Column study of enhanced Cr(VI) removal and removal mechanisms by Sporosarcina saromensis W5 assisted bio-permeable reactive barrier

In this study, the performances of Sporosarcina saromensis W5 assisted bio-permeable reactive barrier, containing activated carbon (AC) or zero-valent iron (ZVI), were investigated by column experiments in removal of Cr(VI) from simulated groundwater. The enhanced Cr(VI) removal performances were observed in biotic columns. Cr (VI) was first detected in effluent on day 24 and day 85 in Bio-AC and Bio-ZVI columns, respectively whereas it breakthrough only on day 4 and day 15 in AC and ZVI columns. Additionally, Cr(VI) removal performances induced by biofilm in Bio-QZ columns were promoted with the increase of influent Cr(VI) concentrations. According to fluorescent images, activated carbon was found to be the best biofilm carrier. Fe-0 may not be suitable for microbial colonization because biofilm depolymerization occurred on Fe-0 surface. Moreover, high concentration of Cr(VI) would lag the evolution of biofilm. Magnetite generating was found on the Fe-0 surface. X-ray photoelectron spectroscopy (XPS) analysis indicated that the removal mechanism of Cr(VI) in biotic columns was biotransformation of Cr(VI) to Craft) species. Our results may provide a new insight in Cr(VI) in-situ remediation from groundwater by Bio-PRB system.

Automated summary

The study found that biologically assisted reactive barriers showed good performance in removing Cr(VI), with bio-activated carbon and bio-zero valent iron helping to improve the removal efficiency of Cr(VI). The biofilm induced Cr(VI) removal performances were enhanced with increasing influent Cr(VI) concentrations.