| As a technology that can combine wastewater treatment with energy utilization,anaerobic biological treatment has the advantages of low operation cost,good biochemical performance and less excess sludge.However,there are many problems in the operation of anaerobic reactor,such as long start-up cycle,difficult formation of granular sludge,sludge loss caused by easy acidification,poor adaptability of inoculated granular sludge and so on.In view of the above problems,the start-up test of the internal circulation degassing anaerobic reactor with stirring and degassing diversion system independently developed by the research group was carried out by using fruit juice wastewater as inlet water.The parameters such as COD removal rate,gas production,p H,effluent sludge concentration,appearance,particle size distribution,mechanical strength,sludge concentration and other properties of granular sludge were detected,and the operation condition of the reactor and granular sludge culture were investigated;Then the treated wastewater was changed into glucose wastewater and starch wastewater,and the changes of various operating parameters of the reactor and the properties of granular sludge were investigated.In view of the fact that the current free precipitation method for measuring the settling rate of granular sludge ignores the influence of pressure and sludge gas production on the settling rate of granular sludge,two groups of closed settling columns with pressurizing device are used in this experiment.Glucose nutrient solution is introduced into one group of settling columns to form a nutrient column,and distilled water is introduced into the other group to form a clean water column.The mature granular sludge domesticated by glucose wastewater in the reactor is used for clean water column under different pressure conditions Nutrient column sedimentation test was conducted to explore the effects of pressure and sludge gas production on the sedimentation performance of granular sludge.It is expected to provide reference for the design and operation of reactor,the cultivation and maintenance of granular sludge in practical engineering,and provide a more reasonable experimental method for the determination of granular sludge sedimentation rate.The main test results and conclusions are as follows:(1)The primary granular sludge was cultured in the reactor in only 20 days,and the initial start-up was completed,and the COD removal rate reached 93%;On the92nd day,the reactor can achieve a COD removal rate of more than 85%under the predetermined load of 14.4kg COD/(m~3·d),and all indicators are good;The optimal speed of the reactor stirring system under the predetermined load is 250r/min,and the gas production of the reactor under the stable operation state is about 21.5L/d.It shows that the reactor has fast start-up speed and can stably remove organic matter in wastewater under high organic load.(2)The treated wastewater was replaced by juice wastewater and glucose wastewater.After 20 days of sludge acclimation,the reactor was well adapted to the change of water quality.After acclimation,the COD removal rate of the reactor was stable at more than 85%,and the gas production was slightly higher than that of treating fruit juice wastewater.The influent was replaced by starch wastewater,and the domestication of sludge took 42 days.During this period,the phenomenon of reactor acidification occurred,the COD removal rate and gas production of the reactor decreased significantly,the adaptability of sludge to starch wastewater was weak,and the floating loss of large particle size sludge occurred.After reducing the volume load,increasing the dosage of sodium bicarbonate and adding the effluent clear liquid to the starch wastewater for pre acidification treatment,the acidification problem of the reactor was solved and the COD removal rate increased rapidly.After the volume load is restored to the design load,the COD removal rate is finally stabilized at more than85%and the gas production reaches 21.5L/d.It shows that the reactor can withstand the impact of water quality changes and maintain efficient wastewater treatment efficiency after domesticating sludge by replacing wastewater in proportion,increasing alkalinity and influent pre acidification.(3)In the process of treating fruit juice wastewater in the reactor,the sludge is gradually granulated,and the particle size is generally 0.5～2mm,of which the particle size within the range of 1.5～2mm accounts for the most.The mechanical strength of granular sludge increased to 87%,the VSS of reactor sludge reached 25.76g/L,and the VSS/TSS ratio was 0.76,indicating that the biological activity of sludge was good.After the influent was replaced by glucose wastewater,the appearance of granular sludge did not change significantly,the proportion of granular sludge with particle size range of 0.5～2mm decreased,the mechanical strength was about 85%,and the VSS/TSS ratio of granular sludge did not change significantly.Granular sludge has strong adaptability to glucose wastewater and maintains good quality parameters.After replacing with starch wastewater,the appearance changes obviously,the proportion of granular sludge with particle size range of 1～2mm decreases,the mechanical strength of granular sludge once decreases to 68%,and then gradually recovers to 78%,and the VSS/TSS ratio is 0.72.Granular sludge has poor adaptability to starch wastewater.Some granular sludge is broken and dissolved.After adapting to the change of water quality,new granular sludge is produced,and the sludge quality is restored.(4)The nutrient column sedimentation experiment shows that the non discharged bubbles on the surface of granular sludge reduce the density of granular sludge,increase the resistance and decrease the sedimentation rate,which has a great impact on granular sludge with particle size≤2mm.With the increase of the pressure of the settling column,the pressure action compresses the bubbles generated in the granular sludge,and the gas volume is inversely proportional to the pressure,so that the influence of gas production on the settling speed of medium particle size(0.5～2mm)granular sludge is significantly weakened,while most of the bubbles generated by R1and R5 particle size granular sludge adhere to the surface of granular sludge,and the pressure has no obvious effect on the removal of bubbles adhered to the surface of granular sludge. |
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