Study On The Effects Of Ammonia Nitrogen And Phosphate On The Production Of VFAs By Anaerobic Fermentation Of Organic Solid Wast

The anaerobic fermentation of organic solid waste to produce volatile fatty acids(VFAs)has been a hot research topic in recent years.The main substances in organic solid waste are three categories,namely carbohydrates,proteins,and lipids.These three categories are all composed of elements such as carbon,nitrogen,and phosphorus.However,during the anaerobic fermentation process of producing VFAs,these three types of substances release different ammonia nitrogen and phosphate,and the conversion rate of VFAs is also different,which leads to different problems,For example,high protein substances can easily lead to ammonia nitrogen inhibition and damage to the anaerobic fermentation environment,high phosphate content can inhibit ammonia nitrogen removal and inhibit acid producing enzyme activity,resulting in a decrease in VFAs production.Most of the ammonia nitrogen and phosphate are produced during the hydrolysis stage,so it is advantageous to control the production and accumulation of these two substances during the hydrolysis and acidification stages of anaerobic fermentation.This article mainly focuses on anaerobic fermentation of three types of organic solid waste.After selecting appropriate substrates,the effects of ammonia nitrogen and phosphate on anaerobic fermentation-hydrolysis and acidification stages were studied.Through the analysis of various basic indicators,acid production efficiency,and microbial community,the influence and mechanism of ammonia nitrogen and phosphate on hydrolysis and acidification stages were clarified.,Provide theoretical reference for regulating ammonia nitrogen and phosphate in the actual anaerobic fermentation acid production process.Among the three types of substances,rice has a good fermentation effect on acid production,with the highest VFAs content reaching 10013.01 mg/L,and the release of ammonia nitrogen and phosphorus is relatively low at 204.28 mg/L and 11.65 mg/L,respectively.Therefore,rice is determined as a suitable substrate for subsequent experiments.The results of the experiment on the effects of ammonia nitrogen and phosphate on anaerobic fermentation are as follows: during the hydrolysis stage,ammonia nitrogen with a concentration of 500 mg/L or above has a significant impact on protein dissolution;The ammonia nitrogen concentration of 0-1000 mg/L has little effect on the dissolution of polysaccharides,while the ammonia nitrogen concentration of 1500 mg/L has a significant impact on the dissolution of polysaccharides and also has a significant impact on SCOD.The concentration of phosphate has little effect on the dissolution of proteins and polysaccharides.Acidification stage: 0-200 mg/L ammonia nitrogen concentration has no significant effect on the generation of VFAs;At an ammonia nitrogen concentration of 500-1500 mg/L,the generation of VFAs is limited and the production volume is low.Compared with the blank group,the production of VFAs at phosphate concentrations of 100 and 300 mg/L was relatively low,while VFAs at phosphate concentrations of 600 mg/L and 1000 mg/L continued to decrease during the subsequent stages of anaerobic fermentation without an upward trend.The numerical simulation results of protein and VFAs indicate that the fit between protein and VFAs is good at ammonia nitrogen concentration of 500 mg/L and phosphate concentration of 100 mg/L and below.The above experimental data indicates that at concentrations of 500 mg/L and above,ammonia nitrogen will have an impact on both the hydrolysis and acidification stages of anaerobic fermentation.The phosphate concentration has no effect on the hydrolysis stage of anaerobic fermentation,but it will have an impact during the fermentation stage,especially at a phosphate concentration of 600 mg/L or above.From a microbial perspective,it can be further explained that Firmicutes,Proteobacteria,Actinobacteria,and Bacteroidetes are the dominant phyla in the experiment on the effect of ammonia nitrogen on anaerobic fermentation.And Streptococcaceae under Firmicutes is more suitable than Clostridiaceae＿1 for environments with medium to high concentrations of ammonia nitrogen,while the Proteobacteria phylum and its subfamilies,the Enterobacteriaceae family,are suitable for survival in high concentrations of ammonia nitrogen.In the experiment on the effect of phosphate on anaerobic fermentation,Firmicutes,Proteobacteria,and Actinobacteria were the dominant phyla,while Lactobacillaceae,Acetobacteraceae,and Clostridiaceae＿1 had higher relative abundance in the family level community,respectively.The analysis results indicate that Lactobacillaceae and Clostridiaceae＿1 are more adaptable to environments with high phosphate concentrations.