Process Issues Caused by ‘Slime’: The Use of Analytical Chemical and Molecular Microbial Methods (MMM) to Identify and Treat Flow Issues, a Case Study
In order to treat onshore produced water, reduce oil in water and chemical oxygen demand (COD), a plant design incorporating bioreactors was constructed to allow for produced water disposal to the environment. However, since the attempted commissioning of the plant, process issues have been encountered due to the formation of an unidentified ‘slime’ upstream of the bioreactor, resulting in an inability to transfer the produced water for treatment in the bioreactors (due to fear of fouling the patented matrix).
Here we used analytical chemical techniques such as Fourier transform infrared spectroscopy (FTIR) in conjunction with 454 DNA pyrosequencing to identify the slime. An in-depth site audit was carried out to isolate the cause of the problem and recommend steps to eradicate the issue.
Initial analysis by FTIR indicated that the slime was biological in origin. Microscopic analysis suggested it was a complex mix of Prokaryotic and Eukaryotic microorganisms, forming a microbial mat, intercalated with oil droplets. Extraction with 90% acetone and scanning spectroscopy identified the presence of chlorophyll a. DNA sequencing using 454 pyrosequencing of eubacterial, fungal and algal genes confirmed that the slime was microbial in nature and revealed the dominant microorganisms present.
The site audit identified areas which were contributing to the problem and recommendations were given to rectify this, to reduce microbial slime formation. This case study shows how cutting-edge molecular microbial methods (MMM) such as 454 pyrosequencing can add value to conventional analytical approaches to identify and solve water treatment process problems within the oil industry.