Formation of PCDD/PCDF

One option of recycling used contaminated packaging is to recover its high energy content. This can be performed in a normal multi-fuel power plant by co-combustion of packaging-derived fuel (PDF) or refuse-derived fuel (RDF) with fossil fuels, such as coal or peat. This work includes the results of 17 co-combustion tests and an evaluation of the results by the Principal Component Analysis (PCA) and the Partial Least Squares Projections to Latent Structures (PLS). PCA and PLS calculations showed that especially Pb, but also Cr, and Cu correlated with lower chlorinated furans (PCDFs) in the fly ash. Correlation between Sn and lower chlorinated dioxins (PCDDs) in the fly ash was also noticed. CO and PAH emission in the flue gas correlated with total PCDD/Fs in the flue gas. In a real full-scale combustion process, a single parameter in fuel, flue gas or a combustion parameter did not provide a guide to PCDD/F formation or to a level of the total PCDD/F emission, but correlations between different parameters and PCDD/Fs could be found. Although PDFs and RDF had catalytic heavy metals and chlorine, the co-combustion results showed that they can be co-combusted with peat and coal in a fluidized-bed boiler at least up to 26 % with very low total PCDD and PCDF emissions.     

Formation characteristics of PCDD and PCDF during pyrolysis processes

In recent years, pyrolysis processes have become technologies developed to industrial scale and discussed as alternatives to the existing waste combustion technology. However, little information is published regarding PCDD/F formation characteristics during pyrolysis processes. Two common shredder fractions – industrial light shredder (ILS) and refrigerators (REF) – both with high chlorine and copper content were pyrolysed for this pyrolysis study using a pilot plant with a capacity of 100 kg/h. At oxygen concentrations below 2% and temperatures between 430°C and 470°C, considerable amounts of PCDD/F were formed during the pyrolysis. More than 90% of total TEQ was found in the oil fraction (gas phase). The PCDD/PCDF ratio and the homologue pattern differed significantly from those formed during waste incineration. Considering mono- to octachlorinated congeners, up to 400 times more PCDF were formed compared to PCDD. For the investigated pyrolysis conditions, the formation of low chlorinated congeners was highly favoured. The distribution of TEQ within the individual congeners were very similar in all investigated runs. More than 80% of total TEQ stem from 2,3,7,8-substituted T₄CDF and P₅CDF. The isomer pattern, however, did not show significant differences compared to the common waste incineration pattern suggesting that the basic formation routes are similar.     

Destruction of PCDD/PCDF by non-thermal methods

The physical, chemical and biological processes for the destruction of PCDD/PCDF and the treatment of dioxin-contaminated wastes are reported. Tests and their results, carried out in laboratories and pilot plants with PCDD and similar compounds, are discussed. The development and testing of suitable catalysts for the chemical conversion of dioxins and other chlorohydrocarbons are examined. The application conditions, the necessary pretreatments of wastes, and the destruction efficiencies of the different methods are examined. A technical, economic, and environmental assessment according to the tested results is considered.     

PCDD/PCDF reduction by the co-combustion process

A novel process, termed the co-combustion process, has been developed and designed to utilise the thermal treatment of municipal solid waste (MSW) in cement clinker production and reduce PCDD/PCDF emissions. To test the conceptual design; detailed engineering design of the process and equipment was performed and a pilot plant was constructed to treat up to 40 tonnes MSW per day. The novel process features included several units external to the main traditional cement rotary kiln: an external calcinations unit in which the hot gas calcined the limestone thus making significant energy savings for this chemical reaction; the lime generated was used in a second chamber to act as a giant acid gas scrubber to remove SOx and particularly HCl (a source of chloride); an external rotary kiln and secondary combustion unit capable of producing a hot gas at 1200 degrees C; a gas cooler to simulate a boiler turbogenerator set for electricity generation; the incorporation of some of the bottom ash, calcined lime and dust collector solids into the cement clinker. A PCDD/PCDF inventory has been completed for the entire process and measured PCDD/PCDF emissions were 0.001 ng I-TEQ/Nm(3) on average which is 1% of the best practical means [Hong Kong Environmental Protection Department, 2001. A guidance note on the best practicable means for incinerators (municipal waste incineration), BPM12/1] MSW incineration emission limit values.     

The emission inventory of PCDD/PCDF in Taiwan

Establishment of a country or region-based dioxin inventory was considered a crucial step toward elimination of worldwide dioxins/POPs contaminations, although no harmonized method for the preparation of an inventory is available at present. In this study, we used limited data and information to generate an inventory of dioxin emissions from some major sources in Taiwan. A total of 67.25 g I-TEQ of dioxins released annually was estimated. Unlike most of the industrialized countries, municipal waste incineration is not the highest contributor for dioxins released into the atmosphere. In contrast, secondary copper smelting accounts for more than 39% of the total dioxin emissions, and is higher than those from all waste incinerators combined (23.7%). Cement kilns and electric arc furnaces for steels also produced significant portion (both >10%) of dioxins into the environment, followed by secondary aluminum smelting (6.53%), industrial oil combustion (5.02%) and power plants fueled by coal (5.01%). Other known sources are either insignificant with respect to their dioxin emissions or not included in this inventory due to lack of information or uncertainty of the results. Data presented in this report provide a general picture of dioxin emissions in Taiwan, but were mostly based on less reliable or representative information, especially with respect to emission factors from different emission sources. It is necessary to establish background information relative to our own environment at present. Upon available, the inventory should be updated accordingly for proper environmental management on dioxins.     

Atmospheric baseline levels of PCDD and PCDF in the region of Oporto

An external monitoring plan (EMP) is being implemented in the region of Oporto, Portugal, to follow the potential effects of a future incinerator of municipal solid waste. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) were measured during 1998 and the first semester of 1999, prior to the working up of the incineration unit. The baseline levels obtained through this intensive monitoring work are presented and discussed in the present paper.     

Control of PCDD/PCDF emissions from refuse-derived fuel combustors

This paper presents preliminary results of performance tests conducted at the Mid-Connecticut Refuse-Derived Fuel Facility in February 1989. The objectives of these performance tests were to evaluate the effects of combustion and flue gas cleaning process conditions on air pollution emissions and residue properties.     

Intra- and inter- laboratory variability in paper industry PCDD/PCDF analysis

Studies were conducted to quantify variability for pulp industry wastewater effluent, pulp and sludge analyses. Intralaboratory variability studies indicated that there is a potential for greater between batch variability in results than for within a batch. Intralaboratory relative standard deviations for replicate analyses ranged from 6% to 60%. Interlaboratory studies, using standard reference materials showed relative standard deviations from 4% to 135%. There appeared to be little dependance of variability on concentration, suggesting matrix effects were very important. In general, effluent variability was greater than observed for pulps or sludges. Analysis of reference standards indicated that 13% to 17% variability can be attributed to differences in calibration standards. A limited study of full congener PCDD/PCDF analysis variability showed it to be greater than observed for TCDD/TCDF.     

A survey of PCDD and PCDF in French long-life half-skimmed drinking milk

A national survey was carried out in order to assess the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in long-life half-skimmed drinking milk produced and consumed in France. 151 Samples were collected from 33 dairy establishments selected for their production amounts following a random sampling scheme. 148 of the 151 results were finally used for statistical assessment. The mean concentration of 2,3,7,8-TCDD toxicity equivalent found is 0.65 pg/g of milk fat. This result is far below the threshold recommended by the European Union.     

Kinetics of carbon degradation and PCDD/PCDF formation on MSWI fly ash

The native carbon oxidation and PolyChloroDibenzo-p-Dioxins and PolyChloroDibenzoFurans, PCDD/F, formation were simultaneously studied at different temperatures (230-350 degrees C) and times (0-1440 min) in order to establish a direct correlation between the disappearance of the reagent and the formation of the products. The kinetic runs were conducted in an experimental set up where conditions were chosen to gain information on the role of fly ash deposits in cold zones of municipal solid waste incinerators in PCDD/F formation reaction. The carbon oxidation measured as the decrease of total organic carbon of fly ash was in agreement with the carbon evolved as sum of CO and CO(2). The carbon mass balance indicated an increase in the efficiency of carbon conversion in CO and CO(2) with temperature. The CO and CO(2) formation was the result of two parallel pseudo first order reactions thus giving significant information about the reaction mechanism. PCDD/F formation as a function of temperature showed that the maximum formation was achieved in a narrow range around 280 degrees C; the time effect at 280 degrees C was a progressive formation increase at least up to 900 min. The PCDF:PCDD molar ratio increased with temperature and time, and the most abundant homologues were HxCDD, HpCDD, OCDD for PCDD, and HxCDF, HpCDF within PCDF. These experimental results supported the hypothesis that the formation mechanism was the de novo synthesis.     

Emission factors of PCDD and PCDF for road vehicles obtained by tunnel experiment

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDF) were determined in air at the inlet and outlet of a longitudinally ventilated tunnel with separate tubes for each traffic direction. In addition, measurements of traffic density, traffic composition, ventilation rate and other air pollutants were carried out. The data allowed to estimate the PCDD/PCDF emissions based on a car fleet of about 20'–30'000 cars. Furthermore, the varying percentage of heavy duty vehicles made it possible to differentiate between emission factors for light (LDV) and heavy duty (diesel) vehicles (HDDV). Depending on driving conditions, the estimated emission factors were in the order of 0.04–0.5 ng/km 2,3,7,8-TEQ (Nordic model) for LDV and 0.8–9.5 ng/km for HDDV.     

PCDD/PCDF, dl-PCB and PBDE serum levels of Slovak general population

Blood serum specimens from 81 non-occupationally exposed adults residing in four areas close to municipal and waste incinerators as well as metallurgical industry plant and 44 adult subjects coming from control area of Slovakia were analysed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (dl-PCBs) and polybrominated diphenylethers (PBDEs). The concentration of total WHO(98)TEQ PCDD/F/dl-PCBs in whole group of donors from areas where known sources causing dioxin contamination are present was significantly higher than in control group of donors (p<0.001). Correlation between the age of donors and PCDD/F and dl-PCB levels was confirmed (Spearman's r(PCDD/Fs)=0.543, r(dl-PCBs)=0.521, p<0.001). Furthermore, this study presents first results concerning the PBDE congeners in human serum of Slovak general population. The total concentration (congeners 28, 47, 99, 100, 153, 154, 183) in control group was approximately 1.5-times higher in comparison to that of residents coming from areas with supposed environmental pollution. The most abundant congeners in all samples were BDE-47 and BDE-153 with median values of 0.24 ng g(-1) lipid and 0.23ngg(-1) lipid, respectively. The positive association between PBDE values and age of donors was not found.     

Investigation of different treatment techniques for PCDD/PCDF in fly ash

A number of different pretreatment and extraction procedures were compared with regard to recovery of PCDD/PCDF from fly ash. Highest results were obtained using an acid digestion with excess dilute HCl, followed by freeze drying of the residue and hot extraction by toluene.     

The behavior of PCDD and PCDF during thermal treatment of waste incineration ash

The polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) content of three fly ash samples with different elemental compositions from different municipal waste incinerators were analyzed before and after thermal treatment at 300 °C or 500 °C. Gas phase emissions during the treatments were also collected and analyzed. Substantial reductions in the total PCCD/F content of the ashes were observed after treatment at 500 °C, seemingly due to degradation rather than dechlorination. Treatment at 300 °C resulted in an increase in the PCDD/F content of the three ashes. Initial concentration of PCDD/F in the untreated ashes did not reflect the outcome of the treatment at the different temperatures. In addition, the composition of the ash was found to influence the rate of decomposition and formation of PCDD and PCDF during thermal treatment; the results showed that Cu, Fe, Ca and S play important roles in these processes.     

Status of the PCDD and PCDF contamination of commercial milk caused by milk cartons

Within the scope of this study, possible migration of polychlorinated dibenzodioxins and -furans (PCDDs/PCDFs) from cartons (produced using bleached cardboard) into cow's milk was investigated. Three different types of carton were examined. The milk samples were taken at different times of storage and analysed for PCDDs/PCDFs. In contrast to a similar study carried out in 1990, the I-TEQ-results of all cartons analysed may be considered very low. No significant migration of toxic (2,3,7,8-chlorine-substituted) PCDDs/PCDFs could be observed. This is due to the very low PCDD/PCDF concentrations in modern cardboards as a result of the elemental chlorine-free (ECF) bleaching processes used. As far as the milk samples are concerned, no influence of the cardboards (according to the I-TEQ data) could be ascertained. I-TEQ concentrations in milk did not noticeably change during storage times of three, six and eight days. The I-TEQ-data obtained for all milk samples was found to be in the range typical of background concentrations in cow's milk in Germany. Although 1,2,7,8-TCDF is not included in the calculation of the TEQ (no 2,3,7,8-chlorine-substitution), analysis of this congener in cardboard samples was also carried out as a matter of general interest for cardboard investigations and an indicator of pulp bleaching with free chlorine.     

Effects of selected metal oxides on the dechlorination and destruction of PCDD and PCDF

OCDD and OCDF spiked silica/graphite based model fly ash containing various copper compounds and metal oxides were thermally treated under oxygen deficient conditions. All copper compounds tested showed a considerable dechlorination/hydrogenation reaction at 260 °C. After 30 min at 340 °C, less than 1% of the spiked OCDD and OCDF was recovered as T₄CDD/F to OCDD/F. Other compounds tested demonstrated a lower rate of dechlorination compared to the copper compounds. However, all other metal oxides showed a small dechlorination effect at 260 °C, which was considerably increased at 340 °C.

The model fly ash containing the different copper compounds or metal oxides showed comparable PCDD and PCDF isomer patterns after thermal treatment. However, small differences were observed among the different tested compounds. The PCDD and PCDF isomer patterns on the model fly ashes were similar to patterns found during dechlorination experiments on fly ashes from waste incineration processes.

Model fly ash containing Ca(OH)₂ exhibited the highest destruction potential, but a low dechlorination potential. In contrast, model fly ash containing any of the remaining compounds tested, was found to predominantly dechlorinate the spiked OCDD and OCDF.     

Thermal behavior of PCDD/PCDF in fly ash from municipal incinerators

The effect of thermal treatment of fly ash on the behaviour of PCDD/PCDF was studied in the range between 120 and 600° C. Annealing at 300° C (2 hrs) resulted in an increase of PCDD/PCDF concentration by a factor of 10 to 15. At 600° C degradation to concentrations below 0.1 ng/g is observed.     

PCDD/PCDF congener profiles in soil and herbage samples collected in the vicinity of a municipal waste incinerator before and after pronounced reductions of PCDD/PCDF emissions from the facility

Congener profiles are the fractional distribution of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) congeners in an environmental release, or in an environmental or biological sample. In 1999, an adaptation to the EU legislation on pollutant emissions from the stack was carried out in an old municipal solid waste incinerator (MSWI) from Montcada (Barcelona, Spain). The main goal of the present study was to determine if the environmental PCDD/F levels in the area under direct influence of the facility were mainly due to PCDD/F emissions from the plant. For this purpose, soil and herbage samples were collected near the MSWI before (1998) and after (2000) the technical improvements were performed. PCDD/F congener profiles were determined and compared with those from samples collected in a suburban area of Constantí (Tarragona, Spain) outside of direct emissions from any MSWI. The results of the present study suggest that the MSWI here assessed is not the main responsible for the environmental PCDD/F concentrations in the area under evaluation. Other PCDD/F emission sources in the same area seem also to have a notable impact on the atmospheric levels of these pollutants.     

Concentrations of PCDD/PCDF in soil close to a secondary aluminum smelter

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) were analyzed in samples of the emissions from a secondary aluminum smelter (ALS) and soil samples around the plant. The purpose was to estimate the impact of the emissions on the surrounding environment.PCDD/F soil concentrations were higher in the proximity of the plant, exceeding the limit adopted in Italy in soils for green areas and residential uses and the upper limit of several reference concentrations. The most contaminated sites were less than 500 m from the plant and the dioxin concentration with the distance from the ALS.Principal component analysis (PCA) showed that emissions from the ALS were the source of PCDD/F contamination in the soils closest to the plant. Multivariate data analyses such as PCA are therefore useful to identify sources of emission causing contamination.