Enhanced volatile fatty acids accumulation in anaerobic digestion through arresting methanogenesis by using hydrogen...

Volatile fatty acids (VFAs) can be accumulated as a final product of anaerobic digestion via arresting methanogenesis. Herein, hydrogen peroxide (H₂ O₂ ) was studied to inhibit methanogenesis for enhancing VFA accumulation with glucose as a substrate. The addition of 0.06 wt.% H₂ O₂ significantly reduced methane production and led to a VFAs concentration of 1233.1 ± 55.9 mg L^-1 , much higher than 429.3 ± 5.6 mg L^-1 in the control that did not have H₂ O₂ addition. The dominated VFAs with H₂ O₂ were acetic acid and propionic acid. A low H₂ O₂ dosage of 0.03 wt.% produced 466.3 ± 3.9 mg L^-1 more VFAs than that of O₂ addition at the similar (theoretical) dosage, but when the dosage was relatively higher, the VFA accumulation with O₂ addition became more than that with H₂ O₂ addition, likely because of stronger oxidation of VFAs by the overly added H₂ O₂ . A hypothetical mechanism for H₂ O₂ inhibition suggests that at a low H₂ O₂ concentration the inhibition is mainly toward methanogenesis to limit their consumption of VFAs and a high H₂ O₂ concentration starts to inhibit hydrolysis and acidogenesis and/or oxidize VFAs. Those results encourage further exploration of H₂ O₂ -based arresting methanogenesis for VFAs production.