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.