基于污染物运移的填埋场屏障系统服役性能评价方法研究

发布时间：2018-09-19 06:38

【摘要】：垃圾填埋场产生的有毒性渗滤液和填埋气对填埋场底部、填埋场周边土壤和大气环境造成了很大的威胁。国内外研究成果表明即使填埋场建造了标准的防渗系统,仍有相当多的场地对地下水、周围土体和大气环境造成了污染。本文在国家自然科学基金面上项目“垃圾填埋场覆盖屏障气体运移特性与长期服役性能评价方法”和国家自然科学基金青年基金项目“垃圾填埋场复合衬垫在高应力和高水头作用下的防污性能研究”、973计划“填埋场服役性能模拟、灾害评价及可持续防控”、国家自然科学基金重大国际合作项目“城市垃圾填埋场水气产生、运移及系统化工程控制”和浙江省公益性技术应用研究计划项目“垃圾填埋场复合衬垫长期性能的离心模型试验与污染防控技术”的基础上研究了填埋场屏障系统服役性能的评价方法。本文首先对国内外填埋场渗滤液和填埋气污染物迁移机理及影响因素进行了汇总和分析。在此基础上通过提出的解析方法和数值方法分析了填埋场饱和与非饱和衬垫系统和覆盖层系统中渗滤液及填埋气的运移问题。探讨了不同类型衬垫系统和覆盖层系统的有效性。最后在国内外对填埋场现场试验研究的成果上,针对淮南填埋场进行了现场试验研究并给出填埋场现场分析的定量方法。本文所做工作及相应的研究成果如下： (1)分别比较了国内外对填埋场底部衬垫系统及顶部覆盖层系统的组成差别及设计标准。对国内外填埋场渗滤液和填埋气的性质及国内外文献报道的渗滤液和填埋气主要污染物在填埋场土层中的环境土工参数进行了汇总和统计分析,给出了这些参数的设计取值范围; (2)由于固体垃圾中很大部分都是有机污染物,有机污染物的降解作用很重要。结合一阶降解理论,并在此基础上针对国内衬垫系统中土工聚合粘土垫(GCL)+衰减层(AL)复合衬垫系统,首次给出了考虑降解作用下污染物在GCL+AL复合衬垫系统的一维解析解。研究结果表明,如果GCL半衰期小于1年,在预测GCL+AL系统中有机污染物迁移时可以忽略GCL中有机物的降解作用； (3)结合非饱和单层土中含水量线性分布,得到了污染物在非饱和衬垫土层中的一维扩散解析解。该解析解简单方便,并能考虑含水量线性变化时污染物的扩散问题,同时指出非饱和问题对污染物浓度变化的影响； (4)分析了国内外填埋场设计中用于控制填埋气释放的覆盖层系统组成。建立了饱和覆盖层中填埋气的一维扩散模型,模型考虑了随时间变化的气体浓度边界。基于菲克定律及线性方程的叠加原理,得到了气体污染物通过饱和复合覆盖层的一维扩散解析解,在此基础上比较了国内不同类型覆盖层系统对填埋气控制性能的有效性,可以有效地应用于基于性能的填埋场复合覆盖层系统的初步设计； (5)对于国内覆盖层系统类型,饱和情况下GM+GCL、CCL、GM+CCL对气体扩散的控制性能依次减弱。对于GM/GCL,GCL含水饱和度从0.85增加到1时,覆盖层顶部通量减小了82.5%。饱和时GM/GCL系统顶部气体达到稳态的时间是非饱和情况下的约100倍。对于GM/CCL, CCL含水饱和度从0.1增加到0.85时,覆盖层顶部通量减小了近1个数量级； (6)针对垃圾填埋场内部生物降解产生的气体(以甲烷为主)和氧气等在非饱和覆盖层中的运移问题,建立了气体在成层非饱和覆盖层中的一维扩散模型。模型考虑了覆盖层含水量瞬态变化和气体扩散的耦合作用。对于lm厚的覆盖层,气体运移20d到100d时,祸合含水量瞬态变化时得到的气体相对浓度较含水量稳态变化时得到的浓度小近8倍。并总结了非饱和土中气体扩散系数变化的经验公式,比较得到不同气体扩散系数形式对祸合结果有较大影响; (7)根据国外对覆盖层顶部大气压强实测数据的基础上,拟合得到压强的变化规律,并提出了大气压强对填埋气运移作用明显时压强波动幅度的取值范围,对实际填埋场区域压强波动对气体控制的研究有很好的参考作用； (8)最后借助于对填埋场污染物的研究理论和分析方法研究了国内淮南某垃圾填埋场污染物的现场运移特性,给出了在成层粘土层中污染物运移及预测的分析方法。现场试验表明17年后,Cl-在填埋场底土中的运移深度已经达到了底土下部的老粘土层;COD的运移深度则在3m左右。将一维对流扩散理论与实测结果的比较可知对流弥散作用对于污染物的运移较为重要；以地表面为接触面得到拟合结果不能很好地表示实际污染物的运移,参考前人研究成果研究了有效接触面问题。最佳的拟合结果得到的有效接触面为地表面之上50cm。将一维对流-弥散解析解与实测数据的拟合比较则可得到粘土层相关运移参数的取值范围,可为污染物进一步运移提供依据。
[Abstract]:Toxic leachate and landfill gas produced by landfills pose a great threat to the bottom of landfills, the soil and atmospheric environment around landfills.
In this paper, the National Natural Science Foundation of China (NSFC) project "Evaluation Method of Gas Transport Characteristics and Long-term Service Performance of Landfill Cover Barrier" and the National Natural Science Foundation of China (NSFC) Youth Foundation of China (NSFC) project "Study on the Antifouling Performance of Composite Liner of Landfill under High Stress and High Water Head" are presented. Planning, Disaster Assessment and Sustainable Prevention and Control, Major International Cooperation Project of National Natural Science Foundation of China, Water and Gas Generation, Transportation and Systematic Engineering Control of Municipal Waste Landfills, and Research Program of Zhejiang Provincial Public Welfare Technology Application, Centrifugal Model Test of Long-term Performance and Pollution Prevention and Control Technology of Composite Liner of Waste Landfills Based on this, the evaluation method of landfill barrier system service performance is studied. In this paper, the migration mechanism and influencing factors of landfill leachate and landfill gas pollutants at home and abroad are summarized and analyzed. The migration of leachate and landfill gas in the system is discussed. The effectiveness of different types of liner systems and overlay systems is discussed. Finally, on the basis of the results of field tests at home and abroad, the field tests of Huainan landfill are carried out and the quantitative methods of field analysis are given. The results are as follows:
(1) Comparing the composition differences and design standards of landfill bottom liner system and top cover system at home and abroad, the characteristics of landfill leachate and landfill gas at home and abroad, and the environmental geotechnical parameters of major pollutants in landfill soil were summarized and statistically analyzed. The design range of these parameters is given.
(2) Because most of the solid waste is organic pollutants, the degradation of organic pollutants is very important. Based on the first-order degradation theory, the GCL+AL composite liner system considering the degradation of pollutants in the domestic liner system is proposed for the first time. The results show that if the half-life of GCL is less than one year, the degradation of organic compounds in GCL can be neglected in predicting the migration of organic pollutants in GCL + AL system.
(3) Combined with the linear distribution of water content in unsaturated monolayer soil, the analytical solution of one-dimensional diffusion of pollutants in unsaturated liner soil is obtained.
(4) The composition of landfill cover system used to control landfill gas release in landfill design at home and abroad is analyzed. A one-dimensional diffusion model of landfill gas in saturated cover is established, which takes into account the time-varying gas concentration boundary. On the basis of the analytical solution of one-dimensional diffusion of layers, the effectiveness of different types of landfill systems on the control performance of landfill gas is compared, which can be effectively applied to the preliminary design of performance-based landfill composite cover system.
(5) For the types of domestic overburden systems, the control performance of GM+GCL, CCL and GM+CCL on gas diffusion decreases in turn under saturation. For GM/GCL, when the water saturation of GCL increases from 0.85 to 1, the flux at the top of the overburden decreases by 82.5%. The time when the gas at the top of the GM/GCL system reaches steady state at saturation is about 100 times that under unsaturation. When L and CCL water saturation increased from 0.1 to 0.85, the flux at the top of the overburden decreased by almost 1 orders of magnitude.
(6) A one-dimensional gas diffusion model in layered unsaturated overburden was established for the transport of gases (mainly methane) and oxygen produced by biodegradation in landfill. The coupling effect of transient change of water content and gas diffusion in the overburden was considered. For lm-thick overburden, the gas diffusion was considered. The relative concentration of gases in the transient change of the combined water content is about 8 times less than that in the steady state change of the water content at 20 to 100 days of migration.
(7) Based on the measured data of atmospheric pressure at the top of the overburden abroad, the variation law of pressure is fitted and the range of pressure fluctuation amplitude when atmospheric pressure has obvious effect on landfill gas migration is put forward, which has a good reference for the study of pressure fluctuation in the actual landfill area on gas control.
(8) Finally, with the help of the theory and analysis method of pollutants in landfill site, the characteristics of pollutants migration in a landfill site in Huainan were studied, and the analysis method of pollutants migration and prediction in layered clay layer was given. Comparing the one-dimensional convection-diffusion theory with the measured results, it can be seen that the convection-dispersion effect is more important for the transport of pollutants; the fitting result with the surface as the contact surface can not well represent the actual transport of pollutants, and the effective contact is studied by referring to the previous research results. The best fitting results show that the effective contact surface is 50 cm above the surface. Comparing the one-dimensional analytical solution of convection-dispersion with the measured data, the range of the relevant transport parameters of clay layer can be obtained, which can provide a basis for further transport of pollutants.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：X705;TU993.3

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