Bench scale column studies were used to examine the partitioning of microorganisms between groundwater and a geologic medium and to examine the effect of hydrogeology (i.e., porous-versus fracture-flow) on organism partitioning. Replicated columns were constructed with intact basalt core segments that contained natural fractures and with the same basalt crushed into particles. The columns were perfused with groundwater, and upon reaching a steady state, the columns were sacrificed and the attached and unattached communities were analyzed by multiple approaches. The analyses included the total number of cells, the phylogenetic affiliation of the cells (i.e., the ␣, ␤, and ␥ subclasses of the class Proteobacteria and gram positives with high G؉C DNA content) by fluorescent in situ hybridization (FISH), number and taxonomic affiliation by fatty acid methyl ester profiles of culturable heterotrophs, most-probable-number estimates of methanotrophs and phenol oxidizers, and whole-community sole carbon source utilization patterns from Biolog GN microplates. In the packed columns, about 99% of the total biomass (per cubic centimeter of porous medium) was attached to the geologic medium. Lack of equitable units precluded a comparison of attached and unattached biomasses in the fractured columns where the attached biomass was expressed per unit of surface area. Compositional differences in the attached and unattached communities were evidenced by (i) the recovery of Pseudomonas stutzeri, an Enterococcus sp., and Bacillus psychrophilus from the groundwater and not from the basalt, (ii) differences between community carbon source utilization patterns, and (iii) the relative abundances of different phylogenetic groups estimated by FISH in both column types. In the packed columns, attached communities were depleted of members of the ␣-and ␤-Proteobacteria subclasses in comparison to those in the corresponding groundwater. In the fractured columns, attached communities were enriched in gram-positive Bacteria and ␥-Proteobacteria and depleted of ␤-Proteobacteria, in comparison to those in the corresponding groundwater. Segregation of populations and their activities, possibly modified by attachment to geologic media, may influence contaminant fate and transport in the subsurface and impact other in situ applications.Although the presence of microbes in both geologic media and groundwaters is undisputed (44), little work has described the partitioning of populations and activities between communities that colonize geologic media and those that exist planktonically in groundwaters. Clearly, the relative mobility of the microorganisms (i.e., attached or unattached) would have a great influence on processes related to subsurface contaminant fate and transport (29, 57), the stability of geologic radioactive waste repositories (45), microbially enhanced oil recovery, and solution mining. For example, consider the strategies required to deliver a substrate or nutrient to an attached organism versus a planktonic organism that might be ...

No abstract

High-solids (HS) and low-solids (LS) potato process effluents were tested as substrates for surfactin production. Tests used effluents diluted 1:10, unamended and amended with trace minerals or corn steep liquor. Heat pretreatment was necessary for surfactin production from effluents due to indigenous bacteria, whose spores remained after autoclaving. Surfactin production from LS surpassed HS in all cases. Surfactin yields from LS were 66% lower than from a pure culture in an optimized potato starch medium. LS could potentially be used without sterilization for surfactin production for low-value applications such as environmental remediation or oil recovery.

Summary A field test was performed at the Coleville field to evaluate the ability of indigenous bacteria to remove sulfides from reservoir brine. Ammonium nitrate and sodium phosphate were injected continuously at two injectors for nearly 50 days. Sulfide levels at the two injectors declined by 42 to 100% and by as much as 50 to 60% at two adjacent producers. Concentrations of indigenous sulfide oxidizing, nitrate-reducing bacteria increased at injectors and producers while concentrations of sulfate-reducing bacteria remained unchanged or decreased slightly. Stimulation of indigenous beneficial bacteria has potential application as a cost-effective, low toxicity means to remove and control sulfides in reservoir brines. Introduction Produced water from oil reservoirs frequently contains soluble sulfide (H2 S, HS– and S2–) as a consequence of the activities of sulfate-reducing bacteria (SRB). The presence of sulfides in produced brine creates serious problems for the petroleum industry due to their toxicity, odor, corrosiveness, formation of insoluble metal sulfides, and lowering of the sales quality of produced gas. Removal and control of sulfide in reservoir brines typically involves the injection of chemicals such as sulfide scavengers and biocides, whereas, protection from the corrosive nature of sulfides is often accomplished using corrosion inhibitors. Some of the problems with the use of these chemicals include their lack of selectivity, stability, and compatibility. Additionally, many of these chemicals are expensive, toxic, and hazardous. An alternative method to remediate sulfide in reservoir brines is through selective manipulation of the indigenous bacteria. Jenneman et al.1 and Jack et al.2 demonstrated that indigenous bacteria in a sulfide-laden environment (e.g., sewage and oil field reservoir brines) could be manipulated by changing the dominant electron acceptor from sulfate to nitrate such that nitrate-reducing bacteria (NRB) oxidize the sulfide present and out-compete the SRB for common electron donors, e.g., organic acids. This approach was subsequently shown to be applicable to other produced brines from oil and gas fields3,4 as well as gas storage fields.5 During a microbially enhanced oil recovery field test, McInerney et al.6 added ammonium nitrate to injected brine at the Southeast Vasser Vertz Sand Unit in Payne County, OK and reported a 40-60% reduction in sulfide at three adjacent producers that was attributed to the activity of indigenous NRB. Sublette et al.,7 at the Salt Creek field in Wyoming, demonstrated that the non-indigenous NRB, Thiobacillus denitrificans strain F, when added to produced brine successfully removed sulfides using oxygen as an oxidant. Jack and Westlake8 reported that although the introduction of 100 ppm nitrate to an oil field brine resulted in significant changes in biofilm populations and a reduction in iron sulfide concentrations, the nitrate addition also resulted in an increase in SRB counts and a six-fold increase in corrosion rates. More recently, Hitzman and Dennis9 as well as Giangiacomo and Dennis10 successfully demonstrated that the application of a patented combination of nitrate, nitrite and molybdate 11 could be used to reduce sulfide concentrations and control SRB in a process referred to as biocompetitive exclusion. This process is designed to stimulate indigenous NRB to out-compete SRB for a common electron donor, i.e., fatty acids. Reservoir Description. The Coleville field (CV) is located near Kindersley in Saskatchewan, Canada. The field was discovered in 1951 and has been on water injection since 1958. The wells produce from the Bakken sandstone at a depth of 823 m and a bottom hole temperature of 29°C. The permeability of the formation averages between 0.49 and ?m 2 with streaks up to 3.0 ?m2. The oil is heavy, asphaltic crude with an API gravity of 13. Currently, produced water is reinjected at a rate of 4770 m3/d with less than 5% of this being make-up water from the Belly River formation. The injected brine contains total dissolved solids of less than 7500 mg/L and a pH of 7.5 at reservoir pressure. Chloride, bicarbonate and sulfate are the principal anions with sodium, calcium and magnesium the major cations. Fatty acids such as formate, acetate and propionate are below detectable levels >10 mg/L). Throughout the field, sulfide concentrations in the produced brine range from a few mg/L to greater than 200 mg/L. Souring is believed to have occurred through the activity of SRB at the time water injection was initiated. The presence of sulfides, SRB, and chlorides in the brine has contributed to a corrosive environment, which has lead to the need to apply corrosion inhibitors at the producers and a biocide at the water plant. Due to the high cost and hazardous nature of these chemicals, manipulation of indigenous bacteria through nitrate injection was evaluated as a means of removing sulfide and controlling SRB. Biological Sulfide Oxidation. During laboratory tests, the addition of 5 mM KNO3 and 100 ?M NaH 2PO4 to CV reservoir brine resulted in the complete oxidation of over 100-mg/L sulfide within 15 hours.12 This oxidation was later found to be due to the presence of a unique group of sulfide-oxidizing NRB indigenous to the CV brine.13 These NRB oxidize sulfide without the apparent requirement for organic compounds according to the equation: 5HS−+2NO3−+7H+→5S0+N2+6H2O.12 Therefore a prominent feature of this reaction involves the oxidation of sulfide to elemental sulfur via the activity of indigenous, sulfide-oxidizing NRB.