Differential corrosion rates of carbon steel by combinations of Bacillus sp., Hafnia alvei and Desulfovibrio gigas established by phospholipid analysis of electrode biofilm

Abstract

Abstract--The corrosion rates of carbon steel by monocultures and various combinations of aerobic (Bacillus sp.), fermentative (Hafnia alvei) and sulfate-reducing (Desulfovibrio gigas) bacterial biofilms in an aerobic, continuously flowing freshwater reactor containing 0.4 mM sulfate showed marked differences. Biofilm formation and electrode colonization resulted in decreases in the open circuit potential (OCP). The corrosion rate was measured non-destructively as the admittance (1/Rot) by electrochemical impedance spectroscopy (EIS) on a four sided working electrode which allowed estimates of the reproducibility. The monocultures each induced greater corrosion initially but with time the rates of corrosion decreased to that of the sterile control. The D. gigas was unable to grow in the bulk phase but formed an apparently non-living biofilm. The admittance (the measure of corrosion) was greatest when the sulfate-reducing bacterium, D. gigas, was present in a consortium. The consortia containing D. gigas + H. alvei showed a significantly higher corrosion rate than the triculture or the other dicultures.The microbial biomass and the bacterial community structure actually on the electrode surfaces were examined by viable counts, most probable number (MPN) estimations and phospholipid fatty acid (PLFA) profiles determined after extraction and gas chromatographic analysis. The rate of corrosion was not directly related to the total microbial biomass or the number of species on the coupon. The rate of corrosion did not del~end on the ratio of heterotrophic to sulfate-reducing bacteria (SRB) or absolute number of SRB. The P][FA analysis showed the organisms on the working electrodes were more stressed/ starved than when grown in the bulk phase for inocula. This study demonstrates that different combinations of bacteria growing on the same substrata (electrode) in the same bulk phase induce very different corrosion rates. The maximum corrosion rate with the isolate combinations was within 70% of an enrichment with a community composition (determined by PLFA analysis) like that of the native corrosion tubercules.

Acid-volatile sulfide and simultaneously extracted metals in surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea: Concentrations, spatial distributions and the indication of heavy metal pollution status

“…DH1, YH2 and YHH1, although there was no heavy metal pollution according to AVS-SEM theory at these stations. Sulfide ions released from AVS can combine with hydrogen ions to form H 2 S which has a strong neurotoxicity, and can produce toxic effects on aquatic life and even on humans; H 2 S can also corrode ships, industrial equipment and pipelines (Jack et al, 1992;Kim and Kim, 2001).…”

Assessment of sediment quality based on acid-volatile sulfide and simultaneously extracted metals in heavily industrialized area of Asaluyeh, Persian Gulf: concentrations, spatial distributions, and sediment bioavailability/toxicity

“…Sulfide ions derived from AVS can react with hydrogen ions to generate H 2 S that has a severe neurotoxicity and can cause toxic effects on aquatic organisms and even on humans. H 2 S can also cause corrosion in industrial equipment, pipelines, ships, and waterfront constructions (Jack et al 1992;Kim and Kim 2001). Heavy metals can be reacted with AVS to decrease their biotoxicity, although AVS of extremely high content is also detrimental to aquatic life (Li et al 2014a).…”

Assessment of heavy metal impact on sediment quality of the Xiaoqinghe estuary in the coastal Laizhou Bay, Bohai Sea: Inconsistency between two commonly used criteria

“…When AVS is oxidized in the aerobic environment, the metals combining with AVS could be released into the water column. In addition, divalent sulfur ions released from AVS-rich sediments can combine with hydrogen ions to form H 2 S which has a strong neurotoxicity and can produce toxic effects on aquatic life and even on humans; H 2 S can also corrode ships, industrial equipment and pipelines (Jack et al, 1992;Kim and Kim, 2001). Therefore, AVS itself with extremely high concentration is a potential environmental threat.…”