Heavy metal content of combustible municipal solid waste in Denmark.

Data on the heavy metal composition of outlets from Danish incinerators was used to estimate the concentration of Zn, Cu, Pb, Cr, Ni, Cd, As and Hg in combustible waste (wet as received) at 14 Danish incinerators, representing about 80% of the waste incinerated in Denmark. Zn (1020 mg kg(-1)), Cu (620 mg kg(-1)) and Pb (370 mg kg(-1)) showed the highest concentration, whereas Hg (0.6 mg kg(-1)) showed the lowest concentration. The variation among the incinerators was in most cases within a factor of two to three, except for Cr that in two cases showed unexplained high concentrations. The fact that the data represent many incinerators and, in several cases, observations from a period of 4 to 5 years provides a good statistical basis for evaluating the content of heavy metals in combustible Danish waste. Such data may be used for identifying incinerators receiving waste with high concentrations of heavy metals suggesting the introduction of source control, or, if repeated in time, the data must also be used for monitoring the impacts of national regulation controlling heavy metals. It is recommended that future investigations consider the use of sample digestion methods that ensure complete digestion in order to use the data for determining the total heavy metal content of waste.     

Heavy metal content in soil reclaimed from a municipal solid waste landfill

Residues reclaimed from a municipal solid waste (MSW) landfill were characterized for the concentrations of a number of heavy metals. The residue fractions analyzed included a fine fraction (<0.425 mm), an intermediate fraction (>0.425 and <6.3 mm) and a fraction consisting of paper products that could ultimately degrade to a smaller size. The intermediate fraction appeared to be organic in nature, while the fine fraction was more soil-like. In general, the metal concentrations were greatest in the intermediate fraction and lowest in the fine fraction. The effect of sample age on the elemental content was also investigated. The concentrations of several elements were greater in older samples (sample approximately 8 years in age) when compared to newer samples (sample approximately 3 years in age). Limitations associated with the land application of residual soil (composed of the fine and intermediate fractions) were assessed by comparing measured concentrations to regulatory threshold values. In general, most metal concentrations were below regulatory thresholds for use in unrestricted settings. At the concentrations measured, however, several elements might limit reuse options, depending on which regulatory threshold serves as a benchmark. Elevated concentrations of arsenic presented the greatest limitation with respect to common US thresholds while elevated cadmium concentrations presented the greatest limitation when compared to UK thresholds. The source of the arsenic was determined to be the waste, not the cover soil.     

Sensorized waste collection container for content estimation and collection optimization

The concurrent effects of a fast national growth rate, of a large and dense residential area and a pressing demand for urban environmental protection create a challenging framework for waste management in Pudong New Area, Shanghai. The complexity of context and procedures is indeed a primary concern of local municipal authorities due to problems related to the collection, transportation and processing of residential solid waste. In order to design and implement a suitable urban solid waste system, the first task is to forecast the quantity and variance of solid waste as it relates to residential population, consumer index, season, etc. The system here discussed addresses exactly these issues, by means of an intelligent, sensorized container. The container has been prepared and tested in the Pudong New Area, Shanghai.     

Economic viability study of a separate household waste collection in a developing country

This article reports a study of the economic viability of a separate household waste collection project, and considers its social and environmental benefits. The study was developed from the database obtained through the pilot project on separate collections in João Pessoa, the capital of Paraíba, in the northeast region of Brazil. The pilot project had been supported by the local municipal council since September 2000. The methodology applied to this study of economic viability is based on the economic quantification of the benefits and costs involved in the process of a separate collection of household waste. The benefits to the environment, owing to the reduction of the final disposal of household waste, were also evaluated. The results of this research are encouraging for the benefit cost relation (B/C) of both the quantified economic components and the environmental aspects. The values found for the relation B/C ranged from 1.27 to 1.77 depending on the economic quantification of the direct and indirect benefits to the components involved in the project, i.e., the waste collectors, the municipal council, the sellers of recycled material, and the recycling industry.     

Attitude towards the incorporation of the selective collection of biowaste in a municipal solid waste management system. A case study

European waste legislation has been encouraging for years the incorporation of selective collection systems for the biowaste fraction. European countries are therefore incorporating it into their current municipal solid waste management (MSWM) systems. However, this incorporation involves changes in the current waste management habits of households. In this paper, the attitude of the public towards the incorporation of selective collection of biowaste into an existing MSWM system in a Spanish municipality is analysed. A semi-structured telephone interview was used to obtain information regarding aspects such as: level of participation in current waste collection systems, willingness to participate in selective collection of biowaste, reasons and barriers that affect participation, willingness to pay for the incorporation of the selective collection of biowaste and the socioeconomic characteristics of citizens who are willing to participate and pay for selective collection of biowaste. The results showed that approximately 81% of the respondents were willing to participate in selective collection of biowaste. This percentage would increase until 89% if the Town Council provided specific waste bins and bags, since the main barrier to participate in the new selective collection system is the need to use specific waste bin and bags for the separation of biowaste. A logit response model was applied to estimate the average willingness to pay, obtaining an estimated mean of 7.5% on top of the current waste management annual tax. The relationship of willingness to participate and willingness to pay for the implementation of this new selective collection with the socioeconomic variables (age, gender, size of the household, work, education and income) was analysed. Chi-square independence tests and binary logistic regression was used for willingness to participate, not being obtained any significant relationship. Chi-square independence tests, ordinal logistic regression and ordinary linear regression was applied for willingness to pay, obtaining statistically significant relationship for most of the socioeconomic variables.     

Greenhouse gases emission from municipal waste management: The role of separate collection

The municipal solid waste management significantly contributes to the emission in the atmosphere of greenhouse gases (e.g. CO₂, CH₄, N₂O) and therefore the management process from collection to treatment and disposal has to be optimized in order to reduce these emissions. In this paper, starting from the average composition of undifferentiated municipal solid waste in Italy, the effect of separate collection on greenhouse gases emissions from municipal waste management has been assessed. Different combinations of separate collection scenarios and disposal options (i.e. landfilling and incineration) have been considered. The effect of energy recovery from waste both in landfills and incinerators has also been addressed. The results outline how a separate collection approach can have a significant effect on the emission of greenhouse gases and how wise municipal solid waste management, implying the adoption of Best Available Technologies (i.e. biogas recovery and exploitation system in landfills and energy recovery system in Waste to Energy plants), can not only significantly reduce greenhouse gases emissions but, in certain cases, can also make the overall process a carbon sink. Moreover it has been shown that separate collection of plastic is a major issue when dealing with global warming relevant emissions from municipal solid waste management.     

Sources of heavy metal contamination in Swedish wood waste used for combustion

In this paper, wood waste (RWW) recovered for heat production in Sweden was studied. Previous research has concluded that RWW contains elevated amounts of heavy metals, causing environmental problems during waste management. This study extends previous work on RWW by analysing which pollution sources cause this contamination. Using existing data on the metal contents in various materials, and the amounts of these materials in RWW, the share of the elevated amounts of metals in RWW that these materials explain was quantified. Six different materials occurring in RWW were studied and the results show that they explain from 70% to 100% of the amounts of arsenic, chromium, lead, copper and zinc in RWW. The most important materials contributing to contamination of RWW are surface-treated wood, industrial preservative-treated wood, plastic and galvanised fastening systems. These findings enable the development and evaluation of strategies aiming to decrease pollution and resource loss from handling RWW. It is argued that source separation and measures taken further downstream from the generation site, such as treatment, need to be combined to substantially decrease the amount of heavy metals in RWW.     

Sociological survey in a municipality with a high level separate collection programme in an area of historic unpopularity

Behaviours, opinions and knowledge of citizens on MSW and separate collection were investigated in the city of Mercato San Severino (about 22,000 people), in the Campania region of Southern Italy that is an area suffering from a serious solid waste emergency that has lasted over 17 years due to the absence of treatment facilities. The image of heaps of rubbish in the streets of Naples and other nearby cities is only one side of the coin. Mercato San Severino has adopted an effective kerbside collection system since 2001 and a pay-as-you-throw program during 2005, guaranteeing more than the minimum level of recycling required by the Italian legislation. Structured questionnaires were administered to a sample of 500 people in 2010. Chi-square tests of independence were applied to state whether the differences were statistically significant (5%). About 90% of the sample stated that the success of the separate collection program was due to either the citizens and local authority or only the local authority, highlighting the leading role of the local authority and confirming that trust is the key to any social program success. The registered level of knowledge was better than that of nearby university students and citizens. The higher the education level, the greater the level of knowledge was.     

Heavy metal removal from contaminated sludge for land application: a review

In recent years, various methods for heavy metal removal from sewage sludge have been extensively studied in order to minimize the prospective health risks of sludge during land application. In this paper, a comparative review and critical analysis of the application of chemical extraction, bioleaching, electroreclamation, and supercritical fluid extraction (SFE), in removing heavy metals from contaminated sludges is presented. Moreover, speciation studies, which can indicate ease of leachability of the different forms of heavy metals in sludge, are also presented. Experimental studies revealed a broad range in metal extraction efficiencies of the different extraction technologies. Acid treatment seemed to effectively remove Cd, attaining as much as 100% removal for some studies, as compared to bioleaching. SFE also gave higher removal efficiency than bioleaching. Cr, Pb and Ni seemed to be also effectively removed by the acid treatment. For the removal of Cu, Mn and Zn, the bioleaching process seemed to be appropriate with maximum removal efficiencies of 91%, 93% and 96% for the three metals, respectively, and as high as 64% minimum removal efficiency for Zn. The SFE process also gave good results for Cu, Mn and Zn removal. Electroreclamation exhibited better removal efficiency for Mn, but is still inferior to acid treatment and bioleaching processes. For chemical extraction, because of the adverse impacts that can result from the use of inorganic acids and complexing agents, interest can be directed more toward utilizing organic acids as extracting agents because of their biodegradability and capability to remove metals at mildly acidic condition, hence requiring less acid. The bioleaching process, although it seems to give a higher yield of metal extraction with lower chemical cost than chemical extraction, may be limited by the inability of the system to cope with the natural environmental conditions, requires strict monitoring of aeration rate and temperature and has applicability to only low sludge solids concentration. A full-scale study would be useful to better assess the efficiency of the process. The electroreclamation technology is limited by its relatively higher energy consumption and limited applicability to sludge. The SFE method, on the other hand, is limited by the complexity of the process and the cost of ligands suitable for effective metal extraction. Both of these technologies are still in their early stage of application and hence there is a need for further basic and applied studies. Finally, the common advantage for almost all treatment technologies studied is that the extraction efficiencies for some metals are high enough to remove metals from sludge to levels suitable for land application.     

Technical, economic and environmental analysis of a MSW kerbside separate collection system applied to small communities

The main aim of this study was to evaluate the costs and environmental impacts induced by a fixed model of MSW kerbside separate collection system for communities up to 10,000 inhabitants, in order to evaluate the convenience for the smaller municipalities to unite and form more economically and environmentally sound systems. This topic is important not only due to the large number of small municipalities (e.g. in Italy 72% of the municipalities has less than 5000 inhabitants) but also to the fact that separate collection systems are typically designed to take into account only the technical and economic aspects, which is a practice but not acceptable in the light of the sustainable development paradigm. In economic terms, between 1000 and 4000 inhabitants, the annual per capita cost for vehicles and personnel decreased, with a maximum at approximately 180€/inhabitants/year; while, from 5000 up to 10,000 inhabitants, the annual per capita cost was practically constant and equal to about 80€/inhabitants/year. For the municipalities of less than 5000 inhabitants, from an economic point of view the aggregation is always advantageous. The environmental impacts were calculated by means of the Life Cycle Assessment tool SimaPro 7.1, while the economic-environmental convenience was evaluated by combining in a simple multicriteria analysis, the annual total per capita cost (€/inhabitants/year) and the annual total per capita environmental impact (kEco-indicator point/inhabitants/year), giving the same importance to each criteria. The analysis was performed by means of the Paired Comparison Technique using the Simple Additive Weighting method. The economic and environmental convenience of the aggregation diminishes with the size of the municipalities: for less than 4000 inhabitants, the aggregation was almost always advantageous (91.7%); while, for more than or equal to 5000 inhabitants, the aggregation was convenient only in 33.3% of the cases. On the whole, out of 45 cases examined, for the municipalities from 1000 to 9000 inhabitants, the aggregation was both economically and environmentally convenient in 60.0% of the cases.     

Implementing separate waste collection and mechanical biological waste treatment in South Africa: A comparison with Austria and England

The degradation of organic compounds found in municipal solid waste (MSW) under the anaerobic landfill conditions produces gas and liquid emissions that can protract well into the landfill after-care period. The European Landfill Directives regulate the amount and nature of the organic compounds disposed into landfills. In South Africa and other developing countries, MSW is still landfilled without any kind of pre-treatment. This paper presents a pilot project of mechanical biological waste treatment (MBWT) in South Africa implemented at municipal level in the city of Durban using passively aerated open windrows. Based on case studies from Austria, England and South Africa, a waste minimisation model which can facilitate full-scale implementation of MBWT in developing countries is presented. MSW was treated in open windrows for 8 weeks. Composting temperature reached a maximum of 65 °C in less than 10 days. The results of eluate tests on waste samples from the windrows at the end of composting show a reduction of BOD₅ and BOD₅/COD ratios equal to 35.7% and 16.7%, respectively. The percent waste composition of the treated MSW was 28.3% putrescibles, 17.4% garden refuse, 13.3% plastic, 12.4% fabrics, 12% paper and other elements. The waste composition shows that more than 40% of un-treated organic material and also more than 40% non-biodegradable and recyclable materials are still landfilled without any form of biological treatment or resource recovery. A simple wet and dry waste collection model can promote recycling, treatment of biological waste before landfilling, resource recovery, labour intensive jobs and hence sustainable landfilling in the South African scenario as well as in similar developing countries.     

Valorization of titanium metal wastes as tanning agent used in leather industry

The development of new tanning agents and new technologies in the leather sector is required to cope with the increasingly higher environmental pressure on the current tanning materials and processes such as tanning with chromium salts. In this paper, the use of titanium wastes (cuttings) resulting from the process of obtaining highly pure titanium (ingots), for the synthesis of new tanning agent and tanning bovine hides with new tanning agent, as alternative to tanning with chromium salts are investigated. For this purpose, Ti waste and Ti-based tanning agent were characterized for metal content by inductively coupled plasma mass spectrometry (ICP-MS) and chemical analysis; the tanned leather (wet white leather) was characterized by Scanning Electron Microscope/Energy Dispersive Using X-ray (Analysis). SEM/EDX analysis for metal content; Differential scanning calorimetric (DSC), Micro-Hot-Table and standard shrinkage temperature showing a hydrothermal stability (ranged from 75.3 to 77 °C) and chemical analysis showing the leather is tanned and can be processed through the subsequent mechanical operations (splitting, shaving). On the other hand, an analysis of major minor trace substances from Ti-end waste (especially vanadium content) in new tanning agent and wet white leather (not detected) and residue stream was performed and showed that leachability of vanadium is acceptable. The results obtained show that new tanning agent obtained from Ti end waste can be used for tanning bovine hides, as eco-friendly alternative for chrome tanning.     

电力系统常用油品中磨损金属测定方法的研究

采用干、湿两种消解方法。进行了电力系统常用油品的消解方法研究，对消解后试液采用ICP／AES无机进样系统进行测定。通过对测定结果的统计、处理和汇总，以及方法精密度和准确度验证，最终得出了用直接燃烧灰化法代替ASTMD5708标准中的湿法消解来进行样品消解浓缩，使整个操作更为简便、省时。     

Heavy metal speciation in various types of fly ash from municipal solid waste incinerator

Fly ash (FA) from municipal solid waste incinerators has been known as hazardous waste, which is mostly because of the high content of heavy metal and dioxins. Besides the content, the form of the heavy metals in fly ash is also very important, because it is tightly related with the leaching behavior of fly ash in diverse circumstances. To evaluate the environment potential risk of fly ash, the Tessier chemical extraction method was adopted. In this study, four kinds of fly ash were examined, one sample from China (CFA) and the other three from Japan (RFA, CaFA and NaFA). Five metal elements were detected and they were Ni, Cr, Cd, Pb, and Cu. The result of total heavy metals’ concentration showed CFA has the lowest content. As to the Tessier chemical extraction experiments, the results show that Cd, Pb, and Cu have higher leaching risk in the environment than other heavy metals. The result of leaching test experiment showed that the more exchangeable speciation of Cd, Cr and Pb in FA, the more it could leach out in natural environment.     

脱硫用电石渣的重金属浸出特性及其对环境的影响

针对电厂用脱硫剂电石渣,分析了其基本组成及重金属浸出特性,为电厂脱硫设施的参数设计和环境影响评价提供依据和参考。研究结果表明,脱硫用电石渣主要成分为Ca（OH）2,含量在40%～50%之间;在8种重金属的含量中,只有Cd的含量超出土壤质量三级标准的要求,基本不会对土壤造成污染。浸出毒性试验表明,电石渣及其脱硫产物属于非危险废物,其各种重金属的浸出浓度主要受其本身重金属含量和最终pH的影响,这种影响在Pb、Cu和Cd上表现得较为突出,酸性环境下更有利于他们的浸出;碱性环境下有利于Pb和Ni的浸出。     

Public opinion and awareness towards MSW and separate collection programmes: A sociological procedure for selecting areas and citizens with a low level of knowledge

The principal aim of this study was to define and apply a procedure based on a structured questionnaire survey useful to analyze the people’s environmental knowledge in order to select the areas and age groups with a low level of knowledge in a municipality (in Southern Italy) and, therefore, suggest a specific educational campaign for each. The detailed sampling procedure made it possible to carry out a meticulous statistical analysis of the results. The youngest and oldest people showed the lowest level of awareness for each district. A high level of education did not necessarily imply a high level of environmental awareness as well as a greater acceptance of MSW facilities. The satisfaction level of the recycling program was higher amongst the oldest age group. All the citizens in the several areas were unanimous in pointing out the presence of dirt in the street as the main shortcoming of the bring separate collection program. Only the youngest age group self-criticised, considering that they revealed a low level of participation to the separate collection program. While, the oldest people retaining them less influential, claimed that the citizens were not responsible for the failure of the separate collection program. The prevailing opinion of the sample was that people protested against the construction of waste facilities because they were not well-informed, with the most significant opinion of all the age subdivisions being that incineration is a hazardous treatment. The presence of criminal organizations was indicated as the main reason why the Campania Region suffers a serious solid waste emergency. While, the percentage of people pointing their finger at politicians increases with the average age of the respondents with there being a very strong correlation (r² = 0.9903).     

Effect of seasonal changes in quantities of biowaste on full scale anaerobic digester performance

A 750,000l digester located in Roppen/Austria was studied over a 2-year period. The concentrations and amounts of CH4, H2, CO2 and H2S and several other process parameters like temperature, retention time, dry weight and input of substrate were registered continuously. On a weekly scale the pH and the concentrations of NH4+ -N and volatile fatty acids (acetic, butyric, iso-butyric, propionic, valeric and iso-valeric acid) were measured. The data show a similar pattern of seasonal gas production over 2 years of monitoring. The consumption of VFA and not the hydrogenotrophic CH4 production appeared to be the limiting factor for the investigated digestion process. Whereas the changes in pH and the concentrations of most VFA did not correspond with changes in biogas production, the ratio of acetic to propionic acid and the concentration of H2 appeared to be useful indicators for reactor performance. However, the most influential factors for the anaerobic digestion process were the amount and the quality of input material, which distinctly changed throughout the year.     

The use of life cycle assessment for the comparison of biowaste composting at home and full scale

Environmental impacts and gaseous emissions associated to home and industrial composting of the source-separated organic fraction of municipal solid waste have been evaluated using the environmental tool of life cycle assessment (LCA). Experimental data of both scenarios were experimentally collected. The functional unit used was one ton of organic waste. Ammonia, methane and nitrous oxide released from home composting (HC) were more than five times higher than those of industrial composting (IC) but the latter involved within 2 and 53 times more consumption or generation of transport, energy, water, infrastructures, waste and Volatile Organic Compounds (VOCs) emissions than HC. Therefore, results indicated that IC was more impacting than HC for four of the impact categories considered (abiotic depletion, ozone layer depletion, photochemical oxidation and cumulative energy demand) and less impacting for the other three (acidification, eutrophication and global warming). Production of composting bin and gaseous emissions are the main responsible for the HC impacts, whereas for IC the main contributions come from collection and transportation of organic waste, electricity consumption, dumped waste and VOCs emission. These results suggest that HC may be an interesting alternative or complement to IC in low density areas of population.     

Heavy metal mobility and potential availability in animal manure: using a sequential extraction procedure

In this study, dairy cow manure, goat manure, and chicken manure were collected from three farms and analyzed to find out the concentration of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn. The concentration and potential of mobility and availability of heavy metals were studied in the animal manure samples. BCR Sequential extraction procedure was used to determine the binding forms of the metals. In this study, pseudo total concentrations of Mn and Zn were found out to be predominant in all the types of animal manure samples. According to the results, it was traced that Cr, Cu, and Ni were observed to be at the second highest level while Cd, Co, and Pb were seen at the lowest level in all the manure samples. When extractable amounts of heavy metals are taken into consideration, it is seen that the amount of the mobile fractions of heavy metals except for Cr and Ni are higher in comparison with that of immobile fraction in all the animal manure samples. It was also viewed that Mn, Cd, and Zn are more available in dairy cow manure and chicken manure whereas Cd, Co, and Mn are more available in goat manure.     

广州市生活垃圾分类收集跟踪调查及分析

通过对广州市八个生活垃圾分类收集示范点的调研,指出了当前推广垃圾分类收集工作中尚存在的问题,并提出解决的对策.