Activated carbon modified with nano manganese dioxide triggered electron transport pathway changes for boosted anaerobic treatment of dyeing wastewater

Herein, an expanded granular sludge bed (EGSB) reactor with activated carbon (AC)-nano manganese dioxide (MnO2) added was employed for azo dye wastewater treatment to investigate its effectiveness at decolorizing of azo dyes and removing COD. The results showed that the treatment of azo dye wastewater with the AC-MnO2 modified EGSB reactor gave an 83% average decolorization efficiency, which was more efficient than the pure AC modified EGSB reactor. Moreover, the COD removal and changes in the intermediate products were controlled by AC-MnO2. Additionally, there was a sharp increase in the sludge conductivity, while there was a significant decrease in the coenzyme F420 concentration with long-term operation. Moreover, electrochemical analysis showed that the addition of AC-MnO2 can enhance electron transfer in anaerobic system. The AC-MnO2 can act as redox mediator; in the presence of the Mn4+/Mn2+ cycle, accelerating the electron transfer between the microbial cells and dyes, thereby promoting the decolorization of azo dyes. This caused a decrease in the methanogenic activity. Furthermore, high-throughput sequencing showed that the relative abundances of Pseudomonas and Desulfovibrio were significantly high among the acidogenic bacteria community, while Methanobacterium and Methanosaeta had very low abundances from among the methanogenic archaea community.

Automated summary

The study demonstrated that the EGSB reactor modified with activated carbon and nano manganese dioxide showed efficient decolorization of azo dye wastewater with an average efficiency of 83% and enhanced COD removal. The addition of AC-MnO2 facilitated electron transfer in the anaerobic system, promoting decolorization of azo dyes by acting as a redox mediator. This resulted in decreased methanogenic activity and specific bacterial and archaeal community compositions.