Performance Of Two-phase Anaerobic Fermentation Of Food Waste

Along with our country urbanization speed up and people living standard rise, the output of food waste increased year by year. Food waste is the main part of the domestic urban organic waste, has become an important aspect of environmental pollution. The treatment of food waste should be directed towards resources. Anaerobic fermentation technology can not only solve the problem of food waste, but also can produce renewable energy-biogas, has become the development direction of the future.After decades of exploration and research by domestic and foreign researchers, anaerobic fermentation theory has been very mature. Single-phase anaerobic fermentation process of food waste is simple, and related scientific research workers have done a lot research for it, and haveget many research results, also single-phase anaerobic fermentation technology in the industry has been large-scale application. But the research of two-phase anaerobic fermentation technology which is more advanced, faster response speed and moregas production, more stability and controllability, and higher equipment utilization is relatively less, the application of practical engineering is much less, Therefore, to explore the reaction conditions and process operation parameters of two-phase anaerobic fermentation of food waste has a very important significance.In this paper, raw material-food waste from school dining room was used, the performance of two-phase anaerobic fermentation of food waste was studied. First, by means of batch type feeding, studied the effect of hydrolysis and acidification of food waste in different temperature, different load and different inoculation amount. Explored the changing rule of pH value, volatile fatty acids (VFA) content and the main component of the products in the in the acidification phase. In the stage of acidification, At35℃, pH falling rapidly then rising, The highest content of VFA is15g/L. The main products are ethanol and acetic acid, and ethanol is tend to converted into acetic acid. Hydrolysis acidification process basically completed in the first4days though different organic load. In the late of response, the different organic load the fermentation type is also different. When the load of feed is40gTS/L, the hydrolytic acidification effect is better, main products are ethanol and acetic acid, and ethanol and VFA concentration is high. The reaction canget target acidification pro ducts--ethanol and acetic acid when the vaccination rate was30%. And the effect is better than no vaccinated and the vaccination rate is50%.Then feeded through different load, studied the changing rule ofgas production and the methane content in thegas in stage of alkylation which used acidification products and analyzed the nature of the discharge liquid. In the stage of alkylation, the accumulation of propionic acid can produce inhibition to methane bacteria when the material liquid with much propionic acid and at high load and thegas effect is poor. Material liquid with high content of ethanol and acetic acid when high load feed is able to keep highgas production and high methane content. High content of butyric acid can make thegas peak much earlier; it has the advantages of producing methane at low load feed. VS removal rate is the largest when the acidification of discharging is40gTS/L and the alkylation feed is20gVS/L, Reached82%, thegas production reached852mL every unit to remove VS.Finally, based on the batch type experiment, the expansion of laboratory experiments of two-phase anaerobic fermentation of food waste were carried out feed in batch continuous way. Under the condition of batch continuous feed, explored the food waste acidification and alkylation performance in the process of anaerobic fermentation. In acidification phase, when the hydraulic retention time(HRT)=8, pH stability keep in4.3-4.6, acetic acid content is20g/L, ethanol is18g/L, propionic acid for2g/L in acidification product, the quality of acidification product isgood. The content of CO2in thegas at acidification phase is little, so the loss of organic matter is little. In alkylation phase, the pH value of fermented liquid is relatively stable in different hydraulic retention time, maintain between7.05and7.5, Methane content in thegas every day stay in the range of64%to70%, the highestgas daily production wasgot when HRT=20, reached average daily32L, VS removal rate reached80.66%, thegas production reached878.2mL every unit to remove VS, VFA and SCOD content in the fermented liquid is smaller, the organic material was used thoroughly. Taken together, we think HRT=20is more appropriate in the process of alkylation reaction.