| With the steady progress of the national water management,the municipal wastewater treatment plant is bound to face more stringent water quality standards,which is crucial for the reduction of total nitrogen.As a common urban sewage treatment process,AAO also faces the question of how to further improve its denitrification effect.At present the technology mainly exist the following drawbacks: one is the matrix competition and different sludge age make the treatment effect is relatively poor,the contradiction of the two is denitrifying process need to consume organic matter,and sewage plants generally lack of carbon source,the water is difficult to guarantee the denitrification effect,thus affecting the overall total nitrogen removal.Therefore,it is necessary to study the deformational mechanism of AAO technology to find a way to further improve the denitrification efficiency,and to lay a theoretical and technical foundation for the implementation of AAO process.This study is part of project of Research and demonstration of the technology of nitrogen removal and phosphorus removal in urban wastewater.In view of the present AAO process denitrification efficiency is difficult to further improve,to carry out the aeration partition effect on the performance of denitrification AAO system,analysis of A/O value size on the properties of AAO process denitrification effect and its mechanism.Under the AAO system,the experimental study of nitrification and denitrification was carried out,and the operating conditions of the optimum reaction effect were proved.The main work and results of this paper are as follows:(1)The AAO process characteristics were analyzed,and it was pointed out that the change of aeration partition ratio was very important to the system denitrification performance,and the design reactor was studied experimentally.The operation effect of the AAO pilot reactor in four kinds of aeration zones was compared,and the results showed that.The optimum denitrification effect was obtained when the pilot reactor system was A/O=6.5/7.5.The system effluent TN was 4.6mg/L,and the nitrogen removal efficiency reached 90.8%.In this area,the nitrification effect of the system is not weakened,and long enough anoxic time increases the denitrification performance of the system,and the system has the highest nitrogen removal efficiency.At the same time,the proportion of different aeration partitions can also affect the microbial population characteristics of activated sludge system,the analysis results show that the reactor system in 6.5/7.5 of A/O activated sludge samples species richness in slightly higher than the system of 4/10 of A/O activated sludge samples species richness,and the relative abundance of the denitrifying bacteria in the samples of the former than the latter.(2)In AAO process for new denitrification technology research,according to the theory of simultaneous nitrification,chose by adding the packing way for aerobic area,induction of AAO reactor system meet the SND process occurs in the microenvironment.After introducing the suspension filler,the removal effect of COD and TP is basically unchanged.The effluent TN and nitrate concentration of the system were obviously decreased.At the same time,the influence factors of the reaction system were studied,and it was found that the low DO level was more conducive to the occurrence of SND process.MLSS is higher,the stronger the denitrification performance of the system,at the same time the carrier of suspended packing area were also more likely to form the hypoxic microenvironment,thus enhances the SND phenomenon in the region,and to control the pH between 7.5 ~ 8,are more likely to get the best denitrification effect. |
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