人工回灌条件下地下水中DBPs的迁移转化机制

发布时间：2018-03-05 23:19

本文选题：人工回灌　切入点：消毒剂　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来由于人类活动对地下水的过度开采,导致地下水位持续下降,出现地下水位降落漏斗、地裂缝、海水入侵等一系列环境地质问题。人工回灌技术是有效恢复地下水位和控制环境地质问题恶化的重要手段。然而由于拟回灌水源与回灌目标含水层中的地下水在水化学组分上存在差异和回灌过程水动力场的变化,均会对回灌后地下水水质产生一定的影响。人工回灌技术的广泛应用对地下水水质的影响引起国内外学者的广泛关注。拟回灌水源中消毒剂的存在与地下水中天然有机物反应生成消毒副产物(DBPs),从而引起地下水水质安全风险。但长期以来,缺乏回灌水源中消毒剂的使用对地下水水质影响的认识,我国对于人工回灌过程中DBPs污染缺乏系统研究,消毒副产物在地下水中的迁移转化机制研究还有待于查明。因此,研究人工回灌条件下消毒副产物形成规律、迁移转化机制,为保障人工回灌过程中地下水安全提供必要的理论依据。本文以山东省水利科学研究院委托课题《寿光市引弥回灌和地下水库建设工程可行性研究》为依托,以寿光弥河回灌试验场地为研究区,在分析回灌场地的地质、水文地质条件的基础上,选择次氯酸钠作为拟回灌水源消毒剂,腐殖酸模拟地下水中有机物,选择氯消毒副产物中检出率最高、危害性最大的三氯甲烷作为重点监测对象,通过开展形成机制实验、静态实验、动态模拟实验,揭示DBPs三氯甲烷在人工回灌条件下的形成规律及迁移转化机制,通过建立三氯甲烷的迁移转化数值模型和解析模型进行预测,并确定回灌水源中有效氯浓度阈值。本次研究结果表明:1.水中有效氯与有机物腐殖酸反应生成三氯甲烷不是瞬时完成的,生成量随接触时间的延长而增大最终趋于稳定。当水中有机物浓度一定(TOC=5mg/L或TOC=10mg/L),有效氯浓度范围为0.25~4mg/L时,三氯甲烷的生成量与消毒剂投放量呈线性关系,有效氯浓度继续增大,生成量趋于稳定。此外三氯甲烷的生成潜力与水质条件有关,生成量随p H的降低和离子强度的增大而减小,且水中二价阳离子的抑制作用大于一价阳离子。2.吸附动力学实验结果表明:拟二级动力学方程能较好地拟合回灌场地三种介质(粉土、细砂、中粗砂)对三氯甲烷的吸附量随时间的变化规律,吸附容量分别为2.22μg/g,1.57μg/g,1.40μg/g;等温吸附实验结果表明:实验采用的场地介质对三氯甲烷的等温吸附符合Freundlich模型,吸附能力为:粉土细砂中粗砂。3.生物降解实验结果表明,回灌场地三种含水层介质(粉土、细砂、中粗砂)中,三氯甲烷的生物降解过程可用Monod方程来描述。三氯甲烷在三种含水层介质中的衰减速率大小顺序为:粉土细砂中粗砂,即随着介质粒径的增大,有机质含量和微生物数量的降低,三氯甲烷的生物降解速率逐渐减小。此外,三种介质对三氯甲烷的生物降解速率均随初始浓度的增大而增大。4.结合场地水文地质条件建立室内动态模拟实验,对回灌过程中三氯甲烷的迁移规律进行了研究:(1)含水介质对三氯甲烷迁移的影响细砂、中粗砂作为含水层介质进行土柱模拟实验研究含水介质类型对三氯甲烷迁移的影响,实验结果表明三氯甲烷在中粗砂中的迁移能力大于细砂,主要是由于细砂的高比表面积提供了更多的吸附点位;此外,在相同达西流速条件下,孔隙流速随孔隙度的增大而减小,使得三氯甲烷与介质间的剪切力减小,吸附作用增强,迁移能力减弱。(2)水化学条件对三氯甲烷迁移的影响回灌水源中消毒剂初始浓度影响三氯甲烷的迁移速度,随着初始浓度的增大,流出液中三氯甲烷的相对浓度峰值增大。地下水中p H的降低,H+与三氯甲烷发生竞争吸附,随着p H的增大,H+浓度降低,此时介质对三氯甲烷的吸附作用增强,不利于三氯甲烷的迁移;随着离子强度的增大,金属阳离子可以中和更多的负电荷,静电作用力减弱,抑制三氯甲烷的迁移;此外,二价阳离子(Ca~(2+))对三氯甲烷影响大于一价阳离子(Na+),Ca~(2+)与含水层介质作用形成键桥,使得介质的吸附点位增多,促进含水层介质对三氯甲烷的吸附。(3)水动力条件对三氯甲烷迁移的影响实验结果表明三氯甲烷的迁移能力随流速的增大而增大,降低了三氯甲烷在含水介质中的滞留,且提高了释放量。一方面,随着流速的增大,三氯甲烷与多孔介质的接触时间减少,减少三氯甲烷与介质的碰撞,使得吸附量降低;另一方面,流速的变化影响三氯甲烷与多孔介质间的剪切力矩,随着流速的增大,剪切力增大。5.根据场地水文地质条件和室内实验结果构建了回灌场地地下水中三氯甲烷的迁移转化数值模型和解析模型,开展回灌场地距回灌井最近的监测井中三氯甲烷的预测,预测结果表明,当回灌水源有效氯浓度1mg/L时,高p H、低离子强度、高流速条件下三氯甲烷均有可能超过《生活饮用水卫生标准》(60μg/L),通过解析模型确定当监测井浓度峰值不超过60μg/L时三氯甲烷的初始浓度,根据三氯甲烷的生成规律,预测回灌水源有效氯浓度限值。
[Abstract]:In recent years, due to excessive exploitation of human activities on groundwater, resulting in declining groundwater levels, underground water level drawdown funnel, ground fissures, seawater intrusion and a series of environmental and geological problems. Artificial recharge technology is an important means to effectively restore the underground water level and control the environmental geological problems of evil. However due to the recharge and recharge target of groundwater in water chemical component differences and recharge process of hydrodynamic field, both to recharge after the groundwater quality has certain effect. The widespread use of artificial recharge technology of underground water caused widespread concern of scholars at home and abroad. To recharge the natural organic matter the water disinfectant and the existence of underground water in reaction of disinfection by-products (DBPs), which caused the groundwater quality safety risk. But for a long time, the lack of recharge water source in the use of disinfectants Understanding the impact on groundwater quality, our country for the artificial pollution of DBPs irrigation process lacks system research, mechanism of migration and transformation of disinfection by-products in groundwater research remains to be identified. Therefore, research on formation of disinfection by-products in artificial recharge conditions, migration and transformation mechanism, to provide the necessary theoretical basis for the protection of artificial recharge. The safety of groundwater irrigation process. In this paper, Shandong Academy of water conservancy project commissioned in Shouguang City, MI recharge and lead < underground reservoir construction project feasibility study "as the basis, taking Shouguang Mi River recharge test site for the study area, the geological analysis of recharge area, based on the hydrogeological conditions, selection of sodium hypochlorite as to recharge water disinfectant, humic acid simulated organic compounds in groundwater, selection of chlorine disinfection by-products in the highest detection rate, the most harmful chloroform as the focus of the monitoring of elephant pass To carry out the formation mechanism of experiment, static test, dynamic simulation experiments revealed that the DBPs chloroform in the artificial formation mechanism of migration and transformation law under the irrigation condition, through the establishment of chloroform migration conversion of numerical and analytical models to predict and determine the concentration of effective chlorine water recharge threshold. The results of this study show that: 1. in water chlorine and organic matter humic acid formation of chloroform is not instantaneous, formation with the extension of exposure time increased and stabilized. When the concentration of organic matter in water (TOC=5mg/L or TOC=10mg/L), the effective chlorine concentration range is 0.25~4mg/L, production and delivery of chloroform disinfectant is a linear relationship between the concentration of effective chlorine, continue to increase in addition, production tends to be stable. Generating potential and water quality conditions related to the generation of chloroform, H and P decreased with increasing ionic strength. And two valence cations in water decreased, the inhibitory effect is greater than the experimental results showed that the adsorption kinetics of cation.2.: pseudo two order kinetic equation can better fit the recharge of three media site (silt, fine sand, coarse sand) variation of adsorption of chloroform with time, adsorption capacity of 2.22 g/g, 1.57 g/g, 1.40 g/g; isothermal adsorption experiment results show that the ground medium isothermal adsorption of chloroform with the Freundlich model, the adsorption capacity for silty sand sand.3. biodegradation experiment results show that the recharge site three aquifer (silt, fine sand, coarse sand) in the degradation process of Monod equation can be used to describe the chloroform in chloroform. Three kinds of aquifer medium attenuation rate size order: coarse silty fine sand, medium with the increase of particle size, organic matter content and microorganism Reduce the number of the biodegradation rate of chloroform decreased gradually. In addition, the biodegradation rate of three kinds of medium of chloroform were increased with the increasing initial concentration of.4. binding site hydrogeological conditions establish the indoor dynamic simulation experiment of recirculation migration process three methyl chloride were studied: (1) water medium to fine sand effects of trichloromethane migration, sand as aquifer medium soil column simulation experiments of aqueous media types on the effects of trichloromethane migration, the experimental results show that the migration ability of chloroform in the sand than in fine sand, fine sand is mainly due to the high surface area provides more adsorption; in addition, in the same Darcy flow conditions, pore velocity decreases with the increase of porosity, the shear stress of chloroform and the medium decreased, adsorption enhanced migration ability reduction Weak. (2) water chemical conditions on the effect of chloroform migration of recirculation water in the initial concentration of disinfectant migration velocity of chloroform, with the increase of the initial concentration, the relative concentration of the peak in the effluent of chloroform increased. Reducing the groundwater in P H, H+ could compete with chloroform, with increase of P H concentration, H+ the adsorption effect of medium on the lower chloroform increased, is not conducive to the migration of chloroform; with the increase of ionic strength, metal cations and more negative charge, electrostatic force weakened, inhibited migration of three methyl chloride; in addition, the two divalent cations (Ca~ (2+)) of chloroform effects than monovalent cations (Na+). Ca~ (2+) form a key bridge and aquifer medium, the adsorption medium level increase, promote the adsorption of aquifer media chloroform. (3) the hydrodynamic condition of chloroform migration. The experimental results show that the ring migration ability of chloroform increases with the increase of flow rate, reduce the retention chloroform in aqueous media, and increase the release amount. On the one hand, with the increase of flow rate, the contact time of chloroform and porous media decreased, reduce the collision of three methyl chloride and medium, the adsorption capacity is reduced; on the other on the one hand, the change of flow rate affect the shear torque between chloroform and porous media, with the increase of flow rate, shear stress of.5. increased according to the site hydrogeological conditions and laboratory experiment results of a numerical model and analytical model of migration in groundwater recharge chloroform site transformation, to carry out prediction of recharge recharge well away from the recent monitoring wells the chloroform, the prediction results show that when the recharge of effective chlorine concentration 1mg/L P, high H, low ionic strength, high velocity condition may exceed < chloroform The hygienic standard for drinking water > (60 mu g/L) was determined by analytical model. The initial concentration of trichloromethane was determined when the concentration of monitoring well did not exceed 60 g/L. According to the law of trichloromethane generation, the effective chlorine concentration limit of reflow water was predicted.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X523

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