EXPERIMENTAL ANALYSIS OF METHANE PRODUCTION BY MIXED ANAEROBIC FERMENTATION OF FOOD WASTE AND SLUDGE

The sludge has low organic matter content, low C/N, and poor biodegradability. The gas production rate and organic matter degradation rate of the sludge are both low. Mixed anaerobic fermentation of high organic content and easily biodegradable food waste and sludge is an effective way to increase the gas production rate of sludge alone. After sludge and food waste are mixed in a certain ratio, the nutrient elements and trace elements of the fermentation substrate can be optimized, and the buffering capacity of the system can be improved, thereby increasing the methane production rate, shortening the fermentation cycle, increasing the removal rate of organic matter and the anaerobic fermentation tank volume utilization rate. This study explores the effect of vegetable oil content on the anaerobic fermentation of sludge and food waste, and the effect of low-temperature heat treatment on the anaerobic fermentation of sludge and food waste. The CSTR reactor is used for dehydrated sludge and food waste mixed anaerobic fermentation. The aerobic fermentation experiment studies the operation of mixed anaerobic fermentation of dehydrated sludge and food waste. Experimental results show that when the vegetable oil content is 0-30%, the methane production rate increases with the increase of the vegetable oil content. When the vegetable oil content is 30%, the methane production rate reaches the highest, which is 449 mL/g-VS. When the vegetable oil content is 40%-50%, the anaerobic fermentation process is completely inhibited, and mixed fermentation can improve its oil tolerance. Low-temperature heat treatment can increase the initial methane production rate of anaerobic fermentation, and after low-temperature heat treatment of the mixed substrate, the methane production rate and the initial methane production rate of anaerobic fermentation increase with the increase of heat treatment time and temperature. In the mixed anaerobic fermentation of dehydrated sludge and food waste, the gas production varies greatly, the start-up period is long, and the gas production rate is low.