再生水回补河湖条件下污染物的迁移转化机制研究

发布时间：2018-06-06 14:42

本文选题：再生水 + 硝态氮　；参考：《中国农业大学》2017年博士论文

【摘要】：再生水已成为北京市河湖生态用水的重要水源,但再生水污染物渗漏可能对地下水环境造成潜在污染风险,因此探讨再生水回补河湖后对地表水和地下水环境影响的研究十分重要。本文通过室内土柱模拟渗滤系统,研究了4种不同水力条件下(定水头淹水、交替淹水落干、定流速和侧向补水)渗滤系统对再生水中硝态氮(NO_3-N)、氨态氮(NH4-N)、化学需氧量(COD)和总氮(TN)的去除效果及其影响因素;同时以北京市清洋河为研究对象开展野外观测试验,探讨再生水补给后,地表水和地下水水质的时空变化特征;并构建了一维和二维水氮迁移模型,分别对室内土柱一维水氮迁移转化过程和野外河道再生水补给渗滤系统的二维水氮迁移转化过程进行了模拟研究。主要研究和结果如下:(1)当水力负荷在0.25-2.65 cm d-1范围内时,系统对N03-N的去除率随着水力负荷的增大而减小,侧向补水系统对N03-N的去除效果最佳,去除率高达96%。N03-N的去除主要取决于系统内部微生物的分布情况,土层中反硝化细菌数量越大,相应土层对NO_3-N的去除率越高。水温在15～32 ℃范围内变化时,定水头淹水和交替淹水落干系统对N03-N的去除率与温度分别呈指数和幂函数关系。当再生水中NH4-N浓度较低时,较长的水力停留时间和充分的有氧环境可促进NH4-N的去除。(2)交替淹水落干渗滤系统对再生水中COD的去除率(51%)略高于定水头淹水系统对COD的去除率(41%)。COD的去除主要发生在渗滤系统上部0～40 cm 土层范围内。交替淹水落干系统对TN的去除率(84%)明显高于定水头淹水系统(51%),两渗滤系统对TN的去除效率与温度呈正相关关系,温度高于30℃时,交替淹水落干系统对TN去除率高达90%以上。(3)NO_3-N和TN是清洋河的主要污染因子,N03-N和TN浓度沿河道水流方向逐渐下降,而COD和BOD5浓度沿河道水流方向逐渐增大。底泥部位对NO_3-N的去除率为85%,是NO_3-N去除的主要部位,N03-N的变化受渗流区水温的影响明显。渗流带的吸附和硝化作用是NH4-N去除的主要作用机制,可去除92%的NH4-N,NH4-N的变化主要受饱和带温度和有机质含量的影响。距河岸距离越大,迁移时间越长,河岸渗滤过程对COD的去除率越高,河岸渗滤系统对COD的去除率达54%。(4)利用是室内和野外试验数据对构建的一维和二维水氮运移模型进行率定验证,表明率定验证后的模型能够较好地模拟不同水力条件下的水氮迁移过程。结果发现,温度与反硝化速率常数之间呈指数相关,可通过该相关关系对不同温度下反硝化速率常数进行修正。模型模拟了不同温度和不同河水NO_3-N浓度情景下浅层地下水中N03-N的迁移过程,结果发现,当温度在5-25℃范围内时,每提高10℃时,河岸渗滤系统对N03-N的去除率可提高0.5-1.6倍。建议再生水补给期内(每年的3～11月),控制补给再生水中NO_3-N浓度不高于30mgL-1;为降低对地下水污染的风险,适宜的补水时段为温度较高的夏季(高于20 ℃)。
[Abstract]:Reclaimed water has become an important source of water for ecological water in Beijing River and lake, but the leakage of reclaimed water may cause potential pollution risk to the groundwater environment. Therefore, it is very important to study the influence of reclaimed water on the surface water and groundwater environment after reclaiming the river lake. In this paper, 4 different kinds of water power are studied through the indoor soil column simulated percolation system. The effect of the removal of nitrate nitrogen (NO_3-N), ammonia nitrogen (NH4-N), chemical oxygen demand (COD) and total nitrogen (TN) in reclaimed water and its influence factors under the conditions of water head flooding, alternate flooding and drying, constant flow rate and lateral water supplement. The field observation test was carried out in the Yanghe River, Beijing city as the research object, and the surface of the reclaimed water was discussed. The spatial and temporal characteristics of water and groundwater quality are characterized, and one and two dimensional water and nitrogen migration models are constructed. The one-dimensional water and nitrogen migration and transformation process of the indoor soil column and the two-dimensional water and nitrogen transfer process of the recharge filter system in the field are simulated respectively. The main research and results are as follows: (1) when the hydraulic load is in 0.25-2.65 cm In the range of D-1, the removal rate of N03-N decreases with the increase of hydraulic load, and the removal efficiency of N03-N is the best. The removal rate up to 96%.N03-N depends mainly on the distribution of microbes in the system. The greater the number of denitrifying bacteria in the soil layer, the higher the removal rate of the corresponding soil layer to NO_3-N. The water temperature is 1. When the range of 5~32 C is changed, the removal rate of N03-N and the temperature are exponential and power function respectively. When the NH4-N concentration in the regenerated water is low, the longer hydraulic retention time and the sufficient aerobic environment can promote the removal of NH4-N. (2) the alternately flooded and dry infiltration system for the regenerated water COD The removal rate (51%) is slightly higher than that of the fixed water head submergence system (41%). The removal of.COD is mainly in the upper 0~40 cm layer of the percolation system. The removal rate of TN in the alternate flooding system (84%) is obviously higher than that of the fixed water head (51%). The removal efficiency of TN is positively correlated with the temperature of TN, and the temperature is higher than that of the system. At 30, the removal rate of TN is more than 90%. (3) NO_3-N and TN are the main pollution factors of the Qing the Yanghe River. The concentration of N03-N and TN gradually decreases along the river flow direction, while the COD and BOD5 concentration increases along the river flow direction. The removal rate of NO_3-N in the sediment is 85%, the main part of NO_3-N removal, the change of N03-N The influence of water temperature in the percolation zone is obvious. The adsorption and nitrification of the percolation zone are the main mechanism of NH4-N removal, which can remove 92% NH4-N. The change of NH4-N is mainly influenced by the temperature of the saturated zone and the content of organic matter. The greater the distance from the riverbank, the longer the migration time is, the higher the removal rate of the riparian filtration process to the COD, and the river bank filtration system to COD The removal rate of 54%. (4) is used to verify the rate of one and two two-dimensional water and nitrogen migration models constructed by indoor and field test data. The results show that the model can well simulate the process of water and nitrogen migration under different hydraulic conditions. The results show that the correlation between temperature and denitrification rate constants is exponential, and the correlation can be obtained through the correlation. The denitrification rate constant under different temperatures was corrected. The model simulated the migration process of N03-N in shallow groundwater under different temperatures and different water NO_3-N concentrations. The results showed that when the temperature was in the range of 5-25 degrees C, the removal rate of the riparian percolation system to the N03-N could be increased by 0.5-1.6 times per increase of 10 degrees C. The reclaimed water was recommended. During the period of the period (3~11 months per year), the concentration of NO_3-N in recharge recharge water is not higher than 30mgL-1. In order to reduce the risk of groundwater pollution, the appropriate time for water replenishment is a higher temperature in summer (higher than 20).
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X52

【参考文献】