Pseudomonas putida Biofilm Facilitates Fine Solids, Water and Oil Separation from Oil Sands Tailings

Abstract

Aims: The generation of the tailings, poor settling slurry contaminated with emulsified bitumen, significantly increases the negative impact of oil sands operations on the environment and human health (contamination of surface and ground water with hydrocarbons and naphthenic acids, methane emission), as well as operation cost. Poor effectiveness of conventional tailings settling and clean-up technologies contributes to the daily increase of the quantity of tailings deposited in ponds covering now more than 130 km2. There is an urgent need for development of novel tailings settling technologies. The aim of the present study is a comparative analysis of the impact of Pseudomonas putida planktonic and biofilm populations on oil, solids and water separation in tailings, and the investigation of the mechanisms involved in bioseparation. Methodology: Mature fine tailings (MFT) were exposed to Pseudomonas putida planktonic populations and biofilms at agitation followed by static conditions for settling. Oil-solids-water separation was determined by water and oil release from MFT in comparison with untreated tailings. Interaction of tailings with microbial populations was investigated with scanning electron microscopy (SEM), confocal scanning laser microscopy (CSLM) and energy-dispersive X-ray (EDAX) spectroscopy. Results: The exposure of mature fine tailings to microbial cultures, and especially to biofilms, significantly increase tailings densification, dewatering and bitumen release. The separation efficiency is associated with fine clay aggregation due to the interaction with the microbial cells, biofilm colonies and extracellular polymeric substances (EPS). Conclusion: The mechanism driving the observed biodensification is the aggregation of fine solids via flocculation by biofilm-produced EPS and bacterial cells. Microorganisms were also observed to destabilize emulsions and enhanced residual bitumen release from tailings.