An anaerobic reactor packed with a pair of Fe-graphite plate electrodes for bioaugmentation of azo dye wastewater treatment

An anaerobic reactor packed with a pair of Fe-graphite plate electrodes (supplied with 1.2 V) was developed to enhance azo dye wastewater treatment. The results showed that decolorization and COD removal of the azo dye wastewater in this hybrid reactor (R1) reached 83.4% and 84.7% at a dye concentration of 1200 mg/L, respectively. These values were significantly higher than the sum of the same values in a single anaerobic reactor (R2) and a single electrode reactor (R3). Salinity enhanced the performance of R1 to a certain extent, but weakened that of R2. After a long period of operation, reactor R1 still performed better than the control, even when the voltage supplied to the electrode was off. Taken together, these results indicate that there was a coupling effect between the electrode reaction and biodegradation. 16S rDNA analysis revealed that anaerobic microorganisms in R1 were richer and more diverse. This increased richness and diversity was partially related to the Fe2+ leaching induced by the electrochemical reaction and increased production of extracellular polymeric substances, which benefited microbial growth and function.

► Azo dye wastewater treatment was improved in an anaerobic reactor when packed with a pair of Fe-graphite electrodes.
► The removal efficiencies in this electric-anaerobic reactor were increased as dosing NaCl.
► As voltage for the electrodes was cut off, the performance of this hybrid reactor was still higher.
► The reason for the enhanced performances was ascribed to the richer and more diverse microbial communities.