Recuperative thickening equipped with ammonia stripping system to upgrade thermophilic and mesophilic digestion of...

In order to further upgrade the high-solid anaerobic digestion of hydrothermal sewage sludge, recuperative thickening (RT) and ammonia stripping (AS) through in situ biogas self-circulation were integrated to conduct a continuous operation. Four digesters including thermophilic and mesophilic systems with RT and corresponding control tests without RT were set. They were subjected to the conditions with and without assistance of AS, respectively. Single RT was found almost not to affect biogas production at a longer hydraulic retention time, but led to about 26.0 % lower volatile solids in the effluent. The RT improved mesophilic anti-shock ability while aggravated the accumulation of toxicants in the thermophilic system. Given the occurrence of ammonia inhibition, the AS was added to showcase its advantages in propelling the conversion of organic acids to methane. Consequently, the methane production and organic removal of thermophilic systems was pulled back to the similar level with that of the mesophilic systems. Ultimately, combined RT and AS led to improved methane production, removal of pollutants and process stability.