Enhancing effect of conductive materials and rumen microorganisms on the anaerobic digestion performance of a real traditional Chinese medicine wastewater

This work evaluated the effect of different concentrations of conductive materials and rumen microorganisms on the anaerobic digestion (AD) performance of real traditional Chinese medicine (TCM) wastewater. The experiments first determined the optimal organic concentration of 0.25 L/L for the AD system and removed suspended solids from real TCM wastewater to reduce the inhibition effect on methanogenesis. Analysis of the modified Gompertz model showed that the addition of activated carbon, biochar, cow manure, and rumen fluid at doses of 12 g/L, 12 g/L, 12 mL/L, and 125 mL/L, respectively, had the greatest effect on CH₄ production, increasing the cumulative CH₄ yield by 13.5 %, 10.4 %, 26.8 %, and 32.9 %. Through microbial community and metabolism pathway analyses, the conductive materials promoted direct interspecies electron transfer (DIET) between Clostridium and Methanothrix, and the acetoclastic methanogenic pathway dominated by acetyl-CoA synthase. Rumen microorganisms enhanced AD performance by promoting the growth of hydrogenotrophic methanogens and the abundance of genes dominated by formylmethanofuran dehydrogenase in the hydrogenotrophic methanogenic pathway, illustrating the relationship between microbial community and metabolism pathway. Rumen microorganisms increased CH₄ production more than conductive materials in real TCM wastewater. This study helps to better understand the internal mechanisms by which different materials enhance AD performance.