Effect of mixing on performance of continuous dry thermophilic digestion of dairy manure

摘要

3 months pilot-scale experiment of continuous dry thermophilic anaerobic digestion of undiluted dairy manure was conducted in an 8 m3 plug-flow type anaerobic reactor. The reaction started up within 1.5 months using mesophilic digested chicken manure as inoculum. The impact of mixing on performance of digestion was evaluated during the last 1.5 months, with the loading rate and hydraulic retention time being maintained about 10.4 kg VS/(m3·d) and 15 days respectively. No significant difference in biogas production, pH value and total ammonia content were observed among 3.85 r/min continuous mixing, 7.7 r/min continuous mixing and 3.85 r/min batch mixing. Under these mixing conditions, operation was stable with an average pH of 7.6-7.9, methane production field of 163.8-170.7 L/(kg·VS), and a biogas composition of 54.5%-58.5% methane. Low-speed batch mechanical mixing was more suitable in dry anaerobic digestion.