Exposure to bioaerosols and noise at a Finnish dry waste treatment plant.

Repeated measurements were carried out during two different campaigns between 1998 and 2001 to assess the occupational hygiene at a Finnish dry waste treatment plant. The analytical determinations were done in four different places within the processing hall of the plant: near a conveyor belt, near a jigger screen, near an after-crusher and near a bailer. Measurements were also carried out in a coffee room for employees. Concentrations of bacteria, fungi and actinomycetes were determined by two methods (six-stage impactor and Camnea method) and levels of endotoxins, dust and noise were also investigated. High concentrations of microbes and endotoxins and the noise level were found to be a real problem in the waste processing hall. Microbe concentrations were highest during management of the dry waste fraction. Endotoxin concentrations all exceeded the threshold value of 200 EU m(-3) irrespective of the measurement place, with the only exception near the after-crusher where the average concentration was always as low as 60 EU m(-3). The noise level exceeded the Finnish threshold value of 85 dBA. Problems were not easily solved through technical modifications and more radical improvements are needed. Improvements in reliability are also required in the measuring methods before their application in waste treatment plants. In particular, a new method of dust collection is recommended.     

Mechanical-biological waste treatment and the associated occupational hygiene in Finland

A special feature of waste management in Finland has been the emphasis on the source separation of kitchen biowaste (catering waste); more than two-thirds of the Finnish population participates in this separation. Source-separated biowaste is usually treated by composting. The biowaste of about 5% of the population is handled by mechanical-biological treatment. A waste treatment plant at Mustasaari is the only plant in Finland using digestion for kitchen biowaste. For the protection of their employees, the plant owners commissioned a study on environmental factors and occupational hygiene in the plant area. During 1998-2000 the concentrations of dust, microbes and endotoxins and noise levels were investigated to identify possible problems at the plant. Three different work areas were investigated: the pre-processing and crushing hall, the bioreactor hall and the drying hall. Employees were asked about work-related health problems. Some problems with occupational hygiene were identified: concentrations of microbes and endotoxins may increase to levels harmful to health during waste crushing and in the bioreactor hall. Because employees complained of symptoms such as dry cough and rash or itching appearing once or twice a month, it is advisable to use respirator masks (class P3) during dusty working phases. The noise level in the drying hall exceeded the Finnish threshold value of 85 dBA. Qualitatively harmful factors for the health of employees are similar in all closed waste treatment plants in Finland. Quantitatively, however, the situation at the Mustasaari treatment plant is better than at some Finnish dry waste treatment plants. Therefore is reasonable to conclude that mechanical sorting, which produces a dry waste fraction for combustion and a biowaste fraction for anaerobic treatment, is in terms of occupational hygiene better for employees than combined aerobic treatment and dry waste treatment.     

Occupational hygiene in terms of volatile organic compounds (VOCs) and bioaerosols at two solid waste management plants in Finland

Factors affecting occupational hygiene were measured at the solid waste transferring plant at Hyvinkää and at the optic separation plant in Hämeenlinna. Measurements consisted of volatile organic compounds (VOCs) and bioaerosols including microbes, dust and endotoxins.The most abundant compounds in both of the plants were aliphatic and aromatic hydrocarbons, esters of carboxylic acids, ketones and terpenes. In terms of odour generation, the most important emissions were acetic acid, 2,3-butanedione, ethyl acetate, alpha-pinene and limonene due to their low threshold odour concentrations. At the optic waste separation plant, limonene occurred at the highest concentration of all single compounds of identified VOCs. The concentration of any single volatile organic compound did not exceed the occupational exposure limit (OEL) concentration. However, 2,3-butanedione as a health risk compound is discussed based on recent scientific findings linking it to lung disease.Microbe and dust concentrations were low at the waste transferring plant. Only endotoxin concentrations may cause health problems; the average concentration inside the plant was 425 EU/m³ which clearly exceeded the threshold value of 90 EU/m³. In the wheel loader cabin the endotoxin concentrations were below 1 EU/m³. High microbial and endotoxin concentrations were measured in the processing hall at the optic waste separation plant. The average concentration of endotoxins was found to be 10,980 EU/m³, a concentration which may cause health risks. Concentrations of viable fungi were quite high in few measurements in the control room. The most problematic factor was endotoxins whose average measured concentrations was 4853 EU/m³.     

Work safety in waste treatment

Accident risks in waste treatment were studied at five sanitary landfills, two plants using mainly manual sorting and one incineration plant in southern Finland. Work hazards were detected by means of safety analysis. In addition, accident statistics were used. Work safety problems were found at all work stages. At the sanitary landfills, the major safety problems were posed by operation of the compactor or other machinery and by hazardous wastes. In waste sorting, common problems are odour and dust, lacerations and back injuries. Falling into the waste compactor or paper silos may cause fatal injury and its probability was also high. The highest noise level measured was 97 dB(A). In waste incineration, the most serious hazards were caused by fires, clogging of the funnels and cleaning of the grate. Most deficiencies in work safety can be remedied at a moderate price. The corrective measures involve technical solutions, working methods, supervision, training and occupational health services. The accident rates for workers in the four waste treatment plants were slightly lower than the average for industry.     

Combined incineration of industrial wastes with in-plant residues in fluidized-bed utility boilers--decision relevant factors.

In Austria more than 50% of the high-calorific industrial residues and wastes generated are utilized for energy recovery in industrial utility boilers. This study investigated full-scale trials of combined incineration of in-plant residues with various industrial wastes. These trials were carried out in order to learn how the alternatively used fuel influences the incineration process itself as well as the quantity and quality of the various incineration products. The currently used fuel, which consisted of in-plant residues as well as externally acquired waste wood and the refuse-derived fuel (RDF) mixtures used during the full-scale trials are characterized in terms of material composition as well as chemical and physical parameters. An input-output mass balance for the incineration plant (two fluidized bed combustion units, 20 and 30 MW, respectively) has been established, based on the data collected during the full-scale incineration trials. Furthermore, pollutant concentrations in the off-gas as well as the solid incineration residue are reported. It is not only the pollutant content but also a variety of other internal as well as external factors that have to be considered if a company is to decide whether or not to thermally utilize specific waste types. Therefore a strengths and weaknesses profile for several types of waste and the specific industrial boiler is also presented.     

Report: environmental assessment of Darmstadt (Germany) municipal waste incineration plant.

The focus of this study was the emissions from waste incineration plants using Darmstadt (Germany) waste incineration plant as an example. In the study the emissions generated by incineration of the waste were considered using three different approaches. Initially the emissions from the waste incineration plant were assessed as part of the impact of waste management systems on the environment by using a Municipal Solid Waste Management System (MSWMS) assessment tool (also called: LCA-IWM assessment tool). This was followed by a comparison between the optimal waste incineration process and the real situation. Finally a comparison was made between the emissions from the incineration plant and the emissions from a vehicle.     

Airborne contaminants at waste treatment plants

Airborne contaminants in Finnish waste treatment plants were studied at two plants using mainly manual sorting and one incineration plant. Air samples were analysed for mesophilic and thermotolerant bacteria, mesophilic fungi, endotoxin, dust and heavy metals (lead, cadmium). The concentrations of mesophilic bacteria in the working air of the waste treatment plants were under 2 × 10⁴ colony forming units (cfu) m⁻³ and the concentrations of mesophilic fungi were under 7 × 10⁴ cfu m⁻³. There was no seasonal variation in the concentrations of bacteria, but the concentrations of fungi were highest in autumn at the waste incineration plant. The concentrations of microbes recorded with two sampling methods, the Andersen and Nuclepore filter methods, differed but were usually of the same order of magnitude. The identified bacteria did not include any potent pathogens. In manual sorting the level of organic dust reached 38 mg m⁻³, whereas the 8-h hygiene limit value for organic dust is 5mg m⁻³ and the 15-min hygiene limit value is 10 mg m⁻³. The endotoxin levels were all below 30 ng m⁻³ and the concentrations of heavy metals were low.     

An assessment of the current and future options for domestic waste management in Kaunas, Lithuania.

The main purpose of this study was to carry out a retrospective analysis of solid waste generation in Kaunas city from 1994 to 2003 and to calculate the theoretical waste generation in the future. This paper also presents measurements of the annual variations of waste amounts and calculations on a theoretical waste incineration facility. Two waste treatment scenarios were considered. Scenario A: waste deposit at the landfill with 'implementation of domestic waste separation and recycling'. Scenario B: waste removal to a landfill with 'multi-treatment: household separation, recycling and energetic recovery'. Three levels of waste treatment were proposed. The first level was implementation of the recycling system, which included household waste separation. The next step involved mechanical-biological treatment. The third level was the construction and operation of a new waste incineration plant in Kaunas. Two sites in Kaunas city were proposed; however, more detailed analysis, including the economic factors, will need to be done.     

Simulation of the flue gas cleaning system of an RDF incineration power plant

Because of the stringent pollutant emission standards introduced with the European Union guidelines for waste incineration, it is very important to optimize the flue gas cleaning systems which are able to result in a low environmental impact according to the emission limits. In this paper a thermochemical model has been proposed for the simulation of the flue gas cleaning system of an RDF incineration plant. The model simulates the operation of the flue-gas treatment section and the combustion section by using a simplified approach. The combustion includes the grate incinerator and the post-combustion chamber, while the cleaning section includes the NO(x) reduction process (urea injection) and the scrubbing of SO(2) and HCl (Ca(OH)(2) as sorbent). The modelling has been conducted by means of ASPEN PLUS code. The simulation results have been validated with the operating data. The model proposed by the authors can be a useful tool in both evaluating the efficiency of the gas cleaning system by verifying the environmental pollution of an incinerator power plant in nominal operating conditions and in forecasting the efficiency of the cleaning system in off-design operating conditions.     

Why energy from waste incineration is an essential component of environmentally responsible waste management

This paper outlines the key factors involved in adopting energy from waste incineration (EfWI) as part of a waste management strategy. Incineration means all forms of controlled direct combustion of waste. 'Emerging' technologies, such as gasification, are, in the author's view, 5 to 10 years from proven commercial application. The strict combustion regimen employed and the emissions therefrom are detailed. It is shown that EfWI merits consideration as an integral part of an environmentally responsible and sustainable waste management strategy, where suitable quantities of waste are available.     

Combustion characteristics of Malaysian municipal solid waste and predictions of air flow in a rotary kiln incinerator

Malaysia is in dire need of alternatives to landfilling for solid waste management. Recently, landfills have faced the problems of overfilling, overflowing of leachates leading to pollution of water resources, and uncontrolled dust emissions adversely affecting the local environment. With the rising cost of urbanization coupled with the high rate of waste generation, one possible method of waste treatment that is receiving particular attention by the government is incineration. Incineration of solid waste is rather new in Malaysia, with limited usage in handling small sources of waste generation such as the municipal solid waste (MSW) of resort islands; however, its potential in ameliorating the problems associated with solid waste treatment may make it an attractive alternative to landfill. This article presents the results of test runs conducted to investigate the performance of a locally designed and manufactured rotary kiln incinerator (RKI). The test runs were conducted using MSW collected from the Shah Alam municipality. The combustion efficiency was analyzed by looking at the temperature profiles and chemical species concentrations. To complement the combustion characteristics measurements, predictions of the air flow in the incinerator during the process were also investigated. The overall performance of the RKI suggests that it is suitable for treating MSW.     

Life cycle assessment of solid refuse fuel production from MSW in Korea

Solid refuse fuel (SRF) produced from waste materials is a promising fuel that can be utilized for energy recovery in industries. This study considered both characterization and weighting modeling as life cycle assessment (LCA) results. This study aimed to analyze the flows of materials and energy and to evaluate the environmental impact of SRF plants using LCA and compared them with an incineration plant. Based on the results of material and energy flow analysis, SRF products had various energy potentials depending on the treatment method of municipal solid waste (MSW) and replaced the current fossil fuels by SRF combustion. Global impacts were mainly influenced by energy consumption, especially drying methods in the production of SRF, and affected the results of the weighting analysis. The SRF plant with a bio-drying option was evaluated as the best effective practice in the weighting analysis. The LCA results in this study indicated 0.021–9.88 points according to drying methods for SRF production and 1.38 points for incineration. In the sensitivity analysis, the environmental impact of SRF production was found to be significantly affected by the drying methods for MSW and the utilization of fossil energy. Thus, improvement of the drying options could significantly reduce the environmental impact.     

Mechanisms contributing to the thermal analysis of waste incineration bottom ash and quantification of different carbon species

The focus of this study was to identify the main compounds affecting the weight changes of bottom ash (BA) in conventional loss on ignition (LOI) tests and to obtain a better understanding of the individual processes in heterogeneous (waste) materials such as BA. Evaluations were performed on BA samples from a refuse derived fuel incineration (RDF-I) plant and a hospital waste incineration (HW-I) plant using thermogravimetric analysis and subsequent mass spectrometry (TG–MS) analysis of the gaseous thermal decomposition products. Results of TG–MS analysis on RDF-I BA indicated that the LOI measured at 550 °C was due to moisture evaporation and dehydration of Ca(OH)₂ and hydrocalumite. Results for the HW-I BA showed that LOI at 550 °C was predominantly related to the elemental carbon (EC) content of the sample. Decomposition of CaCO₃ around 700 °C was identified in both materials. In addition, we have identified reaction mechanisms that underestimate the EC and overestimate the CaCO₃ contents of the HW-I BA during TG–MS analyses. These types of artefacts are expected to occur also when conventional LOI methods are adopted, in particular for materials that contain CaO/Ca(OH)₂ in combination with EC and/or organic carbon, such as e.g. municipal solid waste incineration (MSWI) bottom and fly ashes. We suggest that the same mechanisms that we have found (i.e. in situ carbonation) can also occur during combustion of the waste in the incinerator (between 450 and 650 °C) demonstrating that the presence of carbonate in bottom ash is not necessarily indicative for weathering. These results may also give direction to further optimization of waste incineration technologies with regard to stimulating in situ carbonation during incineration and subsequent potential improvement of the leaching behavior of bottom ash.     

Laboratory scale studies on gaseous emissions generated by the incineration of an artificial automotive shredder residue presenting a critical composition

Car manufacturers must eliminate automotive shredder residues (ASR). Two ways of incineration are of interest: at 850°C in municipal waste incinerators or at higher temperatures, above 1100°C in cement plants. These processes reduce the mass and the volume of waste to be disposed of in landfills and energy recovery might be possible. Regulations govern the emission of gaseous effluents to control environmental risk. To determine gaseous effluents from a pilot sacle or an industrial incineration plant, an artificial ASR was made by mixing three representative organic polymers present in the real ASR, namely polyvinylchloride, polyurethane and rubber. This mixture was incinerated at 850 and 1100°C in laboratory experiments and the analyses of the principal gaseous effluents such as carbon oxides, nitrogen oxides, volatile organic compounds, hydrochloric and hydrocyanic acids and sulphur compounds are presented and discussed. Lastly, in order to simulate artificial ASR behaviour, the composition of the combustion gases at equilibrium was calculated using a Gibbs energy minimisation code.     

Results of the German dioxin measurement programme at MSW incinerators

This paper described the findings and data resulting from the German National Dioxin Measurement Programme at 11 plants with 15 incineration units. The programme's main focus was to provide answers to the question of the causes of dioxins and furans formation in the plant and to look for ways to reduce dioxin and furan emissions, including waste management measures and technical measures taken inside the plants. The investigations confirmed the finding that a major proportion of the dioxin and furan emissions is due to de novo synthesis. Two areas have to be mentioned here, the cooling zone behind the combustion chamber and the dust removal system.Significant differences in dioxin and furan concentration levels were ascertained between variations of operating parameters, e.g. much air, little air, extremely unfavourable operating conditions (i.e. start-up and shut-down without auxiliary burners) and the normal operating conditions specific to a plant. To comply the limit value of 0.1 ng I-TE m⁻³ it is necessary that conventional thermal treatment plants take additional measures to remove dioxins and furans from the flue gas. The measurements were carried out from 1985 to 1990. In addition, samples of fractions of household waste were analysed for their dioxins and furans.     

Assessment and comparison of the environmental performances of a regional incinerator network

In Emilia-Romagna region (Northern Italy) the integrated waste treatment system consists of material collection and recycling, incineration with energy recovery and landfill as final disposal. In particular, at least one incineration plant is working in almost every province of the region. In this work, a screening life cycle assessment approach is applied to seven different incinerators, to compare the different plant technologies and identify the most relevant environmental impacts and processes. The characterization method used in the life cycle impact assessment step is Eco-indicator 99. The functional unit is 1 ton of waste input. As a first result, it can be noted that while the combustion systems are rather similar, the main variables are ascribable to gas cleaning options and efficiency in energy recovery, which result in quite different environmental performances. Among heavy metals, particular attention must be paid to Cd and As, due to their high toxicity, despite their low quantities. The impact due to dioxin emission is orders of magnitude lower than other contaminants (e.g., heavy metals). Furthermore, a catalytic system could be useful for a complete removal of organic contaminants and for a more effective abatement of nitrogen oxides. Finally, the environmental impact assessment sorts the various plants according to their age, i.e., the most recent plants provide the best environmental performances for the same quantity of combusted waste.     

Recovery and distribution of incinerated aluminum packaging waste

A study was performed into relations between physical properties of aluminum packaging waste and the corresponding aluminum scraps in bottom ash from three typical incineration processes. First, Dutch municipal solid waste incineration (MSWI) bottom ash was analyzed for the identifiable beverage can alloy scraps in the +2mm size ranges using chemical detection and X-ray fluorescence. Second, laboratory-scale pot furnace tests were conducted to investigate the relations between aluminum packaging in base household waste and the corresponding metal recovery rates. The representative packaging wastes include beverage cans, foil containers and thin foils. Third, small samples of aluminum packaging waste were incinerated in a high-temperature oven to determine leading factors influencing metal recovery rates. Packaging properties, combustion conditions, presence of magnesium and some specific contaminants commonly found in household waste were investigated independently in the high-temperature oven. In 2007, the bottom ash (+2mm fraction) from the AEB MSWI plant was estimated to be enriched by 0.1 wt.% of aluminum beverage cans scrap. Extrapolating from this number, the recovery potential of all eleven MSWI plants in the Netherlands is estimated at 720 ton of aluminum cans scrap. More than 85 wt.% of this estimate would end up in +6mm size fractions and were amenable for efficient recycling. The pot furnace tests showed that the average recovery rate of metallic aluminum typically decreases from beverage cans (93 wt.%) to foil containers (85 wt.%) to thin foils (77 wt.%). The oven tests showed that in order of decreasing impact the main factors promoting metallic aluminum losses are the packaging type, combustion temperature, residence time and salt contamination. To a lesser degree magnesium as alloying element, smaller packaging size and basic contaminations may also promote losses.     

Waste disposal technology transfer matching requirement clusters for waste disposal facilities in China

Even though technology transfer has been part of development aid programmes for many decades, it has more often than not failed to come to fruition. One reason is the absence of simple guidelines or decision making tools that help operators or plant owners to decide on the most suitable technology to adopt. Practical suggestions for choosing the most suitable technology to combat a specific problem are hard to get and technology drawbacks are not sufficiently highlighted. Western counterparts in technology transfer or development projects often underestimate or don’t sufficiently account for the high investment costs for the imported incineration plant; the differing nature of Chinese MSW; the need for trained manpower; and the need to treat flue gas, bunker leakage water, and ash, all of which contain highly toxic elements.This article sets out requirements for municipal solid waste disposal plant owner/operators in China as well as giving an attribute assessment for the prevalent waste disposal plant types in order to assist individual decision makers in their evaluation process for what plant type might be most suitable in a given situation. There is no ‘best’ plant for all needs and purposes, and requirement constellations rely on generalisations meaning they cannot be blindly applied, but an alignment of a type of plant to a type of owner or operator can realistically be achieved. To this end, a four-step approach is suggested and a technology matrix is set out to ease the choice of technology to transfer and avoid past errors. The four steps are (1) Identification of plant owner/operator requirement clusters; (2) Determination of different municipal solid waste (MSW) treatment plant attributes; (3) Development of a matrix matching requirement clusters to plant attributes; (4) Application of Quality Function Deployment Method to aid in technology localisation.The technology transfer matrices thus derived show significant performance differences between the various technologies available. It is hoped that the resulting research can build a bridge between technology transfer research and waste disposal research in order to enhance the exchange of more sustainable solutions in future.     

Trace element partitioning in ashes from boilers firing pure wood or mixtures of solid waste with respect to fuel composition,chlorine content and temperature

Trace element partitioning in solid waste (household waste, industrial waste, waste wood chips and waste mixtures) incineration residues was investigated. Samples of fly ash and bottom ash were collected from six incineration facilities across Sweden including two grate fired and four fluidized bed incinerators, to have a variation in the input fuel composition (from pure biofuel to mixture of waste) and different temperature boiler conditions. As trace element concentrations in the input waste at the same facilities have already been analyzed, the present study focuses on the concentration of trace elements in the waste fuel, their distribution in the incineration residues with respect to chlorine content of waste and combustion temperature.Results indicate that Zn, Cu and Pb are dominating trace elements in the waste fuel. Highly volatile elements mercury and cadmium are mainly found in fly ash in all cases; 2/3 of lead also end up in fly ash while Zn, As and Sb show a large variation in distribution with most of them residing in the fly ash. Lithophilic elements such as copper and chromium are mainly found in bottom ash from grate fired facilities while partition mostly into fly ash from fluidized bed incinerators, especially for plants fuelled by waste wood or ordinary wood chips. There is no specific correlation between input concentration of an element in the waste fuel and fraction partitioned to fly ash. Temperature and chlorine content have significant effects on partitioning characteristics by increasing the formation and vaporization of highly volatile metal chlorides. Zinc and cadmium concentrations in fly ash increase with the incineration temperature.     

Behavior of PAHs from sewage sludge incinerators in Korea

Although production of sewage sludge increases every year, its proper treatment has only been recently raised as a new issue, as current landfill and ocean dumping arrangements are expected to become increasingly difficult to manage in the future. The Korean Ministry of Environment plans to diversify its processing facilities and expand its processing systems by 2011, with the purpose of processing all sludge produced in Korea. According to this plan, incineration (including incineration of municipal wastes) will process 30% of the entire sewage sludge throughout the country in 2011. This study reviews the characteristics of PAH, which is one of the organic substances found in sewage sludge during the incinerating process. The total amount of PAH produced from sewage sludge incineration was found to be 6.103 mg/kg on average, and investigation performed on 16 PAHs of inlets and outlets of the air control devices at five full-scale incineration facilities showed that concentrations of the PAHs on the inlet and on the outlet ranged from 3.926 to 925.748 microg/m(3) and from 1.153 to 189.449 microg/m(3), respectively. In the case of the incineration facility fed with municipal waste (95%) and sewage sludge (5%), the total of the PAH emissions concentration was higher than that found at the incineration facilities used exclusively to treat sewage. The combustion of waste vinyl and plastics contained in municipal waste fed into the facility might contribute to the high levels of PAHs in the stack gas. However more investigation is needed on the production mechanism of PAHs at different operating conditions of the incineration facilities, such as the types of waste, and other relevant factors.