Monitoring of odor compounds produced by solid waste treatment plants with diffusive samplers

Nuisance caused by odors is one of the most important problems for waste management plants. To control an odor nuisance, it must first be quantified. The analytical difficulties in odor measurements are related to the high number of volatile components (belonging to several chemical classes), above all when the concentration is lower than the detection limit of the technique used for the measurement. In this work, 2-butanone, alpha-pinene, tetrachloroethylene, dimethyldisulfide, beta-pinene, limonene, phenol and benzoic acid are determined, because they are representative of some important classes of compounds with higher odor impact. The compounds are sampled with thermal desorbable radial diffusive samplers Radiello containing Tenax cartridges. The analytical repeatability and the complete thermal desorption of the cartridges were verified for each odor compound; the relative standard deviations for repeated samples and the recovery percentage were, respectively, less than 7% and about 97% for all compounds. The measurements of the linearity of sampling showed no systematic difference according to the collection period. The comparison between the odor threshold and the limit of detection demonstrated that this method is reliable for the recognition and quantification of odor compounds, allowing Public Administration to impose legal limits and the control agencies to verify them.     

In-situ emission characteristics of odorous gases from two food waste processing plants

Odorous gas emission is the main environmental concern of food waste treatment. Two typical food waste processing plants, one for animal feed production by hydrothermal hydrolysis + aerobic fermentation (Plant A), and the other for biogas production by anaerobic digestion (Plant B), were selected to conduct in situ monitoring of fugitive odorous gas emission for five consecutive days, and the emission characteristics of NH₃ and total volatile organic compounds (TVOC) were compared in this paper. The results showed that the two processes had different emission characteristics of odorous gases. Closed-operated hydrothermal hydrolysis had positive effects on overall fugitive odor control in plant A. Meanwhile, more fugitive odor gases may be released into the environment during the pretreatment with high-temperature and seemingly-open facilities in plant B. The emission strength of odor gases at night was generally lower than that in the day since more fresh food waste was received in the day and the higher temperature and lower air pressure in the day were favorable to gas emission. In general, the process of hydrothermal hydrolysis + aerobic fermentation was more advantageous in controlling odor than the process of anaerobic digestion.     

Pyrolysis of mixtures of sewage sludge and manure: a comparison of the results obtained in the laboratory (semi-pilot) and in a pilot plant

A pilot-scale pyrolysis process was carried out for the treatment of a mixture of two types of waste, sewage sludge and cattle manure, comparing the results with others obtained under laboratory conditions (semi-pilot scale). The aim of this study was to obtain the energetic valorization of the products. Owing to the specific characteristics of the plant, two products were obtained from the process: gas and carbonized solid. As no liquid fraction was obtained, the gas fraction is a greater percentage made up of both condensable and non-condensable compounds, which were obtained separately at the laboratory scale. The pilot plant was designed so that the gases produced by thermolysis were burnt continuously in a combustion chamber, while the carbonized fraction was fed in batches for co-combustion. To determine composition and combustion ability, the gas and solid products from the pilot process were characterized by chromatographic analysis of the gaseous fraction and chemical analysis and programmed-temperature combustion of the carbonized solid. The composition of the combustion gases, rich in light hydrocarbons, and the carbon present in the carbonized fraction enable the energetic valorization of these products. The combustion gases were subjected to a cleaning process and their composition analysed twice: before and after the gas cleaning treatment. The study led to a positive assessment of the possible use of the process products as fuel, provided that the combustion gases are treated. As most of the sulphur and chlorine from the original waste are mainly concentrated in the solid fraction, the use of char as a fuel will depend on the effectiveness of clean-up techniques for combustion gases. During gas cleansing, neutralizing with sodium bicarbonate proved effective, especially for the acidic compounds HCl, HF and SO(2).     

Effects of flue gas composition on the catalytic destruction of chlorinated aromatic compounds with a V-oxide catalyst

When using catalytic flue gas cleaning, several flue gas compounds may influence oxidation reactions of hazardous volatile organic compounds, possibly leading to lower reaction rates and, thus, to an incomplete destruction. Experimental investigations were performed with regard to the influence of selected flue gas compounds, like hydrogen chloride, sulfur dioxide, oxygen, and water vapour, on the catalytic destruction behavior of chlorobenzenes under flue gas cleaning conditions of an incineration plant. For this purpose, a metal oxide catalyst was operated at different temperatures at a space velocity of 3600 h-1 in a laboratory-scale fixed bed reactor with model flue gases, and with real flue gases generated from the TAMARA waste incineration plant. The results obtained from the studies with model flue gas were analyzed with respect to reaction kinetics. These kinetics were applied for comparison with the experimental data gained in the real flue gas.     

Material flow analysis of RDF-production processes

The authors evaluate the possibilities of modifying the chemical characteristics of refuse-derived fuels (RDF) that are processed from residual household waste by mechanical operations to achieve and assure quality targets for relevant chemical concentrations, especially for heavy metals and chlorine. Quality assurance in the production of RDF demands that, together with an enrichment of the calorific value, highly toxic waste components are selectively separated and concentrated in a small stream to produce high yields of a relatively low polluted fuel. Based on the method of material flow analysis, a process evaluation is developed that considers the aspect of minimizing hazardous chemicals along with classical process data such as yield and product quality. Data on specific concentration of hazardous chemicals in waste components and their distribution in residual household waste as well as the results from large-scale test runs using different separation techniques demonstrate that mechanical operations alone are insufficient for separating hazardous chemicals. In the test runs, chemical compounds such as chlorine, cadmium and lead were often concentrated in the product. Even using optimized techniques, the ability to reduce hazards in the product is limited due to the distribution of the element concentration in the various components of the waste stream.     

Problems associated with the measurement of PCDD and PCDF emissions from waste incineration plants

Fly ash and stack gases from municipal waste and industrial incinerators in the F.R.G. have been analyzed for dioxins (PCDD and PCDF). Most of the currently used procedures of stack gas sampling for PCDD/PCDF have been compared and were found to be equally effective. Differences are found, however, in the recovery of surrogates added to the sampling train before sampling, which makes it difficult to validate the sampling procedure. The analysis for PCDD%PCDF in stack gas or fly ash samples from municipal waste incinerators can no longer be considered an analytical problem. Thirty samples of stack gas from a single (old) municipal waste incinerator showed wide variation in PCDD/PCDF emission, indicating that single measurements are not useful in characterizing a plant for average PCDD/PCDF emission. It will be extremely difficult to correlate plant operating conditions to PCDD/PCDF stack gas emissions or PCDD/PCDF fly ash concentrations, because the effects produced by changing conditions are obscured by the variations which occur in PCDD/PCDF concentrations during steady conditions. The variations found under steady conditions can be explained by the proposed mechanisms of PCDD/PCDF formation and decomposition at low temperatures catalyzed by fly ash. Incineration of hospital waste and pyrolytic reclamation of copper in cables and aluminium produced significant emission of PCDD/PCDF. A major noncombustion source of higher chlorinated PCDD/PCDF (tetra- to octa-isomers) is pentachlorophenol, a widespread preservative which contributes to the PCDD/PCDF concentrations found, for example, in sewage sludge, river sediments and house dust.     

A goal-oriented characterization of urban waste

More stringent requirements for the protection of the environment coupled with new incentives for materials recovery, lead modern waste management practice on the line of a more differentiated approach. Separation, or more precisely, non-mixing at the source, is one of the most promising strategies. However, before deciding which categories of urban waste should be collected separately, it is useful to have more detailed knowledge regarding the characteristics of waste. A 5-year investigation has produced enough information to answer such questions as “if one decides to convert food and garden waste to compost instead of burning them, how much less cadmium would be released into the atmosphere?” or, “if the quantities of mercury released into the environment should be drastically reduced, which categories of waste should be collected and treated separately?” This paper discusses sampling and analytical techniques and defines what is a representative sample. It presents the methods applied to determine the annual flow of various chemical elements from 52 waste categories from a European urban area. The results determined through this approach are compared to the total outputs in the gas, wastewater, cinders and fly ashes of the incinerator which currently burns these wastes.     

Characterization and determination of the odorous charge in the indoor air of a waste treatment facility through the evaluation of volatile organic compounds (VOCs) using TD–GC/MS

Municipal solid waste treatment facilities are generally faced with odorous nuisance problems. Characterizing and determining the odorous charge of indoor air through odour units (OU) is an advantageous approach to evaluate indoor air quality and discomfort. The assessment of the OU can be done through the determination of volatile organic compounds (VOCs) concentrations and the knowledge of their odour thresholds. The evaluation of the presented methodology was done in a mechanical–biological waste treatment plant with a processing capacity of 245.000 tons year^?1 of municipal residues. The sampling was carried out in five indoor selected locations of the plant (Platform of Rotating Biostabilizers, Shipping warehouse, Composting tunnels, Digest centrifugals, and Humid pre-treatment) during the month of July 2011. VOC and volatile sulphur compounds (VSCs) were sampled using multi-sorbent bed (Carbotrap, Carbopack X, Carboxen 569) and Tenax TA tubes, respectively, with SKC AirCheck 2000 pumps. The analysis was performed by automatic thermal desorption (ATD) coupled with a capillary gas chromatography (GC)/mass spectrometry detector (MSD). One hundred and thirty chemical compounds were determined qualitatively in all the studied points (mainly alkanes, aromatic hydrocarbons, alcohols, aldehydes, esters, and terpenes), from which 86 were quantified due to their odorous characteristics as well as their potentiality of having negative health effects. The application of the present methodology in a municipal solid waste treatment facility has proven to be useful in order to determine which type of VOC contribute substantially to the indoor air odorous charge, and thus it can be a helpful method to prevent the generation of these compounds during the treatment process, as well as to find a solution in order to suppress them.     

Organometals of tin, lead and mercury compounds in landfill gases and leachates from Bavaria, Germany

Organo-Sn, -Pb and -Hg compounds were monitored in gases and leachates of 11 municipal waste landfills and one hazardous waste landfill from Bavaria, Germany, with the objectives to estimate the methylation of Sn, Pb and Hg and to assess the risk of their release into the adjacent environment. In the gases, tetramethyl Sn predominated (>80% of total gaseous Sn) with concentrations up to 160mug Sn m(-3). Dimethyl-Hg and tetramethyl-Pb were only occasionally detected with concentrations up to 2.9 and 2.1mugm(-3) as Hg or Pb, respectively. In all leachates, trimethyl-Sn dominated with a maximum concentration of 2100ng Sn L(-1). No organo-Pb compounds were found, and monomethyl-Hg was detected in only one leachate. The concentrations of trimethyl-Sn were up to 100-fold higher in the condensate water than in leachates, and the concentrations of organo-Sn compounds were lower in the adjacent groundwater than in the corresponding leachates. The high abundance of methylated Sn species in the gases and leachates indicates Sn methylation, suggesting the landfill as a source for organo-Sn compounds. In comparison, methylation of Hg and Pb was of little importance, probably due to low Hg concentrations and low rates of Pb methylation in the landfill. The risks of organo-Sn compounds release to the adjacent air is low due to flaring of landfill gases. However, there is probable release of organo-Sn compounds, especially trimethyl-Sn, to the adjacent groundwater.     

Absorption of odourous substances using selective gas-liquid separation processes

Absorption is one of the most widely used techniques for treating odourous waste gases. An improvement of the effectiveness of gas scrubbers can be achieved by using adapted washing liquids. A screening test is proposed as a low cost tool for testing washing liquids on industrial waste gases. The odour index is used to identify the main cause of the specific smell and to simplify the analysis of absorptive performances of washing liquids. The method is verified by experiments at a chocolate factory and a fat and oil refinery.     

Greenhouse gases accounting and reporting for waste management – A South African perspective

This paper investigates how greenhouse gases are accounted and reported in the waste sector in South Africa. Developing countries (including South Africa) do not have binding emission reduction targets, but many of them publish different greenhouse gas emissions data which have been accounted and reported in different ways. Results show that for South Africa, inventories at national and municipal level are the most important tools in the process of accounting and reporting greenhouse gases from waste. For the development of these inventories international initiatives were important catalysts at national and municipal levels, and assisted in developing local expertise, resulting in increased output quality. However, discrepancies in the methodology used to account greenhouse gases from waste between inventories still remain a concern. This is a challenging issue for developing countries, especially African ones, since higher accuracy methods are more data intensive. Analysis of the South African inventories shows that results from the recent inventories can not be compared with older ones due to the use of different accounting methodologies. More recently the use of Clean Development Mechanism (CDM) procedures in Africa, geared towards direct measurements of greenhouse gases from landfill sites, has increased and resulted in an improvement of the quality of greenhouse gas inventories at municipal level.     

Treatment of Sydney N.S. tar pond sludge in a pilot‐scale rotary kiln

Tar pond wastes from Sydney, Nova Scotia, containing 50 ppm or more of polychlorinated biphenyls (PCBs) were treated in a pilot‐scale rotary kiln. In order to use the existing feed system attached to the rotary kiln, the wastes were first oven‐dried. Stack gas sampling was conducted during the test, which included measurement of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), semi‐volatile organic compounds (SVOCs), HCl, and metals. The purpose of this study was to determine emissions from treatment of the tar pond waste using rotary kiln technology. It was found that the dried sludge could sustain combustion in the kiln without any supporting fuel. The emissions of polychlorinated dibenzodioxins/furans (PCDD/Fs) were higher than the Canadian Council of Ministers of the Environment (CCME) air emissions guidelines, and the reasons for this are discussed. © 2008 Wiley Periodicals, Inc.     

Municipal solid waste in situ moisture content measurement using an electrical resistance sensor

Moisture content (MC) is a crucial parameter for degradation of solid waste in landfills. Present MC measurement techniques suffer from several drawbacks. A moisture sensor for measurement of in situ moisture content of solid waste in landfills was developed. The sensor measures the electrical resistance across the granular matrix of the sensor, which in turn can be correlated to moisture content. The sensor was also equipped with a thermocouple and tubing that permits simultaneous measurement of temperature and gas sampling. The electrical conductivity of the surrounding moisture and the temperature in the matrix both affect the resistance measurements. This paper describes the results of laboratory experiments designed to select the appropriate granular media particle size, measure the influence of moisture electrical conductivity and temperature, and develop calibration relationships between measured resistance and gravimetrically determined moisture content. With a few limitations, the sensor is able to detect MC of solid waste under conditions allowing moisture movement into the sensor. The application of this technique shows promise for use in bioreactor landfills where high moisture contents are expected and desired.     

The evaluation of an analytical protocol for the determination of substances in waste for hazard classification

The classification of waste as hazardous could soon be assessed in Europe using largely the hazard properties of its constituents, according to the the Classification, Labelling and Packaging (CLP) regulation. Comprehensive knowledge of the component constituents of a given waste will therefore be necessary. An analytical protocol for determining waste composition is proposed, which includes using inductively coupled plasma (ICP) screening methods to identify major elements and gas chromatography/mass spectrometry (GC–MS) screening techniques to measure organic compounds. The method includes a gross or indicator measure of ‘pools’ of higher molecular weight organic substances that are taken to be less bioactive and less hazardous, and of unresolved ‘mass’ during the chromatography of volatile and semi-volatile compounds. The concentration of some elements and specific compounds that are linked to specific hazard properties and are subject to specific regulation (examples include: heavy metals, chromium(VI), cyanides, organo-halogens, and PCBs) are determined by classical quantitative analysis. To check the consistency of the analysis, the sum of the concentrations (including unresolved ‘pools’) should give a mass balance between 90% and 110%. Thirty-two laboratory samples comprising different industrial wastes (liquids and solids) were tested by two routine service laboratories, to give circa 7000 parameter results. Despite discrepancies in some parameters, a satisfactory sum of estimated or measured concentrations (analytical balance) of 90% was reached for 20 samples (63% of the overall total) during this first test exercise, with identified reasons for most of the unsatisfactory results. Regular use of this protocol (which is now included in the French legislation) has enabled service laboratories to reach a 90% mass balance for nearly all the solid samples tested, and most of liquid samples (difficulties were caused in some samples from polymers in solution and vegetable oil). The protocol is submitted to French and European normalization bodies (AFNOR and CEN) and further improvements are awaited.     

Enrichment of elements in industrial waste incineration bottom ashes obtained from three different types of incinerators,as studied by ICP-AES and ICP-MS

The elemental composition of the industrial waste incineration bottom ash (IWIBA) samples collected from three different types of incinerator with different kinds of wastes were compared. The major-to-ultratrace elements in the IWIBA samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). As a result, ca. 40 elements in the concentration range from milligrams per gram to submicrograms per gram could be determined with relative standard deviations of less than 5%. The IWIBA sample from petrochemical wastes contained lower concentrations of the elements, because fewer mineral constituents were contained in the input waste materials. On the contrary, the elemental concentrations in the IWIBA sample from industrial solid wastes provided the highest values for most elements, while the elemental compositions of the IWIBA sample from food wastes were similar to those of municipal solid waste incineration bottom ash. In addition, it was found from the analytical results that the levels of various heavy metals such as Cr, Mn, Fe, Ni, Cu, As, Zr, Mo, Sb, Ba, and Pb were higher in the IWIBA samples than in municipal solid waste incineration bottom ash. The enrichment factors of the elements in the IWIBA samples were estimated from the analytical results to compare the elemental distributions in incineration bottom ashes in relation to their mining influence factors, which are the indices for human use of the elements.     

Selective separation of virgin and post-consumer polymers (PET and PVC) by flotation method

More and more polymer wastes are generated by industry and householders today. Recycling is an important process to reduce the amount of waste resulting from human activities. Currently, recycling technologies use relatively homogeneous polymers because hand-sorting waste is costly. Many promising technologies are being investigated for separating mixed thermoplastics, but they are still uneconomical and unreliable. At present, most waste polymers cause serious environmental problems. Burning polymers for recycling is not practiced since poisonous gases are released during the burning process. Particularly, polyvinyl chloride (PVC) materials among waste polymers generate hazardous HCl gas, dioxins containing Cl, etc., which lead to air pollution and shorten the life of the incinerator. In addition, they make other polymers difficult to recycle.Both polyethylene terephthalate (PET) and PVC have densities of 1.30–1.35 g/cm³ and cannot be separated using conventional gravity separation techniques. For this reason, polymer recycling needs new techniques. Among these techniques, froth flotation, which is also used in mineral processing, can be useful because of its low cost and simplicity.The main objective of this research is to recycle PET and PVC selectively from post-consumer polymer wastes and virgin polymers by using froth flotation. According to the results, all PVC particles were floated with 98.8% efficiency in virgin polymer separation while PET particles were obtained with 99.7% purity and 57.0% efficiency in post-consumer polymer separation.     

Analytical methods for waste minimisation in the convenience food industry

Waste creation in some sectors of the food industry is substantial, and while much of the used material is non-hazardous and biodegradable, it is often poorly dealt with and simply sent to landfill mixed with other types of waste. In this context, overproduction wastes were found in a number of cases to account for 20–40% of the material wastes generated by convenience food manufacturers (such as ready-meals and sandwiches), often simply just to meet the challenging demands placed on the manufacturer due to the short order reaction time provided by the supermarkets. Identifying specific classes of waste helps to minimise their creation, through consideration of what the materials constitute and why they were generated. This paper aims to provide means by which food industry wastes can be identified, and demonstrate these mechanisms through a practical example. The research reported in this paper investigated the various categories of waste and generated three analytical methods for the support of waste minimisation activities by food manufacturers. The waste classifications and analyses are intended to complement existing waste minimisation approaches and are described through consideration of a case study convenience food manufacturer that realised significant financial savings through waste measurement, analysis and reduction.     

Using an integrated approach for quantifying VOC source areas for site remediation

Locating and quantifying free-phase volatile organic compounds (VOCs) in the subsurface represent one of the more difficult challenges facing hazardous waste site remediation programs. Successful remediation programs require reliable data on the size and extent of potential VOC contamination sources. Improving subsurface quantification of VOCs requires a large number of reliable low-cost samples. Satisfying this objective relies on improved sampling techniques, field analysis of samples, and a modified quality assurance program. This paper describes an integrated approach using conventional split-spoon samplers, microcore sampling, hexane extractions, and a field gas chromatograph with an autosampler as part of a technical demonstration for innovative remediation technologies. Using this approach, it was possible to delineate a subsurface source of free-phase VOCs at a cost of $15 per sample. The distribution of dense nonaqueous phase liquid determined by this sampling approach agreed with the conceptual model for the site.     

Emissions from baled municipal solid waste: II. Effects of different treatments and baling techniques on the emission of volatile organic compounds.

This paper focuses on the volatile organic compound emissions from baled municipal solid waste (MSW). The analytical methodology was based on sampling with adsorbent tubes once a month during seven occasions within a time period of 1 year. Automated analyses were carried out on-line work-up with thermal desorption directly connected to a gas chromatograph-mass spectrometer. The effect of different baling techniques, cylindrical and rectangular baling was compared. It was found that cylindrically baled MSW emitted larger concentration of esters than their rectangular counter parts. Conversely, aromatic compounds emissions dominated in rectangularly baled MSW. This indicates that different degradation mechanisms operate in the waste bales. Cylindrical and rectangular bales are generally wrapped with six layers of 250 microm thick low density polyethylene (LDPE). It was observed that by wrapping an extra six layers of LDPE film onto the bales, the emissions from cylindrical bales increased while emissions from the rectangular counterpart decreased. Over time, the volatile organic compound emissions from cylindrical bales decreased two orders of magnitudes from 96.2 +/- 20.8 microg m(-3) in September 2003 to 0.80 +/- 0.07 microg m(-3) in July 2004. The rectangular bales exhibited an almost identical relative emission reduction from 54.4 +/- 4.3 microg m(-3) in September 2003 to 0.46 +/- 0.02 microg m(-3) in July 2004. Future work will concentrate on full-scale storages, taking into account waste type, storage size, temperature development and the different baling techniques among other variables.     

Thermal conversion of municipal solid waste via hydrothermal carbonization: comparison of carbonization products to products from current waste management techniques

Hydrothermal carbonization (HTC) is a novel thermal conversion process that may be a viable means for managing solid waste streams while minimizing greenhouse gas production and producing residual material with intrinsic value. HTC is a wet, relatively low temperature (180-350 °C) thermal conversion process that has been shown to convert biomass to a carbonaceous residue referred to as hydrochar. Results from batch experiments indicate HTC of representative waste materials is feasible, and results in the majority of carbon (45-75% of the initially present carbon) remaining within the hydrochar. Gas production during the batch experiments suggests that longer reaction periods may be desirable to maximize the production of energy-favorable products. If using the hydrochar for applications in which the carbon will remain stored, results suggest that the gaseous products from HTC result in fewer g CO(2)-equivalent emissions than the gases associated with landfilling, composting, and incineration. When considering the use of hydrochar as a solid fuel, more energy can be derived from the hydrochar than from the gases resulting from waste degradation during landfilling and anaerobic digestion, and from incineration of food waste. Carbon emissions resulting from the use of the hydrochar as a fuel source are smaller than those associated with incineration, suggesting HTC may serve as an environmentally beneficial alternative to incineration. The type and extent of environmental benefits derived from HTC will be dependent on hydrochar use/the purpose for HTC (e.g., energy generation or carbon storage).