The effect of dissolved stainless steel alloy elements on the activity and growth of SRB

Sulphate reducing bacteria have an important role in the sulphur cycle, and therefore in wastewater treatment systems. They are able to form biofilms on metallic surfaces, leading to fouling and corrosion problems. These bacteria are among the micro-organisms most frequently implicated in microbial corrosion of iron and ferrous alloys. Alloying elements added to steels for the improvement of their corrosion resistance such as molybdenum and nickel can be dissolved in bulk liquid during the corrosion processes and therefore available to the micro-organisms. That may affect bacterial metabolism and adhesion. In this study, suspended cultures of sulphate reducing bacteria (SRB) were subjected to several nickel concentrations in order to evaluate the effect of the dissolved metal on bacterial metabolism. Simultaneously, SRB biofilms were developed on stainless steel 304 and on polymethylmethacrylate (PMMA) in order to study surface effect on biofilm formation. Results showed that nickel (Ni) in all tested concentrations between 0.006 and 5 mg/L had a positive effect on the growth of Desuljovibrio desulfuricans. Additionally, biofilms formed on stainless steel presented higher metabolic activity, confirmed by sulphate removal and acetate concentration in the effluent stream. Metal elements present in stainless steel may affect SRB activity. This can be the case of nickel that represents around 8% of stainless steel 304 and that had a positive impact on suspended SRB cultures, under the tested concentrations