Organics removal from shale gas wastewater by pre-oxidation combined with biologically active filtration

Biological treatment technology is increasingly explored in shale gas wastewater (SGW) treatment owing to its cost effectiveness and requires efforts to improve its efficacy. In this work, ozone and ferrate(VI) oxidation pre-treatment were evaluated to enhance the performance of the subsequent biologically active filtration (BAF) in the removal of organic contaminants. The oxidation improved the SGW biodegradability and organic composition under relative high salinity (~20 g/L). Due to the degradation activity of microorganisms, the organics removal efficiency in the BAF system was observed to gradually improve and then reaching stability in long-term continuous-mode operation. The removal rate of dissolved organic carbon (DOC) of the ozone-BAF (O3-BAF) and the ferrate(VI)-BAF (Fe(VI)-BAF) systems was 83.2% and 82.8%, respectively, higher than that of BAF alone (80.9%). This increase was attributed to higher activity and content of microorganisms in O3-BAF and Fe(VI)-BAF systems. Two uncultured bacterial species with high abundance of 7.2-21.0% and 2.24-22.31% in genus Rehaibacterium and genus Methyloversatilis were significantly correlated with DOC removal and fluorescent organics removal, respectively. More research is needed to understand whether the species were new and their specific function. This study provides valuable suggestions for extracting safe water from SGW with an efficient treatment train.