Thermophilic and mesophilic temperature phase anaerobic co-digestion (TPAcD) compared with single-stage co-digestion of sewage sludge and sugar beet pulp lixiviation

Volatile solids removal efficiency from the TPAcD system depended on the sludge exchange rate, but fell within the 72.6-64.6% range. This was higher than the value of 46.8% obtained with single-stage thermophilic digestion and that of 40.5% obtained with mesophilic digestion. The specific methane yield was 424-468 ml CH4 per gram of volatile solids removed, similar to that of single-stage mesophilic anaerobic digestion. The increase in microbial activity inside the reactor was directly proportional to the organic loading rate (OLR) (or inversely proportional to the HRT) and inversely proportional to the size of the microbial population in single-stage anaerobic co-digestion systems.