【作者】 杨洋；

【导师】 郭宗楼；

【作者基本信息】 浙江大学 ， 农业水土工程， 2018， 硕士

【摘要】 近些年乡镇工业发展迅速、城乡人口不断聚集,使得水环境和水生生态系统遭到了一定程度的破坏,污水产生量也随之不断增加。水污染严重是我国目前实现可持续发展利用水资源的难题之一。因此,为保护水资源,促进经济可持续发展,如何有效治理废水污染是亟待解决的问题关键所在。目前,我国用于解决水体污染的各种治理方法层出不穷。例如被广泛采用的人工湿地系统处理工艺,具有十分广阔的应用前景,虽然该技术目前已经获得了大量的试验数据及经验参数,但是在实际工程项目中,该技术还存在很多问题,如占地面积大、易受水力负荷及布水方式影响、易产生堵塞饱和等。因而,本研究针对目前人工湿地存在的主要问题,结合实际情况,将曝气工程与人工湿地进行组合,适当改进,构建了人工曝气生态净化系统,在国内外研究基础上,针对嘉兴石臼漾水厂水源生态湿地示范工程中的义庄河河道人工生态微孔曝气工程的特性,首次尝试利用基于计算流体动力学(CFD)的数值模拟方法进行模拟与分析。通过对液固两相混合物湍流模型与活性污泥2号模型的分析与耦合,建立了河道液-固两相湍流反应动力学模型,对各污染物进行建模,实现了对河道内水质浓度场分布的模拟与研究,并结合实际测量数据验证了模型的准确性;同时还针对该人工生态曝气工程探讨了曝气器外围速度场的演变过程及其基于多相流的曝气过程,结合速度矢量图,气相体积分数分布云图等综合考虑溶解氧浓度对系统的影响,为进一步确定该系统优化方向及最佳工艺参数提供理论依据和技术支持,取得了如下主要成果:(1)针对目前人工湿地存在的主要问题,结合实际情况,以嘉兴市石臼漾水源生态湿地工艺项目为依托,将义庄河道曝气工程与人工湿地进行组合,适当改进,构建了人工曝气生态净化系统,并对其构造、净化机理及水力学特性进行了分析。(2)对嘉兴石臼漾水厂水源生态湿地示范工程中义庄人工曝气生态净化系统的安装背景资料作了简要概述,将该工程曝气模型进行一定程度的简化。(3)通过对液固两相混合物湍流模型与ASM2模型的分析与耦合,建立河道液-固两相湍流反应动力学模型,找出Fluent中各源项的共同点,即为各组分的实际反应速率与Fluent中的各源项可以相互转换,对各污染物进行建模,实现了对河道内水质浓度场分布的模拟与研究,同时结合实际测量数据验证模型。虽然模拟与实测结果在相比之下存在一定的偏差,但该模型的模拟结果基本能反映出水质浓度随时空变化的总体特征,也可将模型进行进一步优化研究。(4)通过对稳态进水条件下水质的模拟,可知河道内有良好的好氧和缺氧交替环境,硝化和反硝化进行顺利,其中氨氮、总磷水质提高了一个类别,总氮的去除效果明显,但由于其进水绝对数值太高,未能达到提高一个类别的目标,同时也说明了工程河道现有运行状态良好,具有一定的抗冲击负荷能力,本模型模拟出的各指标模拟值均高于实测值,相对误差除氨氮以外,其余指标的相对均控制在10%以内;通过对动态进水条件下水质的模拟,得出了同一横断面上各点浓度平均值随时间变化的分布结果和不同位置处水质浓度的模拟值与实测值的对照图,可以看出模拟结果与实际测量值基本吻合,各污染物水质浓度在时间上和空间上的分布及变化趋势基本一致,但仍存在一定的偏差,在靠近曝气管道的区域,COD、总磷及氨氮的浓度都有较为明显的下降,然而总氮浓度的下降趋势并不明显,从污染物的垂直分布特征来看,在该曝气区域内河道污染物在深度0-50cm之间浓度普遍较高,表层以下浓度逐渐下降,50-100cm间污染物浓度下降幅度较大,随后浓度波动较小。(5)采用与耦合模型相同的模型结构简化方案,探索液气两相流模型应用于该系统的模拟结果,在GAMBIT和FLUENT的软件平台上建立了液气两相流模型,通过分析系统内部不同截面的压力场,速度场,气相体积分布的变化,反映了在该人工生态曝气工程的运行情况下对水体流场引起的变化,与第三章水质浓度净化结果对比可知,在靠近曝气管道的区域,水体的流动更为剧烈,压力变化更为明显,气相体积分数更高,污染物浓度有较为明显的下降,得出若需提高曝气充氧效果,提升系统净化效率,应当布置合理的曝气管道结构,尽可能多的增加水体的流动,这为进一步探索结构因素对该系统的内在影响与联系提供了可行的研究方法,为进一步提升该系统处理效率提供依据。更多还原

【Abstract】 In recent years,rapid development of township and village industries,urban and rural populations continue to gather,making the water environment and aquatic ecosystems have been a certain degree of damage,the amount of sewage production also continue to increase.The serious water pollution is one of the difficult problems in our country to realize the sustainable development and utilization of water resources.Therefore,in order to protect water resources and promote sustainable economic development,how to effectively control wastewater pollution has become the key problem to be solved.At present,China’s various methods for the treatment of water pollution in an endless stream.Such as widely used artificial wetland system processing technology,has a very broad application prospects,although the technology has received a large number of test data and empirical parameters,the technology still exists many problems in the actual engineering project,such as covering Large area,easily affected by the hydraulic load and water distribution methods,producing clogging and saturation,etc.Therefore,this research is aimed at the main problems existing in constructed wetlands,utilizing the combination of aeration engineering and artificial wetlands,proposing artificial aeration ecological purification system.Based on the research materials and experimental results in domestic and overseas.This research simulating the artificial ecological micropore aeration project in Yizhuang River of Jiaxing Shijiuyang ecological wetland demonstration project by numerical simulation method based on computational fluid dynamics(CFD),analyzing and coupling the turbulence model of liquid-solid two-phase mixture and activated sludge model 2,establishing a turbulence kinetic model of liquid-solid two-phase in the aeration channel.By modeling for each pollutant,achieving the simulation of water quality concentration distribution in the river,verifying the accuracy of the model based on the actual measurement data,discussing the evolution of the velocity field around the aerator and its multiphase flow Aeration process,considering the influence of dissolved oxygen concentration to the system combined with the velocity vector figure,the gas volume fraction distribution cloud figure and so on,providing the theory basis and technical support for further optimization direction and the best craft parameter to the system.The following main achievements have been obtained:(1)Aiming at the main problems existing in the constructed wetlands,utilizing the artificial ecological micropore aeration project in Yizhuang River of Jiaxing Shijiuyang ecological wetland demonstration project,proposing artificial aeration ecological purification system,analyzing its structure,purification mechanism and hydraulic characteristics.(2)The brief introduction of the installation background of the project is made,and the aeration model of this project is simplified to a certain extent.(3)By analyzing and coupling the turbulence model of liquid-solid two-phase mixture and activated sludge model 2,establishing a turbulence kinetic model of liquid-solid two-phase in the aeration channel,obtaining the common points of each source term in Fluent,modeling for each pollutant,achieving the simulation of water quality concentration distribution in the river,verifying the accuracy of the model based on the actual measurement data.Although the simulated and measured results have some deviations in comparison,the simulation results of this model can reflect the general characteristics of water quality concentration with time and space,and can be further optimized.(4)Through the simulation of water quality under steady-state influent condition,it can be seen that there is a good aerobic and anoxic alternate environment in the aeration channel.The nitrification and denitrification proceeded smoothly,the water quality of ammonia nitrogen and total phosphorus increased by one class.The total nitrogen removal effect is obvious,but its water intake absolute value is too high to achieve the goal of raising a category,it’s also shows the aeration project is running well in the river,with a certain impact load capacity.The simulated values of each model are higher than the measured values,and the relative error is less than 10%except ammonia nitrogen;Through the simulation of water quality under dynamic influent condition,the results of the distribution of the mean value of the concentration at different points on the same cross section and the comparison of the simulated and measured values of the water quality concentration at different positions are obtained.It can be seen that the simulation results were consistent with the actual measured values in time and space although there were still some deviations.The concentration of COD,TP and NH3-N in the areas close to the aeration pipes have relatively apparent decline except TN.According to the vertical distribution characteristics of pollutants,The concentration of pollutants in the aeration area is generally higher in the depth of 0-50cm,it’s gradually decreased below the surface layer and decreased significantly in the depth of 50-100cm,followed by small fluctuations in concentration.(5)Using the same simplified model as the coupled model,exploring the results of the liquid-gas two-phase flow model which applied to the simulation of the system.The liquid-gas two-phase flow model was established on GAMBIT and FLUENT software platform.Through the analysis of the change of the pressure field,velocity field and gas volume distribution in different sections,reflecting the changes in the water flow field caused by the artificial ecological aeration project(for example,the turbulence of the water around the pipe aerator is more intense,Gas volume fraction gradually decreases with increasing depth in the vertical direction,etc.),providing a feasible method to further explore the internal influence and connection of the structural factors on the system,a basis for further improve the efficiency of the system.更多还原