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多层改性滤料对城市雨水的净化与节流作用研究

发布时间:2018-08-14 08:45
【摘要】:目前我国大部分城市地区存在绿化面积小、建筑物及道路占地面积比例巨大的现象。一方面,城市化的加快使可渗水面积减少,当短时间内降雨量较大时极易导致城市内涝灾害发生;另一方面大量受污染的雨水径流进入城市周围水体后使水源水质受到冲击,造成水资源的污染。我国较多城市因雨水问题影响城市发展,且目前我国处于水资源匮乏现状,对径流雨水进行渗、蓄、治、排的处理,具有重大意义。采用将滤料过滤与天然基质土壤渗滤结合的方式处理城市雨水可有效截留、吸附雨水径流中的污染物,同时滤料层会延缓地表径流的产生时间、减小径流水量,从而起到“渗、蓄、治、排”的作用,减轻雨水对水源的污染及城市洪涝灾害情况。因此,研究以不同组合滤料与天然基质土壤渗滤结合的系统处理城市雨水具有重要的经济与环保意义。实验用水为模拟实际城市雨水径流的人工配水,根据对三次实际径流雨水的收集、测定、分析,最终确定人工配水中COD、氨氮、总氮、总磷、浊度等指标的取值范围。通过三场降雨的水质分析及参考相关文献表明:实际雨水径流中有机物、氨氮、总氮、浊度等含量较高,在降雨初期的20~30 min内路面与屋面径流中污染物浓度普遍偏高,随着降雨历时的增加在降雨中、后期污染物浓度快速降低,说明产生了冲刷效应。降雨前干旱期越长,初期径流中污染物浓度越大,且随降雨历时的变化幅度较大。为考察不同种类滤料对径流中COD及氨氮的去除能力,选取0.5~1 mm石英砂、1~2mm石英砂、0.5~1 mm沸石、1~2 mm沸石、1~2 mm陶粒、2~4 mm陶粒、0.5~1 mm碎砖块为备选滤料,进行静态吸附实验,选出三种最优滤料进行后续改性及动态实验。静态吸附结果表明:1~2 mm陶粒对COD的吸附效果最好,吸附量为0.369 mg·g-1,0.5~1mm沸石对氨氮的吸附效果最好,吸附量为0.066 mg·g-1。从实用性、经济性、来源情况及自身性能等方面综合考虑,选取沸石、陶粒及石英砂作为本研究渗滤系统的滤料,进行后续的改性及动态试验。将静态吸附实验中选出的三种滤料分别进行氧化铁涂层及氯化钠改性并用于动态实验。通过电镜扫描图片发现,改性后石英砂从原来的光滑表面变成了附着氧化铁晶体颗粒的粗糙表面。陶粒表面孔隙变大,且同样有晶体堆积。沸石外表更加蓬松,孔隙略有增大。通过X射线衍射发现改性后石英砂增加了赤铁矿(Fe2O3)及磁铁矿(Fe3O4)成分,陶粒增加了磁赤铁矿(γ-Fe2O3)和针铁矿(α-FeO(OH))两种成分。沸石增加了苏打石(NaHCO3)、泡碱(Na2CO3·10H2O)及冰盐(NaCl·2H2O)三种成分。静态实验结果表明改性陶粒对COD吸附效果最好,平衡吸附量为0.37 mg·g-1,比未改性前提高了7.15%,改性沸石对氨氮吸附效果最好,吸附量为0.074 mg·g-1,比未改性前提高了12.12%。将改性后的滤料与基质土壤结合,进行单一种类改性滤料与基质土壤结合的人工降雨动态实验。研究表明单一滤料与基质土壤结合时,滤料组的最终出水中污染物浓度均低于纯土壤对照组。但对污染物的去除存在选择性,改性陶粒对COD的去除效果最好,平均出水浓度为15.12 mg·L-1。改性沸石对氨氮的去除效果最好,平均出水浓度为0.48mg·L-1。组合滤料与基质土壤结合时,进行了四种不同种类、粒径及滤层厚度组合方案的对比,动态实验结果表明:方案Ⅱ-2(15 cm改性陶粒+10 cm改性石英砂+5 cm改性沸石)的出水COD平均浓度为12.24 mg·L-1,氨氮平均浓度为0.71 mg·L-1,且在大雨及暴雨条件下分别能将产流时间推迟325、190 min,将径流量削减54.22 mm、60.95 mm。从对污染物的去除效果以及对水量的节流效果角度综合分析,认为方案Ⅱ-2为最佳组合方案。
[Abstract]:On the one hand, the acceleration of urbanization reduces the seepage area, and when the rainfall is large in a short time, it is very easy to cause urban waterlogging disaster; on the other hand, a large number of polluted rainwater runoff enters the water body around the city. Water quality is impacted and water resources are polluted. Many cities in China are in short supply of water resources because of rainwater problems. It is of great significance to treat runoff rainwater by infiltration, storage, treatment and drainage. It can effectively intercept and absorb pollutants in rainwater runoff, at the same time, the filter layer will delay the generation time of surface runoff, reduce the amount of runoff, thus play a "seepage, storage, treatment, drainage" role, reduce the pollution of rainwater to water sources and urban flood disaster. Therefore, the study of different combination of leachate and natural matrix soil infiltration system. The experimental water is used to simulate the actual urban rainwater runoff. According to the collection, determination and analysis of the three actual runoff rainwater, the range of COD, ammonia nitrogen, total nitrogen, total phosphorus and turbidity in the artificial water distribution is finally determined. Literature shows that organic matter, ammonia nitrogen, total nitrogen, turbidity and so on are higher in the actual rainwater runoff, and the pollutant concentration in the road surface and roof runoff is generally higher in the early 20-30 minutes of rainfall. With the increase of rainfall duration, the pollutant concentration decreases rapidly in the middle and later periods of rainfall, indicating that the scouring effect occurs. In order to investigate the removal capacity of COD and ammonia nitrogen from runoff by different kinds of filter media, 0.5-1 mm quartz sand, 1-2 mm quartz sand, 0.5-1 mm zeolite, 1-2 mm zeolite, 1-2 mm ceramsite, 2-4 mm ceramsite and 0.5-1 mm broken brick were selected as the alternative filters for static adsorption experiments. The results of static adsorption showed that 1~2 mm ceramsite had the best adsorption effect on COD, zeolite with adsorption capacity of 0.369 mg g 1,0.5~1 mm had the best adsorption effect on ammonia nitrogen and adsorption capacity of 0.066 mg g 1. Particles and quartz sand are used as filters of the leaching system in this study for subsequent modification and dynamic tests. Three filters selected from static adsorption experiments are coated with ferric oxide and modified with sodium chloride respectively and used for dynamic experiments. The surface of the modified quartz sand was found to be composed of hematite (Fe2O3) and magnetite (Fe3O4), and ceramsite (gamma-Fe2O3) and goethite (alpha-FeO (OH). Zeolite was increased. The static experiment results show that the modified ceramsite has the best adsorption effect on COD, and the equilibrium adsorption capacity is 0.37 mg g 1, which is 7.15% higher than that of the unmodified zeolite. The adsorption capacity of the modified zeolite is 0.074 mg g 1, which is 12.12% higher than that of the unmodified zeolite. The artificial rainfall dynamic experiment was carried out by combining the modified filter with the matrix soil. The results showed that the pollutant concentration in the final effluent of the filter group was lower than that of the pure soil control group when the single filter was combined with the matrix soil. The average effluent concentration was 15.12 mg L-1. Modified zeolite had the best removal effect on ammonia nitrogen, and the average effluent concentration was 0.48 mg L-1. When combined with matrix soil, four different kinds of filter materials, particle size and filter thickness were compared. The dynamic experimental results showed that scheme II-2 (15 cm modified ceramsite + 10 cm) was the best. The average concentration of COD in effluent of CM modified quartz sand + 5 cm modified zeolite is 12.24 mg It is considered that scheme II -2 is the best combination scheme.
【学位授予单位】:兰州交通大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:X52;TU992

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