岸边湿地硝酸盐迁移转化特性模拟研究
发布时间：2018-08-26 09:45
【摘要】：我国《地表水环境质量标准》(GB3838-2002)对湖、库水体的总氮浓度和集中式生活饮用水地表水源地的硝酸盐氮(N03--N)浓度有严格的标准限值要求,对一般河流水体的总氮和NO3--N浓度无限值要求,而入湖河流是面源N03--N污染进入湖、库水体的重要输移通道。在削减NO3--N的方法中,天然或人工湿地是最具发展前景的方法之一,因此岸边湿地的建立对陆源性面源NO3--N污染进入水体起重要拦截作用。利用模拟岸边湿地试验装置,以硝酸盐为主要研究对象,开展湿地物理结构和运行参数影响研究,以期获得最适湿地结构参数和运行参数,同时基于污染物削减的一级动力学原理,建立湿地N03--N去除动力学模型及其拓展式,为岸边湿地的优化设计和运行管理提供依据。物理结构因素：长宽比、植物密度和水深；运行参数：水温、碳氮比(R)、进水NO3--N浓度(Cin)、进水水力负荷(q)和进水pH。结果表明：(1)湿地结构因素中,长宽比和水深是NO3--N削减的重要影响因素,植物(菖蒲)密度并非重要影响因素。本试验条件下,长宽比为4：1的湿地的NO3--N+NO2--N去除率最高。较0.15 m水深和0.30m水深湿地,0.40 m水深的湿地具有更优的N03--N削减效率,水深较大利于NO3--N削减。空白(菖蒲0株.m-2)、密度1(14株·m-2)和密度2(28株·m-2)湿地的NO3--N+NO2--N平均去除率间差别较小。(2)①环境温度的上升利于NO3--N的削减,NO3--N+NO2--N去除率随温度的上升而提高,分三个阶段：第一阶段为水温低于13℃的低速增长期(增速1.3%/℃)；第二阶段为13℃～24℃间的快速增长期(2.0%/℃)；第三阶段为24℃～28℃间的增速减缓期(1.5%/℃)。水温大于13℃时,出水NO2--N浓度(CNO2--N)随水温升高而减小,水温小于13℃时,CNO2--N随水温升高而增大。②NO3--N去除率随R的增加而快速提高,R为4时,去除率达96%。CNO2--N随R的增加表现为先上升后下降。③伴随Cin的增加,出水NO3-N浓度先增大后降低,CNO2--N持续增大,且增速加快。NO3--N+NO2--N面积去除率随进水浓度的升高而增大。④NO3--N+NO2--N去除率随着q的增加而降低。面积去除率随q的提高而增大,其过程为先快速增加,后增速减缓,最后趋于稳定。⑤进水pH降至5.0时,NO3--N去除率下降明显,湿地反硝化作用受限。(3)建立的一级动力学模型拓展式对试验湿地硝酸盐削减效果的预测具备准确性。基于一级动力学模型,将水温、R、Cin、q因素耦合入一级反应速率常数(K),构建模型拓展式。拓展式能有效降低模型参数的不确定性,提高模型的设计精度。结果显示,湿地去除NO3--N符合一级动力学模型；K与水温间符合Arrhenius公式(拟合系数R2：0.96),温度系数e值为1.06;K20与R间符合指数关系(R2：0.95)；K20与Cin间为线性关系(R2：0.94);K20与q间呈现二次函数关系(R2：0.93)。将水温、R、Cin、q因素拟合入K以构建一级动力学模型拓展式,拓展式准确性评价结果表明其预测具备准确性(ε：0.97;R2：0.99)。岸边湿地对控制陆源NO3--N污染进入水体有重要价值。湿地结构因素和运行参数的影响研究可为岸边湿地的设计、运行和管理提供重要的理论依据。同时,一级动力学模型拓展式的构建完善了湿地N03--N削减模型参数,提高动力学模型在湿地设计和效果预测中的可靠性和适用性。
[Abstract]:China's "Surface Water Environmental Quality Standard" (GB3838-2002) has strict standard limits on the total nitrogen concentration of lakes, reservoirs and the nitrate nitrogen (N03-N) concentration of surface water sources for centralized drinking water. It has unlimited requirements on the total nitrogen and NO3-N concentration of general river water bodies, while the river entering the lake is non-point source N03-N pollution entering the lake and the reservoir water bodies are polluted by N03-N. Natural or constructed wetlands are one of the most promising methods to reduce NO3-N. Therefore, the establishment of coastal wetlands plays an important role in intercepting the entry of terrestrial non-point source NO3-N pollution into water. Based on the first-order kinetic principle of pollutant reduction, the N03-N Removal Kinetic Model and its extended formula were established to provide the basis for the optimal design and operation management of coastal wetlands. Running parameters: water temperature, C/N ratio (R), influent NO3-N concentration (Cin), influent hydraulic load (q) and influent pH. The results show that: (1) Among the structural factors of wetland, the aspect ratio and water depth are the important factors affecting the reduction of NO3-N, and the density of plant (Acorus calamus) is not the important factor. Compared with 0.15 m depth and 0.30 m depth wetlands, the wetlands with 0.40 m depth had better N 03-N reduction efficiency, and the water depth was significantly higher than that with NO3-N reduction. The removal rate of O3-N+NO2-N increases with the increase of temperature, which can be divided into three stages: the first stage is the low-speed growth period when the water temperature is lower than 13 (6550 NO2--N) decreases with the increase of water temperature. When the water temperature is less than 13 ~C, the removal rate of CNO 2--N increases rapidly with the increase of water temperature. When R is 4, the removal rate of NO3--N reaches 96%. CNO 2--N increases first and then decreases with the increase of Cin. The removal rate of NO3 - N + NO2 - N increased with the increase of influent concentration. The removal rate of NO3 - N + NO2 - N decreased with the increase of influent concentration. The removal rate of NO3 - N increased with the increase of influent concentration. The process increased rapidly first, then slowed down, and finally stabilized. Based on the first-order kinetic model, water temperature, R, Cin and Q were coupled into the first-order reaction rate constant (K), and the extended model was constructed. The extended model can effectively reduce the uncertainty of the model parameters and improve the design accuracy of the model. The results show that the removal of NO3-N by wetland conforms to the first-order kinetic model; K and water temperature conform to Arrhenius formula (fitting coefficient R2:0.96), temperature coefficient e value is 1.06; K20 and R conform to exponential relationship (R2:0.95); K20 and CI are linear relationship (R2:0.94); K20 and Q present quadratic function relationship (R2:0.93). The water temperature, R, Cin, Q factors are fitted into K with K. The results show that the prediction is accurate (e:0.97; R2:0.99). At the same time, the extension of the first-order dynamic model improves the N03-N reduction model parameters and improves the reliability and applicability of the dynamic model in wetland design and effect prediction.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X52
本文编号：2204477
[Abstract]:China's "Surface Water Environmental Quality Standard" (GB3838-2002) has strict standard limits on the total nitrogen concentration of lakes, reservoirs and the nitrate nitrogen (N03-N) concentration of surface water sources for centralized drinking water. It has unlimited requirements on the total nitrogen and NO3-N concentration of general river water bodies, while the river entering the lake is non-point source N03-N pollution entering the lake and the reservoir water bodies are polluted by N03-N. Natural or constructed wetlands are one of the most promising methods to reduce NO3-N. Therefore, the establishment of coastal wetlands plays an important role in intercepting the entry of terrestrial non-point source NO3-N pollution into water. Based on the first-order kinetic principle of pollutant reduction, the N03-N Removal Kinetic Model and its extended formula were established to provide the basis for the optimal design and operation management of coastal wetlands. Running parameters: water temperature, C/N ratio (R), influent NO3-N concentration (Cin), influent hydraulic load (q) and influent pH. The results show that: (1) Among the structural factors of wetland, the aspect ratio and water depth are the important factors affecting the reduction of NO3-N, and the density of plant (Acorus calamus) is not the important factor. Compared with 0.15 m depth and 0.30 m depth wetlands, the wetlands with 0.40 m depth had better N 03-N reduction efficiency, and the water depth was significantly higher than that with NO3-N reduction. The removal rate of O3-N+NO2-N increases with the increase of temperature, which can be divided into three stages: the first stage is the low-speed growth period when the water temperature is lower than 13 (6550 NO2--N) decreases with the increase of water temperature. When the water temperature is less than 13 ~C, the removal rate of CNO 2--N increases rapidly with the increase of water temperature. When R is 4, the removal rate of NO3--N reaches 96%. CNO 2--N increases first and then decreases with the increase of Cin. The removal rate of NO3 - N + NO2 - N increased with the increase of influent concentration. The removal rate of NO3 - N + NO2 - N decreased with the increase of influent concentration. The removal rate of NO3 - N increased with the increase of influent concentration. The process increased rapidly first, then slowed down, and finally stabilized. Based on the first-order kinetic model, water temperature, R, Cin and Q were coupled into the first-order reaction rate constant (K), and the extended model was constructed. The extended model can effectively reduce the uncertainty of the model parameters and improve the design accuracy of the model. The results show that the removal of NO3-N by wetland conforms to the first-order kinetic model; K and water temperature conform to Arrhenius formula (fitting coefficient R2:0.96), temperature coefficient e value is 1.06; K20 and R conform to exponential relationship (R2:0.95); K20 and CI are linear relationship (R2:0.94); K20 and Q present quadratic function relationship (R2:0.93). The water temperature, R, Cin, Q factors are fitted into K with K. The results show that the prediction is accurate (e:0.97; R2:0.99). At the same time, the extension of the first-order dynamic model improves the N03-N reduction model parameters and improves the reliability and applicability of the dynamic model in wetland design and effect prediction.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X52
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