Highly-efficient Anaerobic Digestion of Refractory Organic Waste Using Subcritical Water Hydrolysis as Pretreatment Process

Abstract

In this study, subcritical water hydrolysis was developed to treat refractory organic waste as a pretreatment process for high-efficiency anaerobic digestion. Sewage sludge and cyanobacteria as representative refractory waste were used. Different treatment temperatures were investigated and methane fermentation from the two pretreated wastes by subcritical water hydrolysis were carried out. The results showed that the optimum treatment temperature is 180°C. 0.8 g/l of formic acid, 8.6 g/l acetic acid, 9.9 g/l propionic acid and 0.6 g/l butyric acid were produced from sewage sludge and 405.8 µg/l of microcystin in cyanobacteria was completely removed in the pretreatment process at 180°C. The cumulative methane production was 43.2 ml and 54 ml from pretreated sewage sludge and cyanobacteria, respectively. Both of them were much higher than those produced from untreated one. Therefore, efficient anaerobic digestion of refractory organic waste using subcritical water hydrolysis as pretreatment process could be achieved.