Microbiologically influenced corrosion (MIC) is a serious problem in the oil and gas industry, as well as other industries such as water utilities. Sulfate reducing bacteria (SRB) biofilms are often found to be the main cause for MIC pitting attacks. Pitting corrosion due to SRB has been found to be responsible for pipeline failures. MIC pitting was identified as the primary suspect for the 2006 Alaska oil pipeline leak. Acid producing bacteria and other microorganisms have also been found to contribute to MIC.
In addition, biofouling by microbes, especially microbes in the form of biofilms, is a major problem in many industries, such as oil and gas, water utilities, power plants (especially cooling systems, such as chilled water systems and cooling towers), and fresh-water and salt-water shipping. Microbes in biofilms are far more difficult to treat than planktonic cells of the same microbes. One particular type of biofouling is reservoir souring, which is often the result of biogenic H2S production by SRB. Current treatments for SRB are partially effective; however, SRB are very resilient because the sessile SRB in biofilms formed on rock and soil surfaces underground are very difficult to eradicate. In shale oil and gas production, biofouling by microbes can plug the rock and soil pores resulting in reduced flow of oil and gas. In addition, biofouling is particularly troublesome in membrane filtration processes. The biofilms form and grow on the membrane and reduce throughput and shorten the membrane life span. Moreover, biofouling is also a problem in common households such as in kitchens and bathrooms. In biofouling situations, the recalcitrance of the biofilm makes it far more difficult to treat than treating a system with only planktonic cells. Unfortunately, an overwhelming majority of microbes prefer to organize as a biofilm community.
Mechanical cleaning, including line pigging, and biocide treatment are common methods for mitigating the effects of biofilms. Tetrakis hydroxymethyl phosphonium sulfate (THPS), a non-oxidizing biocide, is widely used due to its broad-spectrum and excellent biodegradability. Such biocides are generally effective for treating planktonic cells. However, the sessile cells in a biofilm, whether it is corrosive or only causes fouling, are far more difficult to treat than planktonic cells because the biofilm provides good protection from antibacterial agents and other unfavorable environmental influences. In fact, the biocide dosage required to eradicate sessile cells in an established biofilm is often tenfold higher, or more, than the dosage needed to eradicate planktonic cells.