An investigation into the microbial degradation of Benzyldimethyl Hexadecylammonion Chloride used in oilfield chemical formulations.

Abstract

Benzyldimethyl Hexadecylammonium Chloride (BDHAC) is a quaternary ammonium compound (QAC) used in corrosion inhibitor formulations. It has both corrosion inhibition and biocidal properties. Studies have suggested that QACs in produced water are often discharged to the marine environment during oil exploration and production. The fate of these compounds on release to the marine environment, especially the ones with a benzyl ring, is not well understood. On reaching the marine environment, QAC adsorb onto sediment and may become bioavailable and toxic to the benthic communities. Therefore bioremediation of sediment could be useful to help preserve the marine environment. A biodegradation study was carried out using an enrichment culture technique with marine sediment, to identify which marine bacteria degraded BDHAC and subsequent degradation products. Following enrichment in the presence of BDHAC, different strains of bacteria, isolated from marine sediments, were shown to degrade BDHAC in a minimal salts medium. The bacteria identified by 16S rDNA sequencing, were shown to belong to several genera and were identified as Marine bacterium, Bacillus subtilis, Bacillus niabensis, Sporosarcina sp., Thalassospira sp, Rhodospirillaceae and Staphylococcus equorum. Investigations revealed that these bacteria were capable of degrading BDHAC when it was present at high concentrations, in the range 2 – 4 mg/ml. In media containing BDHAC, up to 90% of the substance was degraded within 43 days. Quantification of BDHAC after biodegradation experiments were performed by Colorimetric Dye Binding Assay (CDBA) and Electrospray Ionisation Tandem Mass spectrometry (ESI-MS/MS). Preliminary analysis of samples by ESI-MS/MS produced a peak with a parent-daughter ion transition of 136.0 91.0, corresponding to N, N-dimethylbenzylamine. The presence of this potential metabolite suggested the cleavage of the C alkyl-N bond as a step in BDHAC catabolism. This research will contribute to an understanding of the potential of the isolated strains of bacteria in bioremediating BDHAC contaminated sites. It will also assist operators and regulators in the oil and gas industry to understand the fate of BDHAC in the environment when the compound is used in corrosion inhibitor formulations. This understanding will assist environmental risk assessment of oil production facilities.