Volatile Fatty Acids (VFAs) Production By Anaerobic Fermentation Of Sludge At Different Temperatures And Hydrogen Production From Representative Components Of The Anaerobic Digestion Liquid Of Sludge In Microbial Electrolysis Cell

The environmental problems of sludge have received much attention.However,sludge contains high organic matters,and volatile fatty acids(VFAs)accumulation during anaerobic digestion can be utilized as organic matters.Microbial electrolytic cell(MEC)is an emerging hydrogen production technology.Combining sludge anaerobic fermentation with acid production and MEC hydrogen production can achieve the dual goals of waste treatment and production capacity.In this paper,the effects of different temperatures and different water contents on the acid production of sludge by anaerobic fermentation were studied by batch test.Through the semi-continuous operation of MEC,the main five representative components(sodium acetate,glucose,bovine serum albumin,sodium butyrate and sodium valerate)in the sludge fermentation broth were utilized to investigate the hydrogen production efficiency and mechanism of organic matter degradation and also the effect of different matrix initiation methods on the operation of different substrates;According to the actual composition of the fermentation broth,the simulated fermentation broth was prepared,and the hydrogen production of each component in the fermentation broth was studied in MEC,and the mechanism of hydrogen production by the MEC of the sludge acidogenic fermentation broth was investigated.Under different temperature conditions,the overall acid production of sludge anaerobic fermentation was 75?>55?>95?>35?.Acetic acid was the most important organic acid in VFAs,which accounted for more than 50%,and expressed under various temperature conditions that the activity and quantity of the acetogenic bacteria of the FTHFS gene were 55?>35?>75?>95?,reflecting that the acetogenic bacteria at 35?and 55? increased with the increase of time.The higher the anaerobic fermentation temperature,the stronger the sludge hydrolysis,and the sCOD,carbohydrate and soluble protein content in the sludge all increased significantly.The higher the solid content of sludge,the higher the content of TVFA,sCOD,carbohydrate and soluble protein.When started-up by sodium acetate,the hydrogen production,hydrogen yield and COD degradation rate of different substrates as MEC substrates were as follows: sodium acetate>glucose>protein>sodium butyrate>sodium valerate;When glucose is used as substrate,the advantage of hydrogen production started-up by using glucose as substrate was more obvious compared with sodium acetate only in the first cycle.When using bovine serum albumin as MEC substrate,started up by bovine serum albumin obtained higher hydrogen yields and hydrogen rate compared with sodium acetate,and greater degradation of sCOD and soluble proteins can be achieved.When the actual fermentation broth and several simulated fermentation broths were applied to the production of hydrogen by MEC,the hydrogen production and average hydrogen production rate were as follows: no butyric acid control group > simulated fermentation broth > actual fermentation broth > no valeric acid control group > no acetic acid control group.It is further verified that the presence of butyric acid is not conducive to the hydrogen production by MEC.In the actual fermentation broth,there are more hydrogen-consuming bacteria,resulting in a decrease in hydrogen yield.