Anaerobic co-digestion of thermo-alkaline pretreated microalgae and sewage sludge: Methane potential and microbial community.

To improve methane production from sewage sludge (SS), co-digestion of SS and microalgae (MA) was studied and the application of thermo-alkaline pretreatment to MA was evaluated. The results showed that thermo-alkaline pretreatment at 90°C for 120 min on MA was the optimum pretreatment condition. Furthermore, when the volatile solids (VS) ratio of SS and MA was 1:2, the methane yield reached maximum (368.94 mL/g VS). Fourier transform infrared (FT-IR) and thermogravimetric analysis confirmed the synergetic effects of thermo-alkaline pretreated MA on its co-digestion with SS. The analyses of microbial community indicated that Methanobacterium and Methanosarcina were the dominant methanogens during the co-digestion process. However, the relative abundance of Methanosarcina in thermo-alkaline pretreated groups was higher compared to unpretreated groups. The microbial community structure might be affected by thermo-alkaline pretreatment rather than by the MA dosage in the co-digestion.