Enhanced methane production and wastewater sludge stabilization of a continuous full scale thermal pretreatment and thermophilic anaerobic digestion

- Continuous full scale thermophilic AD with thermal pretreatment was studied.
- Thermal sludge pretreatment at 160 °C for 30 min was the optimum condition.
- Total solids removal efficiency was 54.7% at 3.50 kg VS/m3·d.
- 0.35 m3·CH4/kg VSadd was obtained at the sludge load lower than 2.49 kg VS/m3·d.

A continuous full scale thermophilic anaerobic digestion (AD) of wastewater sludge in conjunction with thermal pretreatment was developed for enhanced CH4 production as well as sludge stabilization and reduction. Continuous thermal sludge treatment obtained 45.5, 51.7, and 26.1% of hydrolysis based on TS, VS, and COD at 160 °C for 30 min. After AD, TS, VS, and COD removal efficiencies reached 54.7, 60.4, and 59.2%, respectively, at 3.50 kg VS/m3·d. Maximum CH4 yield (0.35 m3 CH4/kg VSadd) was obtained at 2.49 kg VS/m3·d and less, and the yield decreased with increasing sludge load while net available energy production increased. Continuous thermal sludge treatment and thermophilic AD enhanced CH4 production and solids reduction and showed stable performance for full scale application.