Evaluating the potential impact of hydrochar on the production of short-chain fatty acid from sludge anaerobic digestion

Abstract

In this study, waste activated sludge (WAS) was used as feedstock to generate hydrochars at different temperatures (220°C and 260°C) and their effect on sludge anaerobic digestion was evaluated. Experimental results showed that the maximum yield of short-chain fatty acid (SCFA) enhanced by hydrochar (220°C) and hydrochar (260°C) were 507.33 and 270.80mg chemical oxygen demand (COD)/L respectively, which were much higher than that in blank (141.49mg COD/L). Mechanism investigation confirmed that hydrochar remarkably accelerated the solubilization and hydrolysis of organic matters, enhanced the acidification of hydrolyzed products, and inhibited the activity of methanogenic bacteria as well as promoted the activities of key enzymes. Meanwhile, the organic matters especially humic substances existed in the hydrochar played an important role during anaerobic digestion.

Keywords: Acidification; Humic substances; Hydrochar; Hydrolysis; Waste activated sludge.