Effect of Applied Voltage of Bes on Anaerobic Digestion Cycle of Excess Sludge

Abstract

Bioelectrochemical is a potential measure for treating waste activated sludge(WAS) and recovering energy by improving methane production efficiency of anaerobic digestion(AD). A lab-scale digester, which equipped with a MEC bioanode and cathode(MEC-AD), was operated under three voltages (0V, 0.6V, 0.8V) at 35 ± 1℃ in order to examine the effects of the microbial electrolysis cell (MEC) reactions on anaerobic digestion of WAS . The concentration of acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid and iso-valeric acid increased with the increasing of voltage due to the direct oxidation of the short-chain fatty acids at the bioanode as well as the indirect contribution of low acetic acid concentration on beta-oxidation. The time required for COD and protein degradation of the MEC-AD at 0.6V and 0.8V were shortened more than 7 days compared to 0V. At the end of the reaction, the concentration of sugar and protein in the MEC-AD at both 0.6V and 0.8V were 300 mg/L and 200 mg/L lower than that at 0V, respectively. Compared to 0V, The methane production cycle at 0.6V of MEC-AD was shortened about 7 days as well, indicating that the applied voltage was a very effective way to achieve high-efficiency anaerobic digestion of WAS.