Monitoring and disinfection of biofilm-associated sulfate reducing bacteria on different substrata in a simulated recirculating cooling tower system

Microbial biofilm and corrosion in cooling systems are the most common problems that damage expensive equipment, cause loss of production, and increase maintenance costs. Sulfate reducing bacteria were considered the major bacterial group involved in microbiologically influenced corrosion (MIC). We investigated the survival and enumeration of biofilm-associated SRB on coupons of galvanized steel, stainless steel, and copper, which are materials used in the manufacturing of cooling systems. We also investigated the effect of monochloromine on SRB as in mixed species mature biofilms formed on coupons by simulating recirculating cooling water conditions, due to the better penetration feature in biofilms than the residual chlorine. It was concluded that SRB count increased with time in bulk water and the surfaces (P < 0.01). Experimental results supported by statistical analyses show that monochloromine is poorly effective on SRB colonies formed on galvanized and stainless steel surfaces

MIC and Cracking of Mild and Stainless Steels

Microbiologically influenced corrosion (MIC) is basically an electrochemical corrosion in which the extent and severity of the corrosion process is determined by organisms such as, but not limited to, bacteria. This work will discuss both electrochemical and mechanical features of MIC of three types of steels of frequent use, that is, mild, stainless and duplex stainless steels. The bacteria investigated in this study are single-type cultures of marine isolates of sulphate reducing bacteria, iron reducing bacteria as well as their mixed cultures. This is important because in nature, it is the impact of mixed communities of bacteria that can affect corrosion of engineering materials. Also, to the best knowledge of this author, for the first time the stress corrosion cracking of these steels in biotic cultures containing these bacteria have been characterised and compared with abiotic environments. In conducting this research, techniques such as SSRT (for conducting mechanical tests), OCP (as one of the safest electrochemical methods for studying MIC) as well as XRD, EDXA and metallography have been employed