Microbial ecology of sulphide-producing bacteria in water cooling systems

Abstract

Microbiological induced corrosion (MIC) can result in damage and economic losses in various industries. Although the importance of sulphate-reducing bacteria (SRB) in MIC has been widely recognized for many years, there has been increasing evidence that other organisms in addition to SRB have been involved in the corrosion process. There is no information available regarding the ecology of SRB in industrial cooling water systems. The problem has been detecting and quantifying these organisms. The potential of using species specific fluorescent antibodies (FA) prepared against authentic SRB-strains for studying the ecology of SRB in industrial cooling water systems was investigated. Culture conditions influenced the expression of surface antigens, causing the antisera to be extremely specific and unsuitable for the identification of SRB enriched from industrial cooling water systems. Caution should be exercised when using FA for ecological studies. Different isolation media and carbon sources for the isolation and detection of SRB were evaluated. Iron sulphite (IS)-medium yielded the highest numbers when used to enumerate SRB from pure culture and industrial water samples. H2S-producing bacteria that utilized lactate, acetate, formate or palmitic acid as different carbon sources were also isolated from industrial water samples. Using IS-medium Shewanella putrefaciens was the dominant sulphide producing bacteria isolated from industrial cooling water systems. Corrosion studies indicated that S. putrefaciens could play an important role in microbially induced corrosion Since enumerating SRB by conventional methods is difficult, laborious and time consuming, the Malthus system, using conductance measurements, can be used for counting SRB cells in pure culture and thus for laboratory biocide evaluations.