Emission of dioxin and related compounds from italian municipal waste incinerators

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and the T(4)CDD emission per tonne of refuse burnt, this observation is based on limited data but, if validated, could prove a useful diagnostic aid (see Hasselriis in this issue) . Karasek et al. (1986) have also demonstrated a similar relationship between excess air and dioxin content of EP ash on a large single unit . The variability of the results from similar grate types indicated that local operational practices or variability in the feed were significant factors . It was observed that, with combustion optimization, quite low residual PCDD/F levels could be achieved, but due to a lack of suitable instrumentation many plants could not optimize their combustion . As there will invariably be some dioxin in fly ash, optimization of particulate abatement plant is also important, here again the use of instrumentation to indicate plant performance would be beneficial . Acknowledgement The authors are pleased to acknowledge the support of the Land Waste Division of the U .K . Department of the Environment who sponsored the work reported . References ASTMS (1984), DRAFT Analytical Procedures to Assay Stack Effluent Samples and Residual Combustion Products for Polychlorinated Dibenzo-p-dioxin (PCDD) and Polychlorinated Dibenzofurans (PCDF) . Sponsored by the American Society of Mechanical Engineers . U .S . Environmental Protection Agency . See also Velzy, C . O . (1986), Chemosphere, 15, 1179 . Crummett, W . B . (1983), Status of analytical systems for the determination of PCDDs and PCDFs, Chemosphere, 12,429-446 . Karasek, K . W., Gonnard, M . F . & Finet, C . (1986), Control of the Emission of Dioxins in the Emission of Fly Ash from Incinerators of Urban Waste . TSM-L'Eau . Jantounen, M . J., Liimatainen, A ., Ramdahl, T ., Itkonen, A . (1986), Rapid changes in peat fly ash mutagenicity after release into the atmosphere, Environmental Science and Technology, 20, 684-689 .

Smith, W . B . et al. (1982), Sampling and Data Handling Methods for Inhalable Particulate Sampling. Southern Research Institute, 2000 Ninth Avenue, South Birmingham, AL 35255, NTIS PB 82-24987 . Tong, H . Y ., Shore, D . L ., Karasek, F . W ., Helland, P . & Jellum, E . (1984), Identification of organic compounds obtained from incineration of municipal waste by HPLC fractionation and gas chromatography-Mass spectrometry, Journal of Chromatography, 285, 423-441 . Woodfield, M . J . & Bushby, B . B . (1984), Interim Report on the Design and Development of a Sampling and Analytical Procedure for the Determination of Low Volatility Carbonaceous Material in Flue Gases . Warren Spring Laboratory, Stevenage, U .K . REPORT : EMISSION OF DIOXIN AND RELATED COMPOUNDS FROM ITALIAN MUNICIPAL WASTE INCINERATORS . By Aulo Magagni, Managing Director of Municipal Public Cleaning Company (A .M .N .I .U.P .), Padova, Italy, and Gieorgio Boschi, Head of Environmental Service (A .M .N .I .U .P.). A recent Italian law leading to regulations which became effective in 1986 requires waste incinerators to be equipped with post-combustion chambers that will achieve the following minimum operating conditions : free O z content of 6% in wet gas at exit of chamber ; gas velocity of 10 m s - ', average at entrance to chamber ; contact time of 2 s; and temperature of 950°C .



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This regulation forced the closing of about 50 large and small incinerators leaving only four that met the requirements . The rationale behind the law was based on reports in the literature on the destruction of organic wastes and was not at that time supported by any experimental data from local incinerators . Measurements on existing incinerators The Italian National Research Council (CNR) recently carried out a study of 10 Italian incinerators that did not have post-combustion chambers and three that are now equipped with them (Ghezzi & Giuliano 1985, Giuliano 1984) . Emissions of tetrachlorodibenzo-p-dioxin (TCDD) are shown in Table 1 . The post-combustion chamber TABLE 1 Emissions of TCDD from Italian incinerators using ESP Temperature (°C) Code

Combustion chamber

Post-combustion

(A) Old incinerators without post-combustion 1 973-1273 2 3 4 5 6

873-1023 1123-1323 773-1273 1123-1173 1048--1228

TCDD (ng m -3 ) 189 19 71 16 85 10

(B) Modern incinerators without post-combustion 7 8 9 10

1173-1223 1173-1323 1073-1323 1123-1273

21 0 .2 9 19

(C) Modern incinerators with post-combustion 11 1073-1273 1223-1323 12 13

1073-1273 1123-1273

1223-1323 > 1223

0 .1-1 .5 0 .8 1 .2-21

alone does not appear to be sufficient to ensure low emissions of TCDD . Of the 10 incinerators without post-combustion chambers, four are of modern design and have electrostatic precipitators (ESP), as do the three fitted with post-combustion facilities as a result of this study . There is no significant difference between the emissions from the two types of modern incinerators . Two with post-combustion and one without are able to keep TCDD emission levels below 1 ng m -3 . None of the old-style incinerators were able to give levels below 10 ng m -3 . A recent series of measurements of TCDD emissions were carried out in an incinerator fitted with post-combustion facilities followed by a wet-dry lime scrubber and an ESP (Benfenati et al . 1986) . In this device a slurry of lime (milk of lime) is spray dried by the flue gases leaving solid lime particles with adsorbed pollutants which are removed in the ESP . The lime scrubber-ESP system removed less than half of the TCDD emitted from the post-combustion chamber, even though the ESP captured 98% of the particulates .



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Acknowledgement The help of Prof. Michele Guiliano of the Politecnic of Milan is gratefully acknowledged . References Benfenati, Pastorelli, Castelli, Fanelli, Carminati, Farneti & Lodi (1986), Studies on the tetrachlorodibenzo-p-dioxin (TCDD) and tetrachlorodibenzofurans (TCDF) emitted from an urban incinerator, Chemosphere, 15, 557 . Ghezzi & Giuliano (1985), L'incenerimento ed i microinquinanti organoclorurati effetti della postcombustine (Incineration and organochlorinated micropollutants : post-combustion effects), Ingegneria Sanitaria, 14 .

Giuliano (1984), L'emissioni di microinquinanti dai form di incenerimento di rifiuti solidi urbani (Micropollutants emission from municipal solid wastes incinerator), Ingegneria Sanitaria, 13 .

REPORT : LIMITS TO STATISTICAL EVALUATION OF INCINERATOR EMISSIONS . By R . B . Dean, Editor Waste Management & Research, based on a talk presented at the ISWA-WHO-DAKOFA specialized seminar, Emission of Trace Organics from Municipal Solid Waste Incinerators, Copenhagen, 20-22 January 1987 . 1 . Introduction This Symposium has presented abundant data related to the emissions of Dioxin and related substances from municipal solid waste (MSW) incinerators . There are many apparent conflicts between different sets of this data and some attempts have been made to interpret these disparate results . The present paper, most of which was prepared after the Seminar presentations, endeavours to point out some of the reasons for the wide range of values presented .

2 . Sources of variability An MSW incinerator is not a steady-state reactor . There are large fluctuations in all the operating variables, both in time and space . The time fluctuations may be shorter than I s and are apparent at every time scale up to the life of the equipment . Space variations occur on every cross-section to the direction of flow and may only be damped out when the gases reach the top of the incinerator stack . Fluctuations have their origin in the raw material which, even on the scale of a truck load, varies according to the economic level of the district where it was collected and on the time of year : does it contain melon rinds or Christmas wrappings? The heterogeneity is even more apparent on smaller scales . For example, Brunner et al . (1986) quote a value of 3 mg of mercury per kg of MSW . This corresponds to 3 g, or about one small wrist watch battery per ton of MSW . The component of first concern, from the point of view of combustion, is water, because it has the greatest quenching effect and is high in fruit and vegetable residues but low in fats and dry paper . Even more spectacular are explosions of paint cans and flares of fast burning polystyrene foam blocks . The fire box of an operating municipal incinerator provides a vivid example of heterogeneous behaviour with temperatures represented by colours from red to bright yellow .