垃圾焚烧发电过程中的二次污染物控制处理技术

概述了二口恶英、重金属、酸性气体、灰渣等垃圾焚烧二次污染物的形成机理，并详细介绍了通过控制垃圾焚烧条件、尾气处理以及吸附等方法，可以有效控制二口恶英类污染物的排放；重金属的控制可以用除尘器或使用相应的吸附剂处理；采用较为成熟的烟气处理技术，可以控制处理酸性气体；灰渣可采用固化稳定化和酸或其他溶剂提出法处置。     

垃圾焚烧厂焚烧底灰的处理研究

系统地研究了常州市环境卫生综合厂垃圾焚烧车间的底灰。研究结果表明，根据中国现行的污染控制标准，该厂的底灰属于一般废物，可以以建筑垃圾的方式处理。但对底灰的分选和分类研究结果表明，底灰含有一定量的未燃烬的有机废物，也有一些可回收利用的废物。因此，底灰应该先分选后，再对无利用价值的渣土作填埋或其他处置。     

Effects of chlorides on emissions of toxic compounds in waste incineration: study on partitioning characteristics of heavy metal

Chlorides derived from plastics and food residue content in MSW will affect the formation and partitioning of metal chlorides in the incineration discharges. Our study investigated the effects of waste-derived chlorides on the partitioning of heavy metals in a single-metal combustion system. The results indicate that the heavy metal partitioning behaviors are mainly affected by the presence of chloride, alkaline metals (i.e., Na, K) and moisture in the wastes. The configuration of the metal partitioning is determined by the availability of chlorine, hydrogen, and alkaline metals, or the extent to which the elements may divide from their compounds at a given combustion temperature. The effects of chlorides, including PVC, C2Cl4, FeCl3, NaCl and KCl, were also discussed.     

Treatment Technologies for Hazardous Wastes: Part 1 Treatment Alternatives for Dioxin Wastes

The 1984 Amendments to the Resource Conservation and Recovery Act (RCRA), called the Hazardous and Solid Waste Amendments, (HSWA) direct the EPA to determine if dioxin bearing wastes should be prohibited from landfills. This determination is to made by November 1986. Barring a determination by the Agency that the land disposal of dioxin wastes does not represent a threat to the environment, ot that appropriate alternative treatment technology is not available, a land disposal prohibition would go into effect at that time.¹ The purpose of this paper is to discuss the state of the art for several treatment processes for dioxin wastes that have been proposed to be used instead of land disposal for disposing of solid and liquid wastes containing dioxins.     

Waste Streams,Technology, and State Requirements

Biomedical wastes are generated by hospitals, laboratories, animal research facilities, and by other institutional sources. The disposal of these wastes is coming under critical public scrutiny, and regulations are being promulgated to control their disposal. Incineration is not a final disposal method since it generates a solid residue (ash) which must be buried or otherwise disposed. The incineration process, however, renders the waste non-toxic, non-hazardous, and non-putrescible, and reduces the volume of material for ultimate disposal by an order of magnitude. In some instances, the residue may have high levels of heavy metals; however, this is the exception rather than the rule.     

Modelling trace metal partitioning in forest floors of northern soils near metal smelters

Trace metal (TM) mobility and toxicity varies with changing soil conditions. Geochemical models can account for the influence of soil characteristics on TM behaviour. We tested the effectiveness of the Stockholm humic model (SHM), and the NICA-Donnan model (NDM) to estimate partitioning coefficients (logKd) in 26 forest floor horizons of podzolic soils enriched in trace metals from deposition by metal smelters. We wanted to know if a consistent approach could be applied to model metal partitioning in forest floors without optimizing each individual soil. When optimized, the SHM reproduced the partitioning of Cd, Cu and Zn but not Pb. It was necessary to revise the affinity constants for the NDM to simultaneously simulate the partitioning of the four metals. Revised affinity constants for the NDM model based on a fixed definition of soil organic carbon, i.e., a fixed ratio of fulvic and humic acids per unit carbon, reproduced metal partitioning more effectively in an independent data set of 16 soils than the use of generic affinity constants available for these models. From the perspective of the applicability of these models to risk assessment, this result suggests geochemical models using affinity constants that have been verified and/or modified against multiple soils from a region can provide good estimates of metal partitioning on a regional scale.     

A Review of Treatment Alternatives for Wastes Containing Treatment Technologies For Hazardous Wastes: Part V

The Hazardous and Solid Waste Amendments to the Resource Conservation and Recovery Act direct the Environmental Protection Agency to determine the available treatment technologies for a number of hazardous waste streams, including halogenated organics. If it is determined that existing technology and capacity is sufficient for the safe management of the designated halogenated organic wastes, these wastes will be prohibited from land disposal, effective July 8,1987. This article summarizes the general characteristics and treatment alternatives for this waste category.     

Remediation of metal polluted mine soil with compost: co-composting versus incorporation

Trace element contamination of post-industrial sites represents a major environmental problem and sustainable management options for remediating them are required. This study compared two strategies for immobilizing trace elements (Cu, Pb, Zn, and As) in mine spoil: (1) co-composting contaminated soil with organic wastes and (2) conventional incorporation of mature compost into contaminated soil. Sequential chemical extraction of the soil was performed to determine temporal changes in trace element fractionation and bioavailability during composting and plant growth. We show that mine spoil can be co-composted successfully and this action causes significant shifts in metal availability. However, co-composting did not lead to significant differences in metal partitioning in soil or in plant metal uptake compared with simply mixing mine spoil with mature compost. Both treatments promoted plant growth and reduced metal accumulation in plants. We conclude that co-composting provides little additional benefit for remediating trace-element-polluted soil compared with incorporation of compost.     

Mercury Emissions from a Hazardous Waste Incinerator Equipped with a State-of-the-Art Wet Scrubber

Abstract

Over a six-week period, eleven tests were performed at the U.S. EPA Incineration Research Facility (IRF) in Jefferson, Arkansas to evaluate the fate of trace metals fed to a rotary kiln incinerator equipped with a Calvert Flux-Forcer/Condensation Scrubber pilot plant as the primary air pollution control system (APCS). Test variables were kiln temperature, ranging from 538 °C to 927 °C; waste feed chlorine content, ranging from 0% to 3.4%; and scrubber pressure drop, ranging from 8.2 kPa to 16.9 kPa. Mercury was among the six hazardous constituent trace metals fed to the IRF’s pilotscale rotary kiln incineration system as part of a synthetic waste feed. This paper focuses on the test results solely with respect to mercury.

As expected, mercury behaved as a very volatile metal throughout the tests; it was not detected in any kiln ash samples. Scrubber collection efficiency for mercury ranged from 67% to >99%, averaging 87%; this was somewhat lower than expected and may be attributable to low scrubber loadings.

The ability to collect and analyze representative scrubber water samples appears to have been affected by the waste feed chlorine content; detection of mercury at higher concentrations during high waste-chlorine-content tests is thought to be largely the result of the formation of mercuric chloride, a more water-soluble species, during those tests. As a result, no firm conclusions may be drawn regarding the true impact of waste feed chlorine content on mercury partitioning to the scrubber water. As expected, no significant relationship was observed between kiln exit-gas temperature and mercury partitioning, nor was there a significant relationship with scrubber pressure drop.     

Geochemical partitioning of Co, Cr, Fe, Sc and Zn in polluted and non-polluted marine sediments

The partitioning of Co, Cr, Fe, Sc and Zn into three fractions (reducible by acidified hydroxylamine hydrochloride, oxidizable by acidified hydrogen peroxide, and the residual after the previous extractions) of Saronikos Gulf surface sediments was determined by using a sequential extraction technique. The metal concentrations were determined by Instrumental Neutron Activation Analysis. With the exception of Sc, the metal content in the reducible and oxidizable fractions increases in the polluted sediments near the Athens Sewage Outfall (ASO) and a Fertilizer Plant (FP). In the non-polluted sediments, the residual fraction is the most important carrier for all metals examined. Oxidizable Cr and Zn correlate well with the organic carbon content of the sediments, but the reducible fraction (mainly Fe/Mn hydroxides) is the most important sink for Co, Cr, Fe and Zn in the polluted sediments near the ASO. The pyrite-rich wastes from the FP are influencing the geochemical partitioning of the metals examined in the sediments in front of the FP and, partially, in the sediments near the ASO.     

Characteristics of dioxins and metals emission from radwaste plasma arc melter system

This study investigated the emission characteristics of PCDD/Fs and the partitioning of three heavy metals (Cd, Hg and Pb) and two radioactive metal surrogates (Co and Cs) in a radwaste plasma arc melter system. Typical mixtures of low-level radioactive wastes were simulated as the trial burn surrogate wastes. The emission of PCDD/Fs and the partitioning of the metals were strongly influenced by the feed waste stream and melter operating temperature, respectively. The emissions of PCDD/Fs, cadmium and lead were greatly enhanced when the polyvinyl chloride was included in the feed waste stream. Most of the nonvolatile cobalt partitioned into the glass. A significant quantity of cesium, cadmium and lead was vaporized during the highest melter temperature test. A lower melter temperature resulted in more cesium, cadmium and lead species remaining in the glass. The results of this study suggest that wet scrubbing as well as a low-temperature two-step fine filtration, or both of them together could not effectively capture the gas-phase or fine particle phase PCDD/Fs and mercury species. In order to effectively treat low-level radioactive waste streams, the tested high-temperature melter should include an adsorption system, which could collect the gas-phase PCDD/Fs and mercury species.     

Medical Waste Disposal

Medical (biomedical) wastes pose numerous potential health and safety hazards. In addition to their infectious and toxic characteristics, the highly variable and inconsistent nature of medical waste streams has increased public concern about storage, treatment, transportation, and ultimate disposal.

In recent years, techniques have been developed to reduce human exposure to the toxic and infectious components of medical wastes. The most commonly used techniques include internal segregation, containment, and incineration. Other common techniques include grinding, shredding, and disinfection, e.g., autoclaving and chemical treatment followed by landfilling.

Of all the available technologies for medical waste treatment and disposal, incineration has been found to be the most effective method overall for destroying infectious and toxic material, volume reduction, and weight reduction in the medical waste stream, incineration destroys the broadest variety of medical waste constituents and can recover energy from the medical waste stream. Incineration also is an appropriate alternative to burial of human pathological remains.     

Simulating the response of metal contaminated lakes to reductions in atmospheric loading using a modified QWASI model

The changes in metal concentration following significant reductions in atmospheric metal loading of two nickel and copper contaminated lakes in Coniston Valley of the Sudbury Basin of Ontario, Canada were simulated by using steady-state and dynamic versions of a modified Quantitative Water Air Sediment Interaction (QWASI) Model. Metal partitioning and precipitation processes were quantified with the aid of US EPA's MINTEQA2 Model. The dynamic model successfully described the recovery of the two lakes and identified key input, loss and partitioning processes. A useful modelling strategy is to develop one or more steady-state models that give an approximate representation of conditions at defined times, then extend this to a dynamic version which can take into account the differing rates of response of components of the system. This modelling strategy can be used for designing and assessing remediation programs for metal contaminated lakes and watersheds.     

Metal partitioning and uptake in central Ontario forests

Evaluation of the potential environmental risk posed by metals depends to a great extent on modeling the fate and mobility of metals with soil-solution partitioning coefficients (Kd). However, the effect of biological cycling on metal partitioning is rarely considered in standard risk assessments. We determined soil-solution partitioning coefficients for 5 metals (Cd, Zn, Pb, Co and Ni) at 46 forested sites that border the Precambrian Shield in central Ontario, where soil pHaq varied from 3.9 to 8.1. Foliage from the dominant tree species and forest floor samples were also collected from each site to compare their metal levels with Kd predictions. Analogous to other studies, log Kd values for all metals were predicted by empirical linear regression with soil pH (r2=0.66-0.72), demonstrating that metal partitioning between soil and soil solution can be reliably predicted for relatively unpolluted forest mineral soils by soil pH. In contrast, whereas the so-called bioavailable water-soluble metal fraction could be predicted from soil pH, metal concentrations in foliage and the forest floor at each site were not consistently related to pH. Risk assessment of metals should take into account the role of biota in metal cycling and partitioning in forests, particularly if metal bio-accumulation and chronic toxicity in the food chain, rather than metal mobility in soils, are of primary concern.     

Evaluation on subcellular partitioning and biodynamics of pulse copper toxicity in tilapia reveals impacts of a major environmental disturbance

Fluctuation exposure of trace metal copper (Cu) is ubiquitous in aquatic environments. The purpose of this study was to investigate the impacts of chronically pulsed exposure on biodynamics and subcellular partitioning of Cu in freshwater tilapia (Oreochromis mossambicus). Long-term 28-day pulsed Cu exposure experiments were performed to explore subcellular partitioning and toxicokinetics/toxicodynamics of Cu in tilapia. Subcellular partitioning linking with a metal influx scheme was used to estimate detoxification and elimination rates. A biotic ligand model-based damage assessment model was used to take into account environmental effects and biological mechanisms of Cu toxicity. We demonstrated that the probability causing 50% of susceptibility risk in response to pulse Cu exposure in generic Taiwan aquaculture ponds was ~33% of Cu in adverse physiologically associated, metabolically active pool, implicating no significant susceptibility risk for tilapia. We suggest that our integrated ecotoxicological models linking chronic exposure measurements with subcellular partitioning can facilitate a risk assessment framework that provides a predictive tool for preventive susceptibility reduction strategies for freshwater fish exposed to pulse metal stressors.     

Allocation plasticity and plant-metal partitioning: meta-analytical perspectives in phytoremediation

In this meta-analysis of plant growth and metal uptake parameters, we selected 19 studies of heavy metal (HM) phytoremediation to evaluate trends of allocation plasticity and plant-metal partitioning in roots relative to shoots. We calculated indexes of biomass allocation and metal distribution for numerous metals and plant species among four families of interest for phytoremediation purposes (e.g. Brassicaceae, Fabaceae, Poaceae, and Solanaceae). We determined that plants shift their biomass and distribute metals more to roots than shoots possibly to circumvent the challenges of increasing soil-HM conditions. Although this shift is viewed as a stress-avoidance strategy complementing intrinsic stress-tolerance, our findings indicate that plants express different levels of allocation plasticity and metal partitioning depending on their overall growth strategy and status as ‘fast-grower’ or ‘slow-grower’ species. Accordingly, we propose a conceptual model of allocation plasticity and plant-metal partitioning comparing ‘fast-grower’ and ‘slow-grower’ strategies and outlining applications for remediation practices.     

Immobilization of metal wastes by reaction with H2S in anoxic basins

Metal wastes are produced in large quantities by a number of industries. Their disposal in isolated waste deposits is certain to cause many subsequent problems, because every material will sooner or later return to the geochemical cycle. The sealing of disposal sites usually starts to leak, often within a short time after the disposal site has been filled. The contained heavy metals are leached from the waste deposit and will contaminate the soil and the groundwater. It is evident that storage as metal sulfides in a permanently anoxic environment is the only safe way to handle metal wastes. The world's largest anoxic basin, the Black Sea, can serve as a georeactor. The metal wastes are sustainably transformed into harmless and immobile solids. These are incorporated in the lifeless bottom muds, where they are stored for millions of years.     

Treatment of Nonhazardous Petroleum-Contaminated Soils by Thermal Desorption Technologies

Spills, leaks, and accidental discharges of petroleum products have contaminated soil at thousands of sites in the United States. One remedial action technique for treating petroleum contaminated soil is the use of thermal desorption technologies.

This paper describes key elements of the U.S. Environmental Protection Agency report titled “Thermal Desorption Applications Manual for Treating Nonhazardous Petroleum Contaminated Soils.”¹ The applications manual describes the types, mechanical and operating characteristics of thermal desorption technologies that are commercially available to treat petroleum-contaminated soils. It also provides step-by-step procedures to rate the critical success factors influencing the general applicability of thermal desorption at a particular site. These factors include site, waste and soil characteristics, regulatory requirements, and process equipment design and operating characteristics. Procedures are provided to determine the types of thermal desorption systems that are most technically suitable for a given application and to determine whether on-site or off-site treatment is likely to be the most cost-effective alternative. Key factors that determine process economics are identified, and estimated cost ranges for treating petroleum-contaminated soils are presented. Spreadsheets are provided that can be used for performing cost analyses for specific applications.

The aforementioned report is applicable only to the treatment of petroleum-contaminated soils that are exempt from being classified as hazardous wastes under the Resource Conservation and Recovery Act (RCRA) or as toxic materials under the Toxic Substances Control Act (TSCA). Although much of the technical discussion in this paper is applicable to the treatment of both nonhazardous and hazardous ortoxic materials, permitting requirements and treatment costs are significantly different forthe individual categories of waste materials.     

Treatment Technologies For Hazardous Wastes: Part IV A Review of Alternative Treatment Processes for Metal Bearing Hazardous Waste Streams

The U.S. Congress and the U.S. Environmental Protection Agency believe that treatment and recovery techniques should be given maximum priority when considering methods for managing the nation's generated hazardous waste. A prohibition for the disposal of certain categories of hazardous wastes either directly onto or into the land without being treated to an accepted degree prior to such disposal practice has been promulgated.¹ Wastes containing toxic metals and cyanide complexes have been selected as a group to be restricted. Due to the high generation rate associated with this category, a large capacity of waste treatment processing will be required. Existing and emerging treatment alternatives which are or have the potential to be employed for waste treatment of metal bearing wastes are presented in this paper.