Enrichment and acclimation of thermophilic desulfurizing bacterial consortium with sulfide removal potential for injection water of the oil reservoir

Abstract:

[Background] The sulfide in the produced water of offshore oilfield often exceeds the limit, which affects the viscosity of the polymer-containing injection water. The efficiency of biodesulfurization is poor due to the poor adaptability of conventional mesophilic sulfide-removing bacteria to the high temperature of the produced water after oil removal. [Objective] To analyze the changes of microbial consortium structure in the process of offshore produced water treatment and acclimate a thermophilic bacterial consortium for desulfurization. [Methods] Water samples were collected from Haisan Station of Shengli Oilfield, and 16S rRNA gene sequencing was performed to reveal the structure of the bacterial consortium. The acclimation was conducted in the inorganic medium at different temperatures (55, 60, and 65 °C) for multiple rounds, and atmospheric and room temperature plasma (ARTP) was employed to obtain the efficient thermophilic desulfurizing bacteria. Metagenome sequencing was employed to study the composition of the enriched bacterial consortium and then the desulfurizing ability of the consortium was determined. [Results] The produced water samples contained abundant thermophilic bacteria and sulfate-reducing bacteria, such as Thermodesulfovibrio, Pseudothermotoga, Thermolithobacter, Fervidobacterium, Thermovenabulales, and Pseudomonas. Hydrogenophilus became the most dominant bacteria in the effluent from the nitrogen gas-floated oil removal. The relative abundance of Hydrogenophilus in the effluent water of the central platform and the polymer injection platform was 76% and 84%, respectively. After the enrichment and acclimation with increasing temperature, Thermus became predominant, with the relative abundance of 89.4%, in addition to a few members of Hydrogenophilus. The efficiency of desulfurization was further improved by ARTP. The acclimated bacterial consortium could rapidly desulfurize the liquid containing 8.88 mg/L sulfide at 65 °C, with a removal rate of 100% and a removal speed up to 0.49 mg/(L·h). [Conclusion] An efficient desulfurizing bacterial consortium adapted to 65 ℃ was obtained, which improved the desulfurization of polymer-containing injection water. This study would be helpful for the development of high-temperature oil fields.