Effects of different concentrations of biocides on biofilm microorganisms in oil pipelines in Irri, Delta State, Nigeria

Abstract

Biofilm can be defined as microbial communities containing large different numbers of microorganisms, which produce a wide range of biopolymers. This leads to adhesion to surfaces within hours of immersion. The attachment results in pit corrosion of oil pipelines. The study to assess the effect of different concentrations of biocides (0, 1,2,3,4 and 5 per cent) on bacterial diversity associated with corrosive biofilms in steel pipelines in Irri, Delta State was conducted in University of Calabar, Nigeria. Microbial communities associated with biofilms promote corrosion of oil and gas pipelines, which is a major problem confronting these industries. The community structure of bacteria in the biofilm formed in oil pipelines is a basic knowledge to understand the complexity and mechanisms of metal corrosion. To assess bacterial diversity, biofilm samples were obtained from mild steel coupons corroded after 127 days of exposure to normal operation and flow of petroleum. Microbial community analysis in biofilms of oil pipeline was determined by traditional cultivation technique. Most of the bacterial species detected in biofilms of oil pipelines included the following Halomonas subglaciescola, Pseudomonas aeruginosa, Klebsiella oxytoca, Bacillus subtilis, Serratia marcescens, Bacillus cereus, Acidithiobacillus ferrooxidans and Staphylococcus epidermidis. The sensitivity test results showed that Ozone (oxidizing biocide) exhibited the best biocidal characteristics and at the concentration of 1 percent, eliminated most of the bacterial species except the Gram positive and spore formers. The next effective biocide was sodium hypochlorite (oxidizing biocide) and then followed by formaldehyde as the least effective biocide. For effective control of biofilm bacteria, Ozone (oxidising biocide) and formaldehyde (non-oxidising biocide and persistent) should be used simultaneously as these biocides are effective against biofilms, bacteria and other microbes and are also environmental friendly biocides. The elimination or inhibition of these organisms in oil pipelines will keep our agricultural lands free of contamination from oil spills cause by corrosion.