垃圾填埋场污染物击穿竖向防渗帷幕时间的影响因素分析及设计厚度的简化计算公式

为了解中国第一代垃圾填埋场中防渗帷幕的服役性能及其影响因素,以苏州七子山填埋场地质条件为例,以COD作为代表性污染物,在前期现场勘查基础上建立了有限差分计算模型,对防渗帷幕被污染物击穿时间的影响因素进行了计算分析,并基于Ogata解析解给出了防渗帷幕击穿时间和设计厚度的简化计算公式。模拟和分析结果表明：场地地质条件对嵌入式防渗帷幕击穿时间影响不十分显著;帷幕上下游水头差、帷幕渗透系数、阻滞因子和厚度对嵌入式防渗帷幕的击穿时间有显著影响,击穿时间与上下游水头差、帷幕渗透系数、阻滞因子、以及帷幕厚度的平方近似呈线性关系;扩散系数对嵌入式防渗帷幕击穿时间的影响不可忽略。     

我国四类衬垫系统防污性能的比较分析

对我国填埋场采用的四类衬垫进行了防污性能的比较分析。评价参数包括渗漏率、污染物击穿时间及衬垫系统底部浓度值。除了2m压实黏土衬垫(CCL)外,其余3种均为包含土工膜(GM)的复合衬垫。分析模型采用了污染物通过有缺陷膜复合衬垫的一维运移解析解。以镉离子(Cd2+)为渗滤液中重金属离子的代表;以苯为其中挥发性有机污染物的代表。研究表明土工复合膨润土垫(GCL)复合衬垫的渗漏率最小,2m黏土最大,两者的差别可在3～5个数量级。GCL复合衬垫对重金属离子具有较好的防污性能,尤其是在高水头及复合衬垫接触较差的情形。厚度较大的2m黏土对挥发性有机污染物的防污性能较好,其击穿时间要比GCL复合衬垫大2～3个数量级。随着水头的增大,CCL复合衬垫的防污性能逐渐地优于2m黏土。在10m水头作用下,CCL复合衬垫底部的100年浓度可比2m黏土小近一个量级。单层膜衬垫的防污性能较差,不适合作为填埋场的衬垫系统。控制填埋场复合衬垫的施工质量和渗滤液水头尤为重要。     

基于污染物击穿时间的填埋场复合衬垫厚度简化设计方法

通过对中国6个典型垃圾填埋场中渗滤液各组分的实测浓度值的统计分析,并与中国生活饮用水卫生标准中的界限浓度值进行对比分析,确定了以渗滤液中不同污染物组分为指示性污染物时的典型击穿标准和极端情况的击穿标准分别为0.1和0.01。基于已有的污染物在复合衬垫GMB+CCL中的一维运移解析解,在分别考虑了以有机物污染物和无机污染物为击穿指标的情况下,利用数值拟合的方法得到了两种情况下复合衬垫中CCL厚度的简化计算公式。以杭州天子岭垃圾填埋场为例,利用简化计算方法对复合衬垫的厚度设计进行了验证;结果表明,若要保证渗滤液中的Pb击穿GMB/CCL复合衬垫的时间大于50 a,则土工膜下覆的CCL的厚度至少需要0.6 m。     

粘土环境岩土工程特性对填埋场衬垫防渗标准的影响

采用溶质运移的一维迁移模型,研究了粘土环境岩土工程特性对填埋场衬垫防渗标准的影响,对目前采用的填埋场粘土类衬垫防渗设计标准及其有效性进行了多参数组合的计算分析;此外,还比较了粘土衬垫与复合衬垫对污染物离子的防渗阻隔性能,对土工膜在衬垫中的作用进行分析;研究表明,应针对不同地区的情况(干旱少雨或多雨等)考虑衬垫的形式。与其他因素相比,粘土的渗透系数对衬垫层渗漏影响最大,以水力渗透系数作为填埋场粘土衬垫的设计标准是可行的,但离子扩散系数的影响也不可忽略;而增强粘土的活性,提高粘土吸附离子的性能,则可延长离子通过衬垫的击穿时间;与单纯的粘土衬垫相比,复合衬垫对离子具有更好的阻隔性能,故在南方多雨地区宜采用复合衬垫;而用污染物的渗漏总量作为填埋场衬垫的设计标准比击穿时间更合理。     

国外垃圾填埋场防渗构造介绍

生活垃圾填埋过程中,由于雨水等流入垃圾中形成的渗滤水中含有多种有害物质,比如铅、锌、砷和铬,以及渗滤水中总有机碳浓度很高,一般都要超过1 000mg/L,因此如果不经处理直接排入地下水或河流中,将严重污染环境。世界各国对于垃圾填埋场的防渗系统都有不同的要求,但一般都是以橡胶、树脂等高分子材料做成的土工膜为主,辅以其它防渗材料。图1是垃圾填埋场防渗系统的一个典型构造。随着科技的发展和新材料的不断出现,欧美国家采用单一防渗构造的已经很少,都把防渗层作为一个复杂系统来考虑,将土工膜与GCL土工毯、复合土等作为复合防渗层一起…     

固化污泥对渗滤液中氟阻滞作用的数值分析

固化污泥是一种新型填埋场底部防渗阻滞材料,为论证其防渗阻滞作用的有效性,需进行典型污染物的穿透试验,但由于固化污泥渗透性很低,采用常规土柱试验很难得到污染物透过其迁移时的相关参数。为解决该问题,用柔性壁渗透试验代替传统土柱试验。渗滤液中污染成分较多,取含量较高且较易穿透的污染物即氟离子作为典型污染物,首先进行穿透试验获得迁移参数,然后结合二维有限元法研究分析其在防渗阻滞层及周边岩土环境中60a内的运动迁移范围、浓度分布情况,并对比分析未设防渗阻滞层的情况。研究表明,在填埋场底部设置固化污泥防渗层对于以氟为代表的阴性污染物有较好的延迟阻滞作用。由于阳性污染物的穿透能力较阴性污染物弱,因而固化污泥防渗层对重金属等阳性污染物也应具有较强的阻滞作用,从而能进一步延迟填埋场渗滤液对周边环境的污染。     

迁移机理下污染物场地隔离屏障的设计研究

重点对迁移机理下污染物填埋场地天然粘土隔离屏障的厚度设计展开研究.运用溶质在饱和土中迁移的一维平流-弥散运移模型,根据影响污染物迁移的基本参数(弥散系数、阻滞因子等),对饱和土隔离屏障建立一套估算污染物击穿屏障的时间、对指定的击穿浓度和设计寿命确定屏障厚度的设计分析方法,绘制了一些便于工程应用的设计图表,分析了扩散系数...     

垃圾填埋场渗滤液对地下水的污染规律及防渗策略分析

简述了垃圾填埋场中渗滤液的产生及其对地下水造成的污染,分析了渗滤液对地下水污染的规律,总结出了垃圾填埋场的稳定化过程阶段不同,会导致垃圾降解速度及污染组分浓度不同。垃圾填埋时间的增长会扩大地下水污染范围,渗滤液中污染物组分浓度越高,地下水流速度越快将加剧污染问题等规律,同时给出了具体的防渗策略,包括设置垃圾填埋场顶部覆盖层、地表水及地下径流的导排、帷幕防渗措施、设置底层集排系统、设置底部衬层等。     

填埋场污染物在有限厚度土层中一维对流-扩散-吸附解析解

为避免垃圾填埋场对地下水的污染,衬垫系统的截污性能至关重要。针对卫生垃圾填埋场衬垫底部设有地下水导排层的工程要求,建立了污染物在有限厚度土层中一维对流-扩散-吸附解析模型并求解,其中模型底部采用Cauchy边界模拟渗滤液污染物透过衬垫向零浓度环境传质。算例结果表明,解析解与商用软件数值解所得浓度场分布完全吻合;参数分析表明,吸附、扩散和对流参数对击穿曲线均有较大影响,为延长击穿时间,应尽可能采用吸附性能好的土层并严格控制衬垫上的水头高度。     

对“污染物运移过程的一维数值分析”讨论的答复

(1)关于填埋场内污染物浓度随时间变化的数学表述填埋场中填埋的生活垃圾成分复杂,受社会经济发展条件、生活习惯、季节、气候条件、填埋场管理、MSW管理、埋龄、初始含水量等多种因素控制。生活垃圾填埋后将发生降解,生成渗滤液和填埋气。例如填埋场管理,有的填埋场将渗滤液回灌,目的是加快生活垃圾降解,加快其固化过程;有的填埋场采用严格的最终封顶层以确保降低降雨(雪)入渗,尽量减少渗滤液生成数量,从而使得生活垃圾的降解和固化过程加长。本文所指污染物为渗滤液中的某种污染成分。由于受上述多种因素的共同影响,准确估计渗滤液中某种污染成分随时间变化非常困难。在研究填埋场污染物运移问题时,主要研究污染物对地下水的长     

Performance issues of barrier systems for landfills: A review

The objective of the paper is to give an update in key topics related to performance issues of barrier systems for landfills. The objective of using barrier systems is to minimize the impact of contaminants on the surrounding environment. To achieve this goal puncture protection of the geomembrane must be ensured. An update is first given with respect to this matter. The question of the stability on slope of geosynthetic barrier systems is then discussed and an insight is given in modeling and laboratory measurement of parameters required to perform reliable modeling, especially as regards the case of piggy-back landfills. Geotechnical centrifuge modelling tests are very important for simulation of landfill stability induced by the failure of geosynthetic interfaces and validation of complicated numerical models, especially for the high food waste content landfills. The seismic design or assessment of landfill stability with respect to geosyntheics needs to be investigated. Finally, the question of transfers through bottom barrier systems is addressed, giving an update especially in the analytical solutions developed in the past 10 years in China in this matter. The breakthrough time based design method for landfill liner system was then summarized. The behaviour of double-liner system and its simplified performance-based design method should be further investigated in the high food waste landfills with high leachate level.     

我国卫生填埋场防渗技术的研究现状及发展探讨

防渗系统是填埋场建设的关键问题之一。从防渗方式、防渗结构、防渗材料等几方面论述了目前我国卫生填埋场防渗技术的研究现状及其应用情况,分析了我国卫生填埋场防渗系统存在的主要问题,并结合当前填埋场防渗系统的研究实际,指出我国填埋场防渗系统建设应进一步改造老填埋场、开发新型防渗材料和提高渗滤液处理工艺。     

寒冷地区冬季自然通风时段选择优化分析

为获得最优的冬季自然通风时段,以兰州地区某地板供暖民用住宅为研究对象,考虑围护结构对室外温度波的衰减和延迟效应,得到建筑围护结构的等热流边界条件。在此基础上,采用FLUENT软件对不同通风时段的室内污染物浓度场进行了数值分析,结果表明:同一开窗方式时,不同时段的通风时长不同,不同进风温度对室内污染物的时空分布及迁移特性影响显著,综合考虑污染物排除效果及舒适性,发现17:00时开始通风为最优通风时段。     

Pollutant concentrations of stormwater and captured sediment in flood control sumps draining an urban watershed

Levee sump systems are used by many riverine communities for temporary storage of urban wet weather flows. The performance and transport of stormwater pollutants in sump systems, however, have not been systematically studied. Although flow of stormwater through a sump system is regulated solely by flood-control requirements, these sumps may function as sedimentation basins that provide purification of stormwater. The objective of this paper is to present a case study of stormwater and sediment analysis for conventional pollutants in flood control sumps in an urban watershed. Two sumps of highly variable physical and hydraulic characteristics were selected for analysis. The results suggest that: (1) first-flush samples may not give an accurate picture of outfall concentrations of stormwater to the sump; (2) time-variable concentrations of pollutants in a sump are related to the hydraulic characteristics of the basin; and, (3) post-event sediment analysis provides verification of pollutant capture in the sumps. This study is an initial step toward development of a more comprehensive management model for flood control sumps that incorporates their hydraulic performance for quantitative assessment of pollutant loads, pollutant discharges, and pollutant removals with respect to the sumps.     

污染物运移过程的一维数值分析

考虑填埋场中固体废弃物的生物降解效应和含水层中土颗料对污染物的吸附性,在有限深度条件下基于对流、弥散和地球化学反应等污染物运移机理,提出了填埋场污染物运移过程数值模拟的一维计算模型。进而采用半解析方法进行数值求解,通过变动参数比较分析确定了控制填埋场污染物运移过程的主要参数。具体数值计算表明:污染物在含水层中运移浓度将于某一特定时间达到峰值,随后逐渐降低。粘土垫的厚度及其渗透性、压缩粘土垫层与含水层的吸附能力是填埋场污染物运移的重要近控制参数。     

Numerical analysis of moisture and gas transport in earthen final covers considering effects of vapor and temperature gradient

Biochemical decomposition of high kitchen wastes in landfills in China results in (i) a high content of vapor in landfill gas (LFG) and (ii) a noticeable temperature gradient across the earthen final cover (EFC). Yet, it is unclear how vapor and temperature gradients affect moisture and gas transport through EFC and microbial aerobic methane oxidation (MAMO). A theoretical model of moisture-gas-heat reactive transport considering MAMO and effects of vapor flow and temperature gradients was developed, and a series of parametric studies were included. The model was verified by published test results. The parametric simulation results show that vapor from landfill wastes can replenish water to EFCs in dry seasons, which results in (i) the relief of water shortage of vegetation and MAMO and (ii) LFG emission reduction. Effects of vapor inflow become more significant under larger temperature gradient. In cold seasons, temperature gradients can promote MAMO to reduce methane emissions, and enhance evaporation to reduce percolation. When evaporation rate at the surface exceeds 30 times vapor influx, vapor inflow has negligible effects on moisture and gas transport in EFCs. Neglecting effects of vapor and temperature gradient can lead to misjudgments on anti-seepage performance and methane emission reduction performance of EFCs.     

Wildlife vulnerability and risk maps for combined pollutants

Ecological risk and vulnerability maps can be used to improve the analysis of pollutant risks and communication to stakeholders. Often, such maps are made for one pollutant at the time. We used the results of wildlife vulnerability analysis, a novel trait-based risk assessment approach, to map overall vulnerability of habitats in Denmark to various metals and one insecticide. These maps were combined with maps of estimated soil concentrations for the same compounds divided by their Maximum Permissible Concentrations. This combination yielded relative risk maps that can be used to assess where the highest risk conditions to wildlife from these individual pollutants in Denmark occur (hot spot identification). In order to show how cumulative risk maps can be made, the maps of the individual pollutants were combined assuming different mechanisms of joint toxicity: no addition, concentration addition, antagonism and synergism. The study demonstrated that with an accurate set of geographical and ecological data one can use the results of vulnerability analysis to make relevant ecological risk maps that show hot spot areas for risks of single or cumulative risks from soil pollutants.     

POLLUTER PAYS THROUGH LOAD-BASED LICENSING: THE IMPACT FOR A COASTAL SEWAGE-TREATMENT WORKS

Implementation of the 'polluter pays'principle through load-based licensing encourages the prevention and reduction of pollution through the financial incentive of lower pollutant fees. It encourages fairness and equity in environmental-protection licence fees among industries, based upon their individual environmental performance in reducing and managing pollution and risks and endeavours, to shift (internalise) external pollution costs from society to the polluter. It takes account of (a) pollutant load, (b) toxicity and (c) sensitivity of the receiving environment to which pollutants are released. This study shows that a coastal sewage-treatment works of 34 Ml/d average capacity will be better off every subsequent year with the implementation of load-based licensing - at least for the period 2000–2005.