Food waste was a troublesome organic waste stream, but a highly desirable substrate for anaerobic digestion to recover energy. Among the diverse reactor configurations, the leaching-bed reactor was reported to be best choice to treating the particular organic waste for platform compounds (volatile fatty acid). In this study, we carried out a series of experiments to investigate the bulking agent and pH control on process performance, and special focus was put on the biodegradability of bulking agent. The supplement of bulking agent greatly improved the leaching rate by 3.6 folds. Although the hydrolytic and acidogenic bacteria were resistant to low pH, the pH control (neutralization) caused a significantly increased volatile fatty acid (VFA) productions from 39.1 g COD/kg VSaddedto 183.4 g VFA/kg VSadded. Comparing with the undegradable bulking agent, the case with supplementing corncob as a bulking agent showed superior VFA yields (225 g COD/kg VSadded) which could be ascribed to the good adhesive properties for microorganisms and biodegradability. The ultimate analysis of the substrate (excluding the bulking agent) also showed that most of food waste was degraded with relative short reaction time. In addition, the TG/DTA and FTIR of residual corncob results indicated some components (cellulose, hemi-cellulose) were degraded, which could contribute to the additional VFA production (14 g COD/kg VSadded). This study suggested that the corncob could be considered as a good bio-compatible bulking agent for leaching-bed reactor, which not only increased the VFA productivity, but provided additional VFA production.
Effect of Volatile Fatty Acid on Hydrogen Fermentation of Organic Waste
