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近年来,我国污水处理行业发展迅速,污水处理率大幅提高,但仍存在处理效率低而处理能耗高等问题[1-2]。在城镇污水处理系统中,含氮污染物是主要的去除对象之一,相关脱氮技术一直以来备受关注。目前常用的废水生物脱氮工艺(A2/O、氧化沟等)虽然具有良好的处理效果[3],但在处理过程中需要消耗大量的能源,而且随着排放标准的不断提高,能源消耗也将进一步增加。因此,开发提质增效和节能降耗的新型生物脱氮技术一直是污水处理领域的研究热点。
在常规城市污水处理生物脱氮系统中,曝气和混合液内回流是保证系统脱氮性能的重要环节,同时也是污水处理过程中耗能最高的环节[4]。硝化-反硝化生物脱氮的第一步,即在好氧区曝气为硝化菌提供溶解氧(DO),通过硝化作用将废水中的氨氮转化为硝酸盐。随后通过内回流将硝酸盐带入缺氧区进行反硝化作用,内回流比越高,则脱氮效率越高,但是能耗也会成比例增加[5-6]。然而在实际运行过程中,曝气系统在给生物池带来溶解氧的同时,也会产生向上的水流推动力,但常规生物脱氮系统的设计与运行并未对此部分动力加以考虑和利用。若能将曝气动力作为内回流的动力[7-9],对于提高污水处理厂脱氮效率、降低运行成本具有重要的意义。
为此,本研究提出一种新型的曝气动力横向内循环反应器(ALIR),利用曝气提供的动力带动水流在好氧区与缺氧区间横向循环流动;以模拟城市污水为处理对象,考察系统的脱氮性能及功能菌活性、关键酶活性的变化特征,分析反应器的脱氮途径,并对微生物群落结构特征进行解析,以期为曝气动力横向内循环反应器的工程应用提供有效支撑。
曝气动力横向内循环反应器脱氮途径与性能分析
Nitrogen removal pathway and performance analysis of aeration-power lateral internal-circulation reactor
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摘要: 为降低城市污水生物脱氮系统处理能耗、提高脱氮效率,使用一种新型曝气动力横向内循环反应器(ALIR)来处理模拟城市污水并对该反应器的脱氮途径与性能进行了研究,采用16S rRNA基因高通量测序技术对微生物群落结构进行了分析。结果表明:反应器在A/O比为1:1、水力停留时间为9 h、污泥龄为20 d、污泥回流比100%的条件下,连续运行90 d后,出水NH4+-N质量浓度低至(3.20±0.93) mg·L−1,平均去除率为92.29%,出水总氮(TN)质量浓度为(11.68±1.31) mg·L−1,TN去除率达到71.81%,同时好氧区平均同步硝化反硝化(SND)率达到26.49%;接种污泥与第80天活性污泥的优势门均为Proteobacteria和Bacteroidetes;与接种污泥相比,第80天污泥中Pseudomonas、Sulfuritalea等反硝化菌属丰度呈下降趋势,具有好氧反硝化功能的Acinetobacter属和Hyphomicrobium属的丰度则明显增加。综上,实验条件下,曝气动力横向内循环反应器可以免除内回流能耗,并获得良好的脱氮效果。该研究结果可为内循环反应器在实际工程中的应用提供参考。Abstract: In order to reduce the energy consumption and improve the nitrogen removal efficiency of biological nitrogen removal system for urban sewage, a new type of aeration-power lateral internal-circulation reactor (ALIR) was used to treat artificial urban sewage, and the nitrogen removal pathway and performance of the reactor was investigated. 16 S rRNA gene high-throughput sequencing technology was used to analyze microbial community structure. The results showed that at A/O ratio of 1:1, hydraulic retention time of 9 h, sludge age of 20 d and sludge return ratio of 100%, the effluent concentrations of ammonia and total nitrogen (TN) were as low as (3.20±0.93) mg·L−1 (92.29%, ammonia removal efficiency) and (11.68±1.31) mg·L−1 (71.81%, TN removal efficiency) after long-term operation for over 90 days, respectively, and the simultaneous nitrification and denitrification (SND) rate was 26.49%. The results of the high-throughput sequencing showed that the dominant phyla in the inoculated sludge and the activated sludge on the 80th day were Proteobacteria and Bacteroidetes. Compared with the inoculated sludge, the relative abundances of denitrifying bacteria in the activated sludge on the 80th day, such as Pseudomonas and Sulfuritalea, showed a decreasing tendency, while these of Acinetobacter and Hyphomicrobium with an aerobic denitrifying function increased significantly. Thus, the aeration dynamic transverse internal circulation reactor had a good nitrogen removal performance without the energy consumption of internal circulation under the experimental operating conditions. This will provide a reference for the application of this reactor in practical engineering.
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