Enhanced syntrophic metabolism of propionate and butyrate via nickel-containing activated carbon during anaerobic digestion

Abstract

The accumulation of volatile fatty acids (VFAs) is commonly occur during anaerobic digestion, affecting methane production rate and system stability. Batch experiments were conducted to investigate the effects of nickel-containing granular activated carbon (GAC-Ni), an industrial waste, on the degradation of acetate (HAc), propionate (HPr) and butyrate (HBu), respectively. The results showed that the maximum methane production rate of the reactors fed with HPr and HBu were increased by 54.06% and 16.55%, respectively, with the supplementation of GAC-Ni. Correspondingly, the degradation rates of HPr and HBu were improved with GAC-Ni addition, which was 1.14–20.70 times and 1.01–2.16 times of the control, respectively. And the microbial analysis revealed that GAC-Ni facilitated the syntrophic relationship between Syntrophomonas and hydrogenotrophic methanogens (i.e. genera Methanolinea and Methanobacterium), leading to faster degradation of HPr and HBu. Additionally, the surface morphology analysis indicated that the presence of Ni in GAC-Ni could promote the formation of condense reticulate structures, which might be beneficial for linking the functional microbes together. This study suggested that GAC-Ni waste could mitigate the accumulation of VFAs in anaerobic digestion reactor by promoting the syntrophic metabolism between VFAs degradation bacteria and methanogens.