Study On Key Technologies For Decentralization Treatment Of Food Waste On-site

With the development of society and improvement of people's living standards, the proportion of food waste in municipal solid waste increases fast. The food waste, without appropriate treatment to the relative high organic substance and moisture content, will make serious threat to both environment and human health. Nowadays, there are many technologies applied to treat the food waste at home and abroad, including landfill, incineration, compost, comminution, feed and anaerobic digestion. However, compared with other technologies, the technology of anaerobic digestion, which accords with the demand of harmonious treatment technology in circular economy, including energy saving, emission reduction, and cleaner production, and will realize harmless, reduction, recycling to the waste, have many advantages, such as reducing treatment capacity, recycling clean energy, making organic compound fertilizer, etc. Moreover, due to the special components of food waste, it is very important to study the key parameter of anaerobic digestion for the normal start-up and stable operation in food waste anaerobic digestion system.This thesis, at the basis of previous researches, mainly studied the key parameters of food waste anaerobic digestion, to provide the basic technical support to deal with the treatment of the decentralized food waste in anaerobic digestion. Three main tests were carried out in the study, including the test of domestication inoculum that studied the effect of different sources and domestication ways to the inoculum, the test of fresh food waste anaerobic digestion that studied the effect of inoculation rate, moisture content, temperature, stir factor on anaerobic digestion process by oethogonal and optimized the parameters, and the test of air-dried food waste anaerobic digestion, which investigated the effect of inoculation rate and moisture content on anaerobic digestion proces. The main content and conclusions includes:(1) Comprehensive overview and summary of production, treatment status and technology about global food waste, at the basis of collecting and reading literature at home and abroad, was stated in this thesis. The mechanism and influencing factors about technology of anaerobic digestion was also summarized in detail.(2) The result of domestication inoculum test showed that different sources and ways of domestication had a great effect on the final status of the inoculum. Moreover, the bacteria flora in domesticated sludge was distributed dispersedly with single shape, and the best way of domestication, which making the activity of methanogenic reached optimal level at 0.406LCH₄/(gVSS·d), was to continuously add food waste 20g per day for 20 days, taking sludge from anaerobic digestion tank as inoculum.(3) In the process of anaerobic digestion, the obvious advantage of air-dried food waste, compared with fresh food waste, was that it could effectively alleviate the acidosis at the initial acidification phase. It was found that TN had obviously increased, the highest rate of COD removal reached 91.8%, and the alkalinity had been improved to more than 25%, which made the system a higher buffer capacity.(4) It was found that suitable inoculation rate and stir frequency were favorable to the growth of mushroom, and the overabuandance might increase the cost, reduce the efficiency of treatment, and even effect the process of anaerobic digestion. If the inoculation rate was 55%, the process of anaerobic digestion, only with the moisture content at 92% and temperature at 55℃, could operate normally. In addition, no matter the food waste was fresh or air-dried, of which the low solid content could goes well while the high content were more inclined to get acidified. When the solid content was 16%, anaerobic digestion system with inoculation rate at 75% only could operate normally.(5) The orthogonal test showed that the optimal combination, in the fresh food waste anaerobic digestion system, was inoculation rate at 75%, moisture content at 92%, stir frequency at twice per day, temperature at 55℃.(6) During the study, it was found that pH, whose value and stabilization had a significant influence on the methane production, was an important parameter that needs to be predicted, controlled to get the optimal value in the process of anaerobic digestion.