Application of an indigenous microorganisms-based fixed-bed GAC-biofilm reactor for passive and sustainable treatment of oil sands process water through combined adsorption and biodegradation processes

In this study, a fixed-bed biofilm reactor (biofilter) was developed and applied for oil sands process water (OSPW) remediation by using granular activated carbon (GAC) as packing media. Using quantitative polymerase chain reaction (qPCR) detection, the total bacterial copy number (16S) in the GAC biofiltration system was found to reach a relatively stable level (1.3 +/- 0.2 x 10(9) copies/g GAC) after 62 days of operation, and the thickness of biofilm on GAC surface was 26.7 +/- 4.3 mu m based on the scan of confocal laser scanning microscopy (CLSM). The established GAC-biofilter showed 95.4% naphthenic acids (NAs) removal from raw OSPW after 2 months of operation. The GAC-biofilter also showed 88.3% NAs removal after a long operation time (2 years), indicating its sustainable bioremediation capacity for OSPW. 16S and 18S rRNA gene-targeted metagenomic sequencing showed that the microbial community in the GAC biofilter had higher diversity and richness than that found in the sand biofilter which was used for OSPW treatment previously. Comamonadaceae and Saccharomycotina were found to be the dominant bacterial and fungal families in the GAC biofilter, respectively. Xenobiotic metabolism function of the microbial community may contribute significantly to the biodegradation of NAs. The GAC biofiltration process is a promising passive OSPW treatment approach that can be used in-situ.