Effects of Calamus-Derived Biochar on the Thermophilic Anaerobic Digestion of Long-SRT Waste Activated Sludge from the Municipal Wastewater Treatment Plant

In order to improve the efficiency of anaerobic digestion of long sludge retention time (SRT) sludge and seek a suitable disposal method for the massive plants harvested from constructed wetlands, we prepared Calamus -derived biochar ( Calamus -BC) and added it to thermophilic anaerobic digestion (TAD) system of long SRT sludge. Moreover, the effect of Calamus -BC supplemental level (0, 5, 10, 15, 20 g/L) on TAD was explored through a series of batch experiments. Results showed that Calamus -BC addition can increase the conductivity and pH in TAD of long-SRT sludge obviously, thereby promoting methane production, reducing total VFAs accumulation and shortening the lag phases. When the Calamus -BC dosage was 15 g/L, the cumulative CH 4 yield reached the highest 246.73 mL/g VS, which was 43.4% higher than the control group. Furthermore, it proved the modified Gompertz model was suitable for the actual evolution of CH 4 production in TAD of long-SRT sludge. This study provided an alternative for efficient biomass stabilization and bioenergy recovery from long-SRT sludge and supplied a feasible resourceful approach for massive Calamus from constructed wetlands in water rehabilitation engineering. Graphical Abstract