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复合垂直流构建湿地的水力学特性的研究
任明迅
Subtype硕士
Thesis Advisor吴振斌
2001
Degree Grantor中国科学院水生生物研究所
Place of Conferral中国科学院水生生物研究所
Keyword构建湿地 水力学特性 污水净化效果
Abstract本文对复合垂直流构建湿地的水力学特性进行了较系统的研究和分析,对构建湿地中水流特征:出水速率与出水量、停留时间、水力负荷等作了探索,丰富了对构建湿地污水净化机理的认识,为构建湿地的设计、建造和运行提供了水力学方面的科学依据。复合垂直流构建湿地(Integrated verticalflow constructed wetlands,IVCWs)具有较表面流和水平流型构建湿地更好的污水净化效果。并在实践中逐渐得到重视,已开始在一些国家和地区(包括我国)开展了大规模的应用。但由于湿地的“黑箱”特性和污水在湿地系统内部存在着垂直和水平两个方向的流动,其水力学特性极其复杂,难以进行直接观察和深入了解。这成为限制污水净化效果显著提高的主要原因。目前只有少数工作对湿地运行中和建造设计时的水力学问题有所注意[6~11],且仍未得到规律性结论。对垂直流构建湿地的水力学特性的研究更是缺乏。本研究通过示踪剂实验等方法对水力学特性进行了深入研究。研究的主要结果如下:植物根系是影响水力学特点的主要因素。其对水力学特点造成的物理效应一是减小了湿地容水体积(孔隙体积),提高了出水量、出水速率;二是增加了表层砂土的水流通道并沟通基质上下层,使污水流动迅速,出水畅快,缩短了停留时间。虽然根系所造成的这种物理效应不利于污水在系统内的长期停留和微生物的缓慢降解作用,但根系还具有吸收、转化污染物质的显著功能,再加上根系周围的富氧环境对好氧微生物活动的促进作用,这种生物学效应又使其净化效果得到了很大程度上的弥补。因此,从这两个效应来考虑,具有须根系的湿地植物比具有根状茎、匍匐茎等的植物有着更好的污水净化效果。在一定条件下,出水速率与出水量较大的系统对BODs、TSS、Tp具有较好的净化效果。通过示踪剂实验对多个构建湿地进行了停留时间的测定。与停留时间理论值的对比发现,对于有植物系统,实测停留时间较长的系统有较好的净化效果。无植物系统由于没有植物根系的导流,停留时间较长。在相同的停留时间条件下,无植物系统比有植物系统的污水净化效果要差,有植物系统具有较好的净化效果。在本实验中,停留时间小有利于KN的去除。由于构建湿地中植物根系和微生物的吸收与分解作用以及系统基质的吸附作用,示踪剂在系统中的实际停留时间(即示踪剂的洗脱时间)比理论值要长得多,尤其是在小试系统中。可见构建湿地对NaCl等离子型污染物质具有较强的吸收功能。同时可以发现,在这一方面湿地基质显示出比植物根系更主要的作用。中试实验结果表明,湿地面积的加大可以提取水中NH_4-N、KN、TP净化效果,但对BOD_5、TSS的去除效果不太理想。在中试2次不同水力负荷的实验中,水力负荷增大引起停留时间、出水速率和出水量的下降,不利于污水的净化处理。但另一方面,进水负荷太小又不能充分发挥湿地的净化潜力。因此湿地系统都存在一个最适水力负荷问题。由于湿地最适水力负荷对提高湿地系统净化效果,准确开展实际应用有着重大意义,有必要在今后的工作中对较佳进水负荷进行研究确定。水力学特性在影响污水流动、迁移,直接影响污水净化效果的同时,对湿地植物、微生物的生长也具有十分重大的影响。特别是水面线和水位、停留时间等特性更容易通过影响生物的生长而间接影响到了污水净化效果。水力学特性的研究结果可以为构建湿地的设计、建设和调控提供更为全面、扎实的理论基础,指导构建湿地的场地选择、工艺流程设计、湿地池的维修改进等等,为实现较好的污水净化效果创造理想的水力学特性。
Other AbstractA series of experiments were carried out to investigate the hydraulic characteristics of integrated verticalflow constructed wetlands (IVCWs) and its effects on their purifying efficiencies. The results of the experiments in Small Scale Plots (SSPs) and Medium Scale Plot (MSP) of the constructed wetlands showed the plant root and rhizome are the main factors affecting the hydraulics and the purifying efficiency. The hydraulic characteristics of a constructed wetland include influent load, effluent quantity and velocity, retention time, porosity volume of the wetland, etc. They are related to almost every flow characteristics and patterns of the in_fluent. Purifying efficiency increased with flow rate and effluent quantity of the plots. For plots with plants in both chambers, these two chambers were connected in the bottom through which the water exchanged. The plots with a longer retention time showed a better purifying efficiency than the plots with a shorter one. Unplanted plot showed a relatively longer retention time and a lower purifying efficiency. The measured retention times were much longer than the theoretic values, especially in SSPs, which may mainly be due to the biological absorption and physical adsorption of the tracer by plant roots, microorganism and substrates. The plots with a slower washout velocity and rate of the tracer showed a higher purifying efficiency. As the SSPs and MSP exhibited a similar pattern, the washout rate was believed to be mainly affected by the substrate while the plant root and microorganism had a relatively minor influence on it. The influent load affected the other hydraulic characteristics and showed rather a complicated variation. Based on the result of experiments in MSP, the higher intluent load had a slower effluent velocity and smaller effluent quantity, as well as a lower purifying efficiency. However, ifthe influent load is too small, the purifying potential would not be fully developed. Therefore, there must have an appropriate influent load for a certain wetland. The hydraulic characteristics are thought to have a great affects on the purifying efficiency by influencing the plant growth and activity of microorganism in wetland.
Pages42
Language中文
Document Type学位论文
Identifierhttp://ir.ihb.ac.cn/handle/342005/12618
Collection学位论文
Recommended Citation
GB/T 7714
任明迅. 复合垂直流构建湿地的水力学特性的研究[D]. 中国科学院水生生物研究所. 中国科学院水生生物研究所,2001.
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