Microbially influenced corrosion (MIC), also known as biocorrosion, has significant impacts on the environment and economy. Typical systems to study biocorrosion are either dynamic (once-through flow) or static (serum bottle incubations). Dynamic systems can be materials and personnel intensive, while static systems quickly become nutrient limiting and exhibit long incubations. A semi-continuous biocorrosion cell was developed to address these issues. Low carbon shim steel was used as a test surface. Initial results revealed that 50 ppm glutaraldehyde (GLT), a common oil field biocide, in an abiotic cell was 3.6 times more corrosive (24.5 × 10-3 mm/y) than a biocorrosion cell inoculated with a sulfate-reducing bacteria (SRB) enrichment (6.73 × 10-3 mm/y). The SRB inoculated cell treated with GLT (50 ppm) reduced the corrosion rate from 6.73 × 10-3 mm/y to 3.68 × 10-3 mm/y. It was hypothesized that a biocide-surfactant combination would enhance biocide activity, thereby lowering corrosion in a semi-continuous biocorrosion cell. The biocide and surfactant were GLT (30 ppm) and Tween 80 (TW80; 100 ppm). MIC of SRB increased in the presence of a non-inhibitory concentration of GLT (23.4 × 10-3 mm/y), compared to the untreated +SRB condition (8.29 × 10-3 mm/y). The non-ionic surfactant alone reduced MIC (4.57 × 10-3 mm/y) and even more so in combination with GLT (3.69 × 10-3 mm/y). Over 50% of 16S rDNA sequences in the biofilm on the test surface were identified as belonging to the genera Desulfovibrio and Desulfomicrobium. The utility of a semi-continuous system for MIC studies and biocide testing was demonstrated. The concept of regular partial medium replacement is applicable to different corrosion cell and corrosion coupon geometries. Biocide-surfactant combinations may have the potential to reduce the concentration of biocides used in the field. In addition, a semi-defined medium for enumerating Acid-Producing Bacteria (APB) was developed, resulting in higher recoveries compared to a standard phenol red medium (e.g., 1.1 × 104 APB/cm2 vs < 4 × 10-1 APB/cm2).
Keywords: Acid-producing bacteria; Biocorrosion; Glutaraldehyde; Microbially influenced corrosion; Sulfate-reducing bacteria; Tween 80.
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