Adhesion energy, spreading coefficient and interfacial tension as an efficient tool for assessing biocide performance

Abstract

It is estimated that microbiologically influenced corrosion (MIC) contributes to 20%-50% of the total cost of corrosion. Biocides are often used to counter MIC. Normally, the choice of a biocide is based on planktonic kill studies as well as cost of the treatment chemicals. Sessile kill studies have significant advantages over planktonic studies but usually take 8 weeks to complete. Furthermore, both sessile kill and planktonic studies only provide phenomenological results and therefore do not explain the mechanisms. To bridge this gap, we have calculated spreading coefficient and work of adhesion from contact angle measurements as a tool for assessing the performance of a biocide. This novel method provides insights into how biocides interact with a biofilm on a surface and is quicker than sessile kill study. Based on surface energy calculations, we have identified parameters that will aide in the prediction of biofilm removal and prevention. For example, surfactants with a positive spreading coefficient on a substrate and having a stronger affinity for the substrate than the biofilm (i.e., a lower interfacial tension) are effective in biofilm prevention. On the other hand, surfactants with a low interfacial tension with a substrate are effective in biofilm removal. Given the diversity of surfaces to which bacteria attach (carbon steel, near wellbore, membrane, etc.), this rapid technique is a good prediction tool for the effectiveness of a biocide application. This paper will provide an overview of the technique and discuss some examples of surfactants that can be used for biofilm removal and prevention.