Chemicomicrobiological Diagnostics of Stress Corrosion Cracking of Trunk Pipelines

Samples of soil, subsoil, electrolyte, corrosion products, and protective coating were taken after excavating pipelines. The depth of stress corrosion cracking of the pipe steel was mostly related to counts of sulfate-reducing and denitrifying bacteria. In certain types of soil, crack depth correlated with the number of acid-producing microorganisms and aerobic chemoorganotrophs (saprophytes). A correlation was found between the extent of stress corrosion cracking of pipelines and the contents of mobile reduced iron, sulfides, organic carbon, and a number of other parameters of the surrounding soil.     

微生物腐蚀及腐蚀机理研究进展

在不同的环境中,不同种类的微生物能在材料上附着繁殖,其生命活动会引起或加剧材料的腐蚀。根据种类及功能的不同,腐蚀微生物可以分为硫酸盐还原菌、硫氧化菌、产酸菌、铁氧化细菌、铁还原细菌、硝酸盐还原菌以及产粘液细菌等。微生物腐蚀几乎能使所有现用的材料受到严重影响,破坏材料的结构与性能,在建筑、运输管道、工业环境(石油化工等)以及海洋环境中造成巨大的安全隐患和财产损失。本文概述了目前发现的腐蚀相关微生物的类群和特性,以及相对应的微生物腐蚀机理,为防护和控制材料的微生物腐蚀提供理论指导。     

Microorganisms in heat supply lines and internal corrosion of steel pipes

In laboratory experiments with batch cultures of thermophilic microorganisms isolated from urban heat supply systems, the growth of sulfate-reducing, iron-oxidizing, and iron-reducing bacteria was found to accelerate the corrosion rate of the steel-3 plates used in the pipelines. In the absence of bacteria and dissolved oxygen, minimal, corrosion was determined. The aforementioned microorganisms, as well as sulfur-oxidizing bacteria, were found to be widespread in water and corrosion deposits in low-alloy steel pipelines (both delivery and return) of the Moscow heat networks, as well as in the corrosion deposits on the steel-3 plates in a testing unit supplied with the network water. The microorganisms were found in samples with water pH ranging from 8.1 to 9.6 and a temperature lower than 90 degrees C. Magnetite, lepidocrocite, goethite, X-ray amorphous ferric oxide were the corrosion products identified on the steel-3 plates, as well as siderite, aragonite, and S0. The effect of microbiological processes on the rate of electrochemical corrosion was evaluated from the accumulation of corrosion deposits and from variation in total and local corrosion of the steel plates in a testing unit.     

Microorganisms in Heat Supply Systems and Internal Corrosion of Steel Pipelines

In laboratory experiments with batch cultures of thermophilic microorganisms isolated from urban heat supply systems, the growth of sulfate-reducing, iron-oxidizing, and iron-reducing bacteria was found to accelerate the corrosion rate of the steel-3 plates used in pipelines. In the absence of bacteria and dissolved oxygen, minimal corrosion was determined. The aforementioned microorganisms, as well as sulfur-oxidizing bacteria, were found to be widespread in water and corrosion deposits in low-alloy steel pipelines (both delivery and return) of the Moscow heat networks, as well as in the corrosion deposits on the steel-3 plates in a testing unit supplied with the network water. The microorganisms were found in samples with a water pH ranging from 8.1 to 9.6 and a temperature lower than 90°C. Magnetite, lepidocrocite, goethite, and X-ray amorphous ferric oxide were the corrosion products identified on the steel-3 plates, as well as siderite, aragonite, and S⁰. The accumulation of corrosion deposits and variation in the total and local corrosion of the steel plates in a testing unit were considered in terms of the influence of microbial processes.     

Corrosion of Iron by Sulfate-Reducing Bacteria: New Views of an Old Problem

About a century ago, researchers first recognized a connection between the activity of environmental microorganisms and cases of anaerobic iron corrosion. Since then, such microbially influenced corrosion (MIC) has gained prominence and its technical and economic implications are now widely recognized. Under anoxic conditions (e.g., in oil and gas pipelines), sulfate-reducing bacteria (SRB) are commonly considered the main culprits of MIC. This perception largely stems from three recurrent observations. First, anoxic sulfate-rich environments (e.g., anoxic seawater) are particularly corrosive. Second, SRB and their characteristic corrosion product iron sulfide are ubiquitously associated with anaerobic corrosion damage, and third, no other physiological group produces comparably severe corrosion damage in laboratory-grown pure cultures. However, there remain many open questions as to the underlying mechanisms and their relative contributions to corrosion. On the one hand, SRB damage iron constructions indirectly through a corrosive chemical agent, hydrogen sulfide, formed by the organisms as a dissimilatory product from sulfate reduction with organic compounds or hydrogen (“chemical microbially influenced corrosion”; CMIC). On the other hand, certain SRB can also attack iron via withdrawal of electrons (“electrical microbially influenced corrosion”; EMIC), viz., directly by metabolic coupling. Corrosion of iron by SRB is typically associated with the formation of iron sulfides (FeS) which, paradoxically, may reduce corrosion in some cases while they increase it in others. This brief review traces the historical twists in the perception of SRB-induced corrosion, considering the presently most plausible explanations as well as possible early misconceptions in the understanding of severe corrosion in anoxic, sulfate-rich environments.     

Characterization of microbial communities in gas industry pipelines

Culture-independent techniques, denaturing gradient gel electrophoresis (DGGE) analysis, and random cloning of 16S rRNA gene sequences amplified from community DNA were used to determine the diversity of microbial communities in gas industry pipelines. Samples obtained from natural gas pipelines were used directly for DNA extraction, inoculated into sulfate-reducing bacterium medium, or used to inoculate a reactor that simulated a natural gas pipeline environment. The variable V2-V3 (average size, 384 bp) and V3-V6 (average size, 648 bp) regions of bacterial and archaeal 16S rRNA genes, respectively, were amplified from genomic DNA isolated from nine natural gas pipeline samples and analyzed. A total of 106 bacterial 16S rDNA sequences were derived from DGGE bands, and these formed three major clusters: beta and gamma subdivisions of Proteobacteria and gram-positive bacteria. The most frequently encountered bacterial species was Comamonas denitrificans, which was not previously reported to be associated with microbial communities found in gas pipelines or with microbially influenced corrosion. The 31 archaeal 16S rDNA sequences obtained in this study were all related to those of methanogens and phylogenetically fall into three clusters: order I, Methanobacteriales; order III, Methanomicrobiales; and order IV, Methanosarcinales: Further microbial ecology studies are needed to better understand the relationship among bacterial and archaeal groups and the involvement of these groups in the process of microbially influenced corrosion in order to develop improved ways of monitoring and controlling microbially influenced corrosion.     

Soil type and microtopography influencing feeding above and below ground by the pine weevil Hylobius abietis

Abstract 1 The influence of soil type and microtopography on above and below ground feeding by adult pine weevils Hylobius abietis (L.) (Coleoptera: Curculionidae) was evaluated in a field experiment with enclosed weevil populations of known size. 2 Four soil treatments, each with a food source at the centre, were presented within each enclosure: (i) a flat surface with fine‐grained, cultivated humus; (ii) a flat surface with sand; (iii) a conical mound of sand; and (iv) a conical pit in sand. The food source consisted of a stem section of Scots pine Pinus sylvestris L. extending both above and below ground. 3 The majority of feeding on the half buried stem sections occurred below ground; only 2.7% of the total bark area consumed was situated above ground. The variation over time in bark area consumed was not significantly associated with any of the tested weather factors. 4 The amount of feeding was 10‐fold higher on food sources placed in fine‐grained humus than those in areas of flat sand. 5 Less pine bark was consumed on mounds of sand than flat sand surfaces, and there was more feeding in sandy pits than on flat sand. These effects on feeding are explained by the observation that the weevils had difficulties climbing the sandy slopes (27° gradient). 6 We conclude that pine weevil damage to conifer seedlings can be considerably reduced by planting on mounds of pure mineral soil and that planting deeply in the soil increases the risk of damage.     

Characterization of corrosive bacterial consortia isolated from petroleum-product-transporting pipelines

Microbiologically influenced corrosion is a problem commonly encountered in facilities in the oil and gas industries. The present study describes bacterial enumeration and identification in diesel and naphtha pipelines located in the northwest and southwest region in India, using traditional cultivation technique and 16S rDNA gene sequencing. Phylogenetic analysis of 16S rRNA sequences of the isolates was carried out, and the samples obtained from the diesel and naphtha-transporting pipelines showed the occurrence of 11 bacterial species namely Serratia marcescens ACE2, Bacillus subtilis AR12, Bacillus cereus ACE4, Pseudomonas aeruginosa AI1, Klebsiella oxytoca ACP, Pseudomonas stutzeri AP2, Bacillus litoralis AN1, Bacillus sp., Bacillus pumilus AR2, Bacillus carboniphilus AR3, and Bacillus megaterium AR4. Sulfate-reducing bacteria were not detected in samples from both pipelines. The dominant bacterial species identified in the petroleum pipeline samples were B. cereus and S. marcescens in the diesel and naphtha pipelines, respectively. Therefore, several types of bacteria may be involved in biocorrosion arising from natural biofilms that develop in industrial facilities. In addition, localized (pitting) corrosion of the pipeline steel in the presence of the consortia was observed by scanning electron microscopy analysis. The potential role of each species in biofilm formation and steel corrosion is discussed.     

Characterization of Microbial Communities in Gas Industry Pipelines

Culture-independent techniques, denaturing gradient gel electrophoresis (DGGE) analysis, and random cloning of 16S rRNA gene sequences amplified from community DNA were used to determine the diversity of microbial communities in gas industry pipelines. Samples obtained from natural gas pipelines were used directly for DNA extraction, inoculated into sulfate-reducing bacterium medium, or used to inoculate a reactor that simulated a natural gas pipeline environment. The variable V2-V3 (average size, 384 bp) and V3-V6 (average size, 648 bp) regions of bacterial and archaeal 16S rRNA genes, respectively, were amplified from genomic DNA isolated from nine natural gas pipeline samples and analyzed. A total of 106 bacterial 16S rDNA sequences were derived from DGGE bands, and these formed three major clusters: beta and gamma subdivisions of Proteobacteria and gram-positive bacteria. The most frequently encountered bacterial species was Comamonas denitrificans, which was not previously reported to be associated with microbial communities found in gas pipelines or with microbially influenced corrosion. The 31 archaeal 16S rDNA sequences obtained in this study were all related to those of methanogens and phylogenetically fall into three clusters: order I, Methanobacteriales; order III, Methanomicrobiales; and order IV, Methanosarcinales. Further microbial ecology studies are needed to better understand the relationship among bacterial and archaeal groups and the involvement of these groups in the process of microbially influenced corrosion in order to develop improved ways of monitoring and controlling microbially influenced corrosion.     

Effect of electrical corrosion protection of oil pipelines on fish migration

Effect of the dc electric field of the corrosion protection of oil pipelines crossing the Ob River on the behavioral response of fish was investigated. It was shown by calculations and measurements that, at the bottom level, the electric field strength was 0.6 V/m, and at a depth of 2 m from the surface, it was 0.4-0.1 V/m and extended to a distance of 50-100 m from the oil pipeline. It was established that the electric field of oil pipelines lowered the migration activities of fish, resulting in a growth of fish number in regions of increased electric field strength.     

Oil field microorganisms cause highly localized corrosion on chemically inhibited carbon steel

Carbon steel pipelines, a means for crude oil transportation, occasionally experience highly localized perforation caused by microorganisms. While microorganisms grown in laboratory culture tend to corrode steel specimens unevenly, they rarely inflict a corrosion morphology consistent with that of pipelines, where centimetre-sized corrosion features are randomly distributed within vast stretches of otherwise pristine metal surface. In this study, we observed that corrosion inhibitors (CIs), widely used for the control of acid gas (H₂S, CO₂) corrosion in oil fields, also affect microbial growth and activity. Inhibited carbon steel resisted biofilm formation and underwent negligible corrosion (< 0.002 mm Fe⁰ year⁻¹), despite 15 months of exposure to oil field waters harbouring a diverse microbiome. In contrast, physical scavenging of CI in these waters led to severe and highly localized corrosion (up to 0.93 mm Fe⁰ year⁻¹) underneath biofilms dominated by methanogenic archaea and sulfate-reducing bacteria. A sharp decline in CI concentration, as well as its active components, quaternary ammonium compounds (QACs), correlated with microbial sulfidogenesis. CIs are ubiquitously present in oil field waters and play an underappreciated role in microbial corrosion mitigation. Physical and biological scavenging of CIs may create local differences in steel inhibition effectiveness and thus result in highly localized corrosion.     

Reducing Wildlife Damage with Cost-Effective Management Programmes

Limiting the impact of wildlife damage in a cost effective manner requires an understanding of how control inputs change the occurrence of damage through their effect on animal density. Despite this, there are few studies linking wildlife management (control), with changes in animal abundance and prevailing levels of wildlife damage. We use the impact and management of wild pigs as a case study to demonstrate this linkage. Ground disturbance by wild pigs has become a conservation issue of global concern because of its potential effects on successional changes in vegetation structure and composition, habitat for other species, and functional soil properties. In this study, we used a 3-year pig control programme (ground hunting) undertaken in a temperate rainforest area of northern New Zealand to evaluate effects on pig abundance, and patterns and rates of ground disturbance and ground disturbance recovery and the cost effectiveness of differing control strategies. Control reduced pig densities by over a third of the estimated carrying capacity, but more than halved average prevailing ground disturbance. Rates of new ground disturbance accelerated with increasing pig density, while rates of ground disturbance recovery were not related to prevailing pig density. Stochastic simulation models based on the measured relationships between control, pig density and rate of ground disturbance and recovery indicated that control could reduce ground disturbance substantially. However, the rate at which prevailing ground disturbance was reduced diminished rapidly as more intense, and hence expensive, pig control regimes were simulated. The model produced in this study provides a framework that links conservation of indigenous ecological communities to control inputs through the reduction of wildlife damage and suggests that managers should consider carefully the marginal cost of higher investment in wildlife damage control, relative to its marginal conservation return.     

Characterization of bacterial community associated to biofilms of corroded oil pipelines from the southeast of Mexico

Microbial communities associated to biofilms promote corrosion of oil pipelines. The community structure of bacteria in the biofilm formed in oil pipelines is the basic knowledge to understand the complexity and mechanisms of metal corrosion. To assess bacterial diversity, biofilm samples were obtained from X52 steel coupons corroded after 40 days of exposure to normal operation and flow conditions. The biofilm samples were directly used to extract metagenomic DNA, which was used as template to amplify 16S ribosomal gene by PCR. The PCR products of 16S ribosomal gene were also employed as template for sulfate-reducing bacteria (SRB) specific nested-PCR and both PCR products were utilized for the construction of gene libraries. The V3 region of the 16S rRNA gene was also amplified to analyse the bacterial diversity by analysis of denaturing gradient gel electrophoresis (DGGE). Ribosomal library and DGGE profiles exhibited limited bacterial diversity, basically including Citrobacter spp., Enterobacter spp. and Halanaerobium spp. while Desulfovibrio alaskensis and a novel clade within the genus Desulfonatronovibrio were detected from the nested PCR library. The biofilm samples were also taken for the isolation of SRB. Desulfovibrio alaskensis and Desulfovibrio capillatus, as well as some strains related to Citrobacter were isolated. SRB consists in a very small proportion of the community and Desulfovibrio spp. were the relatively abundant groups among the SRB. This is the first study directly exploring bacterial diversity in corrosive biofilms associated to steel pipelines subjected to normal operation conditions.     

Soil Ripping and Herbicides Enhance Tree and Shrub Restoration on Stripmines

I evaluated responses by 16 native woody species to differential soil compaction and density of ground cover. The trees and shrubs studied represent sites in southern Illinois that commonly have restrictions to root growth from soil or drainage conditions. The study site was a restored surface coal mine in southern Illinois with a rooting medium compacted by grading and a dense ground cover of pasture species. Soil compaction was alleviated in half the study area before tree planting by mechanically ripping the soil to a depth of 1.2 m. Roots of half the trees and shrubs were dipped in a Terra® slurry before planting, and the ground cover around all planting spots was afterwards sprayed with herbicide. In year 2 after planting the ground cover in half of the unripped and half of the ripped area was further controlled by repeated application of herbicides. Ripping significantly increased height growth of all trees combined and all species individually in each year of the study. Second-year control of ground cover increased height growth of all trees combined and of seven species individually. Some species were damaged by herbicides. Terra® had little evident effect on species performance. Animal damage reduced early survival and growth, especially of Acer (maple) and Cornus (dogwood) species, and later growth of Quercus rubra (red oak). Removal of ground cover with herbicides tended to increase deer browse. Soil ripping, herbicide application, and choosing tree species unattractive to deer can be recommended to increase success in planting trees for forest restoration.     

Biodegradation and corrosion behaviour of <Emphasis Type="Italic">Serratia marcescens</Emphasis> ACE2 isolated from an Indian diesel-transporting pipeline

A facultative anaerobic species Serratia marcescens ACE2 isolated from the corrosion products of a diesel-transporting pipeline in North West India was identified by 16S rDNA sequence analysis. The role of Serratia marcesens ACE2 on biodegradation of commercial corrosion inhibitor (CCI) and its influence on the corrosion of API 5LX steel has been enlightened. The degrading strain ACE2 is involved in the process of corrosion of steel API 5LX and also utilizes the inhibitor as organic source. The quantitative biodegradation efficiency of corrosion inhibitor was 58%, which was calculated by gas chromatography mass spectrum analysis. The effect of CCI on the growth of bacteria and its corrosion inhibition efficiency were investigated. Additionally, the role of this bacterium in corrosion of steel has been investigated by powder X-ray diffractometer (XRD) and scanning electron microscope studies. The presence of high-intensity ferric oxides and manganese oxides noticed from the XRD indicates that ACE2 enhances the corrosion process in presence of inhibitor as a carbon source. This basic study will be useful for the development of new approaches for the detection, monitoring and control of microbial corrosion in petroleum product pipelines.     

Microbiologically influenced corrosion in petroleum product pipelines--a review

Microbiologically influenced corrosion is responsible for most of the internal corrosion problems in oil transportation pipelines and storage tanks. One problematic area in treating gas lines is the occurrence of the stratification of water in the line. Under these conditions, corrosion inhibitors do not come into contact properly and oil and inhibitors undergo degradation. The role of bacteria on oil degradation, the consequences of oil degradation in fuel systems and its influence on corrosion have been explained in detail. Besides, factors influencing on degradation of oil and corrosion inhibitors have also been discussed. Mechanism of microbiologically influenced corrosion in oil pipeline has been explained. Many of the misapplication of biocides/inhibitors occur mainly because the characteristics of biocides/inhibitors are not considered before use in pipeline industry. List of biocides and monitoring programme have been collected from literature and presented.     

Effect of Hydrogenase and Mixed Sulfate-Reducing Bacterial Populations on the Corrosion of Steel

The importance of hydrogenase activity to corrosion of steel was assessed by using mixed populations of sulfate-reducing bacteria isolated from corroded and noncorroded oil pipelines. Biofilms which developed on the steel studs contained detectable numbers of sulfate-reducing bacteria (10⁴ increasing to 10⁷/0.5 cm²). However, the biofilm with active hydrogenase activity (i.e., corrosion pipeline organisms), as measured by a semiquantitative commercial kit, was associated with a significantly higher corrosion rate (7.79 mm/year) relative to noncorrosive biofilm (0.48 mm/year) with 10⁵ sulfate-reducing bacteria per 0.5 cm² but no measurable hydrogenase activity. The importance of hydrogenase and the microbial sulfate-reducing bacterial population making up the biofilm are discussed relative to biocorrosion.     

Phylogenetic characterization of bacterial consortia obtained of corroding gas pipelines in Mexico

Characterization of the microbial populations formed in gas pipelines is essential to understand the metallic surface-microbe interaction, their role in metal corrosion, and to implement efficient monitoring and control strategies. Microbial community analysis in a corroded gas pipeline in a petroleum-producing facility in the Southeast region in Mexico was performed by traditional cultivation techniques and identification based on 16S rRNA gene sequence. In all samples, thin bacterial biofilms were observed and pitting corrosion was reveled after removing the biofilms. Six pure or mixed cultures of anaerobic bacteria were obtained and their 16S rRNA libraries were constructed, respectively. At least two members of each RFLP profile were sequenced and the phylogenetic affiliations of cloned bacterial 16S rRNA genes indicated that native biofilms were mainly colonized by Desulfovibrio vulgaris and Desulfovibrio desulfuricans, sulfate-reducing bacteria members; Citrobacter freundii, an Enterobacteriaceae member; Clostridium celerecrescens and Clostridium sporogenes, spore-forming anaerobic species and Cetobacterium somerae, a microaerotolerant, non-spore-forming fusobacteria. Some of these species have been observed consistently in other steel pipelines previously, but Cetobacterium members and C. celerecrescens are described for the fist time in this corroded gas pipeline. The potential role of each species in biofilm formation and steel corrosion is discussed.     

Vegetation succession at the abandoned Ogushi sulfur mine, central Japan

We surveyed plant community development at the abandoned Ogushi sulfur mine. We found seven communities dominated by the following respective species: Deschampsia flexuosa, Miscanthus sinensis, shrub willow, Gaultheria miqueliana–Betula ermanii, Sasa senanensis–Betula ermanii, willow–Betula ermanii, and Sasa kurilensis–Abies veitchii. We examined the succession of these communities, in which younger communities of low height and ground cover contained seedlings of the successive communities that were taller and had higher ground cover. To understand the development of these different communities, we surveyed damage from mining pollution and effects of immature soils formed by landslides. The average pH (H₂O) was 4.12, and aluminum concentrations were not sufficiently high to damage plant growth, except in areas where sulfur had been mined. The organic carbon and nitrogen content in soil samples were very low because of a delay in soil development caused by a large landslide in 1937. Hence, succession was positively correlated with the soil development stage. The delay in soil development after a large landslide influenced the seven successional steps of the plant communities, but mineral poisons at the abandoned Ogushi sulfur mine had no effect on succession.