活性炭催化臭氧氧化去除水中的腐植酸

针对模拟水样中的腐植酸,采用静态实验对比的方法,分析了单独臭氧氧化和活性炭催化臭氧氧化去除腐植酸的效果。实验结果表明：臭氧氧化和活性炭催化臭氧氧化均可去除水中的腐植酸,且后者的去除效果更佳。在水样pH为中性、反应时间为30m in的条件下,活性炭催化臭氧氧化对腐植酸和COD的去除率分别为64.9%和40.8%,比单独臭氧氧化的处理效果分别高出34.2%和26.1%。臭氧氧化和活性炭催化臭氧氧化反应均受水样pH的影响,碱性条件时,腐植酸去除效果最好,中性条件时次之,酸性条件时最差。     

水催化泔水油生产甘油硬脂酸的清洁生产工艺

探讨了泔水油水解工艺,从酸析、水洗、压力、温度、水解等条件进行研究。本工艺直接用水作催化剂,适应成分复杂的餐饮泔水油,污水处理简单。采用的工艺条件是:压力,3.5 MPa;加水量,35%左右。同时需要指出的是,加水量一般是根据中性油的含量来计算,因为游离脂肪酸不需水解。     

Best Management Practices for Silvicultural Chemicals and the Science Behind Them

Silvicultural chemicals include fertilizers and pesticides applied for forest management. All states east of the Rockies have at least some form of silvicultural chemical best management practices (SCBMPs) and it is widely accepted that SCBMPs effect some protection of water quality. All SCBMPs recommend handling and application precautions and a minimum width streamside management zone (SMZ) on each side of streams for protection of water quality and aquatic ecosystems. Typically these zones increase in width as stream width increases. In areas where cold-water fish are present, additional widths are designated for their protection. Minimum SMZ widths range from 8 to 91 meters on each side of the stream bank for intermittent and perennial streams. Most SMZ recommendations do not cover ephemeral drainages, ditches or canals. SMZs are generally described as being site specific with width dependent on slope, soil type and other conditions as well as the stream's designation as perennial or intermittent. The science behind SCBMPs is often elusive. Spray drift can be controlled through proper selection and use of application technology while considering site specific conditions. SMZs greatly reduce the amount of herbicides reaching streams. Available toxicological data and research on aquatic ecosystem impacts from herbicide use suggest that additional protection from silvicultural chemicals may not be necessary. However, there is evidence to suggest that protection of ephemeral and intermittent channels can further reduce entry of silvicultural chemicals into streams and also reduce sedimentation. This may be the most fruitful area of research we can pursue in light of the knowledge gaps listed.     

Detection of polar organic substances relevant for drinking water

Testfilter systems help in the study of the persistence of organic compounds. Hence, they are remedial measures to control pollution of the environment. The filters used as biological fixed-bed reactors should enable the simulation of the biological degradation of organic compounds before they reach the waterworks. The German chemical industry has used filters based on activated carbon for more than 20 years in order to determine the microbial poorly degradable fraction of the dissolved organic carbon in the sewage effluents. The testfilter systems proved to work well on the basis of group and ‘sum’ parameters. The new challenge was to investigate whether the testfilter concept holds also for a diversification of drinking water relevant and non-relevant single compounds. Therefore, the first task was to develop analytical methods for classes of drinking water relevant compounds in the very complex matrix of waste water. Thereafter, these methods were applied for the detection of the selected compounds in the testfilter systems and their occurrence in the receiving waters. Methods of analysis were developed for the following classes of chemical compounds: aliphatic amines, aromatic sulfonates, halogenated carboxylic acids and organic phosphates. Furthermore the formation of yet unknown drinking water relevant compounds was studied. As a result it was concluded that the major reasons for the formation of these compounds are: (1) formation of by-products during various steps in the chemical synthesis; (2) chemical reactions in the influents of the treatment plants; and (3) metabolism in the waste water treatment plant. Experiments with compounds like 6-[methyl(phenylsulfonyl)amino]hexanoic acid (HPS) and nitrilotriacetic acid (NTA) which are known from the literature to be well degradable, confirmed that the testfilters can be utilized for simulating the performance of the underground passage. On the other hand, persistent compounds, for which 1,5-naphthalenedisulfonate is a characteristic representative, remained in the filter system without being degraded. As far as the testfilters are concerned it was concluded that the activated carbon retains its adsorption capacity to a certain extent even after a long time of operation. Because it is not possible to distinguish between microbial degradation and adsorption, it was necessary to develop a modified filter set-up for testing single substances. ©     

Field Performance of Point Velocity Probes at a Tidally Influenced Site

Conventional methods to estimate groundwater velocity that rely on Darcy's Law and average hydrogeologic parameter values are insensitive to local‐scale heterogeneities and anisotropy that control advective flow velocity and direction. Furthermore, at sites that are tidally influenced or have extraction wells with variable pumping schedules, infrequent water‐level measurements may not adequately characterize the range and significance of transient hydraulic conditions. The point velocity probe (PVP) is a recently developed instrument capable of directly measuring local‐scale groundwater flow velocity and direction. In particular, PVPs may offer distinct advantages for sites with complex groundwater–surface water interactions and/or with spatially and temporally variable groundwater flow conditions. The PVP utilizes a small volume of saline tracer and inexpensive sensors to directly measure groundwater flow direction and velocity in situ at the centimeter‐scale and discrete times. The probes are installed in conventional direct‐push borings, rather than in wells, thus minimizing the changes and biases in the local flow field caused by well installation and construction. Six PVPs were installed at a tidally influenced site in North Carolina to evaluate their implementability, performance, and potential value as a new site characterization tool. For this study, a new PVP prototype was developed using a rapid prototyping machine (i.e., a “three‐dimensional printer'') and included both horizontally and vertically oriented tracer detectors. A site‐specific testing protocol was developed to account for the spatially and temporally variable hydraulic conditions and groundwater salinity. The PVPs were tested multiple times, and the results were compared to the results of several different groundwater flux and velocity estimation tools and methods, including a heat‐pulse flowmeter, passive flux meters, single‐well tracer tests, and high‐resolution hydraulic gradient analysis. Overall, the results confirmed that the PVP concept is valid and demonstrated that reliable estimates of groundwater velocity and direction can be obtained in simple settings. Also, PVPs can be successfully installed by conventional methods at sites where the formation consists primarily of noncohesive soils and the water table is relatively shallow. Although some PVP tests yielded consistent and reliable results, several tests did not. This is likely due to the highly transient flow conditions and limitations associated with the PVP design and testing procedures. PVPs offer particular advantages over, and can effectively complement, other groundwater flow characterization techniques for certain conditions, and objectives may be useful for characterizing complex flow patterns under steady conditions; however, this study suggests that PVPs are best suited for conditions where the flow hydraulics are not highly transient. For sites where the hydraulic conditions are highly transient, the most reliable approach for understanding groundwater flow behavior and groundwater–surface water interactions would generally involve both a high‐resolution hydraulic gradient analysis and another local‐scale method, such as tracer testing. This study also highlighted some aspects of the current PVP design and testing protocol that can be improved upon, including a more robust connection between the PVP and injection line and further assessment of tracer solution density effects on vertical flow. © 2013 Wiley Periodicals, Inc.     

A Novel Approach to Biological Treatment of Contaminated Water

Over the past few years, the focus of our research has been to respond to the recognized needs for novel biological processes that are capable of destroying a wide range of biodegradable pollutants and providing the perfect environment for complex interspecies interactions required for the degradation of environmental contaminants. A new biotechnology process called Biological Permeable Barrier (BPB) was developed to provide high microbial density, stable environmental conditions, and protective measures for microbial activities for in‐situ bioremediation of contaminated groundwater. This patented technology (U.S. Patent 6,337,019 ) is based on the creation of a structured matrix, or Bio‐beads, that provides the perfect environment for organic‐degrading microorganisms to establish biofilms capable of destroying the contaminants in water with remarkable stability and control. For over 240 days, the viability and performance of the BPB (Bio‐beads) system were shown for biodegradation of a targeted contaminant, 2,4,6‐ trichlorophenol (TCP), under a variety of operating and stress conditions (Razavi‐Shirazi, 1997 ). Extensive batch experiments were also conducted to obtain necessary data to determine the rate of TCP diffusion into the Bio‐beads, adsorption properties of the Bio‐beads, and substrate‐use rate of the mixed bioculture as free cells and as immobilized cells (Bio‐beads). A simulated model of BPB was also characterized with its porosity, permeability, and compressibility or deformation under typical field conditions. Our extensive research showed that BPB takes advantage of a controlled biotechnology process to overcome the disadvantages and uncertainties associated with conventional biological processes. A summary of our investigation is presented here. © 2002 Wiley Periodicals, Inc.     

Crystal-chemistry of alteration products of vitrified wastes: implications on the retention of polluting elements

Alteration products of vitrified wastes coming from the incineration of household refuse (MSW) are described. Two vitrified wastes containing 50% and 70% of fly ash and a synthetic stained-glass with a composition close to that of an ancient glass (medieval stained-glass) were altered under different pH conditions (1, 5.5 corresponding to demineralized water and 10) during 181 days. Under acidic condition, the alteration layer is made of an amorphous hydrated silica gel impoverished in most of the initial elements. A minor phase MPO(4)*nH(2)O, where M represents Fe, Ti, Al, Ca and K cations, also constitutes the altered layer of the synthetic stained-glass. Under neutral and basic conditions, the altered layer is made of an amorphous hydrated silica gel and a crystallized calcium phosphate phase. The silica gel is depleted in alkalis and alkali-earth elements but contains significant amounts of aluminium, magnesium and transition elements, whereas the calcium phosphate is a hydroxylapatite-like phase with P-Si substitutions and a Ca/P ratio depending on the pH of the solution. This study shows: (i) the strong influence of pH conditions on the crystal-chemistry of alteration products and thus on the mechanisms of weathering resulting in different trapping of polluting elements, and (ii) that glass alteration does not necessary produce thermodynamically stable phases which has to be taken into account for the prediction of the long-term behavior.     

Scaling methane oxidation: from laboratory incubation experiments to landfill cover field conditions

Evaluating field-scale methane oxidation in landfill cover soils using numerical models is gaining interest in the solid waste industry as research has made it clear that methane oxidation in the field is a complex function of climatic conditions, soil type, cover design, and incoming flux of landfill gas from the waste mass. Numerical models can account for these parameters as they change with time and space under field conditions. In this study, we developed temperature, and water content correction factors for methane oxidation parameters. We also introduced a possible correction to account for the different soil structure under field conditions. These parameters were defined in laboratory incubation experiments performed on homogenized soil specimens and were used to predict the actual methane oxidation rates to be expected under field conditions. Water content and temperature corrections factors were obtained for the methane oxidation rate parameter to be used when modeling methane oxidation in the field. To predict in situ measured rates of methane with the model it was necessary to set the half saturation constant of methane and oxygen, K_m, to 5%, approximately five times larger than laboratory measured values. We hypothesize that this discrepancy reflects differences in soil structure between homogenized soil conditions in the lab and actual aggregated soil structure in the field. When all of these correction factors were re-introduced into the oxidation module of our model, it was able to reproduce surface emissions (as measured by static flux chambers) and percent oxidation (as measured by stable isotope techniques) within the range measured in the field.     

Knowledge based ranking algorithm for comparative assessment of post-closure care needs of closed landfills

Post-closure care (PCC) activities at landfills include cap maintenance; water quality monitoring; maintenance and monitoring of the gas collection/control system, leachate collection system, groundwater monitoring wells, and surface water management system; and general site maintenance. The objective of this study was to develop an integrated data and knowledge based decision making tool for preliminary estimation of PCC needs at closed landfills. To develop the decision making tool, 11 categories of parameters were identified as critical areas which could affect future PCC needs. Each category was further analyzed by detailed questions which could be answered with limited data and knowledge about the site, its history, location, and site specific characteristics. Depending on the existing knowledge base, a score was assigned to each question (on a scale 1-10, as 1 being the best and 10 being the worst). Each category was also assigned a weight based on its relative importance on the site conditions and PCC needs. The overall landfill score was obtained from the total weighted sum attained. Based on the overall score, landfill conditions could be categorized as critical, acceptable, or good. Critical condition indicates that the landfill may be a threat to the human health and the environment and necessary steps should be taken. Acceptable condition indicates that the landfill is currently stable and the monitoring should be continued. Good condition indicates that the landfill is stable and the monitoring activities can be reduced in the future. The knowledge base algorithm was applied to two case study landfills for preliminary assessment of PCC performance.     

联碱厂碳化塔洗水制备磷酸铵镁

采用化学沉淀法，以模拟联碱厂碳化塔洗水为原料，制备磷酸铵镁，并采用SEM和XRD技术对产品的晶形和成分进行分析。通过正交实验和单因素优化实验确定较适宜的反应条件为：反应液pH 9.5，n（Mg）∶n（P）∶n（N）=1.2∶1.1∶1.0，反应温度25 ℃。在此条件下，处理氨氮质量浓度为7 500 mg/L的联碱厂碳化塔洗水，氨氮的利用率为97.4%，制备的磷酸铵镁产物晶形比较规则，呈斜立方正交结构。1 t氨氮质量浓度为7 500 mg/L的联碱厂碳化塔洗水可生产磷酸铵镁0.139 2 t，产品收益约为320.2 元，药剂成本为352.3 元，即废水的处理费用约为32.1 元/t。     

絮凝作用对HEDP防垢性能的影响

絮凝剂ＰＨＰ、防垢剂ＨＥＤＰ是油田水处理常用的药剂。在油田水处理过程中，调节污水的ＰＨ、投加絮凝剂常常与投加防垢剂一起或先后进行。本文对投加絮凝剂和调节ＰＨ对防士兵防垢性能的影响进行了研究。实验结果证明，絮凝剂的絮凝作用和ＰＨ调节产生的Ｆｅ（ＯＨ）２，均会使污水中的ＨＥＤＰ含量发生变化，防垢性能受到影响。     

Water quality impacts on sorbent efficacy for per- and polyfluoroalkyl substances treatment of groundwater

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic compounds that have emerged as chemicals of concern in drinking water and groundwater. Typically, such waters are treated to remove PFAS by passing the water through a bed of sorbent material (e.g., activated carbon and anion exchange resins [AIX]). However, the efficacy of these sorbents varies depending on the types and concentrations of PFAS, in addition to water quality conditions such as organic matter content and conductivity (ionic strength). The choice of sorbent material to effectively treat PFAS in complex natural waters will, therefore, depend upon site water quality and PFAS conditions. To help inform these decisions, a series of evaluations using a rapid small-scale column test approach was conducted with two sorbent materials (a granulated activated carbon [GAC] and an AIX), individually and combined, under conditions where conductivity, pH, and organic carbon concentrations were varied in a semifactorial approach. Artificial groundwater batches were prepared to meet these test conditions and spiked with six PFAS compounds (perfluorobutane sulfonic acid [PFBS], perfluorobutanoic acid [PFBA], perfluorohexane sulfonic acid [PFHxS], perfluorohexanoic acid [PFHxA], perfluorooctane sulfonic acid [PFOS], and perfluorooctanoic acid [PFOA]), passed through small columns packed with ground sorbent material for ∼30,000 bed volumes of water for single sorbent treatments and ∼20,000 bed volumes for combined sorbent treatments, during which samples of effluent were captured and analyzed to quantify breakthrough of PFAS from the sorbent materials over time. AIX was found to be more effective than GAC at removing the tested perfluoroalkyl sulfonic acids (PFBS, PFHxS, and PFOS), but GAC was similarly or more effective than AIX at removing perfluorocarboxylic acids (PFBA, PFHxA, and PFOA) under high conductivity conditions. Overall, the efficacy of AIX at removing PFAS was more strongly impacted by organic carbon and conductivity than GAC, while pH had less of an effect on either sorbent's efficacy compared to the other test conditions.     

Determination of the Burning Characteristics of a Slick of Oil on Water

The burning rate of a slick of oil on a water bed is characterized by three distinct processes, ignition, flame spread and burning rate. Although all three processes are important, ignition and burning rate are critical. The former, because it defines the potential to burn and the latter because of the inherent possibility of boilover. Burning rate is calculated by a simple expression derived from a one-dimensional heat conduction equation. Heat feedback from the flame to the surface is assumed to be a constant fraction of the total energy released by the combustion reaction. The constant fraction (χ) is named the burning efficiency and represents an important tool in assessing the potential of in situ burning as a counter-measure to an oil spill. By matching the characteristic thermal penetration length scale for the fuel/water system and an equivalent single layer system, a combined thermal diffusivity can be calculated and used to obtain an analytical solution for the burning rate. Theoretical expressions were correlated with crude oil and heating oil, for a number of pool diameters and initial fuel layer thickness. Experiments were also conducted with emulsified and weathered crude oil. The simple analytical expression describes well the effects of pool diameter and initial fuel layer thickness permitting a better observation of the effects of weathering, emulsification and net heat feedback to the fuel surface. Experiments showed that only a small fraction of the heat released by the flame is retained by the fuel layer and water bed (of the order of 1%). Ignition has been studied to provide a tool that will serve to assess a fuels ease to ignite under conditions that are representative of oil spills. Two different techniques are used, piloted ignition when the fuel is exposed to a radiant heat flux and flash point as measured by the ASTM D56 Tag Closed Cup Test. Two different crude oils were used for these experiments, ANS and Cook Inlet. Crude oils were tested in their natural state and at different levels of weathering, showing that piloted ignition and flash point are strong functions of weathering level.     

Experimental study of the bio-oil production from sewage sludge by supercritical conversion process

Environment-friendly treatment of sewage sludge has become tremendously important. Conversion of sewage sludge into energy products by environment-friendly conversion process, with its energy recovery and environmental benefits, is being paid significant attention. Direct liquefaction of sewage sludge into bio-oils with supercritical water (SCW) was therefore put forward in this study, as de-water usually requiring intensive energy input is not necessary in this direct liquefaction. Supercritical water may act as a strong solvent and also a reactant, as well as catalyst promoting reaction process. Experiments were carried out in a self designed high-pressure reaction system with varying operating conditions. Through orthogonal experiments, it was found that temperature and residence time dominated on bio-oil yield compared with other operating parameters. Temperature from 350 to 500 °C and reaction residence time of 0, 30, 60 min were accordingly investigated in details, respectively. Under supercritical conversion, the maximum bio-oil yield could achieve 39.73%, which was performed at 375 °C and 0 min reaction residence time. Meanwhile, function of supercritical water was concluded. Fuel property analysis showed the potential of bio-oil application as crude fuel.     

Recovery of yttrium from cathode ray tubes and lamps’ fluorescent powders: experimental results and economic simulation

In this paper, yttrium recovery from fluorescent powder of lamps and cathode ray tubes (CRTs) is described. The process for treating these materials includes the following: (a) acid leaching, (b) purification of the leach liquors using sodium hydroxide and sodium sulfide, (c) precipitation of yttrium using oxalic acid, and (d) calcinations of oxalates for production of yttrium oxides.Experimental results have shown that process conditions necessary to purify the solutions and recover yttrium strongly depend on composition of the leach liquor, in other words, whether the powder comes from treatment of CRTs or lamp. In the optimal experimental conditions, the recoveries of yttrium oxide are about 95%, 55%, and 65% for CRT, lamps, and CRT/lamp mixture (called MIX) powders, respectively. The lower yields obtained during treatments of MIX and lamp powders are probably due to the co-precipitation of yttrium together with other metals contained in the lamps powder only. Yttrium loss can be reduced to minimum changing the experimental conditions with respect to the case of the CRT process. In any case, the purity of final products from CRT, lamps, and MIX is greater than 95%.Moreover, the possibility to treat simultaneously both CRT and lamp powders is very important and interesting from an industrial point of view since it could be possible to run a single plant treating fluorescent powder coming from two different electronic wastes.     

Use of life cycle assessment as decision-support tool for water reuse and handling of residues at a Danish industrial laundry.

This analysis presents the results of a life cycle assessment (LCA) carried out on six alternative options for the recycling of water at a Danish industrial laundry for workwear. The study focuses on the handling and disposal of the wet residues generated when wastewater is treated for recycling, and in accounting for long-term potential toxicity impacts. The analysed options are a combination of two water-upgrading technologies: biofilter and ultrafiltration, and three residue disposal alternatives: biogas followed by incineration of sludge at local wastewater treatment plant, thermal vitrification treatment for production of vitrified sand, and mineralization in a sludge bed. It is concluded from the results that with the current Danish environmental policy priorities, the environmental impacts of highest priority are the toxicity effects derived from the presence of heavy metals in the residues. Heavy metals originate from the dirt in the workwear that is washed in the laundry. It is further concluded that the studied water treatment technologies satisfy both the need of clean water for recycling and simultaneously help controlling a safe disposal of pollutants by concentration of the residues. The results of the study also confirm the potential of LCA as a decision-support tool for assisting water recycling initiatives and for residue handling management. The handling of residues has been identified as a stage of the water recycling strategy that bears important environmental impacts. This holistic perspective provided by LCA can be used as input for the definition of environmental management strategies at an industrial laundry, and the prioritization of investments to the environmental profile of laundry processes. In this case-study, the results of the LCA are made operational by, for example, selecting the water treatment technology which is associated wih a safe disposal of the wet residue. It is important to bear in mind that such prioritization depends on national boundary conditions. In the case study analysed, the boundary conditions steer the weighing of the environmental impacts, following the current Danish environmental policy priorities.     

Current and future solid waste management system in Northern Viet Nam with focus on Ha Noi: climate change effects and landfill management

The contribution investigates the solid waste management system in Ha Noi under consideration of the interrelation between climate change effects and landfill management by means of a cause-and-effect-analysis as well as water balances using the HELP 3.95 model and gas emission data, followed by a Strength, Weakness, Opportunities, Threats (SWOT) analysis. Even landfills are sources of methane (CH₄) emissions they are also impacted by climate change. The main effects on landfill sites are the change of climatic conditions, namely the regional water balance, extreme precipitation and storm events. The results of the water balance model results show that a geomembrane surface sealing can reduce the leachate formation significantly, a fact that is also valid for the climate change scenario with higher precipitation. The risk of flooding and erosion at the landfill sites increases, which will require a customized water management. In parallel landfill gas offers the opportunity for recovery of Greenhouse Gases (GHG) and the generation of renewable energy. Some further management options are wind turbines, photovoltaic systems or biomass for biogas conversion, which was grown on closed landfill sites. The inclusion of climate friendly management options of closed landfills in a “Good Landfill Aftercare Practice” is recommended.     

Reactive transport modeling of remedial scenarios to predict cadmium,copper, and zinc in north fork of Clear Creek,Colorado

The North Fork of Clear Creek (NFCC), Colorado, is an acid‐mine‐drainage‐impacted stream typical of many mountain surface waters affected by historic metal mining in the western United States. The stream is devoid of fish primarily because of high metal concentrations in the water (e.g., copper and zinc) and has large amounts of settled iron oxyhydroxide solids that coat the streambed. The NFCC is part of the Central City/Clear Creek Superfund site, and remediation plans are being implemented that include treatment of three of the main point‐source inputs and cleanup of some tailings and waste rock piles. This article examines dissolved (0.45‐μm filterable) concentrations of cadmium, copper, and zinc following several potential remediation scenarios, simulated using a reactive transport model (WASP4/META4). Results from modeling indicate that for cadmium, remediation of the primary point‐source adit discharges should be sufficient to achieve acute and chronic water‐quality standards under both high‐ and low‐flow conditions. To achieve standards for copper and zinc, however, the modeling scenarios suggest that it may be necessary to treat or remove contaminated streambed sediments in downstream reaches, as well as identify and treat nonpoint sources of metals. Recommendations for improvements to the model for metal transport in acid‐mine drainage impacted streams are made. These recommendations are being implemented by the U.S. Environmental Protection Agency. © 2009 Wiley Periodicals, Inc.     

Critical Review of Norms and Standards for Biodegradable Agricultural Plastics Part Ι. Biodegradation in Soil

A critical review of norms and standards and corresponding tests to determine the biodegradability in soil for biodegradable plastics, possibly applicable also to biodegradable agricultural plastics, is presented. There are only a few norms available at the international level about biodegradable plastics in soil. The criteria, parameters and testing methodologies for the characterization, labelling and validation of the agricultural plastic waste streams with respect to possible biodegradation in soil according to existing international standards are analysed while the relevant controversies are identified. To derive the best suited for agricultural plastics specs and testing methods, the possible developments or adaptation of available specs, is investigated. Considering the existing types of biodegradable plastic products in agriculture and their effective life management at the agricultural field, only a few norms appear to provide suitable tests that could be adapted, following appropriate research work, for testing biodegradability in soil under real field conditions. It is shown that some major revisions are needed, with the support of systematic research work, before a new universal norm and standard testing methods become available for testing agricultural plastics for biodegradation under real, and highly variable, soil conditions. Based on the analysis of the different norms and their content it appears necessary to incorporate provisions for transferability of results to different soils and climates, validation of tests through a positive reference and also, set prerequisites for soil media. Long term biodegradation in soil prediction is another open issue.     

Analysis of high-level waste glass performance by the physical and geochemical simulation code STRAG4

A source term release analysis code for high-level waste glass has been developed for simulation of long-term dissolution behavior under repository conditions. The STRAG4 code consists of models for (a) element diffusion in both the bulk glass and surface layer, (b) glass dissolution kinetics at the interface between glass and water, and (c) geochemical reactions of dissolved elements in underground water. The simulations for various conditions of glass dissolution, including a static and dynamic system, show accordance with the experimental observations even in the relatively complicated case where bentonite is present. Long-term dissolution analyses of a borosilicate waste glass were carried out as preliminary study. The calculations were achieved by considering detrimental effects due to interactions between the glass and surrounded materials which are presumed to be in a repository environment (i.e., compacted bentonite, corrosion products from the iron overpack, and underground water). The environmental conditions such as temperature and geochemical reactions are also taken into account in the calculations. The results suggest the life of the waste glass would be more than 50,000 years even if the glass surface area increased by a factor of 10 due to crack formation.