Study On Efficiency Enhancement And Operation Control Of AO-MBR Process For Flushing Wastewater Under Low-temperature

Hypoxia-aerobic membrane bioreactor（Hypoxic-aerobic membrane bioreactor,AO-MBR）has the advantages of biological treatment technology and membrane separation technology,which is often used in the treatment of flushing sewage.However,under low temperature conditions,the start and stable operation of the flushing sewage treatment system are greatly affected.Low temperature affects the treatment effect of AO-MBR system by affecting microbial activity and metabolism,resulting in low treatment efficiency and unstable operation of the system at low temperature.How to realize low temperature efficiency and stable operation of AO-MBR system is a hot issue.The use of low-temperature microbial enhancement and low-temperature operation control technology can effectively solve the problems of low efficiency and stable operation of AO-MBR process at low temperature,which is of great significance to realize the low-temperature efficiency and stable operation of AO-MBR process.In this paper,taking the flushing sewage separated from the source separation toilet,,studies the starting and stable operation efficiency of AO-MBR treatment system based on low temperature microbial enhancement,and studies the influence of low temperature and parameter change on the system operation efficiency.Study the changing characteristics of microbial population at different temperatures,and carry out the correlation analysis of microbial population structure,pollutant removal and sludge performance.The AO-MBR coupling model was constructed using Biowin software to study the process and parameter regulation methods under different inlet water loads.The results can provide theoretical and technical support for low-temperature efficiency and stable operation of micro-enhanced AO-MBR system.The main contents and conclusions of this paper are as follows:（1）The effect of cryogenic microbial inoculation on the operational characteristics of the AO-MBR system was investigated.Cryogenic microbial enhancement can shorten the start time of the AO-MBR system by 30%and improve the pollutant removal rate.The temperature reduction had a great influence on the removal rate of NH₄⁺-N and TN.When the temperature decreased from 16±1℃to 8±1℃,the removal rate of NH₄⁺-N and TN decreased by 12.5%and 18.6%,respectively.（2）The sludge concentration of the low-temperature microbial enhancement system is relatively high,and the sludge sedimentation ability is good.Low temperature microbial enhancement has a certain impact on the concentration of EPS,with large secretion of proteins,and the relative abundance of low temperature microbial enhancement system Acinetobacter（Acinetobacter）,Flavobacterium（Flavobacteria）and Glutamicibacter（Corynebacterium glutamate）is high.Cryogenic microbial enhancement can significantly improve the metabolic capacity of the system microorganisms and improve the operation efficiency of the system at low temperature.（3）The changes of system sludge and microbial population characteristics were studied at different temperatures.Temperature reduction promotes the secretion of EPS in the system,and some dominant bacteria such as Acinetobacter（Acinetobacter）maintain a high relative abundance in the process of temperature reduction;redundant analysis results indicate a negative correlation between the dominant bacteria and the concentration of effluent pollutants;Under the condition of temperature change,the abundance of carbon metabolism pathway in the microbial genes of the low temperature microbial strengthening system is relatively high.（4）The coupled Biowin model of AO-MBR process at low temperature was constructed,and the system sewage component parameters were calculated according to the conversion relationship between flushing sewage components and model water quality index,and the process stoichiometry parameters and microbial dynamics parameters were corrected.The error of COD,NH₄⁺-N and TN concentration in the measured value is within 10%,so the process coupling Biowin model can be developed with reasonable simulation output.Through model dynamic simulation validation,the measured and simulated values of COD,NH₄⁺-N and TN were compared and linear fitted.The dynamic simulation results of the Biowin model fit well with the measured results.The corrected model was used to simulate the operation regulation of AO-MBR system under different influent loads to predict the optimal operating parameters of the system.At a temperature of 16±1℃,the lower dissolved oxygen concentration（3 mg/L～4 mg/L）and the higher sludge reflux ratio（150%～200%）can ensure the removal of organic matter and nitrogen in the AO-MBR system.