Influence Of Two Regulation Modes On Acidification And Hydrogen Production Anaerobic Bioreactor With Magnetic Field

Anaerobic acidification and hydrogen production technology are widely used in the treatment of many kinds of wastewater.How to regulate environmental factors to obtain different acidification and hydrogen production effect is a hot research issue.Magnetic fields have been found to promote the growth and activity of certain microorganisms.Therefore,this experiment adopted two same size and operating parameters consistent continuous flow anaerobic fluidized bed reactor,which was inoculated with excess sludge.Comparative study the effect of the magnetic fields on the anaerobic acidification and hydrogen production process was conducted,and on this basis,further study the effect of the p H adjustment and short-time aeration on the process were explored.From the perspective of microbial population we preliminarily analyzed the influence mechanism of two kinds of regulation methods under the condition of magnetic fields,by means of three-dimensional fluorescence scanning,SEM,and high-throughput sequencing.The following conclusions were obtained:（1）Magnetic fields can enrich acetic acid-producing ethanol-producing bacteria effectively,and promote the production of hydrogen by ethanol-type anaerobic fermentation.Under the conditions of medium temperature（37℃）,influent organic loading rate of 15 kg COD/m³/d and uncontrolled p H,the maximum hydrogen production rate of the 70～80 m T magnetic reactor was 3.87 mol H₂/mol glu,which was 1.5 times of that of the non-magnetic reactor.The acid production process is dominated by acetic acid and ethanol,accounting for 83.0%.At the same time,the production of caproic acid was promoted,which was 144.9 mg/L,2.3 times that of non-magnetic reactor.The proportion of Ethanoligenens was 71.5%in the magnetic reactor.In the non-magnetic reactor,acetic acid and butyric acid were the main components,both together accounting for 89.5%.The effluent p H of the two reactors ranged from 3.5 to 3.8,and the methane production rate could reach 3 mol CH₄/mol glu.Methanobacterium was the main methanogenic archaea,accounting for 82.5%and 98.7%,respectively.High methane production had some impact on the anaerobic acidification hydrogen production process.（2）Regulation of influent p H would change the metabolic pathway of anaerobic acidification,which is not conducive to anaerobic hydrogen production,and the magnetic fields would inhibit the process of propionic acid production.By adjusting the influent p H to maintain the effluent p H at 4.5,the hydrogen production rate and methane production rate of the magnetic reactor decreased to 0.05 mol H₂/mol glu and1.8 mol CH₄/mol glu,and the acid production process changed from acetic acid production to butyric acid production.The ratio of acetic acid/butyric acid decreased from 5 to 3;caproic acid decreased by 2.2 times.Ethanoligenens accounted for73.1%of the microbial community,and Propionibacterium was not dectected.The production rate of methane decreased to 1.1 mol CH₄/mol glu;the process of acid production changed from acetic acid to propionic acid,and the ratio of acetic acid/propionic acid decreased from 19 to 5.Methanobacterium was still the main methanogenic archaea in the two reactors,accounting for more than 99.0%.（3）After short-term high-intensity aeration,the methane production process could be significantly inhibited,so would flora structure be changed,and the magnetic fields can promote the ethanol production process of lactic acid bacteria.Due to aeration,the magnetic reactor hardly produced any gas,the output of acetic acid reamained basically unchanged,and no more butyric acid and caproic acid were produced.The yield of ethanol reached 550.0 mg/L,and the relative abundance of Ethanoligenens decreased by 3 times,while the relative abundance of other acidogenic bacteria Lactobacillus and Raoultella increased to 30%.Gas production in the non-magnetic reactor decreased from 2.87 L/d to 1.87 L/d;methane production rate decreased from 1.6 to 0.6 CH₄/mol glu;acetic acid and propionic acid production remained basically unchanged;butyrate,valerate and caproic acid were increased by1.9,1.6 and 2.2 times,respectively.The yield of ethanol could reached 267.8 mg/L;The relative abundance of Ethanoligenens decreased less than 5%,and the abundance of Bifidobacterium increased to 19.6%.