Sulfolane attenuation by surface and subsurface soil matrices.

This study was undertaken to evaluate sulfolane (tetrahydrothiophene-1, 1-dioxide) attenuation by soil and subsurface materials collected from a sour gas plant site using batch equilibration systems. The analyzed sample materials used in this study showed a wide range in terms of their selected physical and chemical properties. The reaction of sulfolane with the sample materials was fast initially and followed by slower rates at longer times. There was not much increase in the amount of sulfolane sorbed after about 5 hours of equilibration time irrespective of the temperature of the system. The rate of sorption of sulfolane followed a first-order reaction at both 25 and 8 degrees C temperature conditions and not affected by the temperatures range considered in this study. It appears that the sorption data of sulfolane on the various sorbents could be best described mathematically by the Freundlich equation. Kd values derived at 25 degrees C ranged from 0.05 to 0.88 L/kg and from 0.30 to 1.23 L/kg at 8 degrees C. Furthermore, increasing the ionic strength of the solution didn't affect sulfolane sorption by the various sorbents, which indicates that sulfolane sorption is not consistent with an ion-exchange mechanism but rather occurs through dipole-dipole interactions. Desorption of sulfolane was relative high in all systems. Multiple regression analysis shows a high level of correlation between Kd and several soil parameters. No sulfolane biodegradation was detected under anerobic conditions in any of the microcosms systems after 45 days of incubation at 25 and 8 degrees C, respectively. Sulfolane biodegradation data could be all fitted to zero-order kinetics. Biodegradation rates of sulfolane in the microcosms was the highest in sample depth 0-0.20 m, decreased with sample depth but significantly increased with the addition of nitrogen, and markedly decreased with temperature. At 25 degrees C and no supplement of N, biodegradation rate ranged from 4.26 to 12.70 mg/kg/day but with addition of N, the range was from 9.41 to 16.50 mg/kg/day.

Methane oxidation and formation of EPS in compost: effect of oxygen concentration.

Oxygen concentration plays an important role in the regulation of methane oxidation and the microbial ecology of methanotrophs. However, this effect is still poorly quantified in soil and compost ecosystems. The effect of oxygen on the formation of exopolymeric substances (EPS) is as yet unknown. We studied the effect of oxygen on the evolution of methanotrophic activity. At both high and low oxygen concentrations, peak activity was observed twice within a period of 6 months. Phospholipid fatty acid analysis showed that there was a shift from type I to type II methanotrophs during this period. At high oxygen concentration, EPS production was about 250% of the amount at low oxygen concentration. It is hypothesized that EPS serves as a carbon cycling mechanism for type I methanotrophs when inorganic nitrogen is limiting. Simultaneously, EPS stimulates nitrogenase activity in type II methanotrophs by creating oxygen-depleted zones. The kinetic results were incorporated in a simulation model for gas transport and methane oxidation in a passively aerated biofilter. Comparison between the model and experimental data showed that, besides acting as a micro-scale diffusion barrier, EPS can act as a barrier to macro-scale diffusion, reducing the performance of such biofilters.

Assessing sanitary landfill stabilization using winter and summer waste streams in simulated landfill cells.

This study was undertaken to provide a better understanding and to further define the stabilization processes involved in a typical municipal landfill representative of the city of Calgary, Canada, area. The objectives of this study were: (1) to characterize the composition of the solid waste constituents entering the landfill site, (2) to assess the relative decomposition of various waste components in the simulated test cells, (3) to parametize selected chemical and physical changes occurring during the stabilization process and (4) to determine water absorptive capacity of the different waste constituents. The results of the long term landfill stabilization using simulated landfill cell systems filled with winter and summer waste streams, respectively, have illustrated the potential changes that may occur with time with such systems. Based on the results, it can be inferred that the seasonal variation in waste composition deposited in a landfill will likely effect the rate of decomposition and settlement, chemical and physical characteristics of the leachate, moisture sorbing capacity of the site as well as variation in seasonal contaminants. Assuming that the results from the simulated landfills used during this study can be extrapolated to larger-scale landfill operations, it seems that summer waste streams pose a higher pollution threat to the environment than winter waste streams. The several trends observed in this study and the conclusions reported herein would have wide applications in landfill management.