Demulsification and bio-souring control of alkaline-surfactant-polymer flooding produced water by Gordonia sp. TD-4

[Display omitted] •Isolating procedure of nitrate-reducing bacteria for demulsification was evaluated.•Carbon sources determine bio-demulsifying performance and corresponding mechanisms.•Flocculation and competitive adsorption constitute two bio-demulsifying mechanisms.•Carbon sources determine lasting potential in biological souring control.•The concentration of emulsified crude oil was decreased to less than 40 mg/L. Emulsification and biological souring of alkaline-surfactant-polymer (ASP) flooding produced water constitute two serious issues currently facing the petroleum industry. This study introduced a potential method to solve these two issues synergistically. Nitrate-reducing bacteria (NRB) with alkane-degrading and demulsifying ability were isolated, and their potential and feasibility in the demulsification and bio-souring control were evaluated. The results indicated that carbon sources played decisive roles not only in bio-demulsifying performance and mechanisms but also in the lasting potential of bio-souring control. The sodium acetate induced bio-demulsifying bacteria, Gordonia sp. TD-4, to separate emulsified oil by bio-flocculation-derived demulsification, while oil-soluble carbon sources like paraffin oil induced TD-4 to separate emulsified oil by competitive adsorption-derived demulsification. TD-4 could effectively decrease the concentration of emulsified crude oil in ASP flooding produced water (oil in water emulsion, O/W; initial oil concentration 965 ± 21 mg/L; mean oil droplet diameter 65 nm) to less than 40 mg/L. The potential of electronic donor competition and nitrite accumulation indicated TD-4 could be a bio-augmenter to control bio-souring.