BACTERIAL CORROSION INDUCED BY AEROBIC AND ANAEROBIC MICROORGANISMS

Abstract

The biocide is a chemical substance capable of killing different forms of microorganisms, which is widely used in oilfields to control microbial problems. In this study, the efficacy of biocide (Quaternary-ammonium compounds ‘QACs’ blended with Glutaraldehyde) that is commonly used in Libyan oilfields was investigated against natural micro-flora isolated from an open re-circulating cooling water system. The effects of those chemicals were studied on bacterial isolates used to build up biofilms on stainless steel coupons (AISI 304 and AISI 316). Two bacterial strains have been selected to be carried out in this study and identified as Pseudomonas aeruginosa and Sulfate-reducing bacteria (Desulfobulbus sp).

The strains were grown with increasing concentrations of the Quaternary-ammonium compounds blended with glutaraldehyde. Atomic Force Microscope (AFM) was used to visualize the topographic of biofilms developed on metal surfaces. The efficiency of the biocide was determined by acridine orange (AO) staining. In addition, electrochemical technique (linear Polarization Resistance) gave information on corrosion rate associated with the microbial activity and the biocide effects. The results show that microbial strains have different responses against biocide. While Pseudomonas aeruginosa shows the ability to grow at high concentrations of biocide, Desulfobulbus sp has no resistance—where 25ppm was enough to cause a shock for the growth of microbes—not only the microbial growth but their adhesion and the biofilm formation decrease dramatically.