Influence of inoculum to substrate ratio on solid acidogenic digestion with pig manure and maize straw

摘要

A laboratory-scale study adopting mixture of manure and straw as substrate was carried out to elucidate the impact of inoculum to substrate ratio(ISR) on hydrolysis and acidification digestion with methanogenic effluent recycling. The chemical oxygen demand(COD), pH, and volatile fatty acids (VFAs) concentration were periodically analyzed in order to completely understand the digestion processing. In addition, ammonia-nitrogen was also monitored. The results showed that acetic acid was dominant in fermentation products of different ISRs and the percentage of acetic acid in total volatile fatty acids (TVFAs) increased with the increase of ISR, and acetic acid accounted to 68.74%, 72.02%, 75.89% and 86.65% of TVFAs when ISR were 15%, 25%, 35% and 50%. Propionic acid accounted for 6.68%, 5.92%, 5.54% and 2.67% of TVFAs produced, and the concentration was less than 0.60 g/L. The possible inhibition by free ammonia was null since the values were far below the threshold concentration reported in other literatures, but the potential inhibition maybe happen after long-term recycling of methanogenic effluent.