Research On Deep Denitrification Technology And Microbiological Characterization Of Improved AAO Process

The project is based on the AAO process that is modified by Yixing City,Jiangsu Province,the new 75,000 tons of urban sewage treatment plant.Aiming at the characteristic of its improved AAO process,a pilot reactor was built.The process of the reactor is the same as the municipal wastewater treatment plant in Yixing City.The water is taken from hydrolysis acidification unit,automatic control design is adopted for each drug point of the device.The volume of the reactor is 28.8m~3,and the size of the equipment is 6m x 2.1m x 2.4m(including super high 0.3m),the total residence time is19.3h.The nitrifying liquid generally returns from the end of the aerobic section to the front part of the anoxia section.Considering the retention time in the anoxic section is long and the recirculation points of nitrifying liquid is set in each section of the hypoxia part,study on the effect of two point backflow of anaerobic pool was done and the effect of wastewater treatment before and after the backflow of nitrifying liquid was analyzed.In order to further reduce the total nitrogen,the effect of the carbon source adding in the two points was studied,and the microbial community and diversity were studied before and after carbon source.The results of two-point backflow show that,the average removal rate of nitrate concentration was reduced from 1.32 mg/L to 0.14mg/L,and the average removal rate was reduced from 76.44%to 56.04%.The reason may be that the backflow from two points can destroy the total dissolved oxygen level of anoxic pool,the DO concentration of the middle segment of anoxic pool showed a high tendency,carbon source cannot be fully utilized by denitrifying bacteria because of the fight of carbon source between the bacteria and the denitrifying bacteria.The experiment of carbon source adding showed that:the concentration of nitrates at the end of the anoxic segment was reduced from 4.69mg/L to 2.69mg/L,the average concentration of effluent TN was reduced from 9.70mg/L to 7.97mg/L,the cost of wastewater treatment had risen by 0.08 yuan/ton,providing reference for the actual operation of water plant.The analysis of microbial sequencing before and after adding carbon source showed that:there was a high similarity of the dominant bacteria in the microorganism gate after adding carbon source,but the abundance is generally higher than the reflux operation condition.From the physical and chemical indexes,the relative abundance of both of them can reach up to 97%of the removal rate of ammonia nitrogen.A kind of AOB bacteria genera,and a kind of NOB species were found in the two sequencing results.In addition to heterotrophic bacteria in denitrifying bacteria,some autotrophic denitrifying bacteria were also found,and there were also some unrecognized bacteria in the sequencing.This phenomenon shows that in the process of site operation,there are many kinds of microorganisms in activated sludge.