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A platform for research: civil engineering, architecture and urbanism
Microbially influenced corosion, Victaulic couplings, water treatment and DNA studies
The utilities at a major government office facility include both a condenser and a chilled water system. Although they are similar, the water in the first is regularly aerated, while the other is a closed system. The piping in both is largely carbon steel, with minor cast iron. Both systems used Victaulic couplings rather than welded joints. The joints in the condenser section of the system are deeply corroded, while the chilled water system is in good condition. A study was implemented to determine the root cause of the failures in the condenser system, to review operating procedures to determine if they were involved in the failures, and to recommend future actions to repair the system and prevent further damage. Comparison of the microbiology of the metal surfaces of the joints and the gaskets at those joints in the two systems showed that there were significantly greater concentrations of aerobic and anaerobic bacteria at both of those locations in the condenser water system than in the chilled system, particularly on the gaskets. These bacteria are not detected by the normal plate counts run by the water treatment provider. However, slime-forming and iron-degrading bacteria have been specifically identified in the pipe joints by Polymerase Chain Reaction analysis and DNA sequencing techniques. Chemical analysis of the deposit in one of the joints shows an extremely high sulfur concentration (2.3%), indicative of the presence of active sulfur-reducing bacteria. Water analyses show relatively high sulfur and chloride contents. The design of the specific Victaulic couplings appears to be related to the failures as all the failures occurred in only one model of joint and not in others. In addition, aeration of the condenser water and operating procedures may have had major roles in the failures. Recommendations for improvement are given.
Microbially influenced corosion, Victaulic couplings, water treatment and DNA studies
The utilities at a major government office facility include both a condenser and a chilled water system. Although they are similar, the water in the first is regularly aerated, while the other is a closed system. The piping in both is largely carbon steel, with minor cast iron. Both systems used Victaulic couplings rather than welded joints. The joints in the condenser section of the system are deeply corroded, while the chilled water system is in good condition. A study was implemented to determine the root cause of the failures in the condenser system, to review operating procedures to determine if they were involved in the failures, and to recommend future actions to repair the system and prevent further damage. Comparison of the microbiology of the metal surfaces of the joints and the gaskets at those joints in the two systems showed that there were significantly greater concentrations of aerobic and anaerobic bacteria at both of those locations in the condenser water system than in the chilled system, particularly on the gaskets. These bacteria are not detected by the normal plate counts run by the water treatment provider. However, slime-forming and iron-degrading bacteria have been specifically identified in the pipe joints by Polymerase Chain Reaction analysis and DNA sequencing techniques. Chemical analysis of the deposit in one of the joints shows an extremely high sulfur concentration (2.3%), indicative of the presence of active sulfur-reducing bacteria. Water analyses show relatively high sulfur and chloride contents. The design of the specific Victaulic couplings appears to be related to the failures as all the failures occurred in only one model of joint and not in others. In addition, aeration of the condenser water and operating procedures may have had major roles in the failures. Recommendations for improvement are given.
Microbially influenced corosion, Victaulic couplings, water treatment and DNA studies
Mikrobiologische Korrosion, Victaulische Kopplungen, Wasserbehandlung und DNA-Untersuchungen
Gibbon, Donald L. (author) / Zamanzadeh, Mehrooz (author)
2005
11 Seiten, 16 Bilder, 3 Tabellen, 15 Quellen
Conference paper
English
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