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Mixtures of volatile reduced sulphur compounds (VRSCs) like hydrogen sulphide (H(2)S), methylmercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) are found in gaseous emissions of several industrial activities creating nuisance in the surroundings. Hydrogen sulphide (H(2)S) decreases the removal efficiency of volatile reduced sulphur compounds (VRSCs) in biofilters but the kinetics of this effect is still unknown. Kinetic expressions that represent the rate of bio-oxidation of H(2)S, MM, DMS and DMDS are proposed. In order to observe and quantify this effect, equimolar mixtures of MM, DMS and DMDS were fed into a biotrickling filter inoculated with Thiobacillus thioparus at different H(2)S loads. Experimental results shown a good agreement with the simulations generated by the model considering the kinetic equations proposed. The estimated kinetic constants show that H(2)S and MM have a significant inhibitory effect on the bio-oxidation of DMS and DMDS, having the H(2)S the higher effect., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Biofiltration of reduced sulfur compounds such as hydrogen sulfide has been mainly applied to emissions at mild temperatures (25 to 35 °C). However, an important number of industrial gaseous emission containing sulfur compounds, from diverse industrial sectors (petroleum refinery, cellulose production, smelting, rendering plants and food industries) are emitted at temperatures over 50 °C. Most of the studies on thermophilic systems report that a higher elimination capacity can be obtained at elevated temperature, allowing the design of smaller equipment for the same loading rate than that required for removing the same load under mesophilic conditions. A biotrickling filter inoculated with Sulfolobus metallicus, which operates at three different residence times, 60, 80 and 120 s, and two different temperatures (45 and 55 °C) for treating H(2)S is reported. The input loads of H(2)S were progressively increased from 0 to 100 gS/m(3). The aim of this study was to determine the capacity and ability of S. metallicus to oxidize H(2)S at high temperatures. The better removal capacity of H(2)S obtained was 37.1 ± 1.7 gS/m(3) h at 55 °C for a residence time of 120 s. The difference of the removal capacity of H(2)S between the two temperatures was 4 g/m(3) h on average of sulfur removal for the different residence times.

In the work described here, a biotrickling filter with Thiobacillus thioparus (ATCC 23645) immobilized on polyurethane foam is proposed for the removal of hydrogen sulfide contained in air. The effect of surface velocity of the recirculation medium (5.9-1.2 m/h), sulfate concentration inhibition (3.0-10.7 g/L), pH (6.0-8.2), empty bed residence time (EBRT) (150-11 s) for constant loads of 11.5 and 2.9 g S/m(3)/h, and pressure drop of the system were investigated. The total amount of biomass immobilized on the carrier was 8.2+/-1.3x10(10) cells/g. The optimal values of the operating variables were: pH between 7.0 and 7.5, surface velocity of 5.9 m/h and sulfate concentration below 5 g/L. The critical EC value was 14.9 g S/m(3)/h (removal efficiency of 99.8%) and the EC(max) was 55.0 g S/m(3)/h (removal efficiency of 79.8%) for an EBRT of 150 s. For loads of 2.89+/-0.05 and 11.5+/-0.1 g S/m(3)/h, the removal efficiency was higher than 99% for an EBRT over 90 s.

A biotrickling filter with Nitrosomonas europaea immobilized on polyurethane foam is proposed for treating ammonia contaminated air. The effect of the surface velocity of the recirculation medium, nitrite concentration, pH, empty bed residence time (EBRT) and ammonia inlet load on the NH(3) removal process was investigated. The total amount of biomass immobilized on the carrier was 3.29+/-0.52 x 10(10) cells g(-1) dry carrier. The maximum elimination capacity of the biotrickling filter was 270 g Nm(-3)h(-1) at pH 7.5, an EBRT of 11s, and nitrite concentrations below 100mM. These results show that system studied can be considered as a viable alternative for the treatment of gaseous emissions containing high concentrations of ammonia.

In this work the variation in the elimination capacity of a biofilter as a function of the gas flow and toluene concentration was studied. A bioreactor 0.75 m high x 14.5 cm diameter was used, divided into three equal stages, using compost to support the microorganisms, and sea shells to control the pH. The biofiltration of toluene was evaluated for flows between 0.12 and 0.73 m(3)h(-1) in a concentration range of 1-3.2 gm(-3). It was observed that on increasing the toluene inlet load by 90% (from 37 to 70 gm(3)h(-1)), the conversion by the biofilter varied by only 5% (from 98% to 93%). The biofiltration system used achieved elimination capacities of up to 82 gm(-3)h(-1) for a toluene load of 100 gm(-3)h(-1).