Detection of sulphate-reducing bacteria using NACE serial dilution and SRB rapidcheck II methods

Abstract

Microbiologically Influenced Corrosion (MIC) or bacterial corrosion can be a major problem in process equipment exposed to different types of waters in the production, processing and handling of crude oil and gas. Sulphate-reducing bacteria (SRB) are among the most destructive environmental organism and their industrial impact is widespread. They cause corrosion and stress corrosion cracking of metals and alloys used in petroleum production, cooling water system, waste water treatment and all aqueous process. Hence, there is a constant need to monitor bacterial proliferation in such systems in order to take remedial action. The most commonly used methodology to determine bacterial contamination is the Serial Dilution Technique which is culturing the sample in a laboratory until the numbers of SRB were sufficiently high to be detected by observation of general blackening of the sample. However, this method though very reliable, is quite involved and time consuming as it takes 28 days to analyze the result. So, another method is proposed to speed up this culturing process or bypass culturing altogether and monitor the organisms directly. This method is known as SRB Rapidcheck II. Results from the evaluation indicate that the SRB Rapidcheck II method provided higher SRB-population estimates in this case and results were available in 20 minutes instead of 28 days required by the NACE serial dilution method. Due to alarm activity of sulphate-reducing bacteria in the pipeline, it is recommended to conduct biocide treatment to kill SRB which is anaerobic.