Biotrickling filters for biogas sweetening: oxygen transfer improvement for a reliable operation

An industrial-scale biotrickling filter for the removal of high concentrations of H2S is described in this work. The system has been operating at H2S inlet concentrations between 1000 and 3000 ppmv at acidic conditions. A decrease of pH from 2.6 to 1.8 did not affect the biological activity inside the biofilter while reducing the water make-up consumption up to 75%. The current oxygen supply system, based on direct injection of air to the liquid phase, has demonstrated to be inefficient for a long-term operation leading to elemental sulfur accumulation in the packing material (i.e. promoting clogging episodes). The present study demonstrates it is possible to partially remove (40.3%) the deposited elemental sulfur by bio-oxidation when biogas is not fed. In normal operation conditions, the implementation of an aeration system based on jet-venturi devices has shown quite promising results in terms of oxygen transfer efficiency and robustness. Such improvement of oxygen transfer was translated in a better conversion of H2S to sulfate, which increased around 17%, prolonging the lifespan operation at low-pressure drop.Peer ReviewedPreprin

High H2S concentration abatement in a biotrickling filter: start-up at controlled pH and effect of the EBRT on O2/H2S supply ratio

In this study, a biotrickling filter reactor was set up and used to treat high concentrations of gaseousH2S. Inoculation was carried out at an inlet H2S concentration of 1,000 ppmv (27.8 g H2S m-3 h-1)and sludge from a municipal wastewater treatment plant (MWWTP) was used as inoculum. After 3days, removal efficiency (RE) above 98 % was achieved even after the loading rate (LR) wasincreased up to 55.6 g H2S m-3 h-1 (2,000 ppmv). Operation at such LR, with an empty bed residencetime (EBRT) of 180 s and controlled pH of 6.5-7 was carried out during 3 months. The start-upphase, the effect of decreasing EBRTs at constant inlet concentration and the composition of theprocess end-products in relation to the supplied O2/H2S ratio were studied. Also, a carbon massbalance under steady state conditions was calculated.Peer ReviewedPostprint (published version

Oxidation of biologically produced elemental sulfur under neutrophilic conditions

BACKGROUND: Previous research on a biotrickling filter for the removal of high loads of H2S showed that accumulation of elemental sulfur (S0) when dealing with high H2S concentrations could lead to reactor clogging. Since S0 can also serve as substrate for sulfur-oxidising bacteria, this study investigates the biological oxidation of S0 as a remediation strategy. RESULTS: Results indicated that biological oxidation of S0 inside a clogged biotrickling filter occurred at a comparable rate to those reported for stirred tank reactors. When biologically produced dried and powdered S0 was manually added as a substrate in stirred tank reactor experiments, significantly lower S0 oxidation rates were found compared to those for biological S0 freshly produced in situ. It was speculated that either the powdered S0 particle size or the surface properties hindered S0 bioavailability even in a well-stirred environment. Respirometric experiments with the same powdered S0 and acetone-dissolved S0 confirmed that biological oxidation of S0 was basically limited by the solid S0 bioavailability. CONCLUSIONS: Therefore, results showed that S0 oxidation basically depends on S0 bioavailability and that Sulfate volumetric production rates as high as 3.48 mmol SO42- h-1 L-1 can be achieved inside a clogged biotrickling filter probably due to the high biomass retention capacity. Overall, the results indicate that biological oxidation of S0 can be considered a suitable strategy for unclogging bioreactors clogged with S0.Peer ReviewedPostprint (author's final draft

Minimal and maximal length involutions in finite Coxeter groups

SIGLEAvailable from British Library Document Supply Centre-DSC:6609.268(no 2000/14) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

High H2S concentration abatement in a biotrickling filter: start-up at controlled pH and effect of the EBRT on O2/H2S supply ratio

In this study, a biotrickling filter reactor was set up and used to treat high concentrations of gaseousH2S. Inoculation was carried out at an inlet H2S concentration of 1,000 ppmv (27.8 g H2S m-3 h-1)and sludge from a municipal wastewater treatment plant (MWWTP) was used as inoculum. After 3days, removal efficiency (RE) above 98 % was achieved even after the loading rate (LR) wasincreased up to 55.6 g H2S m-3 h-1 (2,000 ppmv). Operation at such LR, with an empty bed residencetime (EBRT) of 180 s and controlled pH of 6.5-7 was carried out during 3 months. The start-upphase, the effect of decreasing EBRTs at constant inlet concentration and the composition of theprocess end-products in relation to the supplied O2/H2S ratio were studied. Also, a carbon massbalance under steady state conditions was calculated.Peer Reviewe

Performance of OFDM based multimedia wireless local area networks, with and without antenna sectorisation

Available from British Library Document Supply Centre-DSC:DXN051915 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

High H2S concentration abatement in a biotrickling filter: start-up at controlled pH and effect of the EBRT on O2/H2S supply ratio

In this study, a biotrickling filter reactor was set up and used to treat high concentrations of gaseousH2S. Inoculation was carried out at an inlet H2S concentration of 1,000 ppmv (27.8 g H2S m-3 h-1)and sludge from a municipal wastewater treatment plant (MWWTP) was used as inoculum. After 3days, removal efficiency (RE) above 98 % was achieved even after the loading rate (LR) wasincreased up to 55.6 g H2S m-3 h-1 (2,000 ppmv). Operation at such LR, with an empty bed residencetime (EBRT) of 180 s and controlled pH of 6.5-7 was carried out during 3 months. The start-upphase, the effect of decreasing EBRTs at constant inlet concentration and the composition of theprocess end-products in relation to the supplied O2/H2S ratio were studied. Also, a carbon massbalance under steady state conditions was calculated.Peer Reviewe

Biotrickling filters for biogas sweetening: oxygen transfer improvement for a reliable operation

An industrial-scale biotrickling filter for the removal of high concentrations of H2S is described in this work. The system has been operating at H2S inlet concentrations between 1000 and 3000 ppmv at acidic conditions. A decrease of pH from 2.6 to 1.8 did not affect the biological activity inside the biofilter while reducing the water make-up consumption up to 75%. The current oxygen supply system, based on direct injection of air to the liquid phase, has demonstrated to be inefficient for a long-term operation leading to elemental sulfur accumulation in the packing material (i.e. promoting clogging episodes). The present study demonstrates it is possible to partially remove (40.3%) the deposited elemental sulfur by bio-oxidation when biogas is not fed. In normal operation conditions, the implementation of an aeration system based on jet-venturi devices has shown quite promising results in terms of oxygen transfer efficiency and robustness. Such improvement of oxygen transfer was translated in a better conversion of H2S to sulfate, which increased around 17%, prolonging the lifespan operation at low-pressure drop.Peer Reviewe

Oxidation of biologically produced elemental sulfur under neutrophilic conditions

BACKGROUND: Previous research on a biotrickling filter for the removal of high loads of H2S showed that accumulation of elemental sulfur (S0) when dealing with high H2S concentrations could lead to reactor clogging. Since S0 can also serve as substrate for sulfur-oxidising bacteria, this study investigates the biological oxidation of S0 as a remediation strategy. RESULTS: Results indicated that biological oxidation of S0 inside a clogged biotrickling filter occurred at a comparable rate to those reported for stirred tank reactors. When biologically produced dried and powdered S0 was manually added as a substrate in stirred tank reactor experiments, significantly lower S0 oxidation rates were found compared to those for biological S0 freshly produced in situ. It was speculated that either the powdered S0 particle size or the surface properties hindered S0 bioavailability even in a well-stirred environment. Respirometric experiments with the same powdered S0 and acetone-dissolved S0 confirmed that biological oxidation of S0 was basically limited by the solid S0 bioavailability. CONCLUSIONS: Therefore, results showed that S0 oxidation basically depends on S0 bioavailability and that Sulfate volumetric production rates as high as 3.48 mmol SO42- h-1 L-1 can be achieved inside a clogged biotrickling filter probably due to the high biomass retention capacity. Overall, the results indicate that biological oxidation of S0 can be considered a suitable strategy for unclogging bioreactors clogged with S0.Peer Reviewe