Study On The Evaluation And Control Method Of Denitrification Performance Of Activated Sludge Based On Respirogram

In recent years,the discharge standard of sewage treatment has been continuously improved,and there are many problems to be solved in the operation of sewage treatment plants.The activated sludge process is also facing problems of improvement and innovation,so it is urgent to study the improvement and transformation of activated sludge process.The denitrification process of sewage is mainly completed by microorganisms in the reactor,and the denitrification process of microorganisms directly affects the effluent NO₃^--N and the total nitrogen concentration.At present,the denitrification process is seriously affected by the lack of carbon source in most wastewater treatment plants in China,and the effluent nitrogen content seriously exceeds the discharge standard.In order to make the total nitrogen of effluent reach the standard,the sewage treatment plant carries out the operation of the process of sewage treatment and adding carbon source,but these methods undoubtedly increase the cost of sewage treatment.Therefore,through the process control study of sewage treatment system,the efficient use of existing resources has a long practical significance.Respirogram has been widely used in the evaluation of biological characteristics of activated sludge system.It is not clear whether it can be used in the evaluation of anoxic denitrification process.Denitrification is a key link in the process of wastewater treatment process,but it is lack of easy online denitrifying effect evaluation technology.This study studied the influence of denitrification process on the physical and chemical characteristics of activated sludge from the micro change of activated sludge floc,and studied and analyzed the measured data of oxygen consumption rate of activated sludge.The relationship between the respirogram and the denitrification performance of activated sludge was established.And this study proposed a strategy for nitrogen removal performance evaluation and control based on respirogram.The main results of this study are as follows:（1）In the process of anoxic denitrification,nitrate is reduced to gas and escapes from the sludge,which gradually increases the particle size of activated sludge,loosens the structure of sludge flocs,and makes the sedimentation worse.（2）Compared with the SBR system with continuous aeration,the SBR system with anoxic denitrification showed higher denitrification performance.The average particle size of sludge floc in SBR with continuous aeration and SBR with anoxic denitrification was 98.23 m and 111 m,respectively,and the maximum adsorption capacity Q_max in the same period was 316 mg/g MLSS and 354 mg/g MLSS,respectively.The sludge particle size distribution in SBR with anoxic denitrification was wider,the adsorption performance was higher,and the PS content in EPS was higher and the PN/PS was smaller,indicating that the activated sludge flocs structure in the system was relatively loose.（3）Based on the OTUs Alpha diversity analysis,the population structure of sludge did not change much under the short-term denitrification culture,but with the extension of the denitrification culture time,the difference of sludge population structure became obvious.The denitrifying bacteria Thauera was enriched as the dominant bacteria genus of denitrifying bacteria,while the organoaerobic bacteria Zoogloea was gradually eliminated.（4）Whether the type of activated sludge was changed or MLSS was changed,denitrification increased the SOUR_e value and SOUR_q value of activated sludge,and the SOUR_q increased exponentially with the increase of specific denitrification rate.A period of anaerobic adaptation time before denitrification can effectively improve the denitrification rate,but when the anaerobic time reaches 300min,the denitrification performance of sludge deteriorates,the content of effluent nitrate is higher,and the SOUR_eand SOUR_q values decrease.（5）In the field operation of sewage treatment plants,high SOUR_q and SOUR_e values should be avoided to avoid adverse effects of denitrification of anoxic section on subsequent treatment process.In addition,the denitrification performance can be judged according to the change of quasi-endogenous respiration rate ratio(R_q/t).The R_q/tvalue of a stable sewage treatment plant is generally stable in a range.If the R_q/t value significantly decreases,the denitrification performance of the system becomes worse.