Estimation of transport parameters of phenolic compounds and inorganic contaminants through composite landfill liners using one-dimensional mass transport model

One-dimensional (1D) advection–dispersion transport modeling was conducted as a conceptual approach for the estimation of the transport parameters of fourteen different phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and three different inorganic contaminants (Cu, Zn, Fe) migrating downward through the several liner systems. Four identical pilot-scale landfill reactors (0.25 m³) with different composite liners (R1: 0.10 + 0.10 m of compacted clay liner (CCL), L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R2: 0.002-m-thick damaged high-density polyethylene (HDPE) geomembrane overlying 0.10 + 0.10 m of CCL, L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R3: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick bentonite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 1 × 10⁻⁸ m/s, R4: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick zeolite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 4.24 × 10⁻⁷ m/s) were simultaneously run for a period of about 540 days to investigate the nature of diffusive and advective transport of the selected organic and inorganic contaminants. The results of 1D transport model showed that the highest molecular diffusion coefficients, ranging from 4.77 × 10⁻¹⁰ to 10.67 × 10⁻¹⁰ m²/s, were estimated for phenol (R4), 2-MP (R1), 2,4-DNP (R2), 2,4-DCP (R1), 2,6-DCP (R2), 2,4,5-TCP (R2) and 2,3,4,6-TeCP (R1). For all reactors, dispersion coefficients of Cu, ranging from 3.47 × 10⁻⁶ m²/s to 5.37 × 10⁻² m²/s, was determined to be higher than others obtained for Zn and Fe. Average molecular diffusion coefficients of phenolic compounds were estimated to be about 5.64 × 10⁻¹⁰ m²/s, 5.37 × 10⁻¹⁰ m²/s, 2.69 × 10⁻¹⁰ m²/s and 3.29 × 10⁻¹⁰ m²/s for R1, R2, R3 and R4 systems, respectively. The findings of this study clearly indicated that about 35–50% of transport of phenolic compounds to the groundwater is believed to be prevented with the use of zeolite and bentonite materials in landfill liner systems.     

Investigating the effect of compression on solute transport through degrading municipal solid waste

The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to the presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.     

To clean or not to clean: A geostatistical approach for evaluating contaminated soils

Indicator kriging is used to estimate the probability that a discrete area of soil (known as an exposure unit) lies either above or below an action level, warranting a response of either remediation or “no further action.” Resampling procedures are introduced as a way to optimize the number of additional samples needed to meet desired Type I and Type II error rates. This article provides the reader a step-by-step guide to the kriging analysis and a case study illustrating the procedures.     

FGD废水对水力除灰系统影响初探

从理论上分析了FGD废水与灰水的作用机理,研究了FGD废水对循环冲灰系统中的重金属排放和碳钢腐蚀的影响。结果表明：重金属排放浓度取决于灰水pH值,絮凝吸附作用有利于进一步降低重金属残留量。     

A new method for evaluating the sewage sludge pyrolysis kinetics

A new method to simplify calculation the kinetics model is applied to sewage sludge pyrolysis based on the assumption that volatile run out as soon as it formed and during temperature arising process in this study. Difference method widely used to solve math problems is conducted to calculate kinetics parameters. Pyrolysis experiments are carried out at heating rates of 10, 15, 20, and 50 °C/min. All the TG curves are divided into three parts which are beginning decomposition temperature range, main decomposition temperature range, and final decomposition temperature range. The second one is employed to determine the parameters for more than 70% of the total mass loss occurs in this range. According to the developed method, the react order, reaction energy and pre-exponential factor are obtained, which are in the range of 3.9–4.1, 82.3–109.2 kJ/mol and 7.7 × 10⁶–2.8 × 10⁹/min, respectively, which are in the range of that reported previously. As a comparison experimental data with calculated data, the well fitting results indicate that this method is appropriate for simulating sludge pyrolysis kinetics.     

A model for evaluating the social performance of construction waste management

It has been determined by existing literature that a lot of research efforts have been made to the economic performance of construction waste management (CWM), but less attention is paid to investigation of the social performance of CWM. This study therefore attempts to develop a model for quantitatively evaluating the social performance of CWM by using a system dynamics (SD) approach. Firstly, major variables affecting the social performance of CWM are identified and a holistic system for assessing the social performance of CWM is formulated in line with feedback relationships underlying these variables. The developed system is then converted into a SD model through the software iThink. An empirical case study is finally conducted to demonstrate application of the model. Results of model validation indicate that the model is robust and reasonable to reflect the situation of the real system under study. Findings of the case study offer helpful insights into effectively promoting the social performance of CWM of the project investigated. Furthermore, the model exhibits great potential to function as an experimental platform for dynamically evaluating effects of management measures on improving the social performance of CWM of construction projects.     

A system dynamic modeling approach for evaluating municipal solid waste generation,landfill capacity and related cost management issues

As planning for sustainable municipal solid waste management has to address several inter-connected issues such as landfill capacity, environmental impacts and financial expenditure, it becomes increasingly necessary to understand the dynamic nature of their interactions. A system dynamics approach designed here attempts to address some of these issues by fitting a model framework for Newark urban region in the US, and running a forecast simulation. The dynamic system developed in this study incorporates the complexity of the waste generation and management process to some extent which is achieved through a combination of simpler sub-processes that are linked together to form a whole. The impact of decision options on the generation of waste in the city, on the remaining landfill capacity of the state, and on the economic cost or benefit actualized by different waste processing options are explored through this approach, providing valuable insights into the urban waste-management process.     

Laboratory validation study of new vapor‐phase‐based approach for groundwater monitoring

Recent improvements in field‐portable analytical equipment allow accurate on‐site measurement of VOCs present in air at concentrations of less than 0.1 parts per million volume (ppmv). The objective of this project is to determine if the use of these instruments for vapor‐phase measurements of headspace in a monitoring well can serve as a reliable and accurate method for monitoring volatile organic compound (VOC) concentrations in groundwater under equilibrium conditions. As part of a comprehensive research project investigating the utility of this proposed monitoring method, the authors have completed a laboratory validation study to identify instruments and sample‐collection methods that will provide accurate measurement of VOC concentrations in groundwater. This laboratory validation study identified two field‐portable instruments (a gas chromatograph and a photoionization detector) with sufficient sensitivity to measure VOCs in groundwater at concentrations below typical monitoring standards (i.e., 1 to 5 μg/L). The accuracy and precision of these field instruments was sufficient to satisfy typical data‐quality objectives for laboratory‐based analysis. In addition, two sample‐collection methods were identified that yield vapor‐phase samples in equilibrium with water: direct headspace sampling and passive diffusion samplers. These sample‐collection methods allow the field instruments (which measure VOC concentrations in vapor‐phase samples) to be used to measure VOC concentrations in water. After further validation of these sample‐collection methods in the field, this monitoring method will provide a simple way to obtain accurate real‐time measurements of VOC concentrations in groundwater using inexpensive field‐portable analytical instruments. © 2009 Wiley Periodicals, Inc.     

A carbon-13 method for evaluating degradation of starch-based polymers

A new method for evaluating biodegradability of starch-based and certain other polymer blends uses the pre- and postexposure stable carbon isotope composition of material coupled with weight loss data to determine which components have degraded. The naturally occurring stable isotope of carbon.¹³C, is enriched in corn starch (¹³C, approx. –11) compared to petroleum-derived synthetic polymers (¹³C, approx. –32). Results on starch-synthetic polymer blends indicate that the ¹³C signatures of these blends are near-linear mixtures of their component ¹³C. Values of a ¹³C for starch-synthetic polymer blends exposed to biologically active laboratory soil and artificial seawater conditions are depleted in¹³C compared to unexposed samples, suggesting loss of the starch component. Combined with weight loss data for the exposed samples, the ¹³C values are statistically consistent with models requiring loss of the soluble component glycerin, followed by loss of starch, then petrochemical polymer, or simultaneous loss of starch and petrochemical polymer. Replicate ¹³C analyses of starch-synthetic polymer blends increase the statistical power of this relatively inexpensive, accessible technique to discriminate between degrading components.     

Study on the quality and stability of compost through a Demo Compost Plant

This study is concerned with the performance of a Demo Compost Plant for the development of acceptable composting technology in Bangladesh. The Demo Compost Plant was setup at the adjacent area of an existing compost plant located at Khulna city in Bangladesh. Four different composting technologies were considered, where Municipal Solid Waste (MSW) were used as a raw material for composting, collected from the adjacent areas of the plant. Initially the whole composting system was conducted through two experimental setups. In the 1st setup three different types of aerators (horizontal and vertical passively aerator and forced aerator) were selected. For a necessary observation four piles, using only MSW as the input materials in the first three compost pile, the fourth one was the existing Samadhan’s compost pile. Based on the analysis of the experimental findings, the horizontal passively aerated composting technique is suitable for Bangladesh as it had better performance for reducing composting period than that of the others. It was being observed from the quality parameters of compost in the both 1st and 2nd setup that as the waste directly come from kitchen, degradation rate of waste shows a positive result for reducing this waste and there is no possibility of toxic contamination, when it would be used as a soil conditioner. Though there is no significant improvement in the quality of the final product in the 2nd setup as comparing with the 1st setup but it fulfills one of the main objectives of this study is to reduce the whole composting period as well as immediate management of the increasing amount of waste and reducing load on landfill. Selfheating tests reveal that degree of stability of compost with respect to maturation period was remained in the acceptable level, which was further accelerated due to the use of organic additives.     

Techniques for rapidly evaluating the progress of in-situ remediation

Although standard methods of monitoring the progress of in-situ remediation may provide general results for the most permeable zones affected by soil vapor extraction or bioventing, they are essentially unsuccessful at providing information on the degree of heterogeneity within the remediation zone and on the existence of “hot spots.” Data are presented that suggest that monitoring the concentrations of fixed and biogenic gases and measuring soil permeability on a small-scale basis may circumvent the common problems associated with assessing the progress of in-situ remediation. The costs of these monitoring techniques are minor compared to those of designing and operating an in-situ remediation system, and may save additional time and costs by identifying problem areas early in the cleanup process.     

Effect of vadose zone on the steady-state leakage rates from landfill barrier systems

Leakage rates are evaluated for a landfill barrier system having a compacted clay liner (CCL) underlain by a vadose zone of variable thickness. A numerical unsaturated flow model SEEP/W is used to simulate the moisture flow regime and steady-state leakage rates for the cases of unsaturated zones with different soil types and thicknesses. The results of the simulations demonstrate that harmonic mean hydraulic conductivity of coarse textured vadose zones is 3-4 orders of magnitude less than saturated hydraulic conductivity; whereas, the difference is only one order of magnitude for fine textured vadose zones. For both coarse and fine textured vadose zones, the effective hydraulic conductivity of the barrier system and the leakage rate to an underlying aquifer increases with increasing thickness of the vadose zone and ultimately reaches an asymptotic value for a coarse textured vadose zone thickness of about 10m and a fine textured vadose zone thickness of about 5m. Therefore, the fine and coarse textured vadose zones thicker than about 5m and 10m, respectively, act as an effective part of the barrier systems examined. Although the thickness of vadose zone affects the effective hydraulic conductivity of the overall barrier system, the results demonstrated that the hydraulic conductivity of the CCL is the dominant factor controlling the steady-state leakage rates through barrier systems having single low permeability clay layers.     

建设项目环境影响经济损益分析研究

介绍了建设项目环境影响经济损益分析的基本概念和主要内容，阐述了这一方法的应用原则并进行了利弊分析。针对我国开展建设项目环境影响经济损益分析中的一些突出问题提出了改进建议。     

电厂对珍禽保护区的环境影响评价实例探讨

以位于自然保护区边缘的火电厂建设项目环境影响评价为实例,阐述了火电厂生态环境评价中对自然保护区珍稀鸟类的保护方法,以供类似项目的生态环境影响评价借鉴。     

发展工农业复合循环经济 抢占经济和社会制高点

将农业和工业复合起来,是我国当前发展循环经济的一大特色。通过介绍工农业复合循环经济的典型案例,指出发展工农业复合循环经济,可有效缓解我国经济高速持续增长与资源供给和环境保护之间的矛盾,并且工农业复合循环经济模式特别适合在大城市郊区和县级城市集中发展。     

A competing risks approach for time estimation of household WEEE disposal

The recent growth in the number of electrical and electronic devices is viewed as one the priority waste streams in European Union waste management policy. This paper presents the findings of a survey to study domestic habits with respect to Waste Electrical and Electronic Equipment (WEEE) in Spain. A specific problem when performing this estimation arises from the fact that consumers quite often store old appliances at home when they are no longer used. Focusing on four different types of appliance, survival analysis (SA) is used to study both the usage span and the reasons for no longer using each device. The time that the discarded products were kept at home before being disposed of was studied using competing risks (CR) analysis. The results of the analysis provide information on the distribution of the studied variables for the different outcomes as well as the influence exerted by the socio-demographic variables considered. Relations between these characteristics and the storage time of the appliances before disposal emerge based on survey data. For instance, the CR model finds that the storage time of the some appliances (i.e. refrigerator) is related to these social-demographics factors. However, other appliances (i.e. microwave oven) are less influenced by these factors. The attitude and motivation of the respondents to the survey as regards the End-of-Life of appliances were also analysed. A majority of respondents do not store discarded appliances at home. The first reason for storing appliances at home is the possibility of it being useful in the future and the second that the respondents did not know what to do with them.     

Germination test on Komatsuna (Brassica rapa var. peruviridis) seed using water extract from compost for evaluating compost maturity: evaluating criteria for germination and effects of cultivars on germination rate

Germination tests on the Komatsuna (Brassica rapa var. peruviridis) seed using water extract from compost has often been performed in Japan to evaluate compost maturity; however, most of the germination tests have been carried out without using any rationally defined experimental criteria to determine germination and to explain the influence of cultivars. Here, we performed a series of germination tests to examine the applicability of the experimental criteria for germination and the influence of cultivars on germination rate. Germination rate varied according to the criteria introduced in this paper, and two criteria, "seed size (3)" and "5?mm (2)", were selected for testing. In addition, two types of inhibitory influence, stop and slowness, were observed and compared with the criteria. The logistic regression curve of Logit, a function of germination rate to logarithmic value of the dilution ratio of the water extract was parameterized to compare the effects of the cultivars on germination rate. The statistical analysis of the parameters showed that dilution ratio greatly influenced germination rate, and the cultivar itself also influenced the rate. Consequently, the specific experimental criteria for germination and determining the influence of cultivars were proven to be indispensable for evaluating compost maturity using the germination test.     

A review of waste management practices and their impact on human health

This work reviews (i) the most recent information on waste arisings and waste disposal options in the world, in the European Union (EU), in Organisation for Economic Co-operation and Development (OEDC) countries, and in some developing countries (notably China) and (ii) the potential direct and indirect impact of waste management activities on health. Though the main focus is primarily on municipal solid waste (MSW), exposure to bioaerosols from composting facilities and to pathogens from sewage treatment plants are considered. The reported effects of radioactive waste are also briefly reviewed. Hundreds of epidemiological studies reported on the incidence of a wide range of possible illnesses on employees of waste facilities and on the resident population. The main conclusion of the overall assessment of the literature is that the evidence of adverse health outcomes for the general population living near landfill sites, incinerators, composting facilities and nuclear installations is usually insufficient and inconclusive. There is convincing evidence of a high risk of gastrointestinal problems associated with pathogens originating at sewage treatment plants. In order to improve the quality and usefulness of epidemiological studies applied to populations residing in areas where waste management facilities are located or planned, preference should be given to prospective cohort studies of sufficient statistical power, with access to direct human exposure measurements, and supported by data on health effect biomarkers and susceptibility biomarkers.     

火电厂对生态环境影响的总体评价

抛弃了以往在分析污染排放物对环境影响时只对不同污染物进行单独分析的做法,从单位污染物对大气的影响和生产单位有用能的污染物排放量两方面考虑,建立了一个通用的、能综合评价各种污染物对环境总体影响的模型--能源生态效率模型,并对燃烧不同燃料火电厂的能源生态效率作了计算,对能源生态效率的影响因素进行了分析.