Study On The Effect Of Magnetite On The Process And Efficiency Of Anaerobic Digestion Of Sodium Acetate Simulated Wastewater To Produce Methane

Energy security and environmental pollution are perhaps the biggest challenges facing humanity in this century.Recent concerns about public health,environmental protection and resource recovery have made wastewater more of a resource than a waste.Mainstream aerobic wastewater treatment produces large excess sludge and is unable to recover the potential resources available in the wastewater.Anaerobic treatment has been proposed as an alternative to traditional aerobic wastewater treatment technology due to its advantages of energy saving,biogas recovery and reduced sludge production.However,the anaerobic reaction requires a long start-up time;the methanogenic efficiency is low;the long-term stable digestion is difficult to maintain,which limits the widespread use of anaerobic fermentation.Recent studies have shown that electron transfer between anaerobic microorganisms can improve the efficiency of electron transfer and increase the yield of methane by additionally adding auxiliary conductive mineral materials.In order to solve this problem,this study proposes to introduce magnetite in an anaerobic system,and design a natural ore with high conductivity.Sodium acetate as wastewater object,magnetite effect on the anaerobic digestion process and Efficiency of methanogenesis.The experiment was carried out in two stages.The first stage was the magnetite condition optimization experiment,the second stage was the analysis of the anaerobic degradation path of sodium acetate by magnetite and its mechanism analysis.Finally,the mathematical model was used to analyze the magnetite for anaerobic digestion.The trend of the methanogenesis process.In the first stage,the sodium acetate simulated wastewater was used as a substrate,and the sequencing batch anaerobic culture experiment was carried out in the laboratory.By analyzing the methanogenesis rate,the acetic acid degradation rate,the methanogenic pathway and the p H of the anaerobic system,the magnetite was different.The effect of concentration and particle size magnetite on anaerobic digestion and methanogenesis.The results show that the effect of magnetite dosage on anaerobic digestion and degradation of COD shows a phenomenon of“first increase and then decrease”with the increase of dosage.Under the same magnetite particle size,the effect of magnetite dosage on the anaerobic digestion of CH4 is 20 m M?magnetite concentration,based on iron atom?>30m M>40 m M>10 m M>0.Under the same conditions of magnetite dosage,the promotion effect is:particle size 100-150 nm>30-100 mm.Different dosing magnetite particle,the dosage of the anaerobic Effect on the p H of the system is trend substantially coincide:adding magnetite accelerated rate of degradation of the substrate,improving the p H of the system,a weak alkaline environment?p H 7.0-7.8?.Comprehensively compare the effects of magnetite on the macroscopic indicators of anaerobic methanogenesis,and select100-150 nm and 20 m M magnetite as the optimal dosing conditions.The second stage is to study the effect of magnetite on the anaerobic digestion of sodium acetate simulated wastewater and the mechanism of hydrogenation by using the comparison of magnetite with Fe Cl₂/Fe Cl₃and hydrogenation experiments.The main conclusions of the thesis are as follows:Magnetite has a great promotion effect on anaerobic digestion of CH₄,but the main reason is not because its release of Fe2+/Fe3+promotes anaerobic enzyme activity and anaerobic biomass,and finally magnetite The cumulative CH₄yield of the additive group was 150 m L,which was 32.7%higher than that of the Fe²⁺/Fe³⁺dosing group,and 47%higher than the control group.Under the condition of high hydrogen partial pressure of anaerobic system,magnetite still has a good promoting effect on anaerobic digestion of CH₄by sodium acetate and can normally degrade metabolic substrate and produce methane.The control group was inhibited for a long time?inhibition period of up to 8 days?,and it was unable to degrade the metabolic substrate and produce methane normally.The addition of magnetite shortens the stagnation period of the methanogenesis process and increases the rate of methanogenesis.It is speculated that magnetite promotes the efficiencies of anaerobic digestion by increasing the DIET of anaerobic microorganisms.In addition,the study used the fitting of three different models of Gompertz,Logistic and Transference to analyze the maximum cumulative methanogenesis,maximum specific methanogenesis rate,lag time and fitting correlation obtained by fitting each model.Select the mathematical model that best fits this experiment-the Gompertz model.By using the Gompertz equation to fit magnetites of different periods,particle sizes and concentrations,the maximum cumulative methanogenic amount of 403.7 m L/g VSS,the maximum specific methanogenic rate of 3.426 m L/g VSS·h,and the lag time of 16.5 h were obtained.R²=0.9968.In summary,the main way for magnetite to promote anaerobic methanogenesis is as an inter-species electron transport carrier,improve electron transport efficiency,change the acetic acid degradation pathway,and secondly promote the methanogenesis process by releasing Fe²⁺/Fe³⁺.This topic provides a new idea and theoretical basis for the performance of conductive materials in anaerobic digestion.