Effect of anthraquinone-2,6-disulfonate on anaerobic digestion of fracturing flowback fluid under high salinity stress

The anaerobic digestion has been proved to be effective in treating fracturing flowback fluid. However, the high salinity in fracturing flowback fluid seriously inhibits the anaerobic treatment performance. A new strategy was proposed to improve the anaerobic digestion of fracturing flowback fluid under high salinity stress by adding anthraquinone-2,6-disulfonate (AQDS) in this study. The results showed that the addition of AQDS (45 mg/L) effectively alleviated the inhibition of high salinity (25 g/L) on the anaerobic digestion of fracturing wastewater, COD removal efficiency and cumulative methane yield increased by 17.8 % and 30.2 %, respectively. AQDS could alleviate the damage of anaerobic microorganisms caused by high salinity, the proportion of the damaged cells in anaerobic granular sludge decreased from 68.9 % to 38.3 %. Moreover, AQDS promoted the metabolic activity of anaerobic granular sludge under high salinity stress. The specific methanogenic activity, coenzyme F420 and dehydrogenase of anaerobic granular sludge increased by 30.0 %, 21.1 % and 21.4 %, respectively. Electrochemical analysis results showed that the addition of AQDS improved the electron transport of the anaerobic digestion system, and electron transport system activity increased by 62.4 %. This study provides an attractive strategy to alleviate the inhibition of high salinity on anaerobic digestion performance of fracturing flowback fluid. [Display omitted] •AQDS with 45 mg/L improved the anaerobic digestion of fracturing flowback fluid.•The inhibition of the anaerobic digestion by high salinity was alleviated by AQDS.•Proportion of living cells under high salt stress increased by 29.2 % by adding AQDS.•AQDS promoted the metabolic activity of granular sludge with high salinity stress.•ETSA of anaerobic digestion system increased by 62.4 % by adding AQDS.