【作者】 肖海文；

【导师】 邓荣森；

【作者基本信息】 重庆大学 ， 环境工程， 2010， 博士

【摘要】 进行城市降雨径流的处理对降低我国城市非点源污染、促进城市雨水的资源化利用和缓解城市水危机均具有重要的现实意义。人工湿地处理技术适合城市径流特征,在城市非点源污染控制以及城市雨水的资源化利用中具有极大的潜力。目前,人工湿地应用于城市径流处理领域的研究较少,尤其是结合城市径流水文学特征和径流处理人工湿地运行特点及水力学特征的研究更是十分鲜见,使人工湿地在城市非点源污染控制和雨水资源化利用中的实际应用缺乏相应的理论基础和设计、运行参数。论文对重庆市不同下垫面径流的水文学特征进行了监测和考察,分析了城市径流的水质、水量特征;对棕榈湖人工湿地示范工程进行长期跟踪调研,分析了典型城市径流处理人工湿地的运行特征和存在的问题;通过模拟城市径流处理人工湿地的中试试验,较全面地考察了人工湿地在恒定负荷、间歇运行下的净化效果、污染物去除机理和运行影响参数;模拟城市径流处理冲击负荷条件,进行示踪剂试验和冲击负荷下污染物净化试验,探讨了径流处理人工湿地的水流规律和不同类型冲击负荷下人工湿地的污染物去除效果和特点,建立了非稳态条件下人工湿地水力停留时间分布归一化模型和基于停留时间分布的径流处理人工湿地污染物去除模型。城市径流水文学特征研究表明,下垫面性质是城市径流水质的重要的影响因素,有机物和悬浮固体是城市径流污染控制和城市雨水资源化利用应重点考虑的污染物去除对象。在所考察的各下垫面中,CODCr、氨氮、SS、TP、浊度及铅的多场降雨平均浓度EMC A值依次为:屋面径流<住宅区径流<校园径流<高速公路径流,其中,SS的EMC A值分别为9.74、163.97、285.06和645.61mg.L^-1,SS年污染负荷率分别为118.8、1058.7、2658.5和7410.6 kg.ha^-1yr^-1; CODCr的EMC A值分别为28.86、110.59、179.44和394.68 mg.L^-1,CODCr年污染负荷率分别为352.0、714.1、1673.5、4530.3 kg.ha^-1yr^-1。城市径流污染过程具有强烈的随机性,但初始冲刷特征明显,初始冲刷效应强弱与降雨量、降雨类型及污染物类型有关。初期雨量是建立在初始冲刷效应理论基础上、以污染总量控制为目标的降雨径流污染特征参数。论文提出了基于“近似最大雨量Hmax”的初期雨量定义H0/Y%/Hmax,即对于≤Hmaxmm的降雨事件,初期H0mm降雨所产生的径流能携带整场降雨Y%以上的污染物。该定义在传统初期雨量定义的基础上考虑了不同降雨事件总降雨量的影响,使得定义的初期雨量H0值更为准确。恒定负荷、间歇运行试验表明,在水深0.4m、0.1114m³.m^-2.d^-1（HRT为36h）的恒定进水负荷下随机间歇运行,人工湿地对模拟城市径流中的CODCr、SS、TP以及重金属Pb的去除效果良好,各污染物年去除负荷和去除率分别达到2.128kg.m^-2.yr^-1和79.6%、3.581kg.m^-2.yr^-1和94.3%、13.826g.m^-2.yr^-1和59.3%以及2.101g. m^-2.yr^-1和76.8%。温度和季节对COD_Cr、SS、氨氮和Pb的去除效果影响不明显,对TP去除有明显的影响。水力停留时间HRT、水深和运行前间隔天数对污染物总体去除率影响的重要程度依次为:HRT>水深>运行前间隔天数,间歇运行的最优工况为HRT36h,水深400mm。运行试验1年内,人工湿地基质内总固体累积物量增加2.06倍,以无机成分为主,平均增长量达10.02mgTSS.g^-1填料。硝化是人工湿地除氮的限制步骤,受有机物水解氨化和异养微生物活动对DO竞争的影响,氨氮年去除率和去除负荷仅38.4%和21.632g. m^-2. yr ^-1。植物对磷和铅的年吸收量分别为1.816g.m^-2.yr^-1和16.579 mg.m^-2。yr^-1,占年总磷和总铅去除贡献的13.2%和0.79%;沉积于填料固体累积物内的磷和铅分别为5.372 g.m^-2.yr^-1和1.586g.m^-2.yr^-1,分别占年总磷和总铅去除贡献的38.9%和75.02%。在间歇运行停止进水期间,人工湿地水相中COD_Cr浓度随停进水天数的增加而持续下降,但有机物芳构化程度UV254/COD_Cr增加;停止进水期间,系统内DO浓度上升,氨氮浓度大幅度的降低,停止进水对增大系统中硝化菌的竞争力和促进硝化反应是有利的;人工湿地系统内pH值随停进水天数的延长而降低,导致磷的释放,对后续进水磷的吸附沉淀却造成了不利影响。不同水力状态（恒定负荷或冲击负荷）下,人工湿地的水力停留时间分布差异悬殊,采用基于动态流量Q （ s ）的时间变量φ(φ= V _sys/1∫^t_λQ（t）dt )对RTD曲线时间轴进行归一化处理,可消除流量变化对停留时间分布的影响,将系统的混合、扩散等流态特征独立出来。归一化处理后的无量纲RTD曲线对人工湿地所处的水力负荷状态、示踪剂投加量等因素并不敏感,表现出稳定的停留时间分布特征,较原始的RTD曲线更能代表变负荷条件下人工湿地的特征水流规律。建立了CSTRs+PFD并联模型对归一化后的人工湿地停留时间分布进行模拟。模型含4个参数,可对RTD的峰值时间、峰值高度、倾斜度以及平均停留时间和停留时间分布方差等进行调节。将污染物去除一级反应动力学与污染物在人工湿地内的停留时间分布相结合,建立基于停留时间分布的径流处理人工湿地污染物去除模型,对单场降雨非稳态条件下的出水污染物浓度进行预测。模型参数包括归一化RTD函数C ’（φ）和反应容积速率常数kV。通过模拟冲击负荷试验,对COD_Cr去除模型进行参数率定,得到试验人工湿地kV为1.580 d^-1,该模型精确地描述了水力学流态对污染物去除的影响,能良好地模拟人工湿地在不同降雨条件下的出水浓度变化过程,为单场降雨污染物去除效果预测提供了有效途径。按与初始冲刷发生时间的先后分,冲击负荷类型对单场降雨中污染物出水浓度有重要影响,污染物去除效率高低依次为:无冲击>后期单峰冲击>初期单峰冲击>有初期冲击的多次冲击。但值得注意的是,人工湿地单位面积去除负荷大小却依次为:有初期冲击的多次冲击>初期单峰冲击>后期单峰冲击>无冲击,表明人工湿地对冲击负荷具有一定适应性。棕榈湖人工湿地示范工程跟踪调研表明,通过由于前置调蓄池的调节作用,人工湿地能在较均匀的间歇进水方式下运行,对提高人工湿地的处理效率效果明显。2007年,在总降雨量为1423.2mm,总降雨天数为143d的气象条件下,棕榈湖一期人工湿地停水闲置天数为135d,进水运行天数为230天,其中恒定进水负荷运行天数204d,出现水量冲击负荷的进水运行天数26d。单场降雨冲击负荷中可能发生污染物出水EMC达标而去除负荷为负值的情况,表明已出现湿地内部滞留污染物的再悬浮、再溶解和输出现象,因此,单场降雨冲击负荷下污染物的去除效果需从浓度控制和总量控制两方面考虑。旱季的主要运行问题为连续停止进水天数过长,人工湿地内持水量不足,导致湿地生态结构受到不利影响,如湿地优势植物种群的衰退;雨季的主要问题为暴雨冲击负荷下湿地内部滞留污染物的再溶解、再悬浮和输出问题。管理上可通过减少或增加湿地进水流量（调蓄池出水流量）的方法来调节旱季或雨季的缺水或水量盈余。另外,雨季可根据径流水质特点,采用溢流后期雨水的方法来避免长时间冲击负荷导致的湿地内部滞留污染物的输出。更多还原

【Abstract】 Urban runoff treatment is of great importance for non-point pollution prevention, conservation of urban water resource, enhancement of stormwater utilzation and alleviation of municipal water crisis. Constructed wetland is a treatment technology fit for the characteristic of urban runoff, and its application in urban non-point source pollution control and stormwater utilization is urgently expected. However, present researches on constructed wetland for urban runoff treatment is scarce, expecially the research based on the characteristics of running, hydrology and hydraulics of this treament system. As there is lack of basical theory and patameter for design and runing, the development and application of urban runoff treatment constructed wetland are restricted. Precipitation hydrology for different urban cover in Chongqing has been studied and the Characteristics of water qualtity and quality of urban runoff are monitored and analyzed in this study. Demonstration project of palmspring constructed wetland for treatment of urban runoff is under long-period investigetion and its performance trait and problems are discussed. A pilot constructed wetland treating modeled urban runoff is built for experiment study, and performance, mechanism and effecting factors of pollutant removal under intermittent and constant inflow condition is investigated. Under the condition of modeled storm shock loads, tracer study and contaminants removal performance study have been carried out to investigate the hydrodynamics and pollution removal potentials of urban runoff treatment constructed wetlands. Nomalized RTD model and pollutant removal model based on residence time distribution for constructed wetland under non-steady-flow conditions.Research on hydrology of urban storm runoff indicate that characteristic of catchment cover is one of the most important factors which affect the qualtily of urban runoff, and control of organic matter and suspended solid should be given priority in urban runoff pollution prevention and utilization. Rank of average mean event concentration（EMC_A） of COD_Cr, NH₄⁺-N, SS, TP, turbidity and Pb in different catchment are: roof runoff<residential area runoff<campus runoff<highway runoff. In these four cachment, EMCA of SS are 9.74, 163.97, 285.06 and 645.61mg. L^-1 respectively, and annual load of SS are 118.8, 1058.7 , 2658.5and 7410.6 Kg.ha^-1. yr-^-1 respectively. And EMC_A of COD_Cr are 28.86, 110.59, 179.44 and 394.68mg. L^-1 respectively, and annual load of COD_Cr are 352.0, 714.1, 1673.5 and 4530.3Kg.ha^-1.yr^-1 respectively. Though stochastic, pollution process of urban storm runoff showes very obuvious first flush effect, which is correlated with, rainfall, precipitation type and pollutant type. First flush rainfall is a parameter characteristic of storm runoff pollution, which based on first flush theory and focused on totall pollution control. A definition of first flush rainfall based on approximate maximal precipitation event is elicited as H₀/Y%/H_max, that is for precipitation event with rainfall less than H_max （mm）, the first rainfall of H0 （mm） would carriy pollutants more than Y%of the total pollutants in the whole storm event. This definition of first flush rainfall, which has taken total rainfall into consideration, is more definite campared with conventional denfinitionsExperimental study in intermittent and constant inflow condition indicate that with constant inflow load of 0.1114m3.m^-2.d^-1（HRT 36h）and water depth of 0.4m, the pilot constructed wetland showed a good pollutants removal performance for COD_Cr、SS、Tp and Pb. Annual removal loads and rates of these pollutants are 2.128kg.m^-2.yr^-1and 79.6%, 3.581kg.m^-2.yr^-1and 94.3%, 13.826g.m^-2.yr^-1and 59.3% and 2.101g. m^-2.yr^-1and 76.8% respectively. Impact of temperature and season on removal performance of COD_Cr, SS, NH₄⁺-N and Pb is not obvious except for TP. Influence rank of running parameters investigated is: HRT>water depth>resting period, and the most optimal running condition is under HRT of 36h and water depth of 0.4m. Total solid accumulation in substrates of constructed wetland after one year increase about 2.06 times and average 10.02mgTSS.g^-1substrate. Nitrification is the most critial process in nitrogen removal, which is affected by ammonification of organic compounds and compitition of DO between nitifiying bacteria and heterotrophic bacteria. Removal rate and load of ammonia are 38.4% and 21.632g. m^-2. yr ^-1. Removal of TP and Pb by plants assimilation are 1.816g.m^-2.yr^-1and 16.579 mg.m^-2。yr^-1, which contribute to 13.2% and 0.79% of the total removal respectivly. TP and Pb sink into solid accumulation in substrates of constructed wetland are 5.372 and 1.586g.m^-2.yr^-1, which contribute to 38.9% and 75.02%of the total removal respectivly. In resting period of intermittent running condition, concentration of COD_Cr in decreased with increasing resting days, the value of UV₂₅₄/COD_Cr , however, increased. DO concentration increased during resting period, and the concentration of ammonia decresed rapidly, which indicate that with no organic pollutant inflow and natural restoration of DO in resting period, competition potential of nitifiying bacteria and nitrification are enhanced. pH value decrease with increasing of resting days, and phosphors release is observed in constructed wetland and have adverse effect on phosphors removal in subsequent influent.Residence time distribution of constructed wetland is unstable in different hydrologic conditions such as constant flow and pulsed flow. Time variableφ( (φ= V _sys/1∫^t_λQ（t）dt )based on flow rate is used to normalize RTD, and the normalized precedure remove the effects of unstable flow rate, isolating the dipersive and mixing characteristics of the system. Tacer experiment indicated that normalized RTD is relatively stable and not sensitive to effects of flow rate and tracer injection amount. The normalized RTD is modeled with a series of continuous stirred tank in parallel with a plug flow tank with dispersion（CSTRs+PFD）. There are four paramters in this model, which can regulate peak time, peak height, lean dgreen, mean residence time and distribution variance of RTD.更多还原