Study On Improved Method Of Residual Sludge Treatment By Autothermal Thermophilic Aerobie Digestion

Because of the short sludge retention time,good sterilization effect and other advantages,auto-thermophilic aerobic digestion(ATAD)process are widely used in Europe and America,based on differences in the property of sludge,its stabilization effect achieved initial success used China's Independent development of one-stage ATAD process,but in terms of the digestion period and oxygen utilization need to be improved.This subject based on existing ATAD process,batch tested and obtained process parameters by using simulation device,and then verified it by optimizing the ATAD reactor;the combination of ultrasonic pretreatment technology and ATAD effectively sped up the sludge stabilization process,reduced the sludge digestion period;in view of the high transmission rate and high utilization rate of oxygen by using pure oxygen aeration,pure oxygen aeration technology instead of air aeration used in sludge ATAD stabilization,verified the feasibility of the technology,and improved the utilization of oxygen in the aeration process.Through batch tests of the simulation of one-stage ATAD process,examined the sludge concentration,aeration rate,stirring speed influence on the process of sludge stabilization,the VSS removal rate was used as the main index,and determined the parameters of one-stage ATAD process: sludge solid content of 5%~6%,aeration rate 1.67~1.78 L/(h·L sludge),stirring rate of 130~150 r/min.The experiment was carried out with an optimized one-stage ATAD reactor,after digestion of 10.5 days,the VSS removal rate in the system was 40.8%,and the temperature was increased to 56.2?.The mixed sludge was irradiated by low intensity ultrasound(US)with the US intensities of 0.3 W/cm~2 for 10 min,after digestion of 8.5 days,the temperature was raised to 58.3 ?,VSS removal rate reached 42.1%,making it to reach a steady state 2 days ahead of the non-ultrasonic pretreatment test group.The concentration of TP,TOC,ammonia nitrogen and protein in the supernatant of digested sludge had changed,the concentration of TOC in the supernatant of the stabilized sludge dropped to less than 40 percent of the initial concentration,the concentration of TOC increased to initial concentration of 3~4 times,the concentration of ammonia nitrogen and protein was much higher than that of before digestion.The dewatering performance of digested sludge was also obviously changed,and the better the effect of the digestion,the worse the performance of the dehydration.Under the reasonable air aeration,the equal rate of oxygen supply of pure oxygen aeration resulted in the failure,because high concentration of dissolved oxygen coupled with high temperature inhibited the growth of microorganisms.In a reasonable amount of pure oxygen aeration(aeration of 1/20),sludge auto-thermal thermophilic aerobic digestion stabilization was realized,pure oxygen aeration obtained higher oxygen utilization rate of 82.7% which was significantly higher than that of air aeration of 26.3%.Different pure oxygen aeration rate for sludge stabilization effect was different,it was not conducive to sludge stabilization when the aeration rate is lower or higher than the optimum value.