| In recent years,new biological nitrogen removal processes with low energy consumption and high efficiency have developed rapidly,especially the partial nitrification-denitrification and partial nitrification-anaerobic ammonia oxidation processes.The both reduce oxygen consumption and the use of organic carbon sources and in line with the current concept of sustainable development compared with traditional biological nitrogen removal technologies.The partial nitrification process is a critical and restrictive step.Therefore,this paper focuses on high-concentration nitrogen-containing wastewater to achieve the start-up and stable operation of partial nitrification from two aspects of experiment and kinetic simulation.In this study,a partial nitrification system with membrane aeration was constructed and the continuous flow and SBR were used to optimize the start-up and operation of partial nitrification.In the reactor operated in continuous flow mode,operating conditions were as follows:the pH was 7.5,the DO was 0.8mg/L,and the FNA concentration was about 0.1mg/L,finally the system achieved more than 95%stability accumulation of NO2--N within 57 days,the removal load of ammonia nitrogen reached 320 mg·L-1·d-1;On the basis of the successful start with continuous flow,the DO concentration was gradually increased and it was found that the system has a certain stability,but too long aeration time will destroy this stability.Therefore,in order to achieve stable operation of partial nitrification,it is necessary to control the DO concentration during the operation.For the regulation of the destabilizing system,gradually lower the pH and rely on a higher concentration of FNA to achieve 90%N02--N accumulation.In the reactor operated by SBR,the DO was about 0.8mg/L,and the pH of the influent was 8.15 and gradually decreased and controlled at 5.5,the DO+FA control in the early stage and the DO+FNA control in the later stage of each cycle successfully achieved more than 90%accumulation of nitrite within 30 days,and the removal load of ammonia nitrogen reached 267.33 mg·L-1·d-1,The concentration of FNA reached 6.5,and did not produce a obviously inhibition of ammonia-oxidizing bacteria.Both starting methods have successfully achieved the accumulation of more than 90%of nitrite,which has certain engineering application prospects.Based on the start-up study of membrane aeration partial nitrification and the ASM3 model,the kinetic model in a completely mixed reactor was established in this paper.The model contained 4 processes,7 components and 15 Parameters.At the same time,the model was verified by experimental data,and it was concluded that the model has a good simulation effect for partial nitrificationBased on the model,the effects of DO,pH,temperature,and ammonia nitrogen concentration were investigated through AQUASIM software.From the perspective of reaction rate,within a certain range,the oxidation rate of ammonia nitrogen will increase with the increase of DO concentration;the reaction rate will increase with The pH increases in the range of 5-9;the ammonia oxidation rate also increases with increasing temperature in the range of 10?35?.From the perspective of high nitrite accumulating rate,when the system is in the process of nitrification to partial nitrification,the recommended conditions are as follows:the DO is 0.5?1mg/L,the pH is 8?9,and the temperature is 30?35? When the system is in a stable partial nitrification stage,the DO should be 1?3mg/L,the pH should be around 7?8,and the temperature should be between 25?35?.For low-temperature and low-concentration urban sewage,it is difficult to control conditions to achieve partial nitrification;for high-temperature and high-concentration sludge digestion liquid,it is easier to achieve short-range nitrification.The above simulation parameters provide some theoretical guidance for the actual operation of partial nitrification. |
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