Mechanism of Dielectric Barrier Discharge Plasma Coupled with Calcium Peroxide to Improve the Quantity and Quality of Short Chain Fatty Acids in Anaerobic Fermentation of Cyanobacteria

The recycling of high-value carbon resources from waste cyanobacteria is an interesting research direction. In this study, the feasibility of barrier discharge plasma coupled with calcium peroxide (DBD/CaO2) as a novel pretreatment method to improve the quantity and quality of short chain fatty acids (SCFAs) in anaerobic fermentation of cyanobacteria was explored. The relatively excellent SCFAs and acetic acid production were obtained in DBD (58.5 W, 30 min)/CaO2 (0.09 g/g VSS) group, which were 6.7 and 7.5 times that of the control, respectively. DBD and CaO2 synergistically improved the solubilization of cyanobacteria polymers. Cell rupture occurs under the combined influence of physicochemical effect and intracellular oxidative stress. DBD/CaO2 was beneficial to reduce the adverse effect of humus on anaerobic fermentation and improve the biodegradability of dissolved organic matter. The accumulation of microorganisms related to hydrolysis and acidification and the reduction of SCFAs/acetic acid consumers were also related with the accumulation of SCFAs/acetic acid. DBD/CaO2 treatment achieved a 73.2 % removal rate of microcystin-LR on the 5th day of anaerobic fermentation. The contribution order of functional active species to cyanobacteria solubilization and microcystin-LR degradation was e-aq > .OH > O-1(2) > .O-2.O-2(-) .O-2(-) > ONOO- and e-aq > .OH > .O-2 > O-1(2) > ONOO-, respectively. Finally, the synergistic mechanism of DBD and CaO2 in cyanobacteria anaerobic fermentation was expounded. This work provides an attractive and promising technology to recover valuable carbon sources from cyanobacteria.