Rheological Characteristics Of Sludge With High Solid Content And Its Influence On Methane Production Efficiency Of Anaerobic Digestion

The highly viscous,viscoelastic and other rheological properties of high solids sludge lead to a decrease in the heat and mass transfer efficiency of the anaerobic digestion system,which affects the efficiency of anaerobic digestion and methane production of matter in the anaerobic digestion process.The sludge structure changes,which changes the rheological properties of the sludge.This research focus on the anaerobic digestion of excess high-solids,through the BMP batch test,the rheological characteristics of the high-solids sludge anaerobic digestion process are tested,combining the efficiency of methane production and the key metabolism in the anaerobic digestion process.The product changes,focusing on the research on the rheological characteristics of sludge during the anaerobic digestion of advanced sludge based on thermal hydrolysis and its influence on the efficiency of methane production;the anaerobic residual sludge under different rheological characteristics was investigated digestion of methane production characteristics and its effect on key metabolic intermediates;through semi-continuous experiments,the effect of agitation speed on sludge rheological properties and methanogenesis performance during anaerobic digestion of high solids sludge was discussed,with a view to sludge flow The effect of variable characteristics on the efficiency and mass transfer process of anaerobic digestion provides a theoretical basis.The main research conclusions are as follows:1)After high-solid sludge is pretreated by thermal hydrolysis at 100℃,120℃and 150℃,the viscosity of the sludge decreases with the increase of the thermal hydrolysis temperature;the yield stress valueτ₀and the consistency coefficient K gradually decrease,and the fluidity The index n gradually increases,the fluidity of the sludge increases;the storage modulus G′and the loss modulus G″gradually decrease,the linear viscoelastic region LVE shortens,and the sludge viscoelasticity weakens.2)The viscosity and yield stress of advanced anaerobic digested sludge based on thermal hydrolysis are less than those of non-thermal hydrolyzed anaerobic digested sludge,and the sludge flow performance during anaerobic digestion is better than that of non-hot water Decomposes anaerobic digestion of sludge;as the process of anaerobic digestion progresses,the viscosity of sludge first decreases,then increases,then decreases and gradually stabilizes.The yield stress shows an exponential decline.Conventional anaerobic digestion The storage modulus and loss modulus of sludge show a gradual decrease trend,and the storage modulus and loss modulus of advanced anaerobic digestion sludge show a trend of first increasing and then decreasing.In the advanced anaerobic digestion process,the yield stress of the sludge decreases exponentially or linearly as the lag time of methane production increases.3)Adding 4%,8%,and 12%saponite concentrations,the viscosity of the sludge increases,the yield stress index increases,and the cumulative methane production decreases with the increase in viscosity.Under the condition of stirring speed of 28rpm and adding saponite with mass concentrations of 4%,8%and 12%,the cumulative methane production of sludge was reduced by 18.16%,39.48%and 57.71respectively compared with conventional anaerobic digested sludge.%.For the condition of adding saponite at a concentration of 8%,the cumulative methane production at low speeds increased by 41.63%;for the condition of adding saponite at a concentration of 12%,the cumulative methane production at low speeds It is the same as high speed,but the cumulative methane production rate at low speed is higher and the speed is higher,indicating that at high viscosity,increasing the stirring speed is not conducive to the increase of methane production.The adjustment of the rheological properties of anaerobic digestion system by saponite shows that the rheological properties of high-solid sludge have an effect on the reaction rate of anaerobic digestion.4)In the semi-continuous anaerobic reactor,the increase of the stirring speed is beneficial to increase the methane production of the anaerobic digestion of high-solid sludge.The speed of 50rpm is 16%higher than the maximum daily methane production under the condition of 5rpm;The increase of is conducive to the dissolution of organic matter during the anaerobic digestion of high-solid sludge,and improves the degradation rate of organic matter.The concentration of VFAs,protein and polysaccharides at a speed of 50rpm is higher than that of 5rpm,and there is no organic acid and ammonia nitrogen in the digestion system Inhibition:Under the same sludge rheological properties,increasing the stirring speed of the reactor can increase the VS degradation rate of the sludge sample.At the same stirring speed,the degradation rate of sludge VS decreases with the increase of viscosity.