showed that the system attained higher local EC (200 g/m3(r)h) at the reactor outlet. These conditions were related to local humidity conditions. When the mineral medium was added periodically before the EC decreases, EC of approximately 258 g/m3(r)h were maintained with removal efficiencies of 98%. Under these conditions the average moisture content was 60% and 41 mg biomass/g dry support was produced. No sporulation was observed. Evaluation of bacterial content and activities showed that the toluene elimination was only due to S. apiospermum catabolism.

Biomass↗

PubMed2000

Influence of mixing and water addition on the removal rate of toluene vapors in a biofilter.

The effects of successive mixing (homogenization) of packing material (peat), with or without water addition, on the removal of toluene vapors in a biofilter were studied. Over a period of 50 days, an increase in the Elimination Capacity (EC) of approximately 240% was obtained by successive mixing and water additions. After each mixing, a high EC of toluene was maintained only for a short period of 3-4 days. After this time, decreased biofilter performance was observed, probably associated with the development of dried and/or clogged zones. In the long-term experiments, an attenuation of the EC recovery was observed after successive mixing. In this case, an increase of 110% over 4 months of experiment was obtained. The global reduction of EC over time could be explained by the colonization of the biofilter by filamentous fungi which was facilitated by the mixing of the packing material. The most frequently observed fungi were identified as Scedosporium sp. and Cladosporium sp.

Air Pollution↗

PubMed1999

Microbiological and kinetic aspects of a biofilter for the removal of toluene from waste gases

Microbiological and kinetic aspects of a biofilter inoculated with a consortium of five bacteria and two yeast adapted to remove toluene vapors were investigated. Initially the toluene sorption isotherm on peat and the effect of different environmental conditions on the toluene consumption rates of this consortium were measured. The fast start-up of the biofilter and the decay in the elimination capacity (EC) were reproduced using microcosm assays with toluene successive additions. Nutrient limitation and a large degree of heterogeneity were also detected. EC values, extrapolated from microcosms, were higher than biofilter EC when it was operating close to 100% efficiency but tended to relate better as the biofilter EC diminished. In studies on the microbial evolution in the biofilter, an increase in the cell count and variation in the ecology of the consortium were noted. Bacterial counts up to 10 x 10(11) cfu/gdry peat were found in 88 days, which corresponds to about a 10(4) increase from inoculum. Observations with SEM showed a nonuniform biofilm development on the support and the presence of an extracellular material. The results obtained in this work demonstrated that activity measurement in microcosms concomitant to the biofilter operation could be an important tool for understanding, predicting and improving the biofiltration performance. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1999

Cometabolic biodegradation of methyl t-butyl ether by Pseudomonas aeruginosa grown on pentane.

A bacterial strain identified as Pseudomonas aeruginosa was isolated from a soil consortium able to mineralize pentane. P. aeruginosa could metabolize methyl t-butyl ether (MTBE) in the presence of pentane as the sole carbon and energy source. The carbon balance for this strain, grown on pentane, was established in order to determine the fate of pentane and the growth yield (0.9 g biomass/g pentane). An inhibition model for P. aeruginosa grown on pentane was proposed. Pentane had an inhibitory effect on growth of P. aeruginosa, even at a concentration as low as 85 micrograms/l. This resulted in the calculation of the following kinetic parameters (mumax = 0.19 h-1, Ks = 2.9 micrograms/l, Ki = 3.5 mg/l). Finally a simple model of MTBE degradation was derived in order to predict the quantity of MTBE able to be degraded in batch culture in the presence of pentane. This model depends only on two parameters: the concentrations of pentane and MTBE.

Biodegradation, Environmental↗

PubMed1998

Start-up and the effect of gaseous ammonia additions on a biofilter for the elimination of toluene vapors.

Biotechnological techniques, including biofilters and biotrickling filters are increasingly used to treat air polluted with VOCs (Volatile Organic Compounds). In this work, the start-up, the effect of the gaseous ammonia addition on the toluene removal rate, and the problems of the heat accumulation on the performance of a laboratory scale biofilter were studied. The packing material was sterilized peat enriched with a mineral medium and inoculated with an adapted consortium (two yeast and five bacteria). Start-up showed a short adaptation period and an increased toluene elimination capacity (EC) up to a maximum of 190 g/m3/h. This was related to increased CO2 outlet concentration and temperature gradients between the packed bed and the inlet (Tm-Tin). These events were associated with the growth of the microbial population. The biofilter EC decreased thereafter, to attain a steady state of 8 g/m3/h. At this point, gaseous ammonia was added. EC increased up to 80 g/m3/h, with simultaneous increases on the CO2 concentration and (Tm-Tin). Two weeks after the ammonia addition, the new steady state was 30 g/m3/h. In a second ammonia addition, the maximum EC attained was 40 g/m3/h, and the biofilter was in steady state at 25 g/m3/h. Carbon, heat, and water balances were made through 88 d of biofilter operation. Emitted CO2 was about 44.5% of the theoretical value relative to the total toluene oxidation, but accumulated carbon was found as biomass, easily biodegradable material, and carbonates. Heat and water balances showed strong variations depending on EC. For 88 d the total metabolic heat was -181.2 x 10(3) Kcal/m3, and water evaporation was found to be 56.5 kg/m3. Evidence of nitrogen limitation, drying, and heterogeneities were found in this study.

Ammonia↗

PubMed1998

Influence of water content on degradation rates for ethanol in biofiltration.

Treatment of ethanol vapor in a peat biofilter with various initial water contents (70%, 59%, 49%, and 35%) was studied. For water contents ranging from 49% to 70%, elimination capacity was about 30 g/m3/h. For a water content of 35%, elimination capacity decreased to 4 g/m3/h. A low mean CO2 yield coefficient (0.35 g CO2 produced per g ethanol consumed) was found for all of the initial water contents. The value was only 20% of the yield coefficient (1.91 g/g) predicted by stoichiometry. When the packing material was dried from 70% to 59% water content during the biofiltration process, elimination capacity dropped from 27 g/m3/h to 4 g/m3/h. After 24 hours of drying, the biofiltration experiment was restarted and run for two more weeks. During this period, the biofilter did not recover. At 59% water content, the rate of water evaporation was estimated at 59.6 g/m3/h. A simplified mass balance permitted calculation of the biological water production rate, approximately 22.1 g/m3/h.

Air Pollutants, Occupational↗

PubMed1993

Solid state fermentation: acid protease production in controlled CO2 and O2 environments.

The effect of the partial pressure of O(2) and CO(2) on the acid protease production in solid state fermentation by Aspergillus niger on wheat bran was studied. A fermentation system was used, which allowed on-line reactor measurements and continuous data acquisition of pH, temperature, gas flow, pressure drop and CO(2) production. Six paired combinations of CO(2) and O(2) concentrations were studied. The results showed a direct relationship between pressure drop, production of CO(2) and temperature increase. The pH evolution patterns were similar in all cases but different if the measurements were made on-line or on a liquid homogenate of the fermented substrate. Acid protease production was increased when the gas had 4% CO(2), (vol/vol), and it reached its highest level, a 43% increase over air, with a mixture of 4% CO(2) and 21% O(2). The protease production was strongly related to the mold metabolic activity as represented by the total CO(2) evolved.

Journal Article↗

PubMed1993

Growth of Candida utilis in solid state fermentation.

In this work, the growth of the yeast Candida utilis on different solid substrate (wheat bran) and supports (sugarcane bagasse and Amberlite resin) imbibed with a liquid culture medium was studied. Growth was followed by sugars consumption, carbon dioxide production rate (CDPR) and cell count. The results showed the ability of the yeast to grow on the three solid media with fairly good viability and total dextrose consumption in the case of sugarcane bagasse and Amberlite, and partial consumption of wheat bran sugars. After two or three days of culture, a five hundred fold increase in cell population was observed.

Journal Article↗