Enzymatic Pretreatment To Promote Food Waste Solid Phase Hydrolysis Towards Conversion Performance Enhancement By Anaerobic Digestion

Food waste becomes an increasingly serious environmental problem due to perishability,emit odor and toxic gases,produce leachate,spread bacteria and viruses.Anaerobic digestion can make FW become a good source of biomass energy.However,There are two problems in the anaerobic digestion to food waste,high solid content and long hydraulic retention time.Enzymatic pretreatment with high efficiency and specificity,and can oriented conversion solid and liquid protein,lipids,and carbohydrates.Compared with other pretreatment technology,Enzymatic pretreatment is an effective and ideal technology to food waste.In this paper,food waste was the research object,three enzymes were used to pretreat food waste.The solid phase food waste removal rate and the transformation of macromolecular organic matter were investigated before and after the enzyme pretreatment.The solid phase of the food waste was converted to the liquid and hydrolyzed into small molecular substance.Through the anaerobic digestion of the solid phase and liquid phase food waste,the conversion efficiency of the solid phase in the anaerobic process was investigated,the results showed that after enzyme pretreatment the methane production performance of the solid phase and liquid phase food waste all increased.In the end,the the control and enzyme pretreatment food waste ib batch experiment was carried out.The residue and solid phase in anaerobic digestion system were investigated.The hydrolysis rate,solid phase degradation rate and methane production performance all improve.It can provide theoretical and practical basis for shortening HRT and reducing biogas residues by flow reactor.The main contents and results are as follows:(1)By enzyme pretreatment experiments,the effects of three separate enzymes and mixed enzymes on the dissolution of solid phase and SCOD,and the hydrolysis of macromolecular organic matter were studied.The results showed that when the hydrolysis time was 10 h and the concentration of amylase was 16 U/g,protease was 40U/g and lipase was 20 U/g,the effect of hydrolysis was the best.The result show that the SCOD increased by 63.2%,VSS removed by 74.7%,the reducing sugar increased by 82%,and the free amino acid was added to 339 mg/L after the enzyme pretreatment.The average particle size of the food waste in the control group was 193.5 ?m.The average particle size of the kitchen waste was 90.6?m and the particle size was smaller after the enzyme pretreatment.(2)Through solid phase and liquid phase food waste batch anaerobic digestion experiments,the methanogenic properties of the solid phase and liquid phase food waste after enzyme pretreatment and control group were studied.The results showed that the liquid food waste total gas production in the pretreated group and control group is similar,and the solid phase food waste gas production in pretreated group is 15.6% higher than that in control group.TCOD removal rate and cumulative gas production: pretreatment liquid phase > blank liquid > pretreatment solid phase > blank solid phase.For liquid phase food waste,pretreated group the yield of methane increased by 10.3% then that in the control group.For the solid phase,pretreated group the methane yield increased by 23.7% compared with the control group.(3)By sequencing batch anaerobic digestion experiment,the effect of enzyme co-pretreatment on solid phase removal,hydrolysis rate and methane production performance of food waste was studied.After enzyme pretreatment showed that the methane yield of food waste increased by 28.6%,the removal rate of TCOD was14.6% higher than that of control group,the methane yield was 18.4% higher than that of control group.According to the long-term stability and biogas residue of the continuous flow reactor,HRT was suggested for 16 days.Compared with the current continuous flow reactor average HRT=30 days,enzyme pretreatment could reduce the hydraulic retention time by half,and the accumulation of solid phase decreased by 50%,and the treatment and conversion efficiency of food waste were improved.(4)Application prospect of enzyme pretreatment for food waste: solid phasein food waste is the key factor limiting the use of the third generation high efficiency anaerobic reactor.On the basis of the research results of this paper,the optimal enzyme pretreatment technology conditions,the best leachate co-digestion ratio and the third generation of high efficiency anaerobic reactor were used to study the effect of the solid phase transformation,HRT,OLR,and accumulative biomass energy conversion efficiency,which provided a new idea for the treatment of food waste.