Research On Operation Parameters Optimization Of The Modified A~2/O Wastewater Treatment Process In Cold Area

Harbin is located in northeasten China, which is under low temperatureconditions,the low temperature can affect denitrification and phosphorus removal,resulting in water pollution. With respect to the low temperature conditions in thenorth, to determine the best operation parameters in winter water treatmemt plants toimprove denitrification and phosphorus removal is with great significance.Located near the Xinyigou and Ashi river, Harbin Xinyigou sewage treatmentplant was a capacity of200000tons per day, two phase of construction,the recentwater treatment capacity is100000tons.This paper introduced the engineeringdesign of a complete system and process detailed information of the process Aftercommission test, the system got the optimized operation parameters. After onemonth operation with the optimized, the treatment results were analyzed. In thestudy, it was found out that A-A~2/O process operated stably with high impactresistant ability.The best opertating conditions (summer):the mixture reflux ratiothan200%,return sludge ratio75%,water distribution ratio is10%,DO concentrationin aerobic bank2-3mg/L.In this condition the water outlet can achieve the designstandard.And compared with the traditional A~2/O process. Analyzes between theimproved A~2/O process with the traditional A~2/O process the function of theselection tank. It should be noted that the selection tank contributed greatly to thenitrogen removal,which can remove12%of the total TN removal,can improve thedenitrification in the front area to ensure system TN removal so as to relieve thepressure of oxygen denitrification and reduce the energy consumption due to theincrease of reflux ratio.In addition, in this study,the effect of low temperature on denitrification andphosphorus remmoval was analyzed.In the low temperature condition,by changingreflux ratio of the mixture,inlet water distribution ratio, return sludge and DOconcentration in aerobic tank to determine the best operation parameters in winterfor denitrification and phosphorus removal optimization. By changing the mixturereflux ratio,it was found out that the change of the reflux ratio did not havesignificant effect on COD and TP removal.When the mixture reflux ratio increasedfrom100%to200%,TN removal rate increases6.8%;if the mixture reflux ratioincreased from200%to00%,the removal rate TN pnly increases0.7%.Therefore,thereflux ratio should be200%.By changing the return sludge ratio,it was noted that90%is relatively appropriate in winter.Through the separated case controllingoxygen,with the decreased DO concentration:the first case3-4mg/L,middle case2-3mg/L,1-1.5mg/L in the end case.In winter,it is needed to change water distribution ratio of20%in the selection tank,which is favorable.Finally, two sets ofoperation parameters were confirmed,applicable to the Harbin winter and summerwater quality,respectively, and provided the whole running cost of economicanalysis.This study not only offers the best running condition for the sewage treatmentplant,and provided a reliable basis for similar projects in the future,construction andoperation of all the parameters.