Coupling of iron shavings into the anaerobic system for enhanced 2,4-dinitroanisole reduction in wastewater.

Packing of iron powder into anaerobic system is attractive for enhancing removal of recalcitrant pollutants from wastewater, but is limited by various inherent drawbacks of iron powder, such as easy precipitation and poor mass transfer. To address the above issues, iron shavings were packed into an upflow anaerobic sludge blanket (UASB) for enhancing 2,4-dinitroanisole (DNAN) reduction in this study, with system stability and microbial biodiversity emphasized. The results showed that both DNAN reduction and 2,4-diaminoanisole (DAAN) formation could be notably improved in the iron shavings coupled UASB system. Moreover, the ability to resist environmental stress was also strengthened through the addition of iron shavings in the UASB reactor. Compared with a loose and rough surface of the sludge in the control UASB reactor, the sludge in the coupled system presented a compact, rigid and granular appearance under iron shavings simulation. Furthermore, high throughput sequencing analysis indicated that the diversity of microbial community in the iron shavings coupled UASB system was significantly higher than that of the control UASB reactor. Additionally, species related to DNAN reduction and methane production were enriched in the coupled system. The observed long-term stable performance highlights the full-scale application potential of iron shavings coupled anaerobic sludge process for the treatment of nitroaromatic compounds containing wastewater.