Potential Characteristics and Application of Biological Drying Effect of Citric Acid Dehydrated Sludge as a By-Product of Food Wastewater Under Energy-Saving Ventilation Strategy

Abstract

Due to the high concentration of polysaccharide, protein and the extracellular polymer (EPS) of microbial, Citric acid dehydrated sludge was difficult to dehydrate and utilize. In this study, biological drying technology was used to explore the moisture removal and mechanism of citric acid dehydrated sludge by different ventilation rates and control methods as the control factors. At low ventilation rate (0.25L /min kg WM), the moisture removal is the highest of all, and the water removal rate reached 41.71% within 8 days, which is consistent with the first-order dynamic model. There is the highest peak temperature(60℃), the shortest heating time(0.1d) and the longest high temperature holding time(5.9d). Analysis of organic components indicates that lipids are the preferred degradation substances under this ventilation method, and the degradation of lipids and hydrolysable substance are the first reason for the removal of bound water, protein /polysaccharide was the secondary reason. Because the program intermittent ventilation strategy can maintain the highest temperature accumulation(209.39℃), 82.77% of biological heat production was used for water evaporation after drying, the sludge has the advantages of self-sustaining combustion (＞4000 KJ/kg) and lowest cost ($26.61/t). So, the energy-saving ventilation strategy has been a deeply potential for the biological drying treatment of citric acid fermentation sludge of fermentation industrial.

Keywords: Citric acid dehydrated sludge, biological drying, Intermittent ventilation, Lipids, Hydrolysable substance, EPS