Effects of multiple key factors on the performance of petroleum coke-based constructed wetland-microbial fuel cell.

In this study, two constructed wetland-microbial fuel cells (CW-MFC), including a closed-circuit system (CCW-MFC) and an open-circuit system (OCW-MFC) with petroleum coke as electrode and substrate, were constructed to explore the effect of multiple key factors on their operation performances. Compared to a traditional CW, the CCW-MFC system showed better performance, achieving an average removal efficiency of COD, NH4+-N, and TN of 94.49 ± 1.81%, 94.99 ± 4.81%, and 84.67 ± 5.6%, respectively, when the aeration rate, COD concentration, and hydraulic retention time were 0.4 L/min, 300 mg/L, and 3 days. The maximum output voltage (425.2 mV) of the CCW-MFC system was achieved when the aeration rate was 0.2 L/min. In addition, the CCW-MFC system showed a greater denitrification ability due to the higher abundance of Thiothrix that might attract other denitrifying bacteria, such as Methylotenera and Hyphomicrobium, to participate in the denitrifying process, indicating the quorum sensing could be stimulated within the denitrifying microbial community.

Effects of biochar on the microbial activity and community structure during sewage sludge composting.

To explore the contributions of functional bacterial community in composting, we performed medium-scale composting of sewage sludge and sawdust mixtures amended with rice straw biochar at different dosages (5, 10, and 20% of fresh mixture weight) in 400 L bioreactor systems. The dynamics of enzyme activity and bacterial community composition were monitored during the composting. The addition of biochar above 10% inhibited the activity of protease but promoted the activities of cellulase and peroxidase, which also increased the fluctuation of bacterial diversity during the composting. The relationship between the activity of most enzymes and bacterial community was strengthened by the addition of biochar (10% and 20%), which further enhanced the contributions of the functional bacterial communities to composting. Therefore, the study provides evidence for the promoting effects of biochar on the functions of bacterial community.