The Study Of Enhancing SCFAs Production In Waste Actived Sludge Anaerobic Digestion

Anaerobic digestion, as a sustainable technology, has been applied to reduce wastes and result in the production of short-chain fatty acids (SCFAS). However, the SCFAs recovery efficiency is largely limited due to the relatively slow hydrolysis process. In this study, Alkylpolyglycosides (APG) and zero valent iron (ZVI) were used to enhance SCFAs production from WAS.Batch experiments of dosing ZVI showed that ZVI could improve anaerobic fermentation of WAS. According to the experimental data, the solubilization of organic matter was remarkably enhanced in the presence of ZVI during sludge anaerobic fermentation. Specifically, the maximal hrydrolysis efficiency was achieved with ZVI dosage of 0.5 g/gTSS. Acidification process indicated that ZVI did not exert obvious influence on the accumulation and composition of VFAs. Acetic acid accounted for approximately 4.7% of the total VFAs at a fermentation time of 10 d due to methanogenesis. Mechanism investigations showed that ZVI could improved the relative activities key enzymes with hydrolysis. Relative activities of the protease and a-glucosidase were 1.9-fold and 1.8-fold of the blank, respectively.Batch experiments of APG dosing showed that APG could enhance WAS acidification. According to the experimental data, the solubilization of organic matter (protein and carbohydrate) was remarkably enhanced in the presence of APG during sludge anaerobic fermentation. Specifically, the maximal hrydrolysis efficiency was achieved with APG dosage of 0.2 g/gTSS. The maximum concentration of soluble protein and soluble sugars was 2.3-fold and 5.4-fold of the blank, respectively. The maximum concentration of SCFAs was 4.1-fold of the blank. Acidification process indicated that APG could influence on the accumulation and composition of VFAs. Acetic acid accounted for approximately 50% of the total VFAs at a fermentation time of 10 d at APG dosage of 0.2 g/gTSS. Mechanism investigations showed that APG could improved the relative activities key enzymes with hydrolysis. Relative activities of the a-glucosidase was 1.4-fold of the blank. Surface tension in the sludge could be reduced in the prence of APG.Batch experiments of ZVI and APG dosing showed that ZVI and APG could enhance WAS acidification. According to the experimental data, the solubilization of organic matter (protein and carbohydrate) was remarkably enhanced in the presence of ZVI and APG during sludge anaerobic fermentation. Specifically, the maximal hrydrolysis efficiency was achieved with APG dosage of 0.2 g/gTSS and all ZVI dosages. The maximum concentration of soluble protein and soluble sugars was 2.4-fold -fold and 6.5-fold of the blank, respectively. The maximum concentration of SCFAs was 4.4-fold of the blank. Acidification process indicated that APG could influence on the accumulation and composition of VFAs. Acetic acid accounted for approximately 50% of the total VFAs at a fermentation time of 10 d at ZVI dosage of 0.5 g/gTSS and APG dosage of 0.2 g/gTSS. Mechanism investigations showed that APG could improved the relative activities key enzymes with hydrolysis. Relative activities of the protease and a-glucosidase were 1.4-fold and 1.9-fold of the blank, respectively. Surface tension in the sludge could be reduced in the prence of APG At ZVI dosage of 0.5 g/gTSS and APG dosage of 0.2 g/gTSS, the neutral condition (pH=7) or 35℃ were beneficial to SCFAs production.Studies on the hydrolysis and acidification dynamics of WAS about the three ways were also conducted. Results showed the hydrolysis of sludge protein and carbohydrate in the three ways could be descried by first-order kinetics when temperature was 35℃. In the presence ZVI alone, acidification process of WAS could be described by Logistic equation, and in the presence APG alone or with ZVI, acidification process of WAS could be described by zero-ordcr kinetics when temperature was 35℃.