- Email: [email protected]
F and dioxin-like PCB concentrations during municipal solid waste biomethanation and subsequent composting
Chemosphere 98 (2014) 73–77
Contents lists available at ScienceDirect
Chemosphere journal homepage: www.elsevier.com/locate/chemosphere
PCDD/F and dioxin-like PCB concentrations during municipal solid waste biomethanation and subsequent composting M. Muñoz ⇑, M.F. Gomez-Rico, R. Font Department of Chemical Engineering, University of Alicante, P.O. Box 99, E-03080 Alicante, Spain
h i g h l i g h t s The obtained toxic concentrations in all the fractions were low. 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDD and HpCDD showed the highest toxic concentrations. OCDD and 1,2,3,4,6,7,8-HpCDD showed the higher concentrations in almost all samples. The contribution of PCBs to the total toxicity is high.
a r t i c l e
i n f o
Article history: Received 27 February 2013 Received in revised form 19 September 2013 Accepted 1 October 2013 Available online 9 November 2013 Keywords: Biomethanation Composting MSW PCDD/Fs PCBs
a b s t r a c t PCDD/F and dioxin-like PCB concentrations were compared in different samples of a municipal solid waste (MSW) treatment plant: the initial MSW fraction that enters the biomethanation from the digester, the semi-solid digestate obtained after biomethanation of MSW, and the solids after composting the digestate since the final product is destined for land application and special attention must be paid to these compounds for environmental considerations. The initial MSW sample showed low concentrations of PCDD/Fs, although in the biomethanation output sample the concentration was more than ten times higher. The difference was even more significant for PCBs. In compost samples concentrations for both PCDD/Fs and PCBs were in the same range as in biomethanation or lower. Nevertheless, concentrations found for all samples were low and these treatments do not pose a major problem for the environment in the working conditions used. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction In recent years, a great effort has been made to reduce the amount of municipal solid waste (MSW) that is landfilled. According to the EU Landfill Directive (Council Directive 1999/31/EC of 26 April 1999), by 2013 biodegradable municipal waste landfilled must be reduced to 50% of that produced in 1995, and by 2020 to 35% of the amount produced in 1995. Two alternatives are biomethanation and composting from the biodegradable fraction. Biomethanation, or anaerobic digestion, is a complex microbial process in which organic compounds are degraded into methane and carbon dioxide by a variety of anaerobes. This biogas can be used as a fuel after desulfuration of the biogas with hydrogen sulfide, and the fermented solid residue can be used as a fertilizer or raw material for composting. When organic compounds are maintained at 5–70 °C and neutral pH under anaerobic conditions, spontaneous biomethanation will occur. Biogas is produced in this ⇑ Corresponding author. Tel.: +34 965 903 400x3003; fax: +34 965 903 826. E-mail address: [email protected] (M. Muñoz). 0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.10.004
way in landfills but, in addition to this, biomethanation plants exist to treat some fractions of MSW to obtain biogas. Aerobic composting is a well-extended practice of waste reduction that consists of a microbial conversion of material in the presence of suitable amounts of air and moisture into a stabilized product, compost, with the general appearance and other characteristics of a fertile soil. Composting can be performed either directly from the residue or after biomethanation. The literature concerning PCDD/F concentrations in MSW and its treatment is scarce so far, and the discussion of PCDD/F emissions from MSW treatments usually refers to incineration. First of all, untreated MSW has very changeable PCDD/F concentrations. While in the UK an average concentration of 6.3 ng I-TEQ kg 1 was found (Eduljee et al., 1997) in Germany around 73 ng I-TEQ kg 1 was obtained (Landesumweltamt Nordheinwestfalen, 1997). However, PCDD/F concentrations in different stages of the MSW treatment have been reported. PCDD/F concentrations of 5–117 pg ITEQ N m 3 have been found in the biogas produced spontaneously (before its combustion), when MSW is landfilled (Cernuschi, 2001). Nevertheless, the biogas flow coming out from the landfill
74
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
body is very low. Flue gases from combustion of MSW have been found to show higher concentrations of PCDD/Fs than those found in biogas. Zhang et al. (2008) reported 1160–3190 pg I-TEQ N m 3 in combustion of MSW, Lonati et al. (2007) showed values of 1300 pg I-TEQ N m 3 for old plants and 3.2 pg I-TEQ N m 3 for new plants of MSW combustion and 100–5000 pg I-TEQ N m 3 were also reported by Fiedler (1998). Regarding landfill leachate, Concejero et al. (2008) showed that nearly all the congeners were below the detection limit and only OCDD had significant levels, with a total PCDD/F content from 0.01 to 5.22 ppq I-TEQ. Apart from the PCDD/F concentrations obtained in biogas, when biomethanation is used as a treatment for MSW, special attention must be paid to the concentrations resulting in the liquid sludge or semi-solid residue, since its final destination is sometimes the application to land as a fertilizer after composting. No studies have been found on PCDD/Fs in this waste produced anaerobically, although there is evidence of dechlorination of PCDD/Fs by anaerobic cultures and sediments (Adriaens and Grbic’-Galic, 1994). However, lesser chlorinated PCDD/Fs (2,3,7,8-substituted ones) have been found as the accumulating products resulting from reductive dechlorination under anaerobic methanogenic conditions, that could be a matter of environmental concern. Furthermore, during anaerobic treatment of another waste, sewage sludge, an increase of PCDD/Fs was observed mainly due to the rise of 1,2,3,4,6,7,8-HpCDD and OCDD (Weber et al., 1997). On the other hand, composting supposedly degrades some organic pollutants present in the waste, but an enzymatic formation of PCDD/Fs (polychlorinated dibenzo-p-dioxins/furans) can take place during composting under certain conditions, as studied during sewage sludge composting by Weber et al. (1997). In this case, the increase was also due to 1,2,3,4,6,7,8-HpCDD and OCDD, as for anaerobic digestion. Malloy et al. (1993) also found high concentrations of PCDD/Fs (mean value of 56 ng I-TEQ kg 1) during the composting process of MSW, MSW mixed with sewage sludge and yard waste composting, where 1,2,3,4,6,7,8-HpCDD and OCDD were again the dominant congeners, probably due to a potential formation of PCDD/Fs from pentachlorophenol (PCP). However, Eduljee et al. (1997) reported a PCDD/F decrease during MSW composting. They found MSW to contain 6.3 ng I-TEQ kg 1 of waste while compost contained 0.4–3.3 ng I-TEQ kg 1. Therefore, the increase or decrease of the PCDD/F concentrations during composting seems to depend on the process conditions and initial materials containing PCDD/F precursors. Concejero et al. (2008) showed similar concentrations to Eduljee et al. (1997) after studying three MSW composting facilities, 1.53–5.26 ng WHO2005-TEQ kg 1 (or 2.92– 9.22 ng I-TEQ kg 1). These authors completed their study with the analysis of dioxin-like PCBs, obtaining for these compounds 1.15– 3.62 ng WHO2005-TEQ kg 1, and therefore PCBs are as important as PCDD/Fs for environmental considerations. The initial mixture necessary to carry out the composting process consists of waste and a bulking agent (e.g. straw, sawdust, leaves, woodchips, etc) to make it permeable to air. Both bulking agents and MSW could contain the precursors for the PCDD/F formation, such as pentachlorophenol. Pentachlorophenol was used for many years as a fungicide to treat wood to avoid woodworm, although nowadays its use is limited because of its relationship with the formation of PCDD/Fs. Nevertheless, chlorophenols can be still found in leachates from MSW landfills (Ozkaya, 2005). Some ‘‘in vitro’’ studies demonstrated the relationship between some peroxidase enzymes and chlorophenols with the dioxin formation, leading to considerable amounts of higher chlorinated PCDD/Fs (Öberg et al., 1990; Öberg and Rappe, 1992; Wittsiepe et al., 1999). Hence, a PCDD/F formation has been suggested from anaerobic treatment and composting of waste, but the information is contradictory and some other authors reported a reduction in the dioxin
levels after these treatments. Therefore, the aim of this work was to determine PCDD/F concentrations (the 17 2,3,7,8-tetrasubstituted congeners) in different samples: MSW, after biomethanation of MSW, and after composting of the digestate obtained in biomethanation. Dioxin-like PCBs (non-ortho and mono-ortho congeners (Van den Berg et al., 1998)) were also included in this study since their contribution to the toxicity could be significant.
2. Materials and methods MSW, biomethanation digestate and compost were provided by a MSW treatment plant located in the Southeast of Spain, which receives non-hazardous municipal waste. Five samples were analyzed: 1. MSW (biomethanation input): consists of MSW with particle size smaller than 40 mm without ferric materials, which is the most suitable fraction for the process. 2. Biomethanation output. 3. Fresh compost: compost obtained after 21 d of composting formed from the biomethanation output (particle size smaller than 40 mm) and the intermediate particle size fraction (40–80 mm). 4. Mature compost from the fraction with particle size smaller than 12 mm, after more than 1 month of maturation. 5. Rejected fraction: comprises the fraction of final compost after maturation with particle size larger than 12 mm. This fraction is separated from the mature compost, so it is not used as a fertilizer and is disposed of to landfill. It also contains plastic, glass and other non-fermentable materials. The moisture content was determined after drying the samples in a drying chamber at 105 °C for 24 h and weighing the sample before and after drying. The result is expressed as weight percentage with respect to the wet mass (wm). The elemental analysis was carried out in a Carlo Erba CHNS-O EA 1108 apparatus, after drying the samples at 105 °C for 24 h. The method is based on the complete oxidation (combustion) of the sample and analysis of the resultant gases by gas chromatography. The results are expressed as weight percentage with respect to dry mass (dm). The ash content was determined in a Heron 12PR/300 muffle furnace at 900 °C for 8 h, and the result is expressed as percentage with respect to dry mass. The oxygen percentage was calculated by difference, taking into account C, H, N, S and ash contents. In addition to this characterization, a thermogravimetric analysis (TG) of the samples was carried out in a Mettler Toledo thermobalance model TGA/SDTA851e/LF/1600, in order to obtain more information about the changes produced during the processes studied (see Supplementary Information for more details and results). The PCDD/F and PCB analysis was carried out according to the US EPA method 1613 (US EPA, 1994). An amount of approximately 10 g of each wet sample was spiked with the internal standard solutions containing the 13C12 labeled congeners, 1613LCS-PCDD/ Fs and WP-LCS-PCBs (Wellington Laboratories Inc., Canada), and was kept for 3 h with sodium sulfate. Then the samples were extracted in toluene using accelerated solvent extraction with a Dionex 100 apparatus (Dionex Corp., CA, USA). Extraction was followed by a clean-up and purification step consisting of an acid-basic treatment and a clean-up procedure using an FMS Power Prep TM System (FMS Inc., Boston, MA, US) using silica, alumina and carbon columns. The purified extract was analyzed using an Autospec Ultima high resolution mass spectrometer (Micromass, UK), with a positive electron impact (EI+) source and interfaced with a Hewlett–Packard (Palo Alto, CA, USA) 6890 Plus
75
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
gas chromatograph equipped with a PTV inlet with a septumpless head. A DB-5 60 m fused silica capillary column was used for the separation of the isomer specific analysis. Prior to the injection the recovery standards, 13C PCDDs (1,2,3,4-TeCDD and 1,2,3,7,8,9HxCDD) and 13C PCBs (70, 111 and 138), were added. The identification and quantification of each PCDD/F and PCB congener was performed by the isotope dilution method. Quality assurance and quality control (QA/QC) criteria included the recovery percentage of the internal standards, the relative retention time of the target compound compared to the internal standard, and the chlorine isotope ratio falling within 15% of the theoretical chlorine isotope ratio when the two most abundant ions are measured. 3. Results and discussion 3.1. Ultimate analysis Table 1 shows some features of the samples, including elemental analysis, moisture content and ash content. These parameters are important for the determination of changes in material during the biodegradation processes of biomethanation and composting. From Table 1, it can be observed that all samples have similar compositions except for the rejected fraction. The ash content depends on the sample taken. For the rejected fraction it could occur that the analyzed sample contained low concentration of fines so the determined ash content is low compared to other samples. 3.2. PCDD/F and PCB total concentrations Concentrations of the toxic congeners for all the samples analyzed are summarized in Table 2. Toxic PCDD/F concentrations are expressed in I-TEQ (NATO/CCMS, 1988; Kutz et al., 1990) and WHO2005-TEQ basis (Van den Berg et al., 2006). Sum of the toxic congeners refers to the sum of the 17 2,3,7,8-tetrasubstituted congeners. The initial sample that enters the biomethanation process has a low toxic PCDD/F concentration of 0.25 ng WHO2005-TEQ kg 1. However, in the sample taken after biomethanation, the concentration is 2.75 ng WHO2005-TEQ kg 1 implying this is more than 10 times higher than the input, in terms of TEQ, or almost 100 times higher in terms of total concentration in ng kg 1. This remarkable fact could indicate a PCDD/F formation during the process, as appears to occur in the case of anaerobic fermentation of sewage sludge studied by Weber et al. (1997). During composting, a slight increase is also produced, but this could be the result of a concentration of material due to decomposition of biodegradable matter again, or to the fact that the samples are independent (the samples were taken on the same day and they are not consecutive throughout the composting process). The rejected fraction shows lower concentrations that are logical since this fraction corresponds to matter that has not undergone significant changes during these anaerobic and aerobic decompositions. Both total PCDD/Fs and PCBs are on the same order in the WHO2005-TEQ basis, but in the sample from the biomethanation process, a high concentration of PCBs can be observed compared
Table 1 Characterization of samples. Sample
Moisture Elemental analysis (%dm) O (%wm) C H N S Ash By 900 °C difference
MSW (biomethanation input) Biomethanation output Fresh compost Mature compost Rejected fraction
57.6
33.1 4.30 1.94 0.13 33.3
27.3
65.7 33.4 14.9 27.0
27.5 36.7 34.9 38.5
34.2 30.9 25.2 37.1
4.21 4.62 4.12 4.85
1.73 1.89 2.28 1.70
0.26 0.46 0.49 0.35
32.1 25.4 33.0 17.5
to PCDD/Fs. The rejected fraction, as occurred for PCDD/Fs, shows low PCBs concentrations since it is related to the material resulting from composting that did not undergo changes and therefore neither a formation nor a reduction of the PCB concentration could take place. The resultant concentrations in this fraction are similar to those shown for the initial sample. Considering Table 2, it can be pointed out that all the concentrations found are much lower than the guideline value of 17 ng ITEQ kg 1 d.m. proposed as the maximum value for compost samples when the final destination is the application to land (Fiedler, 1998). PCDD/F concentrations in untreated MSW (biomethanation input) are much lower than those obtained in the literature, 6.3– 73 ng I-TEQ kg 1 (Eduljee et al., 1997; Landesumweltam Landesumweltam Nordheinwestfalen, 1997), thus reaffirming that the concentrations in MSW are very changeable. During MSW composting, the PCDD/F concentrations obtained in our work are similar to those obtained by Eduljee et al. (1997), 0.4–3.3 ng I-TEQ kg 1, and Concejero et al. (2008), 2.92–9.22 ng ITEQ kg 1, although the first authors reported a PCDD/F decrease and in this work the concentration is similar. In the case of dioxin-like PCBs after MSW composting, our results are in accordance with those found by Concejero et al. (2008), 1.15–3.62 ng WHO2005-TEQ kg 1, thus corroborating that PCBs are as important as PCDD/Fs for environmental considerations. Figs. 1 and 2 show the concentration of all the 17 2,3,7,8-tetrasubstituted congeners in ng kg 1 and ng WHO2005-TEQ kg 1, respectively. Fig. 3 shows the homologue profile of PCDD/Fs (total concentrations of toxic and non-toxic tetra- through octacongeners). Fig. 4 shows the PCB congeners concentration expressed as ng WHO2005-TEQ kg 1 (Van den Berg et al., 2006). More information, including tables of concentration data for all the congeners, can be found in Supplementary Information. The congeners profile of PCDD/Fs (ng kg 1) found in this work (see Fig. 1) is in accordance with that observed by Grossi et al. (1998) and Malloy et al. (1993) for compost samples from MSW, who found a predominance of OCDD, followed by 1,2,3,4,6,7,8HpCDD. These congeners are the main contributors for other types of waste, such as sewage sludge and compost from sewage sludge (Hamann et al., 1997; Gómez-Rico et al., 2007). In addition to this, during some processes such as semi-anaerobic digestion or composting, OCDD and 1,2,3,4,6,7,8-HpCDD increase their
Table 2 Total PCDD/F and PCB levels in the five samples studied (referred to dry mass). Sample
PCDD/Fs (ng I-TEQ kg
MSW (biomethanation input) Biomethanation output Fresh compost Mature compost Rejected fraction
0.29 3.55 4.70 5.95 1.51
1
)
PCDD/Fs (ng WHO-TEQ kg 0.25 2.75 3.56 4.90 1.22
1
)
PCBs (ng WHO-TEQ kg 0.29 8.65 1.01 1.55 0.39
1
)
PCDD/Fs (sum ng kg 49.2 922 845 1518 922
1
)
PCBs (sum ng kg 497 31 914 3774 14 090 1315
1
)
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
ng/kg dry mass
1400 1200
MSW (Biomethanation input) Biomethanation output
1000
Fresh compost
800
Mature compost
600
Rejected fraction
400 200
8 MSW (biomethanation input) 7
ng WHO2005-TEQ kg-1
76
Biomethanation output
6
Fresh compost
5
Mature compost
4
Rejected fraction
3 2 1
0
0 81
Fig. 1. PCDD/F concentrations in ng/kg.
ng WHO-TEQ kg-1
2.2
MSW (biomethanation input)
2.0
Biomethanation output
1.8
Fresh compost
1.6
Mature compost
1.4
Rejected fraction
1.2 1.0 0.8 0.6 0.4 0.2 0
Fig. 2. PCDD/F levels of the individual congeners in the five samples studied in ng WHO2005TEQ/kg dry mass.
400
MSW (Biomethanation input) Biomethanation output
ng kg-1
350
Fresh compost
300
Mature compost
250
Rejected fraction
200 150 100
77
123
118
114
105
126
167
156
157
169
189
Fig. 4. PCB levels of the individual congeners in the five samples studied in ng WHO2005-TEQ/kg dry mass.
those obtained for other fractions. The compounds that contribute the most to the total toxicity are 23478-PeCDF, 123678-HxCDD, 1234678-HpCDD and OCDD. They have higher concentrations after biomethanation and after maturation of compost, especially 1,2,3,4,6,7,8-HpCDD and OCDD. Relatively similar variations can be observed for PCDD and PCDF. Nonetheless, the highest TEQ concentration for PCDD corresponds to mature compost, whereas for PCDF it corresponds to fresh compost. According to Fig. 3, it can be said that the homologue profile of the total PCDD/F is the same as the toxic congener’s profile. Comparing the values observed in Figs. 1 and 3 it can be said that the concentration of non-toxic congeners is not significant. Concerning Fig. 4 (PCB toxic concentrations expressed as ng WHO2005-TEQ kg-1), it can be observed that congener 126 is the main contributor to the total toxicity, and the concentration of this compound is especially high in the sample corresponding to the biomethanation output. It must be noted that congener 126 has the highest toxicity factor. PCB concentration for MSW or compost from MSW found in the literature is scarce. Kerst et al. (2003) studied PCBs in compost samples from organic household waste (mixture of kitchen waste, garden waste and small amounts of paper) and observed that the major contribution to the WHO2005-TEQ was due to PCB-126 (70% ±4.5), which is in accordance with this work. For compost from livestock waste, PCB-126 was also the main contributor in a study carried out by Ng et al. (2008), and it was formed during the composting process. Therefore, as mentioned for PCDD/Fs, the formation or destruction of PCBs during composting deeply depends on the process conditions.
50 0
Fig. 3. Concentration of ng/kg of the homologues (toxic and non toxic congeners).
concentrations under certain conditions (Öberg et al., 1993; Klimm et al., 1998). Malloy et al. (1993) attributes the occurrence of PCDDs and PCDFs, with relatively high concentrations of 1,2,3,4,6,7,8-HpCDDs and OCDD, to two factors: first, the presence of pentachlorophenol (PCP) containing PCDD/F byproducts that may enter the compost feedstock contaminating the final product, and second, high concentrations of PCP and other chlorophenols in MSW compost may be converted via biological mechanisms to PCDDs and PCDFs, specifically HpCDDs and OCDD. From Fig. 2, it can be observed that the initial sample and the rejected fraction have toxicity concentrations much lower than
4. Conclusions Low concentrations of PCDD/Fs and PCBs were found in samples from MSW, biomethanation of MSW and composting of biomethanation digestate. These compounds show slightly higher concentrations in the biomethanation output sample, but without major problems for the environment. The PCDD/F homologue profile (ng kg 1) was similar for all samples, with a predominance of 1,2,3,4,6,7,8-HpCDD and OCDD, and therefore the possible formation of these compounds during the processes studied is not clear.
Acknowledgment Support for this work was provided by the Project CTQ 200805520 of the Spanish Ministry of Science and Innovation and the project Prometeo 2009/043/FEDER of the Valencian Community.
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.chemosphere.2013.10.004. References Adriaens, P., Grbic’-Galic, D., 1994. Reductive dechlorination of PCDD/F by anaerobic cultures and sediments. Chemosphere 29, 2253–2259. Cernuschi, S., 2001. Environmental evaluation of the waste treatment and disposal plants in the municipality of Bozen. Technical University of Milan, DIIAR. Concejero, M., De la Torre, A., Sanz, P., Martinez, A., 2008. PCDD/Fs, PCBs and HCB in leachate and compost from different Spanish landfills. Organohalogen Compd. 70, 1773–1775. Eduljee, G.H., Dyke, P., Cains, P.W., 1997. The effect of changing waste management practices on PCDD/PCDF releases from household waste recycling and disposal processes. Chemosphere 34, 1615–1622. US EPA, 1994. Method 1613. Tetra- through octa-chlorinated dioxins and furans by isotope dilution HRGC/HRMS. US Environmental Protection Agency, Washington, DC. Fiedler, H., 1998. Dioxin case study from Germany. Puerto Iguazú. Gómez-Rico, M.F., Font, R., Fullana, A., 2007. Study of PCDD/Fs formation during composting of sewage sludge in different conditions. Organohalogen Compd. 69, 1570–1573. Grossi, G., Lichtig, J., Kraub, P., 1998. PCDD/F, PCB and PAH content of Brazilian compost. Chemosphere 37, 2153–2160. Hamann, R., Weber, H., Disse, G., Haupt, H.J., 1997. Determination of the PCDD/F levels in large-scale sewage sludge composting. Organohalogen Compd. 32, 400–402. Kerst, M., Waller, U., Peichl, L., Bittl, T., Reifenhäuser, W., Körner, W., 2003. Dioxinlike PCB in environmental samples in southern Germany. Fresenius Environ. Bull. 12, 511–516. Klimm, C., Schramm, K.W., Henkelmann, B., Martens, D., Kettrup, A., 1998. Formation of Octa- and heptachlorodibenzo-p-dioxins during semi anaerobic digestion of sewage sludge. Chemosphere 37, 2003–2011. Kutz, F., Barnes, D., Bretthauer, E., Bottimore, D., Greim, H., 1990. He international toxicity equivalency factor (I-TEF) method for estimating risks associated with exposures to complex mixtures of dioxins and related compounds. Toxicol. Environ. Chem. 26, 99–109. Lonati, G., Cernuschi, S., Giugliano, M., Grosso, M., 2007. Health risk analysis of PCDD/F emissions from MSW incineration: comparison of probabilistic and deterministic approaches. Chemosphere 67, S334–S343.
77
Malloy, T.A., Goldfarb, T.D., Surico, M.T.J., 1993. PCDDs, PCDFs, PCBs, chlorophenols (CPs) and chlorobenzenes (CBzs) in samples from various types of composting facilities in the United States. Chemosphere 27, 325–334. NATO/CCMS, 1988. Scientific basis for the development of the International Toxicity Equivalency Factor (I-TEF) method of risk assessment for complex mixtures of dioxins and related compounds. Report No 178. North Atlantic Treaty Organization, Committee on the Challenges of Modern Society. Ng, Q.Y., Chan, A.H., Ma, S.W., 2008. A study of polychlorinated dibenzo-p-dioxins/ furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in the livestock waste compost of Hong Kong, PR China. Mar. Pollut. Bull. 57, 381–391. Landesumweltamt Nordheinwestfalen, 1997. Identification of Relevant Industrial Sources of Dioxins and Furans in Europe. Essen. Öberg, L.G., Rappe, C., 1992. Biochemical formation of PCDD/Fs from chlorophenols. Chemosphere 25, 49–52. Öberg, L.G., Glas, B., Swanson, S.E., Rappe, C., Paul, K.G., 1990. Peroxidase-catalyzed oxidation of chlorophenols to polychlorinated dibenzo-p-dioxinas and dibenzofurans. Arch. Environ. Contam. Toxicol. 19, 930–938. Öberg, L.G., Wagman, N., Andersson, R., Rappe, C., 1993. De novo formation of PCDD/ Fs in compost and sewage sludge – a status report. Organohalogen Compd. 11, 297–302. Ozkaya, B., 2005. Chlorophenols in leachates originating from different landfills and aerobic composting plants. J. Hazard. Mater. 124, 107–112. Van den Berg, M., Birnbaum, L., Bosveld, A.T., Brunstrom, B., Cook, P., Feeley, M., Giesy, J.P., Hanberg, A., Hasegawa, R., Kennedy, S.W., Kubiak, T., Larsen, J.C., van Leeuwen, F.X., Liem, A.K., Nolt, C., Peterson, R.E., Poellinger, L., Safe, S., Schrenk, D., Tillitt, D., Tysklind, M., Younes, M., Waern, F., Zacharewski, T., 1998. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environ. Health Perspect. 106, 775–792. Van den Berg, M., Birnbaum, L.S., Denison, M., De Vito, M., Farland, W., Feeley, M., Fiedler, H., Hakansson, H., Hanberg, A., Haws, L., Rose, M., Safe, S., Schrenk, D., Tohyama, C., Tritscher, A., Tuomisto, J., Tysklind, M., Walker, N., Peterson, R.E., 2006. The 2005 world health organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds. Toxicol. Sci. 93, 223–241. Weber, H., Hamann, R., Disse, G., Haupt, H.J., 1997. Influence of different treatment methods for sewage sludge on the levels of chlorinated dibenzodioxins and dibenzofurans. Organohalogen Compd. 32, 394–399. Wittsiepe, J., Kullmann, Y., Schrey, P., Selenka, F., Wilhelm, M., 1999. Peroxidasecatalyzed in vitro formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from chlorophenols. Toxicol. Lett. 106, 191–200. Zhang, H.-J., Ni, Y.-W., Chen, J.-P., Zhang, Q., 2008. Influence of variation in the operating conditions on PCDD/F distribution in a full-scale MSW incinerator. Chemosphere 70, 721–730.
Contents lists available at ScienceDirect
Chemosphere journal homepage: www.elsevier.com/locate/chemosphere
PCDD/F and dioxin-like PCB concentrations during municipal solid waste biomethanation and subsequent composting M. Muñoz ⇑, M.F. Gomez-Rico, R. Font Department of Chemical Engineering, University of Alicante, P.O. Box 99, E-03080 Alicante, Spain
h i g h l i g h t s The obtained toxic concentrations in all the fractions were low. 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDD and HpCDD showed the highest toxic concentrations. OCDD and 1,2,3,4,6,7,8-HpCDD showed the higher concentrations in almost all samples. The contribution of PCBs to the total toxicity is high.
a r t i c l e
i n f o
Article history: Received 27 February 2013 Received in revised form 19 September 2013 Accepted 1 October 2013 Available online 9 November 2013 Keywords: Biomethanation Composting MSW PCDD/Fs PCBs
a b s t r a c t PCDD/F and dioxin-like PCB concentrations were compared in different samples of a municipal solid waste (MSW) treatment plant: the initial MSW fraction that enters the biomethanation from the digester, the semi-solid digestate obtained after biomethanation of MSW, and the solids after composting the digestate since the final product is destined for land application and special attention must be paid to these compounds for environmental considerations. The initial MSW sample showed low concentrations of PCDD/Fs, although in the biomethanation output sample the concentration was more than ten times higher. The difference was even more significant for PCBs. In compost samples concentrations for both PCDD/Fs and PCBs were in the same range as in biomethanation or lower. Nevertheless, concentrations found for all samples were low and these treatments do not pose a major problem for the environment in the working conditions used. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction In recent years, a great effort has been made to reduce the amount of municipal solid waste (MSW) that is landfilled. According to the EU Landfill Directive (Council Directive 1999/31/EC of 26 April 1999), by 2013 biodegradable municipal waste landfilled must be reduced to 50% of that produced in 1995, and by 2020 to 35% of the amount produced in 1995. Two alternatives are biomethanation and composting from the biodegradable fraction. Biomethanation, or anaerobic digestion, is a complex microbial process in which organic compounds are degraded into methane and carbon dioxide by a variety of anaerobes. This biogas can be used as a fuel after desulfuration of the biogas with hydrogen sulfide, and the fermented solid residue can be used as a fertilizer or raw material for composting. When organic compounds are maintained at 5–70 °C and neutral pH under anaerobic conditions, spontaneous biomethanation will occur. Biogas is produced in this ⇑ Corresponding author. Tel.: +34 965 903 400x3003; fax: +34 965 903 826. E-mail address: [email protected] (M. Muñoz). 0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.10.004
way in landfills but, in addition to this, biomethanation plants exist to treat some fractions of MSW to obtain biogas. Aerobic composting is a well-extended practice of waste reduction that consists of a microbial conversion of material in the presence of suitable amounts of air and moisture into a stabilized product, compost, with the general appearance and other characteristics of a fertile soil. Composting can be performed either directly from the residue or after biomethanation. The literature concerning PCDD/F concentrations in MSW and its treatment is scarce so far, and the discussion of PCDD/F emissions from MSW treatments usually refers to incineration. First of all, untreated MSW has very changeable PCDD/F concentrations. While in the UK an average concentration of 6.3 ng I-TEQ kg 1 was found (Eduljee et al., 1997) in Germany around 73 ng I-TEQ kg 1 was obtained (Landesumweltamt Nordheinwestfalen, 1997). However, PCDD/F concentrations in different stages of the MSW treatment have been reported. PCDD/F concentrations of 5–117 pg ITEQ N m 3 have been found in the biogas produced spontaneously (before its combustion), when MSW is landfilled (Cernuschi, 2001). Nevertheless, the biogas flow coming out from the landfill
74
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
body is very low. Flue gases from combustion of MSW have been found to show higher concentrations of PCDD/Fs than those found in biogas. Zhang et al. (2008) reported 1160–3190 pg I-TEQ N m 3 in combustion of MSW, Lonati et al. (2007) showed values of 1300 pg I-TEQ N m 3 for old plants and 3.2 pg I-TEQ N m 3 for new plants of MSW combustion and 100–5000 pg I-TEQ N m 3 were also reported by Fiedler (1998). Regarding landfill leachate, Concejero et al. (2008) showed that nearly all the congeners were below the detection limit and only OCDD had significant levels, with a total PCDD/F content from 0.01 to 5.22 ppq I-TEQ. Apart from the PCDD/F concentrations obtained in biogas, when biomethanation is used as a treatment for MSW, special attention must be paid to the concentrations resulting in the liquid sludge or semi-solid residue, since its final destination is sometimes the application to land as a fertilizer after composting. No studies have been found on PCDD/Fs in this waste produced anaerobically, although there is evidence of dechlorination of PCDD/Fs by anaerobic cultures and sediments (Adriaens and Grbic’-Galic, 1994). However, lesser chlorinated PCDD/Fs (2,3,7,8-substituted ones) have been found as the accumulating products resulting from reductive dechlorination under anaerobic methanogenic conditions, that could be a matter of environmental concern. Furthermore, during anaerobic treatment of another waste, sewage sludge, an increase of PCDD/Fs was observed mainly due to the rise of 1,2,3,4,6,7,8-HpCDD and OCDD (Weber et al., 1997). On the other hand, composting supposedly degrades some organic pollutants present in the waste, but an enzymatic formation of PCDD/Fs (polychlorinated dibenzo-p-dioxins/furans) can take place during composting under certain conditions, as studied during sewage sludge composting by Weber et al. (1997). In this case, the increase was also due to 1,2,3,4,6,7,8-HpCDD and OCDD, as for anaerobic digestion. Malloy et al. (1993) also found high concentrations of PCDD/Fs (mean value of 56 ng I-TEQ kg 1) during the composting process of MSW, MSW mixed with sewage sludge and yard waste composting, where 1,2,3,4,6,7,8-HpCDD and OCDD were again the dominant congeners, probably due to a potential formation of PCDD/Fs from pentachlorophenol (PCP). However, Eduljee et al. (1997) reported a PCDD/F decrease during MSW composting. They found MSW to contain 6.3 ng I-TEQ kg 1 of waste while compost contained 0.4–3.3 ng I-TEQ kg 1. Therefore, the increase or decrease of the PCDD/F concentrations during composting seems to depend on the process conditions and initial materials containing PCDD/F precursors. Concejero et al. (2008) showed similar concentrations to Eduljee et al. (1997) after studying three MSW composting facilities, 1.53–5.26 ng WHO2005-TEQ kg 1 (or 2.92– 9.22 ng I-TEQ kg 1). These authors completed their study with the analysis of dioxin-like PCBs, obtaining for these compounds 1.15– 3.62 ng WHO2005-TEQ kg 1, and therefore PCBs are as important as PCDD/Fs for environmental considerations. The initial mixture necessary to carry out the composting process consists of waste and a bulking agent (e.g. straw, sawdust, leaves, woodchips, etc) to make it permeable to air. Both bulking agents and MSW could contain the precursors for the PCDD/F formation, such as pentachlorophenol. Pentachlorophenol was used for many years as a fungicide to treat wood to avoid woodworm, although nowadays its use is limited because of its relationship with the formation of PCDD/Fs. Nevertheless, chlorophenols can be still found in leachates from MSW landfills (Ozkaya, 2005). Some ‘‘in vitro’’ studies demonstrated the relationship between some peroxidase enzymes and chlorophenols with the dioxin formation, leading to considerable amounts of higher chlorinated PCDD/Fs (Öberg et al., 1990; Öberg and Rappe, 1992; Wittsiepe et al., 1999). Hence, a PCDD/F formation has been suggested from anaerobic treatment and composting of waste, but the information is contradictory and some other authors reported a reduction in the dioxin
levels after these treatments. Therefore, the aim of this work was to determine PCDD/F concentrations (the 17 2,3,7,8-tetrasubstituted congeners) in different samples: MSW, after biomethanation of MSW, and after composting of the digestate obtained in biomethanation. Dioxin-like PCBs (non-ortho and mono-ortho congeners (Van den Berg et al., 1998)) were also included in this study since their contribution to the toxicity could be significant.
2. Materials and methods MSW, biomethanation digestate and compost were provided by a MSW treatment plant located in the Southeast of Spain, which receives non-hazardous municipal waste. Five samples were analyzed: 1. MSW (biomethanation input): consists of MSW with particle size smaller than 40 mm without ferric materials, which is the most suitable fraction for the process. 2. Biomethanation output. 3. Fresh compost: compost obtained after 21 d of composting formed from the biomethanation output (particle size smaller than 40 mm) and the intermediate particle size fraction (40–80 mm). 4. Mature compost from the fraction with particle size smaller than 12 mm, after more than 1 month of maturation. 5. Rejected fraction: comprises the fraction of final compost after maturation with particle size larger than 12 mm. This fraction is separated from the mature compost, so it is not used as a fertilizer and is disposed of to landfill. It also contains plastic, glass and other non-fermentable materials. The moisture content was determined after drying the samples in a drying chamber at 105 °C for 24 h and weighing the sample before and after drying. The result is expressed as weight percentage with respect to the wet mass (wm). The elemental analysis was carried out in a Carlo Erba CHNS-O EA 1108 apparatus, after drying the samples at 105 °C for 24 h. The method is based on the complete oxidation (combustion) of the sample and analysis of the resultant gases by gas chromatography. The results are expressed as weight percentage with respect to dry mass (dm). The ash content was determined in a Heron 12PR/300 muffle furnace at 900 °C for 8 h, and the result is expressed as percentage with respect to dry mass. The oxygen percentage was calculated by difference, taking into account C, H, N, S and ash contents. In addition to this characterization, a thermogravimetric analysis (TG) of the samples was carried out in a Mettler Toledo thermobalance model TGA/SDTA851e/LF/1600, in order to obtain more information about the changes produced during the processes studied (see Supplementary Information for more details and results). The PCDD/F and PCB analysis was carried out according to the US EPA method 1613 (US EPA, 1994). An amount of approximately 10 g of each wet sample was spiked with the internal standard solutions containing the 13C12 labeled congeners, 1613LCS-PCDD/ Fs and WP-LCS-PCBs (Wellington Laboratories Inc., Canada), and was kept for 3 h with sodium sulfate. Then the samples were extracted in toluene using accelerated solvent extraction with a Dionex 100 apparatus (Dionex Corp., CA, USA). Extraction was followed by a clean-up and purification step consisting of an acid-basic treatment and a clean-up procedure using an FMS Power Prep TM System (FMS Inc., Boston, MA, US) using silica, alumina and carbon columns. The purified extract was analyzed using an Autospec Ultima high resolution mass spectrometer (Micromass, UK), with a positive electron impact (EI+) source and interfaced with a Hewlett–Packard (Palo Alto, CA, USA) 6890 Plus
75
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
gas chromatograph equipped with a PTV inlet with a septumpless head. A DB-5 60 m fused silica capillary column was used for the separation of the isomer specific analysis. Prior to the injection the recovery standards, 13C PCDDs (1,2,3,4-TeCDD and 1,2,3,7,8,9HxCDD) and 13C PCBs (70, 111 and 138), were added. The identification and quantification of each PCDD/F and PCB congener was performed by the isotope dilution method. Quality assurance and quality control (QA/QC) criteria included the recovery percentage of the internal standards, the relative retention time of the target compound compared to the internal standard, and the chlorine isotope ratio falling within 15% of the theoretical chlorine isotope ratio when the two most abundant ions are measured. 3. Results and discussion 3.1. Ultimate analysis Table 1 shows some features of the samples, including elemental analysis, moisture content and ash content. These parameters are important for the determination of changes in material during the biodegradation processes of biomethanation and composting. From Table 1, it can be observed that all samples have similar compositions except for the rejected fraction. The ash content depends on the sample taken. For the rejected fraction it could occur that the analyzed sample contained low concentration of fines so the determined ash content is low compared to other samples. 3.2. PCDD/F and PCB total concentrations Concentrations of the toxic congeners for all the samples analyzed are summarized in Table 2. Toxic PCDD/F concentrations are expressed in I-TEQ (NATO/CCMS, 1988; Kutz et al., 1990) and WHO2005-TEQ basis (Van den Berg et al., 2006). Sum of the toxic congeners refers to the sum of the 17 2,3,7,8-tetrasubstituted congeners. The initial sample that enters the biomethanation process has a low toxic PCDD/F concentration of 0.25 ng WHO2005-TEQ kg 1. However, in the sample taken after biomethanation, the concentration is 2.75 ng WHO2005-TEQ kg 1 implying this is more than 10 times higher than the input, in terms of TEQ, or almost 100 times higher in terms of total concentration in ng kg 1. This remarkable fact could indicate a PCDD/F formation during the process, as appears to occur in the case of anaerobic fermentation of sewage sludge studied by Weber et al. (1997). During composting, a slight increase is also produced, but this could be the result of a concentration of material due to decomposition of biodegradable matter again, or to the fact that the samples are independent (the samples were taken on the same day and they are not consecutive throughout the composting process). The rejected fraction shows lower concentrations that are logical since this fraction corresponds to matter that has not undergone significant changes during these anaerobic and aerobic decompositions. Both total PCDD/Fs and PCBs are on the same order in the WHO2005-TEQ basis, but in the sample from the biomethanation process, a high concentration of PCBs can be observed compared
Table 1 Characterization of samples. Sample
Moisture Elemental analysis (%dm) O (%wm) C H N S Ash By 900 °C difference
MSW (biomethanation input) Biomethanation output Fresh compost Mature compost Rejected fraction
57.6
33.1 4.30 1.94 0.13 33.3
27.3
65.7 33.4 14.9 27.0
27.5 36.7 34.9 38.5
34.2 30.9 25.2 37.1
4.21 4.62 4.12 4.85
1.73 1.89 2.28 1.70
0.26 0.46 0.49 0.35
32.1 25.4 33.0 17.5
to PCDD/Fs. The rejected fraction, as occurred for PCDD/Fs, shows low PCBs concentrations since it is related to the material resulting from composting that did not undergo changes and therefore neither a formation nor a reduction of the PCB concentration could take place. The resultant concentrations in this fraction are similar to those shown for the initial sample. Considering Table 2, it can be pointed out that all the concentrations found are much lower than the guideline value of 17 ng ITEQ kg 1 d.m. proposed as the maximum value for compost samples when the final destination is the application to land (Fiedler, 1998). PCDD/F concentrations in untreated MSW (biomethanation input) are much lower than those obtained in the literature, 6.3– 73 ng I-TEQ kg 1 (Eduljee et al., 1997; Landesumweltam Landesumweltam Nordheinwestfalen, 1997), thus reaffirming that the concentrations in MSW are very changeable. During MSW composting, the PCDD/F concentrations obtained in our work are similar to those obtained by Eduljee et al. (1997), 0.4–3.3 ng I-TEQ kg 1, and Concejero et al. (2008), 2.92–9.22 ng ITEQ kg 1, although the first authors reported a PCDD/F decrease and in this work the concentration is similar. In the case of dioxin-like PCBs after MSW composting, our results are in accordance with those found by Concejero et al. (2008), 1.15–3.62 ng WHO2005-TEQ kg 1, thus corroborating that PCBs are as important as PCDD/Fs for environmental considerations. Figs. 1 and 2 show the concentration of all the 17 2,3,7,8-tetrasubstituted congeners in ng kg 1 and ng WHO2005-TEQ kg 1, respectively. Fig. 3 shows the homologue profile of PCDD/Fs (total concentrations of toxic and non-toxic tetra- through octacongeners). Fig. 4 shows the PCB congeners concentration expressed as ng WHO2005-TEQ kg 1 (Van den Berg et al., 2006). More information, including tables of concentration data for all the congeners, can be found in Supplementary Information. The congeners profile of PCDD/Fs (ng kg 1) found in this work (see Fig. 1) is in accordance with that observed by Grossi et al. (1998) and Malloy et al. (1993) for compost samples from MSW, who found a predominance of OCDD, followed by 1,2,3,4,6,7,8HpCDD. These congeners are the main contributors for other types of waste, such as sewage sludge and compost from sewage sludge (Hamann et al., 1997; Gómez-Rico et al., 2007). In addition to this, during some processes such as semi-anaerobic digestion or composting, OCDD and 1,2,3,4,6,7,8-HpCDD increase their
Table 2 Total PCDD/F and PCB levels in the five samples studied (referred to dry mass). Sample
PCDD/Fs (ng I-TEQ kg
MSW (biomethanation input) Biomethanation output Fresh compost Mature compost Rejected fraction
0.29 3.55 4.70 5.95 1.51
1
)
PCDD/Fs (ng WHO-TEQ kg 0.25 2.75 3.56 4.90 1.22
1
)
PCBs (ng WHO-TEQ kg 0.29 8.65 1.01 1.55 0.39
1
)
PCDD/Fs (sum ng kg 49.2 922 845 1518 922
1
)
PCBs (sum ng kg 497 31 914 3774 14 090 1315
1
)
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
ng/kg dry mass
1400 1200
MSW (Biomethanation input) Biomethanation output
1000
Fresh compost
800
Mature compost
600
Rejected fraction
400 200
8 MSW (biomethanation input) 7
ng WHO2005-TEQ kg-1
76
Biomethanation output
6
Fresh compost
5
Mature compost
4
Rejected fraction
3 2 1
0
0 81
Fig. 1. PCDD/F concentrations in ng/kg.
ng WHO-TEQ kg-1
2.2
MSW (biomethanation input)
2.0
Biomethanation output
1.8
Fresh compost
1.6
Mature compost
1.4
Rejected fraction
1.2 1.0 0.8 0.6 0.4 0.2 0
Fig. 2. PCDD/F levels of the individual congeners in the five samples studied in ng WHO2005TEQ/kg dry mass.
400
MSW (Biomethanation input) Biomethanation output
ng kg-1
350
Fresh compost
300
Mature compost
250
Rejected fraction
200 150 100
77
123
118
114
105
126
167
156
157
169
189
Fig. 4. PCB levels of the individual congeners in the five samples studied in ng WHO2005-TEQ/kg dry mass.
those obtained for other fractions. The compounds that contribute the most to the total toxicity are 23478-PeCDF, 123678-HxCDD, 1234678-HpCDD and OCDD. They have higher concentrations after biomethanation and after maturation of compost, especially 1,2,3,4,6,7,8-HpCDD and OCDD. Relatively similar variations can be observed for PCDD and PCDF. Nonetheless, the highest TEQ concentration for PCDD corresponds to mature compost, whereas for PCDF it corresponds to fresh compost. According to Fig. 3, it can be said that the homologue profile of the total PCDD/F is the same as the toxic congener’s profile. Comparing the values observed in Figs. 1 and 3 it can be said that the concentration of non-toxic congeners is not significant. Concerning Fig. 4 (PCB toxic concentrations expressed as ng WHO2005-TEQ kg-1), it can be observed that congener 126 is the main contributor to the total toxicity, and the concentration of this compound is especially high in the sample corresponding to the biomethanation output. It must be noted that congener 126 has the highest toxicity factor. PCB concentration for MSW or compost from MSW found in the literature is scarce. Kerst et al. (2003) studied PCBs in compost samples from organic household waste (mixture of kitchen waste, garden waste and small amounts of paper) and observed that the major contribution to the WHO2005-TEQ was due to PCB-126 (70% ±4.5), which is in accordance with this work. For compost from livestock waste, PCB-126 was also the main contributor in a study carried out by Ng et al. (2008), and it was formed during the composting process. Therefore, as mentioned for PCDD/Fs, the formation or destruction of PCBs during composting deeply depends on the process conditions.
50 0
Fig. 3. Concentration of ng/kg of the homologues (toxic and non toxic congeners).
concentrations under certain conditions (Öberg et al., 1993; Klimm et al., 1998). Malloy et al. (1993) attributes the occurrence of PCDDs and PCDFs, with relatively high concentrations of 1,2,3,4,6,7,8-HpCDDs and OCDD, to two factors: first, the presence of pentachlorophenol (PCP) containing PCDD/F byproducts that may enter the compost feedstock contaminating the final product, and second, high concentrations of PCP and other chlorophenols in MSW compost may be converted via biological mechanisms to PCDDs and PCDFs, specifically HpCDDs and OCDD. From Fig. 2, it can be observed that the initial sample and the rejected fraction have toxicity concentrations much lower than
4. Conclusions Low concentrations of PCDD/Fs and PCBs were found in samples from MSW, biomethanation of MSW and composting of biomethanation digestate. These compounds show slightly higher concentrations in the biomethanation output sample, but without major problems for the environment. The PCDD/F homologue profile (ng kg 1) was similar for all samples, with a predominance of 1,2,3,4,6,7,8-HpCDD and OCDD, and therefore the possible formation of these compounds during the processes studied is not clear.
Acknowledgment Support for this work was provided by the Project CTQ 200805520 of the Spanish Ministry of Science and Innovation and the project Prometeo 2009/043/FEDER of the Valencian Community.
M. Muñoz et al. / Chemosphere 98 (2014) 73–77
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/ j.chemosphere.2013.10.004. References Adriaens, P., Grbic’-Galic, D., 1994. Reductive dechlorination of PCDD/F by anaerobic cultures and sediments. Chemosphere 29, 2253–2259. Cernuschi, S., 2001. Environmental evaluation of the waste treatment and disposal plants in the municipality of Bozen. Technical University of Milan, DIIAR. Concejero, M., De la Torre, A., Sanz, P., Martinez, A., 2008. PCDD/Fs, PCBs and HCB in leachate and compost from different Spanish landfills. Organohalogen Compd. 70, 1773–1775. Eduljee, G.H., Dyke, P., Cains, P.W., 1997. The effect of changing waste management practices on PCDD/PCDF releases from household waste recycling and disposal processes. Chemosphere 34, 1615–1622. US EPA, 1994. Method 1613. Tetra- through octa-chlorinated dioxins and furans by isotope dilution HRGC/HRMS. US Environmental Protection Agency, Washington, DC. Fiedler, H., 1998. Dioxin case study from Germany. Puerto Iguazú. Gómez-Rico, M.F., Font, R., Fullana, A., 2007. Study of PCDD/Fs formation during composting of sewage sludge in different conditions. Organohalogen Compd. 69, 1570–1573. Grossi, G., Lichtig, J., Kraub, P., 1998. PCDD/F, PCB and PAH content of Brazilian compost. Chemosphere 37, 2153–2160. Hamann, R., Weber, H., Disse, G., Haupt, H.J., 1997. Determination of the PCDD/F levels in large-scale sewage sludge composting. Organohalogen Compd. 32, 400–402. Kerst, M., Waller, U., Peichl, L., Bittl, T., Reifenhäuser, W., Körner, W., 2003. Dioxinlike PCB in environmental samples in southern Germany. Fresenius Environ. Bull. 12, 511–516. Klimm, C., Schramm, K.W., Henkelmann, B., Martens, D., Kettrup, A., 1998. Formation of Octa- and heptachlorodibenzo-p-dioxins during semi anaerobic digestion of sewage sludge. Chemosphere 37, 2003–2011. Kutz, F., Barnes, D., Bretthauer, E., Bottimore, D., Greim, H., 1990. He international toxicity equivalency factor (I-TEF) method for estimating risks associated with exposures to complex mixtures of dioxins and related compounds. Toxicol. Environ. Chem. 26, 99–109. Lonati, G., Cernuschi, S., Giugliano, M., Grosso, M., 2007. Health risk analysis of PCDD/F emissions from MSW incineration: comparison of probabilistic and deterministic approaches. Chemosphere 67, S334–S343.
77
Malloy, T.A., Goldfarb, T.D., Surico, M.T.J., 1993. PCDDs, PCDFs, PCBs, chlorophenols (CPs) and chlorobenzenes (CBzs) in samples from various types of composting facilities in the United States. Chemosphere 27, 325–334. NATO/CCMS, 1988. Scientific basis for the development of the International Toxicity Equivalency Factor (I-TEF) method of risk assessment for complex mixtures of dioxins and related compounds. Report No 178. North Atlantic Treaty Organization, Committee on the Challenges of Modern Society. Ng, Q.Y., Chan, A.H., Ma, S.W., 2008. A study of polychlorinated dibenzo-p-dioxins/ furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in the livestock waste compost of Hong Kong, PR China. Mar. Pollut. Bull. 57, 381–391. Landesumweltamt Nordheinwestfalen, 1997. Identification of Relevant Industrial Sources of Dioxins and Furans in Europe. Essen. Öberg, L.G., Rappe, C., 1992. Biochemical formation of PCDD/Fs from chlorophenols. Chemosphere 25, 49–52. Öberg, L.G., Glas, B., Swanson, S.E., Rappe, C., Paul, K.G., 1990. Peroxidase-catalyzed oxidation of chlorophenols to polychlorinated dibenzo-p-dioxinas and dibenzofurans. Arch. Environ. Contam. Toxicol. 19, 930–938. Öberg, L.G., Wagman, N., Andersson, R., Rappe, C., 1993. De novo formation of PCDD/ Fs in compost and sewage sludge – a status report. Organohalogen Compd. 11, 297–302. Ozkaya, B., 2005. Chlorophenols in leachates originating from different landfills and aerobic composting plants. J. Hazard. Mater. 124, 107–112. Van den Berg, M., Birnbaum, L., Bosveld, A.T., Brunstrom, B., Cook, P., Feeley, M., Giesy, J.P., Hanberg, A., Hasegawa, R., Kennedy, S.W., Kubiak, T., Larsen, J.C., van Leeuwen, F.X., Liem, A.K., Nolt, C., Peterson, R.E., Poellinger, L., Safe, S., Schrenk, D., Tillitt, D., Tysklind, M., Younes, M., Waern, F., Zacharewski, T., 1998. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environ. Health Perspect. 106, 775–792. Van den Berg, M., Birnbaum, L.S., Denison, M., De Vito, M., Farland, W., Feeley, M., Fiedler, H., Hakansson, H., Hanberg, A., Haws, L., Rose, M., Safe, S., Schrenk, D., Tohyama, C., Tritscher, A., Tuomisto, J., Tysklind, M., Walker, N., Peterson, R.E., 2006. The 2005 world health organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds. Toxicol. Sci. 93, 223–241. Weber, H., Hamann, R., Disse, G., Haupt, H.J., 1997. Influence of different treatment methods for sewage sludge on the levels of chlorinated dibenzodioxins and dibenzofurans. Organohalogen Compd. 32, 394–399. Wittsiepe, J., Kullmann, Y., Schrey, P., Selenka, F., Wilhelm, M., 1999. Peroxidasecatalyzed in vitro formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from chlorophenols. Toxicol. Lett. 106, 191–200. Zhang, H.-J., Ni, Y.-W., Chen, J.-P., Zhang, Q., 2008. Influence of variation in the operating conditions on PCDD/F distribution in a full-scale MSW incinerator. Chemosphere 70, 721–730.