Abstract
This study investigated high-solids anaerobic digestion of 10-15% influent sewage sludge, combined with pretreatment of waste activated sludge portion. The pretreatment methods employed were thermal treatment of 130 °C and 1 hour at 20 days hydraulic retention time (HRT) for 10% influent, and thermal treatment and ammonia stripping of 80 °C, initial pH of 9 and 3 hours at 30 days HRT for 15% influent. The ammonia concentration in digester was kept at non-inhibitary levels of 2,100 and 3,100 mgN/L for 10% and 15% influent, respectively. Compared with no pretreatmet, VS destruction was improved by 4%, and methane production slightly. At 15% influent, the ammonia of 700 mgN/L in digester was calculated to be removed by the pretreatment, which alleviated severe ammonia inhibition. In coclusion, it is demonstrated that, by applying the pretretreatment, stable and improved performance of high-solids anaerobic digestion can be achieved up to 15% influent sewage sludge.
