Electrostimulation for promoted microbial community and enhanced biodegradation of refractory azo dyes

Excess azo dyes are detrimental to natural water systems and human health. To effectively treat dye wastewater, two-dimensional cylindrical electrodes were introduced into traditional biofilm reactor (BR), and thus a novel two-dimensional biofilm electrode reactor (2D-BER) was developed. In the 2D-BER, at low current density from 0.53 +/- 0.05 mA m-2 to 12.61 +/- 1.24 mA m-2, the electrostimulation increased microbial growth; while at higher current density above 12.61 +/- 1.24 mA m-2, the electrostimulation exhibited an inhibition effect to microor-ganisms. Microbial decolorization in the 2D-BER demanded the participation of co-substrate as carbon source, and the order of decolorization with different co-substrates was glucose > sucrose > starch. An appropriate concentration of glucose improved dye decolorization, but high level of glucose (1 g/L) resulted in a slight decline of decolorization. UV-Vis, FT-IR and GC-MS analysis showed that azo dye was firstly decomposed into various aromatic anilines and then degraded into small molecules. By analyzing the differences in the microbial communities in the 2D-BER and BR, it was found that the electrostimulation prompted the growth and prolif-eration of electroactive decolorization bacteria, such as Bellilinea, Desulfobulbus, Geobacter and Desulfovibrio, thus leading to high decolorization rate constant of 0.0313 h-1 in the 2D-BER. Considering the excellent decolorization due to the synergism of bioelectrochemistry and microbial catalysis, the electrostimulation technology shows good application prospects in azo dye wastewater treatment.

Automated summary

A novel two-dimensional biofilm electrode reactor (2D-BER) was developed to treat dye wastewater. Electrostimulation was found to stimulate microbial growth and enhance dye decolorization. The choice of co-substrate also affected the decolorization efficiency.