Efficiency Optimization And Application Research Of A~2/O Process In Municipal Wastewater Treatment Plant

With environmental pollution become more and more serious，China has a morestringent standard for environmental protection. As the largest sewage treatment plant inHarbin city, Heilongjiang province, Wenchang wastewater treatment plant has beenimplementing the national secondary effluent discharge standards over the years. Inorder to further increase the Songhua River basin remediation efforts to optimize thehydrological environment of the Songhua River, now the Wenchang sewage plant isupgrading, so that the treated water could reach the national Level1(B) emissionstandards. This paper is based on the upgrading of the actual project, concluding theprocess of start-up，adjusting and optimal operation research of the A~2/O process in theupgrading process after lab trials.By establishing lab trials, primarily ascertained parameters of A~2/O process areas follows: the mixture reflux ratio is250%, the sludge reflux was100%, the sludge ageis15d, DO in aeration tank is2.5mg/L~3.5mg/L. Then, This paper consists of thestart-up, adjusting, and final stable operation of the A~2/O process, meanwhile, Ianalyzed the corresponding result of every process one by one, and compared thedifferent effects of the transformation process with former process and experimentalresearch. On one hand, this project demonstrated the technological advantages of theA~2/O process, significantly improved the level of nitrogen and phosphorus removal ofthe wastewater treatment plant; On the other hand, it was found the deficiencycompared to the laboratory testing efficiency, and I explored of the reasons causingsuch results. As a result, workers take a further optimization for the A~2/O processrunning, by orthogonal test method, they control a single variable to adjust theoperating parameters. Finally, we ascertain the best running parameters of the A~2/Oprocess of this upgrading project: the mixture of reflux ratio is200%, the sludge refluxratio is75%, the sludge age is15days.In consideration of low temperature in the cold winter in Harbin, I respectivelyselected30sets of data from winter and summer for comparison, the results show thatlow temperature has adverse effects for denitrification and phosphorus efficiency ofA~2/O process, especially for total nitrogen removal. In order to meet the dischargeeffluent standards in winter, and also for further optimized water quality, appropriateraising the reflux ratio, increasing dissolved oxygen, and extending the hydraulicretention time should be taken into consideration. we could take measures to explore theA~2/O process’s potential or associate denitrification biofilter with the A~2/O process inthe face of wastewater’s low C/N realistic condition. On one side，steps should be takento make sure that the DPBs enrich in the biochemical pool, then we can take advantage of the DPB’s outstanding biochemical characteristics to reduce theconsumption of organic and enhance the effect of nitrogen and phosphorus removalwithout adding additional organic source。On another side, we can lead the treatedwastewater of the A~2/O process in the secondary sedimentation tank into the biofilter fordenitrification which is part of the Wenchang wastewater treatment plant’s third phaseof the project, and add suitable quantity of organic source and adjust other operatingconditions to us the denitrifying bacteria in the biological filter to further reduce thetotal nitrogen of A~2/O process.This paper detailedly describe and analyze the various stages of the A~2/O processincluding adjusting，operation optimization and corresponding effects, hoping that itwould be helpful for other wastewater treatment plant’s construction and renovationproject in the surrounding or other area.