The presence of high levels of sulfate and metal ions (e.g., iron and copper), introduced with substrate feeding or by chemical or electrochemical pretreatment, may impose complex chemical and biological interactions in anaerobic digestion. To effectively investigate the effects of those ions on anaerobic digesters, this study used dairy manure as the model substrate and applied response surface methodology for design and data analysis. The response variables evaluated in this study included H2S concentration and production, biomethane and carbon dioxide production, and acetate and total volatile fatty acids in digestate. Ferrous was found effective in controlling H2S concentration, while cupric lost its effectiveness at the end of 45 days digestion. It was found that copper and sulfate exerted severe inhibition to overall microbial activities as well as methane generation. Ferrous showed slight inhibition on methane generation at baseline concentrations of the other additives, but stimulated methane production when VS (dairy manure fiber) content was high. Co-digestion of feedstock introducing sulfate and copper components should be cautiously done in order to maintain high performance of digester. To the contrary, Fe can be effective both in sulfide control and methane production stimulation, and is recommended for use in anaerobic digestion that requires sulfide control when digestion substrate contains high levels of lignocellulosic biomass.
- hydrogen sulfide
- mesophilic anaerobic digestion
- response surface methodology