Oxygen tolerance capacity of upflow anaerobic solid-state (UASS) with anaerobic filter (AF) system

In order to investigate the oxygen tolerance capacity of upflow anaerobic solid-state (UASS) with anaerobic filter (AF) system, the effect of microaeration on thermophilic anaerobic digestion of maize straw was investigated under batch conditions and in the UASS with AF system. Aeration intensities of 0–431 mL O₂/g_vs were conducted as pretreatment under batch conditions. Aeration pretreatment obviously enhanced anaerobic digestion and an aeration intensity of 431 mL O₂/g_vs increased the methane yield by 82.2%. Aeration intensities of 0–355 mL O₂/g_vs were conducted in the process liquor circulation of the UASS with AF system. Dissolved oxygen (DO) of UASS and AF reactors kept around 1.39 ± 0.27 and 0.99 ± 0.38 mg/L, respectively. pH was relatively stable around 7.11 ± 0.04. Volatile fatty acids and soluble chemical oxygen demand concentration in UASS reactor were higher than those in AF reactor. Methane yield of the whole system was almost stable at 85 ± 7 mL/g_vs as aeration intensity increased step by step. The UASS with AF system showed good oxygen tolerance capacity.