Communications in Soil Science and Plant Analysis, 1997
The objective of this paper is to present a procedure for the preparation and sterilization of a ... more The objective of this paper is to present a procedure for the preparation and sterilization of a surrogate soil organic matter (SSOM) to study the chemical and biological interactions that may occur with trichloroethylene (TCE). For this purpose, the SSOM was prepared by composting sphagnum moss, a readily available and rather homogenous material. Both gamma irradiation and autoclaving were compared for their ability to effectively sterilize the SSOM. The efficiency of gamma irradiation, at varying intensities, was compared with that of autoclaving. Irradiation of SSOM at 50 kGy was found to be the most effective method of sterilization tested. Therefore, the effect of 50 kGy gamma irradiation on the surface properties of the SSOM (as evidenced by the cation exchange capacity (CEC), specific surface area (SSA), pH, infrared spectrophotometry (IRS), and TCE sorption isotherms) were compared with the non‐sterilized SSOM. Although there were differences in the CEC and SSA for the two materials, the IRS of sterilized and unsterilized SSOM were similar as was sorption of aqueous TCE at initial concentrations of 2 to 130 mg‐L‐1.
... structure were also examined by using transmis-sion electron microscopy of thin sections. Sec... more ... structure were also examined by using transmis-sion electron microscopy of thin sections. Sections obtained near the surface contained a diversity of shapes (Fig. 11). Rods and cocci of various sizes, with either gram-positive or gram-negative cell wall structures, were observed ...
This study presents a temperature-based control strategy for the stabilization of an anaerobic re... more This study presents a temperature-based control strategy for the stabilization of an anaerobic reactor during organic overloads. To prove feasibility of the proposed approach the rate of methane production was followed in batch activity tests and reactor runs during mesophilic-thermophilic transitions. Within the first 0.25-6 h of temperature augmentation, an increase in the rate of methane production was observed with higher rates measured under thermophilic (above 40 degrees C) conditions. However, 24 h after startup both in batch tests and reactor runs, the rate of methane production under thermophilic conditions was inferior to that under optimal mesophilic conditions (35 degrees C). Following these results, a control strategy based on short-term augmentation of the reactor temperature was proposed and tested in a 10 L UASB reactor. The control strategy employed a multi-model observer-based estimator to stabilize the effluent COD concentration during organic overloads. The temperature-based control resulted in an increased methanization rate and improved reactor stability overall.
A laboratory-scale permeable biobarrier exhibited high removal efficiencies of benzene at inlet c... more A laboratory-scale permeable biobarrier exhibited high removal efficiencies of benzene at inlet concentrations of 0.4 to 35.1 mg/L and with a limited supply of dissolved oxygen. The supplied oxygen was less than the demand for a complete aerobic oxidation of benzene. Stainless steel pieces or granulated peat moss were used as packing material for microbial support in the biobarrier. Removal efficiencies ranged from 63.9% to 99.9% in the stainless steel-packed biobarrier and from 70.4% to 97.2% in the peat moss-packed biobarrier, while benzene elimination rate changed from 0.2 to 10.4 mg/L-d and from 0.1 to 3.7 mg/L-d in the two biobarriers, respectively. The consumption of sulfate and the presence of sulfate-reducing bacteria suggested the contribution of anaerobic metabolism in the biodegradation of benzene. The biodegradation of benzene under microaerophilic conditions (defined as dissolved oxygen concentrations <2 mg/L) was demonstrated during independent batch experiments. The maximum specific rate of benzene biodegradation with concentrations of 22.0 to 65.9 mg/L under microaero-philic conditions was 2.6 mg/mg biomass-d.
The influence of ultraviolet photolysis as a pretreatment to the aerobic and anaerobic biological... more The influence of ultraviolet photolysis as a pretreatment to the aerobic and anaerobic biological mineralization of a 14C-polyacrylamide was assessed using a series of radiorespirometry bioassays. The polyacrylamide studied was non-ionic with molecular weights ranging between 100,000 and 1 million. Aerobic and anaerobic biomineralization of the unphotolysed (raw) polyacrylamide was found to be only 0.60% and 0.70%, respectively, after 6 weeks of incubation, and hence indicative of the natural recalcitrance of polyacrylamide to microbial degradation. The effectiveness of UV irradiation in the physical breakdown of the polyacrylamide chain into oligomers was demonstrated by the shift in the molecular weight distribution and the positive correlation between the time of irradiation and the degree of its biological mineralization. The molecular weight fraction below 3 kD, which represents only 2% of the raw polyacrylamide, was increased to 41, 60 and 80% after 12, 24 and 48 hours of photolysis, respectively. This in turn, yielded, after 6 weeks of incubation, an aerobic mineralization of 5, 17 and 29% of 150 mg/L polyacrylamide, respectively, and an anaerobic mineralization of 3, 5 and 17%, respectively. Biomass acclimation substantially improved the specific initial rate of biomineralization of the photolysed polyacrylamides, but not the overall percentage of polyacrylamides mineralized.
Microcosm tests simulating bioslurry reactors with 40% soilcontent, containing high concentration... more Microcosm tests simulating bioslurry reactors with 40% soilcontent, containing high concentrations of TNT and/or RDX,and spiked with either 14C]-TNT or14C]-RDX were conducted to investigate the fate ofexplosives and their metabolites in bioslurry treatment processes.RDX is recalcitrant to indigenous microorganisms in soil andactivated sludge under aerobic conditions. However, soilindigenous microorganisms alonewere able to mineralize 15% of RDX to CO2 underanaerobic condition, and supplementation of municipal anaerobicsludge as an exogenous source of microorganismssignificantly enhanced the RDX mineralization to 60%. RDXmineralizing activity of microorganisms in soil and sludge wassignificantly inhibited by the presence of TNT. TNTmineralization was poor (14C]-TNT in the microcosmsrevealed that the removal of TNTduring the bioslurry process was due mainly to thetransformation of TNT and irreversiblebinding of TNT metabolites onto soil matrix. In the case ofRDX under anaerobic conditions,a significant portion (35%) of original radioactivity wasalso incorporated into the biomass andbound to the soil matrix.
Journal of Chemical Technology and Biotechnology. Biotechnology, 1985
Mixing characteristics (using a radioactive tracer) and reactor performance of the upflow blanket... more Mixing characteristics (using a radioactive tracer) and reactor performance of the upflow blanket filter (UBF) reactor operated at different loading rates (up to 32 kg chemical oxygen demand (COD) m−3 day−1) were compared. The results indicated that mixing profiles of the reactor operated with effluent recirculation and without biomass were of the perfectly mixed type. Operation without recirculation resulted in about 18% dead space. The filter made of plastic rings and located in the top third of the reactor had no negative effect on reactor mixing. Operation at loading rates of up to 25 kg COD m−3 day−1 permitted a soluble COD removal rate of 95% with a methane production rate of 5.9 m3 m−3 day−1. At higher loading rates, the efficiency of COD reduction decreased with a decrease of the specific acetoclastic activity to 0.5 kg acetate removed per kg volatile suspended solids (VSS) day−1. At all loading rates studied it was observed that the performance was not related to the mixing characteristics, which had remained of the perfectly mixed type with an occasional small dead space (below 10%). The good mixing characteristics of the UBF reactor coupled with the high biomass content and the effective action of the filter make this reactor one of the most promising designs for the treatment of soluble wastes.
The Gibbs free energy changes in methanogenic granular biomass from sludge-bed reactors were eval... more The Gibbs free energy changes in methanogenic granular biomass from sludge-bed reactors were evaluated using the in situ concentrations and partial pressures of metabolites during the metabolism of acetate, hydrogen, formate and propionate. Based on mass balance calculations it appeared that the degradation of propionate into acetate, hydrogen and bicarbonate was endergonic, even if propionate was effectively degraded. On the other hand, the methane-producing reactions, both from acetate and from hydrogen plus bicarbonate, were found to be exergonic and the free energy change was sufficient for the formation of ATP. Formate was detected in only one of the two reactors. When formate, instead of hydrogen, was considered as the electron carrier between propionate-degrading and methanogenic bacteria, similar thermodynamic results were obtained. The existence of trophic microniches in the granular biomass is suggested to explain propionate degradation even though the Gibbs free energy change in the liquid surrounding the granules was positive. Hence, to make propionate degradation exergonic the dissolved hydrogen concentration surrounding the propionate-degrading bacteria would have to be about 30 times lower than in the free liquid.
Communications in Soil Science and Plant Analysis, 1997
The objective of this paper is to present a procedure for the preparation and sterilization of a ... more The objective of this paper is to present a procedure for the preparation and sterilization of a surrogate soil organic matter (SSOM) to study the chemical and biological interactions that may occur with trichloroethylene (TCE). For this purpose, the SSOM was prepared by composting sphagnum moss, a readily available and rather homogenous material. Both gamma irradiation and autoclaving were compared for their ability to effectively sterilize the SSOM. The efficiency of gamma irradiation, at varying intensities, was compared with that of autoclaving. Irradiation of SSOM at 50 kGy was found to be the most effective method of sterilization tested. Therefore, the effect of 50 kGy gamma irradiation on the surface properties of the SSOM (as evidenced by the cation exchange capacity (CEC), specific surface area (SSA), pH, infrared spectrophotometry (IRS), and TCE sorption isotherms) were compared with the non‐sterilized SSOM. Although there were differences in the CEC and SSA for the two materials, the IRS of sterilized and unsterilized SSOM were similar as was sorption of aqueous TCE at initial concentrations of 2 to 130 mg‐L‐1.
... structure were also examined by using transmis-sion electron microscopy of thin sections. Sec... more ... structure were also examined by using transmis-sion electron microscopy of thin sections. Sections obtained near the surface contained a diversity of shapes (Fig. 11). Rods and cocci of various sizes, with either gram-positive or gram-negative cell wall structures, were observed ...
This study presents a temperature-based control strategy for the stabilization of an anaerobic re... more This study presents a temperature-based control strategy for the stabilization of an anaerobic reactor during organic overloads. To prove feasibility of the proposed approach the rate of methane production was followed in batch activity tests and reactor runs during mesophilic-thermophilic transitions. Within the first 0.25-6 h of temperature augmentation, an increase in the rate of methane production was observed with higher rates measured under thermophilic (above 40 degrees C) conditions. However, 24 h after startup both in batch tests and reactor runs, the rate of methane production under thermophilic conditions was inferior to that under optimal mesophilic conditions (35 degrees C). Following these results, a control strategy based on short-term augmentation of the reactor temperature was proposed and tested in a 10 L UASB reactor. The control strategy employed a multi-model observer-based estimator to stabilize the effluent COD concentration during organic overloads. The temperature-based control resulted in an increased methanization rate and improved reactor stability overall.
A laboratory-scale permeable biobarrier exhibited high removal efficiencies of benzene at inlet c... more A laboratory-scale permeable biobarrier exhibited high removal efficiencies of benzene at inlet concentrations of 0.4 to 35.1 mg/L and with a limited supply of dissolved oxygen. The supplied oxygen was less than the demand for a complete aerobic oxidation of benzene. Stainless steel pieces or granulated peat moss were used as packing material for microbial support in the biobarrier. Removal efficiencies ranged from 63.9% to 99.9% in the stainless steel-packed biobarrier and from 70.4% to 97.2% in the peat moss-packed biobarrier, while benzene elimination rate changed from 0.2 to 10.4 mg/L-d and from 0.1 to 3.7 mg/L-d in the two biobarriers, respectively. The consumption of sulfate and the presence of sulfate-reducing bacteria suggested the contribution of anaerobic metabolism in the biodegradation of benzene. The biodegradation of benzene under microaerophilic conditions (defined as dissolved oxygen concentrations <2 mg/L) was demonstrated during independent batch experiments. The maximum specific rate of benzene biodegradation with concentrations of 22.0 to 65.9 mg/L under microaero-philic conditions was 2.6 mg/mg biomass-d.
The influence of ultraviolet photolysis as a pretreatment to the aerobic and anaerobic biological... more The influence of ultraviolet photolysis as a pretreatment to the aerobic and anaerobic biological mineralization of a 14C-polyacrylamide was assessed using a series of radiorespirometry bioassays. The polyacrylamide studied was non-ionic with molecular weights ranging between 100,000 and 1 million. Aerobic and anaerobic biomineralization of the unphotolysed (raw) polyacrylamide was found to be only 0.60% and 0.70%, respectively, after 6 weeks of incubation, and hence indicative of the natural recalcitrance of polyacrylamide to microbial degradation. The effectiveness of UV irradiation in the physical breakdown of the polyacrylamide chain into oligomers was demonstrated by the shift in the molecular weight distribution and the positive correlation between the time of irradiation and the degree of its biological mineralization. The molecular weight fraction below 3 kD, which represents only 2% of the raw polyacrylamide, was increased to 41, 60 and 80% after 12, 24 and 48 hours of photolysis, respectively. This in turn, yielded, after 6 weeks of incubation, an aerobic mineralization of 5, 17 and 29% of 150 mg/L polyacrylamide, respectively, and an anaerobic mineralization of 3, 5 and 17%, respectively. Biomass acclimation substantially improved the specific initial rate of biomineralization of the photolysed polyacrylamides, but not the overall percentage of polyacrylamides mineralized.
Microcosm tests simulating bioslurry reactors with 40% soilcontent, containing high concentration... more Microcosm tests simulating bioslurry reactors with 40% soilcontent, containing high concentrations of TNT and/or RDX,and spiked with either 14C]-TNT or14C]-RDX were conducted to investigate the fate ofexplosives and their metabolites in bioslurry treatment processes.RDX is recalcitrant to indigenous microorganisms in soil andactivated sludge under aerobic conditions. However, soilindigenous microorganisms alonewere able to mineralize 15% of RDX to CO2 underanaerobic condition, and supplementation of municipal anaerobicsludge as an exogenous source of microorganismssignificantly enhanced the RDX mineralization to 60%. RDXmineralizing activity of microorganisms in soil and sludge wassignificantly inhibited by the presence of TNT. TNTmineralization was poor (14C]-TNT in the microcosmsrevealed that the removal of TNTduring the bioslurry process was due mainly to thetransformation of TNT and irreversiblebinding of TNT metabolites onto soil matrix. In the case ofRDX under anaerobic conditions,a significant portion (35%) of original radioactivity wasalso incorporated into the biomass andbound to the soil matrix.
Journal of Chemical Technology and Biotechnology. Biotechnology, 1985
Mixing characteristics (using a radioactive tracer) and reactor performance of the upflow blanket... more Mixing characteristics (using a radioactive tracer) and reactor performance of the upflow blanket filter (UBF) reactor operated at different loading rates (up to 32 kg chemical oxygen demand (COD) m−3 day−1) were compared. The results indicated that mixing profiles of the reactor operated with effluent recirculation and without biomass were of the perfectly mixed type. Operation without recirculation resulted in about 18% dead space. The filter made of plastic rings and located in the top third of the reactor had no negative effect on reactor mixing. Operation at loading rates of up to 25 kg COD m−3 day−1 permitted a soluble COD removal rate of 95% with a methane production rate of 5.9 m3 m−3 day−1. At higher loading rates, the efficiency of COD reduction decreased with a decrease of the specific acetoclastic activity to 0.5 kg acetate removed per kg volatile suspended solids (VSS) day−1. At all loading rates studied it was observed that the performance was not related to the mixing characteristics, which had remained of the perfectly mixed type with an occasional small dead space (below 10%). The good mixing characteristics of the UBF reactor coupled with the high biomass content and the effective action of the filter make this reactor one of the most promising designs for the treatment of soluble wastes.
The Gibbs free energy changes in methanogenic granular biomass from sludge-bed reactors were eval... more The Gibbs free energy changes in methanogenic granular biomass from sludge-bed reactors were evaluated using the in situ concentrations and partial pressures of metabolites during the metabolism of acetate, hydrogen, formate and propionate. Based on mass balance calculations it appeared that the degradation of propionate into acetate, hydrogen and bicarbonate was endergonic, even if propionate was effectively degraded. On the other hand, the methane-producing reactions, both from acetate and from hydrogen plus bicarbonate, were found to be exergonic and the free energy change was sufficient for the formation of ATP. Formate was detected in only one of the two reactors. When formate, instead of hydrogen, was considered as the electron carrier between propionate-degrading and methanogenic bacteria, similar thermodynamic results were obtained. The existence of trophic microniches in the granular biomass is suggested to explain propionate degradation even though the Gibbs free energy change in the liquid surrounding the granules was positive. Hence, to make propionate degradation exergonic the dissolved hydrogen concentration surrounding the propionate-degrading bacteria would have to be about 30 times lower than in the free liquid.
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