A multi-component two-phase flow algorithm for use in landfill processes modelling

This paper describes the finite difference algorithm that has been developed for the flow sub-model of the University of Southampton landfill degradation and transport model LDAT. The liquid and gas phase flow components are first decoupled from the solid phase of the full multi-phase, multi-component landfill process constitutive equations and are then rearranged into a format that can be applied as a calculation procedure within the framework of a three dimensional array of finite difference rectangular elements.The algorithm contains a source term which accommodates the non-flow landfill processes of degradation, gas solubility, and leachate chemical equilibrium, sub-models that have been described in White and Beaven (2013).The paper includes an illustration of the application of the flow sub-model in the context of the leachate recirculation tests carried out at the Beddington landfill project. This illustration demonstrates the ability of the sub-model to track movement in the gas phase as well as the liquid phase, and to simulate multi-directional flow patterns that are different in each of the phases.     

Environmental behaviour of a construction made of a mixture of hydraulic binders and air pollution control residues from municipal solid waste incineration Part 1. Physico-chemical characterisation and modelling of the source term

The reuse of waste materials requires the development of assessment methods for the long-term release of pollutants (source term) from wastes (or materials containing wastes) in contact with water. These methods depend on the scenario conditions: characteristics of the materials (especially physical structure and composition), contact with water. The scenario studied here is a water storage reservoir for fire fighting. The reservoir construction is made of a mixture of hydraulic binders and air pollution control (APC) residues from a municipal solid waste incinerator (MSWI). The modelling of the source term is performed in 5 steps ranging from the physico-chemical characterisation of the material to the validation of the proposed model by means of field simulation devices. This article presents the first steps of the methodology: physico-chemical characterisation of the source term, identification of the main transfer mechanisms and laboratory scale modelling of the source term. During the physico-chemical characterisation, it has been shown that the solidified waste shows a high basic capacity and that a relative decrease in pH during leaching favours retention of the main pollutants. During the first leaching sequences, the dynamic leaching tests show that the release of pollutants such as cadmium, arsenic, zinc and lead is extremely low but that the release of alkaline species (sodium and potassium) and chloride is very high from the beginning, whereas the release of calcium remains very high even after 3600 h of leaching. Identification of the main transfer mechanisms concludes that the release of soluble pollutants is the combined result of diffusional transfer of pollutants in the solution and the physico-chemical specificity of the species. The modelling based on these features enables a good simulation of the release but reveals a deviation from the experimental results after 500 h for alkaline species and 1000 h for Ca and Cl leaching. However, this deviation only appears after release of the major part of these elements.     

Real time alteration of a nuclear waste glass and remobilization of lanthanide into an interphase

The development of predictive models for the long term evolution of nuclear waste glass requires the complete knowledge of the glass dissolution at the laboratory scale. A new approach was developed to determine the initial reaction during the first steps of experience, a new concept was developed, based on the combination of dynamic leaching test and the characterization of the altered materials. With this experimental set-up it is possible to follow in real time the glass alteration process at a fine temporal scale. The results put in evidence a singular behaviour of the lanthanide, shown by a concentration peak of La, Nd and Ce after 2 h and a quick decrease of their concentration measured on line in the solution during the leaching test. This fact is directly linked to the development of an interphase (altered layer which differs from the initial solid by its texture, structure and chemical composition) at the interface of the glass surface and the leaching solution. This work is an attempt to integrate the formation of the alteration products (here the interphase) during leaching into the dissolution mechanisms of a nuclear waste glass. A model is proposed and discussed.     

人工湿地构造及生物因素研究进展

介绍了近10年报道的不同构造人工湿地(CW)的污水处理性能及CW中微生物、植物、动物的相关研究进展.分析了各种CW构造优缺点、CW与其他技术的结合、CW微生物群落的特征、影响因素和研究手段、CW植物与动物对CW处理性能的贡献及作用机制.提出今后应重点研究:复合人工湿地(ICW)工艺优化;CW强化技术及其参数;CW微生物...     

Assessment of mobility and bioavailability of contaminants in MSW incineration ash with aquatic and terrestrial bioassays

Incineration of municipal solid waste (MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction as well as a source of renewable energy. In the process fly and bottom ash is generated as a waste material. The ash residue may vary greatly in composition depending on the type of waste incinerated and it can contain elevated levels of harmful contaminants such as heavy metals. In this study, the ecotoxicity of a weathered, untreated incineration bottom ash was characterized as defined by the H14 criterion of the EU Waste Framework Directive by means of an elemental analysis, leaching tests followed by a chemical analysis and a combination of aquatic and solid-phase bioassays. The experiments were conducted to assess the mobility and bioavailability of ash contaminants. A combination of aquatic and terrestrial bioassays was used to determine potentially adverse acute effects of exposure to the solid ash and aqueous ash leachates. The results from the study showed that the bottom ash from a municipal waste incineration plant in mid-Sweden contained levels of metals such as Cu, Pb and Zn, which exceeded the Swedish EPA limit values for inert wastes. The chemical analysis of the ash leachates showed high concentrations of particularly Cr. The leachate concentration of Cr exceeded the limit value for L/S 10 leaching for inert wastes. Filtration of leachates prior to analysis may have underestimated the leachability of complex-forming metals such as Cu and Pb. The germination test of solid ash and ash leachates using T. repens showed a higher inhibition of seedling emergence of seeds exposed to the solid ash than the seeds exposed to ash leachates. This indicated a relatively low mobility of toxicants from the solid ash into the leachates, although some metals exceeded the L/S 10 leaching limit values for inert wastes. The Microtox® toxicity test showed only a very low toxic response to the ash leachate exposure, while the D. magna immobility test showed a moderately high toxic effect of the ash leachates. Overall, the results from this study showed an ecotoxic effect of the solid MSW bottom ash and the corresponding ash leachates. The material may therefore pose an environmental risk if used in construction applications. However, as the testing of the solid ash was rather limited and the ash leachate showed an unusually high leaching of Cr, further assessments are required in order to conclusively characterize the bottom ash studied herein as hazardous according to the H14 criterion.     

LDPE/EPDM Multilayer Films Containing Recycled LDPE for Greenhouse Applications

In this paper the reuse of recycled LDPE in combination with the incorporation of EPDM modifier in the production of greenhouse films has been investigated. A three-layer film (60-100-40 micron thickness) containing recycled LDPE in the middle layer and a high UV-stabilized 40-micron outer layer was developed and proven to be commercially successful. Films with 25% and 50% recycled material content were produced. The effect of natural weathering on the film properties over a period of 15 months has been observed. Changes in physical and mechanical property were determined. The addition of EPDM to the raw resin was found to improve the extrudability of the compound and improve the weather resistivity of the film. The EPDM-modified films containing 25% to 50% recycled material retained approximately 95% and 75%, respectively, of their original extensibility after 9 months' exposure to natural weathering. Optimization of EPDM and UV stabilizer concentration was carried out to develop a balanced film with excellent mechanical and physical properties and resistance to weathering conditions. The use of UV stabilizer concentrations slightly higher than commercial practice in the outer layer of the multilayer film can be justified by the cost reduction by the incorporation of recycled LDPE materials.     

Degradation of starch-plastic composites in a municipal solid waste landfill

The rate and extent of deterioration of starch-plastic composites were determined over a 2-year period for samples buried in a municipal solid waste landfill. The deterioration of the starch-plastic composites following exposure was determined by measuring changes in tensile properties, weight loss, and starch content of samples retrieved from the landfill. Elongation decreases of 92 and 44% were measured for starch-plastic composite LDPE and LLDPE films, respectively, while elongation decreases of 54 and 21% were measured for their corresponding control films following 2 years of burial. Starch loss of 25% for LLDPE and 33% for LDPE starch-plastic composite films was measured following 2 years of landfill burial. Starch-plastic composites did not fragment or lose mass during the 2-year landfill burial. The limited degradation observed for the starch-plastic composites was attributed to the ineffectiveness of the prooxidant additive to catalyze the thermal oxidation of the polyethylene or polypropylene component of the starch-plastic composite under the environmental conditions present within the landfill.     

无患子皂苷与柠檬酸协同洗脱污染土壤中镉铅

以某废弃铅锌矿区重金属污染土壤为研究对象,采用无患子皂苷与柠檬酸(CA)协同洗脱污染土壤中的Cd和Pb.以无患子果皮投加量为20 g/L所得水浸提液和浓度为0.3 mol/L的CA配制复配淋洗剂.在浸提液中添加CA后,能有效提高对土壤中Pb的去除率.在浸提液和CA的体积比为1:3、淋洗剂pH为5、淋洗时间为12.0 h...     

The efficacy of an oxidation pond in mineralizing some industrial waste products with special reference to fluorene degradation: a case study

The efficacy of the oxidation pond on the outskirts of the 10th of Ramadan, the main industrial city, in Egypt was examined. Samples of wastewater collected from the inlet and the outlet were screened for some priority pollutants. Acenaphthene and fluorene were the most frequently detected polycyclic aromatic hydrocarbons, while dimethyl phthalate was the most frequently detected phthalate ester. The spectrum of pollutants, their concentrations and frequencies were similar in the inlet and the outlet, indicating an inferior mineralization capability of the pond. Several degradative bacterial strains were isolated from the pond and grown on M56 minimal media supplemented with different pollutants as the carbon source. The efficacy of pure and mixed cultures to break down fluorene, the most frequently detected pollutant was examined. Fluorene degradation was fast in the first 10 days, then followed by a slow phase. Mixed culture had a higher rate of fluorene degradation in comparison to pure cultures. High performance liquid chromatography analysis of fluorene degradation showed three degradative metabolites. But GC/MS analysis detected one compound, identified as acetamide. The present work has indicated the poor efficacy of the pond. Lack of primary treatment of industrial effluent at factory level, coupled with shock loads of toxicants that may damage the microorganisms and their degradative capabilities are presumably main factors behind such inferior performance. Moreover, the type of pollutants discharged into the pond tend to fluctuate and change depending on the rate from the factories discharge and work shifts. Such irregular feeding of persistent pollutants may have led to a wash out of specialized strains of bacteria capable to degrade such persistent pollutants.     

油田高含盐污水雾化蒸发的数值模拟

基于FLUENT软件,对油田高含盐污水的雾化蒸发过程进行了数值模拟,得到了逆流型雾化蒸发塔内的流场分布特性,对比分析了不同操作参数对蒸发效果的影响。结果表明:液滴蒸发速率沿塔体中心轴线自上而下呈加快趋势;进口空气流速与温度是影响液滴蒸发的关键操作参数,提高流速及温度均可加快液滴的蒸发速率;当进口空气流速达到0.4 m/s后,对蒸发速率的影响减弱;当进口空气温度达到313 K后,对蒸发速率的提高作用不大;喷雾锥角的变化对蒸发速率影响不明显;液滴越细化,蒸发速率越快。