Enhancement of the biodegradability of activated sludge by the electric-coagulation multistage A/O membrane bioreactor treating low C/N industrial wastewater

- The biodegradability of pollutants was improved by ECMMBR at low temperatures.
- ECMMBR enhanced the dehydrogenase activity and nitrogen transformation rate.
- ECMMBR enriched the richness and the diversity of communities in activated sludge.

In the biological treatment of the industrial wastewater, low temperatures and low carbon nitrogen ratios (C/N) are great challenges. In this research, one conventional multistage A/O membrane bioreactor (MMBR) and one electric-coagulation multistage A/O membrane bioreactor (ECMMBR) were established to investigate the effect of Fe-C electrodes on the biodegradability of the activated sludge when treating the low C/N industrial wastewater. Results showed that the Fe electrode enhanced nitrogen transformation and the biodegradation of COD and volatile phenols. The dehydrogenase activity, the NH4+-N and NO2−-N degradation rate of the unit sludge were higher in ECMMBR. Moreover, results from high throughput sequencing analysis revealed that ECMMBR may improve Chao and Shannon indices. ECMMBR improved the relative abundance of Luteimonas and Trueperaceae, which were cold-resistant and hydrocarbon-bearing microorganisms. This study demonstrated that the electric field and iron ions may improve the biodegradability of activated sludge, dehydrogenase activity and nitrogen transformation rate and enrich the richness and the diversity of communities in the activated sludge at low temperatures. The research provided a valuable technical method for the biodegradation of the low carbon and high ammonia industrial wastewater.