No abstract

Desulfotomaculum thermobenzoicum TSB converted 4 mol pyruvate to 5 mol acetate in the absence of sulfate. The cells grown on pyruvate without sulfate showed both carbon monoxide dehydrogenase (CODH) and methylmalonyl‐CoA: pyruvate transcarboxylase activities. However, considering the fermentation products, the acetogenesis from pyruvate might be conducted by CODH pathway rather than methylmalonyl‐CoA pathway. Contrary to this finding, Desulfobulbus propionicus MUD fermented 3 mol pyruvate to 2 mol acetate and 1 mol propionate stoichiometrically via methylmalonyl‐CoA pathway. Desulfovibrio vulgaris Marburg, which has neither the CODH pathway nor the methylmalonyl‐CoA pathway, converted pyruvate to acetate, H2 and CO2 as the main products. These results indicate that the fermentation pattern of pyruvate depends on the metabolic characteristics of each sulfate‐reducing bacterium.

Summary As an oil field matures, it produces larger quantities of produced water. Appropriate treatment levels and technologies depend on a number of factors, such as disposal methods or usage aims, environmental impacts, and economics. In this study, a pilot plant with a capacity of 50 m3/day was used to conduct flotation, filtration, and adsorption trials for produced-water treatment at a crude-oil gathering facility. The flexible design of the plant allows for the testing of different combinations of these processes on the basis of the requirements of the water to be treated. The subject water during this study was a complex and changing mixture of brine and oil from different oil fields. Induced-gas-flotation (IGF) trials were conducted, with different coagulant [poly-aluminum chloride (PAC)] -addition rates from 0 to 820 mg•L-1. Inlet-dispersed oil-in-water (OIW) concentrations were quite varied during the trials, ranging from 39 to 279 mg•L-1 (fluorescence-analysis method). Turbidity also varied, ranging from 85 to 279 FTU. Through coagulation/flocculation and flotation, dispersed oils were removed from the water. PAC addition ranging from 60 to 185 mg•L-1 resulted in the reduction of the dispersed-oil concentration to less than 50 mg•L-1 in treated water; and PAC addition ranging from 101 to 200 mg•L-1 resulted in the reduction of the dispersed-oil concentration to less than 15 mg•L-1 in treated water. Turbidity was also reduced through flotation, with trial average reductions ranging from 57 to 78%. Filtration further reduced turbidity at rates greater than 80% through the removal of any suspended solids remaining from flotation. Activated-carbon adsorption reduced OIW concentrations of flotation-/filtration-treated water to 5 mg•L-1 (infrared-analysis method) through the removal of dissolved oil remaining in the water. Results confirmed that such adsorption treatment would be more practical for water with lower chemical-oxygen-demand (COD) concentration because high-COD concentrations in water reduce the lifetime of activated carbon dramatically.

Fick's law has been used to simulate gas systems within soil, although this law can be applied only to binary gas systems and the eŠect of the Knudsen diŠusion is not considered. By contrast, the dusty gas model can be applied to multi-component gas systems with Knudsen diŠusion. Blanc's law is a simpliˆed version of the dusty gas model, but it can be used only for gas systems in which the tracer gas is dilute. Although the dusty gas model is superior to other methods for simulating gas systems within soil, it is not generally used because of its complexity. Numerical techniques such as the Eulerian-Lagrangian method for solving the advection-dispersion equation can be used to simulate the migration of chemical substance in the water or gas phases of soil within the range of every P áeclet number. We derived the compound diŠusion coe‹cient and compound velocity from the dusty gas model and formulated the advectiondiŠusion equation with these values by using the characteristicˆnite element scheme. Results of the model developed here were consistent with the results of column experiments conducted in this study, and the precision of the developed model was veriˆed.

Desulfotomaculum thermobenzoicum strain TSB (DSM 6193) was found to utilize some methoxylated benzoates as carbon and energy source with or without sulfate. 3- or 4-Methoxybenzoate, vanillate (4-hydroxy-3-methoxybenzoate), syringate (3,5-dimethoxy-4-hydroxybenzoate) and 3,4,5-trimethoxybenzoate were converted to corresponding hydroxybenzoates. However, neither 2-methoxybenzoate nor 2,6-dimethoxybenzoate was utilized. The organism grew acetogenically on each of the methoxylated benzoates in the absence of sulfate. 3,4-Dihydroxy-5-methoxybenzoate was detected during conversion of syringate, and syringate and 3,4-dihydroxy-5-methoxybenzoate were detected during conversion of 3,4,5-trimethoxybenzoate as intermediates. These findings indicate that 4-methoxyl-group is most readily cleaved, whereas 2-methoxyl-group is not utilized by the organism.