Optimization Research Of Anaerobic Leaching-bed Reactor On Organic Acid Production From Food Waste

Food waste is a major component of mucicipal solid waste (MSW), which contains a high content of easily spoilage organics. The collection, transportation and disposal of food waste caused a serious environmental pollution. Due to the highly biodegradability, food waste was thought to be a desirable substrate for anaerobic Biomethanization. Currently, anaerobic digestion of food waste is an intensive research field. Different from biogas production, the production of platform compounds, e.g. VFAs (volatile fatty acids) via anaerobic fermentation is attracting great interests. Among diverse reactor configurations, leaching-bed reactor was reported to be the best choice to treating the particular organic waste. In this study, a serie of experiments were carried out to investigate the bulking agent and pH control on process performance, and special focus was put on the biodegradability of bulking agent. The main conclusions are as follows:(1) Firstly, the substrates were characterized by ultimate, proximate analysis and calorific value analysis. The moisture contents were73.61%,70.88%and9.58%for food waste, sewage sludge and corncob, respectively, and the volatile contents were23.14%,8.85%and85.85%for food waste, sewage sludge and corncob, respectively. These results indicated that the food waste and corncob contained high moisture content and high organic content.(2) The addition of corncob greatly improved the leaching rate by3.4folds. In addition, cumulative COD and cumulative VFAs were increased by22.5%and27.8%, respectively. Compared with the literature, however, the obtained total VFA yield was low. The low VFA production might be due to the low pH, which was not improved by adding bulking agent.(3) The pH control (neutralization) significantly increased the VFAs production by4.7times, which was increased from39.1g COD/kg VSadded for control (without pH control) to183.4g VFA/kg VSadded (neutralization). Although hydrolytic and acidogenic bacteria were resistant to low pH, the VFAs production was inhibited by the low pH as observed in the control reactor (without pH control). These results suggested that the pH control was a necessary measure to promote the acidification process.(4) Compared with undegradable bulking agent, corncob as the bulking agent showed a higher VFA yield (225g COD/kg VSadded), which could be ascribed to the better adhesive properties for microorganisms and biodegradability. TG/DTA and FTIR spectroscopy analysis of food waste residue and leachated corncob indicated that most of food waste was degraded with relative short reaction time and some components of corncob were degraded and acidified to VFAs. In addition, TG/DTG results also indicated that the leachated residues had a good pyrolysis and combustion characteristics for further energy utilization.This study suggested that the corncob was a good bio-compatible bulking agent for leaching-bed reactor, which not only increased the VFA productivity, but also contributed to additional VFA production.