- Email: [email protected]
Conclusions of the workshop: standards, measurements and testing for solid waste management
314
trends in analytical chemistry, vol. 17, no. 5, 1998
All the processes of characterisation, sampling, pretreatment, extraction and leaching tests, analysis, etc. have to be considered on this basis. They must be studied and standardised similarly as for soils. In addition, some speci¢c tests, taking into account the high content of organic matter and trace elements, e.g. alkaline extraction, need further studies to be done. The harmonisation and standardisation of methods for soils, composts and other wastes is needed, with the aim of having comparable and more comprehensive data for the different countries of the European Union.
References [ 1 ] M. de Bertoldi, G. Vallini and A. Pera, in J.K.R. Gasser ( Editor ), Composting of Agricultural and Other Wastes, Elsevier Amsterdam, 1984, pp. 27^34. [ 2 ] J. Wiart and M. Verdier, Rapport AGHTM et FNDAE, 1994, 60 pp. [ 3 ] B. Morvan, J. Carre, TSM 2 ( 1995 ) 138^140. [ 4 ] W. de Feyter, in Symposium International sur le Traitement des Deèchets, Pollutec 94, 18^20 October 1994, Lyon, 1994, pp. 199^211. [ 5 ] P. Prudent, Theése Universiteè de Marseille, France, 1993. [ 6 ] A. Gomez and C. Lejeune, in M. de Bertoldi, M.P. Ferranti, P. L'Hermite and F. Zucconi ( Editors ), Compost: Production, Quality and Use, 1986.
Conclusions of the workshop: standards, measurements and testing for solid waste management Ph. Quevauviller*
European Commission, Standards Measurements and Testing Programme, DG XII (M075 3 / 09 ), Rue de la Loi 200, B-1049 Brussels, Belgium The quality of waste treatment processes and of ¢nal ( recycled ) products relies upon the availability of standards and testing methods. There is a clear need to develop ( and validate ) methods, e.g. for the control of treatment processes or for the characterisation of the end-products in view of their use in land¢ll, concrete, construction materials, etc. In this respect, the collaboration between industry and research organisations should be strengthened. In order to stimulate partnership between industry and research for the identi¢cation of possible actions to be undertaken in the ¢eld of standards, measurements and testing for solid waste management, the SMp pT programme of the European Commission organised a workshop. This paper summarises the round-table discussions and expert recommendations, as well as an outline of the programme of the workshop
*Corresponding author.
which was held in Pau ( France ), 5^7 May 1997. z1998 Elsevier Science B.V. Keywords: Solid waste; Waste treatment processes; SMpT Programme
1. Aim and organisation of the workshop The new regulations relating to industrial waste management have the ambitious objective to stop the direct release of wastes by 2002, by stipulating that wastes of different origin should be recycled where possible. The effects of different waste treatment processes should be accurately determined to ensure correct waste management and the industry is aware that signi¢cant efforts are required to optimise these treatments for obvious economic reasons. The quality of treatment processes and of ¢nal ( recycled ) products relies upon the availability of standards ( such as those prepared by CEN or ISO ) and testing methods ( e.g. chemical analysis for the assessment of environmental risks or land¢ll use ). There is a clear need to develop
0165-9936/98/$19.00 PII S 0 1 6 5 - 9 9 3 6 ( 9 7 ) 0 0 1 0 9 - X
ß 1998 Elsevier Science B.V. All rights reserved.
TRAC 2446 1-5-98
315
trends in analytical chemistry, vol. 17, no. 5, 1998
( and validate ) methods e.g. for the control of treatment processes or for the characterisation of the endproducts in view of their use in land¢lls, concrete, construction materials, etc. In this respect, the collaboration between industry and research organisations should be strengthened. The workshop on Standards, Measurements and Testing for Solid Waste Management aimed to stimulate partnership between industry and research for the identi¢cation of possible actions to be undertaken in this ¢eld, to discuss the state of the art of solid waste analysis, to de¢ne the applicability of current methodologies, to investigate where limitations exist and to identify possible aids to progress in this ¢eld. Several topics were debated in round-tables during the workshop. Each topic was introduced by a plenary lecture, followed by discussions chaired by a selected expert. Minutes of the discussions were taken. This paper gives a summary of the round-table discussions. The following topics were discussed in roundtables: Session 1: Session 2: Session 3: Session 4: Session 5:
Field measurements and screening tests. Rapid techniques for physico-chemical characterisation. Elaborated measurement techniques. Modelling, expert systems and databases. Standards, reference materials and quality control.
2. Field measurements and screening tests Discussions started on written standards ( CEN, ISO ) which are being developed but still not widely accepted by industry. Written standards for sampling and sample pretreatment exist for soil analysis ( ISO ) and waste ( draft CEN standard ). The main issue is validation, which is strongly needed and should be carried out, e.g. through interlaboratory testing. The participants stressed that it is not possible to produce standards applicable to all cases but rather guidance documents based on previous experience and validation for the determination of inorganic and organic parameters. It was stressed that inhomogeneities in the samples have a greater in£uence on the total composition than on the leached amounts. Techniques are needed for creating undisturbed samples as well as testing them in the undisturbed conditions and new sampling techniques should be developed for volatile compounds at ¢eld sites. Finally, sample pretreatment methods should be harmonised and preser-
vation methods ( e.g. of leachates ) should be investigated. On-site characterisation ( e.g. identi¢cation of hot spots ) and compliance testing should be supported by ¢eld measurements and screening tests. This is not always applicable to waste-testing schemes: for solid phase, visual testing is applied but is not easy to perform; liquid phase may be studied through e.g. in-site leaching; ¢nally, several ¢eld-testing techniques exist for gas measurements. It is not necessary to obtain quantitative data from screening tests, i.e. a semi-quantitative response should be suf¢cient to decide whether or not analytical measurements need to be carried out ( e.g. upon detection of a contaminant ). Questions arose regarding the robustness of sensors which may give excellent results with simple ( calibrant ) solutions but may fail totally under ¢eld-test conditions; the production of sensors is costly but the low cost of the ¢nal instruments ( including disposable sensors ) makes it worth the effort of development, providing that this includes validation! Industry would be a potential user of sensors for rapid screening tests to map contaminated sites ( e.g. a battery of sensors providing `yes / no' responses ). It was, however, stressed that a number of sensors have already been developed ( many of them through EC-funded projects ) and that it would be timely to establish a compilation of the sensors available on the market in order to discuss their merits in relation to ¢eld applicability and validation. Such a document should be made available to industry and to regulators. In this way, a possible classi¢cation of sensors could be established on the basis of their applicability to real-case analyses and usefulness ( ease of handling ). Land¢ll test areas exist in different countries and they could be used for a large-scale validation of existing technologies; this would offer possibilities to compare methods used for leachate collection, to validate leaching tests and test sampling procedures for solid, liquid and gas phases in relation to different categories of wastes or contaminated soils. Industry needs to develop strategies to test written standards against results obtained by `rapid' techniques; land¢ll test areas could respond to these needs. In terms of development, rapid chemical methods should be adapted to waste analysis ( e.g. colourimetry, spectrometry ). Field measurements are closely dependent on the availability of miniaturised, portable, existing instruments ( e.g. XRF, MS, NIR ). For leachates, fast in-situ methods could focus on e.g. SFE procedures, slurry / microwave digestion, etc.
TRAC 2420 1-5-98
316
trends in analytical chemistry, vol. 17, no. 5, 1998
The development and use of ecotoxicological tests ( biological tests ) which may be used as con¢rmatory tests is on-going. However, these tests are seldom practical for screening owing to time-consuming and costly operating procedures. The group of experts recommended that a collection of available information on inorganic substances in leachates should be established, as well as a list of parameters to be measured at new ¢eld sites. In addition, an overview of the problems in the measurement and testing for organic compounds should be produced; methods for organic compounds are generally lacking and the possibilities of transforming methods for inorganic substances to organic compounds should be evaluated.
3. Rapid techniques for physicochemical characterisation The term `rapid' has different meanings for representatives of different organisations; for industry it should be ¢ve minutes; for research it means that analysis should be carried out immediately after sampling to obtain results within a maximum of ¢ve days. A correct de¢nition could be `the fastest way of measuring parameters'. The following levels of assessment were identi¢ed: e.g. ¢rst step to identify major à Characterisation, problems or to complete main analyses by screen-
à à
ing in the ¢eld. Short procedures (maximum 2^4 days), e.g. compliance tests. In-situ veri¢cation (less than one hour, cheap and simple tests), e.g. for quality control of material delivered for disposal or treatment.
It was agreed that short tests cannot replace characterisation for important decisions such as disposal routes or utilisation acceptance. Short procedures are generally used to check the consistency of the waste under consideration with the one which was previously characterised. One test is generally not suf¢cient; a combination of several short tests is recommended. Discussions concentrated on needs related to regulatory tests, quality control tests in production ( control of effectiveness of waste treatment ) and toxicity tests. For regulatory purposes, a number of different tests exist ( probably more than is necessary!); there is, however, a lack of clear guidance on limits of test
applicability ( conditions vary according to various matrix composition ) and it is felt that regulatory tests should be redesigned or limited to a few ( robust ) tests adapted to generic parameters. Rapid tests for quality control of waste treatment processes should be simple tests tailored to speci¢c parameters e.g. pH, nitrates ( e.g. on waste slurries ). Some speci¢c needs were identi¢ed: e.g. shorter permeability tests ( 4^5 days ) for waste characterisation; a rapid test could be developed on the basis of `pre-equilibrium' test, i.e. rapid analysis and extrapolation of results, which would require full automation, studies of grain size effect and studies of, e.g., shaking energy. It was stressed that the needs are not always for rapid tests but rather for economic ones. Models may be useful but they require a high degree of validation based on databanks and test veri¢cations. The main need at present is certainly the validation of existing tests in relation to de¢ned parameters ( grain size, contact time, etc. ) and the constitution of databanks. Toxicity tests are good complementary tests ( detection of risks not detected by chemical means ) e.g. use of daphnia or bacteria for ecosystems. In-vitro assays are used for evaluating risks for humans ( e.g. using rats, rabbits ). An alternative is to determine `stress enzymes' which are quite sensitive ( e.g. plant analysis ) but not rapid. Rapid toxicity tests should be developed and validated for the analysis of leachates to verify that waste will not inhibit bacteria used in waste treatment. The following priorities emerged from the discussions: of an European database of analytical and à Creation behavioural data on main waste streams and
à à à à
possibly contaminated soils; an Internet site could be a way to gather such information. Establishment of the state of the art of rapid techniques used for organic contaminants. Documenting the correlations between results from three levels of leaching tests, i.e. long ones (some months), short ones (some days) and very short ones (less than one hour), i.e. de¢ning and limiting the type/nature of information that can be correlated from one level to another. Study of the relations between quick solvent extraction, conventional trace organic analysis, and bio-availability. Development of a `Swiss Knife' type of tests (i.e. a compact set of short tests containing three or four
TRAC 2420 1-5-98
317
trends in analytical chemistry, vol. 17, no. 5, 1998
à
different extractions addressing the key parameters of behaviour). Improvement of use of tests and data interpretation by the establishment of a European Pro¢ciency testing scheme on waste analysis, involving control laboratories, industry and research organisations.
4. Elaborated measurement techniques The environmental impact assessment of solid wastes is very much dependent on the possible treatment and eventual utilisation of waste products; these issues cannot be discussed in a general framework without reference to speci¢c types of waste products and their characteristics. Discussions were hence limited to issues related to long term storage of waste products with special emphasis on contaminated soils and waste products such as sludges, dredging wastes and speci¢c industrial waste products ( mining or industrial wastes ), and contaminated soils associated with earlier land¢ll operations. Conclusions were reached with respect to various research needs, in particular to leaching experiments, measurements for waste characterisation and physical / analytical measurements. A summary is given below. A large mass of scienti¢c data and procedures is presently available for certain waste products but this information is not well enough disseminated to all concerned parties in Europe. It would be useful to collate the available information in a set of concise documents and possibly format them in the form of a schematic `decision tree'. For a number of essential issues either the information is not available, or a number of procedures have not been described, or methodological guidelines are sometimes not suf¢ciently clear and detailed; there is a need to de¢ne and collate missing information and possibly amend existing guidelines accordingly. Applied research should obviously be developed in collaboration with industry to study `real-world' problems. Fundamental research is also needed e.g. to establish `lifetimes' of a number of toxic organic compounds in waste deposits, to identify the transformation processes during storage and the movement in the waste, and ¢nally to determine the major physical and chemical factors controlling mobility of organic compounds. This research should be applied to a range of selected compounds, e.g. phenols, PCBs, PAHs and dioxins, as well as some organometallic species ( e.g. organotin compounds in dredging waste ).
Contaminated soils are considered an important area of study. Because of the wide variability in composition of European soils, proper care should be taken to select a limited number of soil types for detailed studies on leaching behaviours, which should be undertaken at the European level. It was stressed that the use of leaching procedures lacks coordination at the European level; there is a strong need to coordinate the development and use of tests which could lead to the de¢nition of set( s ) of standards for studying leaching of components from waste products. These tests should be de¢ned with the aim of providing information on the mobilisation of toxic compounds from wastes. There is a lack of suitable reference materials for testing and validating leaching tests, especially for the leaching of organic compounds; because of non-homogeneity and lack of suf¢cient large samples, existing materials are unsuitable for this type of work. The characterisation of the materials for study of waste products needs improvement. There are particular dif¢culties with the organic material, DOC being too generic a measurement for organic matter content of a waste product. Speci¢c organic products need to be determined directly in wastes used for leaching studies. Analytical methods such as gas chromatography / mass spectrometry and other hyphenated methods, combining chromatography with soft ionisation mass spectrometry, can be used for a more direct characterisation of organic matter. Here again, high organic reference materials are needed which could serve for studies of mobility of organic products and leaching studies in particular. In addition, further research should be devoted to the speciation of the elements in the eluates since chemical species are partly leached as natural complexes with organic complexing agents. Finally, the particular waste products could be characterised with microscopical methods of elemental and structural analysis (TEM, SEM, X-ray and electron diffraction ) in addition to the determination of the particle size. Ecotoxicity testing is an important additional activity and bioassays should be an integral part of detailed studies in the future, e.g. methods mimicking biological processes ( stress enzymes ). While leaching tests are considered to be important for short term assessment, long term behaviour cannot be safely determined from leaching experiments alone. Research should be devoted to other indirect measurement strategies for the determination of the mobility of toxic components in particular wastes. The problem should be addressed directly from well
TRAC 2420 1-5-98
318
trends in analytical chemistry, vol. 17, no. 5, 1998
characterised waste sites where measurements could be performed in a multidisciplinary approach. With respect to chemical measurements, analytical methodology developed for wastes is available for most of the required determinations. However, there is a clear lack of method validation and quality control in many cases which should encourage all parties ( 1 ) to develop simpler and more robust analytical methodologies that are easier to adapt to routine ¢eld exploitation, ( 2 ) to develop / validate more sophisticated techniques for detailed studies ( e.g. speciation ) such as SFE methods, microwave-based techniques, laserbased solid speciation, etc., and ( 3 ) to involve the analysts working in this particular ¢eld in training exercises, round-robin studies and user's networks to boost the accuracy and precision of the data. In all cases, the panel considered that the SMpT programme should continue to play a role as leading European organisation.
5. Modelling It was agreed that as part of the scenario of speci¢c assessment of environmental impact, modelling is an essential element of the overall evaluation. A number of different types of modelling can be considered: modelling (equilibrium condition). à Geochemical Water transport modelling. à Release modelling (dynamic and local equilibà rium). à Chemical interaction/transport modelling. Much can be achieved without developing models that are too sophisticated, i.e. those which are more readily assessed and more easily developed should be used. Models should include the behaviour of inorganic constituents, volatile substances and organic contaminants. Geochemical modelling can be subdivided into solubility controlled by speci¢c mineral phases, sorption onto active surfaces ( iron, manganese ) and complexation with particulate or dissolved organic matter. This type of modelling is primarily equilibrium based; it is a static assessment, i.e. it does not take time into account. Geochemical models can be used to provide information on speciation. Water transport modelling can deal with modelling of uptake, evaporation, reprecipitation, etc. This type of modelling should provide an estimate of timedependent changes in water throughput ( water bal-
ance ). This may be a surface phenomenon ( e.g. construction materials ) or percolation. Water transport models need also to take diffusion into account. Models should consider dry / wet periods as well. This is especially important for situations where the drying and wetting may change the chemistry of the system ( e.g. redox change at the surface of the materials ). Release modelling, e.g. diffusional transport or percolation, is dynamic and deals with changes with time in the contaminants released and the contaminants remaining in the source; such models will be an important part of waste characterisation for the identi¢cation of changes with time. Stability / degradation aspects need also to be considered for release modelling. The changes in systems caused by biological activity should not be disregarded. Modelling needs to take into account changes that occur with ageing ( oxidation, carbonation, remineralisation ). Other factors include changes resulting from temperature variations, freezing, degree of precipitation, geomorphology, ecology, etc. These factors vary with the geographical location of the European Member States. Geology has an effect on element migration. Modelling should consider both water transport and the consequences of contact with water such as weathering. This is particularly important with respect to matrices which are not durable in the long term ( e.g. expansive mineral formation ). Chemical interaction / transport modelling is related to time and spatial distribution; interface modelling also falls in this area. In order to obtain reliable data for models, there is a particular need to develop methods for the in-situ measurement of cation exchange capacity, permeability, organic carbon content, etc. General concern was expressed that models can become too complex; any model relating to more than one compound is already very complex. Models should not be created only from a database but should be developed in close cooperation between modellers and waste researchers who gather real data. There is a hierarchy of models, from simple to sophisticated, which are used regularly. A set of simple models can be developed relatively quickly; it is ¢rst necessary to identify the most important variables and to incorporate them into models. As not all variables are equally important in all situations, the maximum bene¢t can be achieved by identifying those which are important in a speci¢c situation. Many of the models or the components of the models already exist. It was strongly recommended that models addressing key variables should be connected together and developed as an integrated package, allowing predictions of environ-
TRAC 2420 1-5-98
319
trends in analytical chemistry, vol. 17, no. 5, 1998
mental impact. Society and regulators are now increasingly accepting modelling despite its limitations; it was emphasised that modelling is a useful tool and not just an academic exercise. Models can be used, with intelligent applications, as tools in decision-making, e.g. in regulations, treatment or reuse of waste, rapid initial assessment of environmental impact of a material in de¢ned circumstances, etc. It was recommended that selected examples be demonstrated of the intelligent application of models as valuable tools in decision-making. The validation of models and establishment of their limitations are vital issues. There are examples of where correlation is obtained between modelling and the ¢eld. It is recommended that models which are developed as suggested above should be run for well de¢ned ¢eld situations in order to validate them and to increase con¢dence in their application. Validation can only be carried out where it is possible for ¢eld data to be obtained over an appropriate time period. For very long term exposure, archaeological analogues can be used; it should be realised that comparison between prediction based on modelling and ¢eld veri¢cation has larger uncertainties as the time frame increases. Common sense must be used in the validation and application of models. It was emphasised that there cannot be a simple universal model in this complex ¢eld.
6. Expert systems The aspects of expert systems were not discussed in details. These systems are considered to be a useful tool but only displace the problem: the producer should analyse the waste! Expert systems should not be `black magic boxes' for decision-making; they will not replace human expertise based on data evolution. Such systems should only be considered as an aid for decision-making under strict control of experts. Participants felt that there is insuf¢cient state-of-the-art at this stage for developing expert systems, owing to the numerous interactions and parameters. Expert systems should be developed when the expertise warrants it and suf¢cient background information is available.
7. Databases Three different types of databases could be developed for thermodynamic constants ( geochemical models ), characterisation data: physical, chemical,
biological properties ( e.g. for soils, wastes, etc. ) and a database of models ( e.g. environmental assessment models, risk assessment models ). An ecotoxicological database with data on ecotoxicity of products was also identi¢ed as a valuable addition. Data properties can be a problem. Input is needed to improve the quality of data used in modelling. It was emphasised that data should be made available in an anonymous form in order to achieve the maximum bene¢t from the collective data. As the data do not need to be geo-referenced, data ownership may not be a problem. As discussed above, the group recommended as a priority the preparation of a database of existing information on characteristics of the common bulk waste streams in Europe. Such a database would allow workers to share the available information on these wastes and identify the key parameters and contaminants which need to be investigated. Such a database would allow available resources to be focused on obtaining site-speci¢c data rather than wasted on repeating the collection of information which is already available on well characterised materials. Participants take for granted the fact that data used in geochemical modelling is valid for the situation being modelled. Thermodynamic data are not available for several important contaminants relevant to wastes. Some of the data are not well de¢ned since they are derived from simple experimental situations. As discussed above, expansion and improvement of the existing data are needed and additional data are required to expand the range of chemicals, particularly with respect to trace organic compounds. It was recommended that a guidance document on how to establish databases for various purposes, validate data, etc. be prepared, including aspects of ¢eld tests, sampling selection of parameters, storage and within-laboratory quality control. Guidelines on onsite techniques for contaminated soils, including validation aspects, have been established in Scandinavian countries [ 1 ]; this document could perhaps serve as a basis for a comprehensive guidance document, covering aspects of sampling, storage, validation, reporting, databanking, etc. Education and training, in connection with these guidelines, should certainly not be disregarded.
Acknowledgements The scienti¢c committee was chaired by Prof. M. Astruc (Universiteè de Pau et des Pays de l'Adour,
TRAC 2420 1-5-98
320
trends in analytical chemistry, vol. 17, no. 5, 1998
France ) and was composed by Prof. C. Caèmara (Universidad Complutense, Madrid, Spain ), Dr. D. McGrath (Teagasc, Wexford, UK ), Dr. Ph. Quevauviller and Dr. H. van der Sloot ( ECN, Petten, the Netherlands ). The participants are gratefully acknowledged for their contribution to the success of this workshop. A special thank goes to the chairpersons and reporters who produced clear and concise minutes, enabling this summary to be written, namely O. Hjelmar, A.-M. Fallman, D. McGrath, L. Ebdon, R.
Morabito, J. Meèhu, M. Wahlstrom, C. Caèmara, L. Karstensen, F. Adams, H. van der Sloot, L. Heasman and O. Donard.
References [ 1 ] Nordic Guidelines for Chemical Analysis of Contaminated Soil Samples, NORDTEST Tech. Rep. 329, SINTEF Oslo, 1997.
TRAC 2420 1-5-98
trends in analytical chemistry, vol. 17, no. 5, 1998
All the processes of characterisation, sampling, pretreatment, extraction and leaching tests, analysis, etc. have to be considered on this basis. They must be studied and standardised similarly as for soils. In addition, some speci¢c tests, taking into account the high content of organic matter and trace elements, e.g. alkaline extraction, need further studies to be done. The harmonisation and standardisation of methods for soils, composts and other wastes is needed, with the aim of having comparable and more comprehensive data for the different countries of the European Union.
References [ 1 ] M. de Bertoldi, G. Vallini and A. Pera, in J.K.R. Gasser ( Editor ), Composting of Agricultural and Other Wastes, Elsevier Amsterdam, 1984, pp. 27^34. [ 2 ] J. Wiart and M. Verdier, Rapport AGHTM et FNDAE, 1994, 60 pp. [ 3 ] B. Morvan, J. Carre, TSM 2 ( 1995 ) 138^140. [ 4 ] W. de Feyter, in Symposium International sur le Traitement des Deèchets, Pollutec 94, 18^20 October 1994, Lyon, 1994, pp. 199^211. [ 5 ] P. Prudent, Theése Universiteè de Marseille, France, 1993. [ 6 ] A. Gomez and C. Lejeune, in M. de Bertoldi, M.P. Ferranti, P. L'Hermite and F. Zucconi ( Editors ), Compost: Production, Quality and Use, 1986.
Conclusions of the workshop: standards, measurements and testing for solid waste management Ph. Quevauviller*
European Commission, Standards Measurements and Testing Programme, DG XII (M075 3 / 09 ), Rue de la Loi 200, B-1049 Brussels, Belgium The quality of waste treatment processes and of ¢nal ( recycled ) products relies upon the availability of standards and testing methods. There is a clear need to develop ( and validate ) methods, e.g. for the control of treatment processes or for the characterisation of the end-products in view of their use in land¢ll, concrete, construction materials, etc. In this respect, the collaboration between industry and research organisations should be strengthened. In order to stimulate partnership between industry and research for the identi¢cation of possible actions to be undertaken in the ¢eld of standards, measurements and testing for solid waste management, the SMp pT programme of the European Commission organised a workshop. This paper summarises the round-table discussions and expert recommendations, as well as an outline of the programme of the workshop
*Corresponding author.
which was held in Pau ( France ), 5^7 May 1997. z1998 Elsevier Science B.V. Keywords: Solid waste; Waste treatment processes; SMpT Programme
1. Aim and organisation of the workshop The new regulations relating to industrial waste management have the ambitious objective to stop the direct release of wastes by 2002, by stipulating that wastes of different origin should be recycled where possible. The effects of different waste treatment processes should be accurately determined to ensure correct waste management and the industry is aware that signi¢cant efforts are required to optimise these treatments for obvious economic reasons. The quality of treatment processes and of ¢nal ( recycled ) products relies upon the availability of standards ( such as those prepared by CEN or ISO ) and testing methods ( e.g. chemical analysis for the assessment of environmental risks or land¢ll use ). There is a clear need to develop
0165-9936/98/$19.00 PII S 0 1 6 5 - 9 9 3 6 ( 9 7 ) 0 0 1 0 9 - X
ß 1998 Elsevier Science B.V. All rights reserved.
TRAC 2446 1-5-98
315
trends in analytical chemistry, vol. 17, no. 5, 1998
( and validate ) methods e.g. for the control of treatment processes or for the characterisation of the endproducts in view of their use in land¢lls, concrete, construction materials, etc. In this respect, the collaboration between industry and research organisations should be strengthened. The workshop on Standards, Measurements and Testing for Solid Waste Management aimed to stimulate partnership between industry and research for the identi¢cation of possible actions to be undertaken in this ¢eld, to discuss the state of the art of solid waste analysis, to de¢ne the applicability of current methodologies, to investigate where limitations exist and to identify possible aids to progress in this ¢eld. Several topics were debated in round-tables during the workshop. Each topic was introduced by a plenary lecture, followed by discussions chaired by a selected expert. Minutes of the discussions were taken. This paper gives a summary of the round-table discussions. The following topics were discussed in roundtables: Session 1: Session 2: Session 3: Session 4: Session 5:
Field measurements and screening tests. Rapid techniques for physico-chemical characterisation. Elaborated measurement techniques. Modelling, expert systems and databases. Standards, reference materials and quality control.
2. Field measurements and screening tests Discussions started on written standards ( CEN, ISO ) which are being developed but still not widely accepted by industry. Written standards for sampling and sample pretreatment exist for soil analysis ( ISO ) and waste ( draft CEN standard ). The main issue is validation, which is strongly needed and should be carried out, e.g. through interlaboratory testing. The participants stressed that it is not possible to produce standards applicable to all cases but rather guidance documents based on previous experience and validation for the determination of inorganic and organic parameters. It was stressed that inhomogeneities in the samples have a greater in£uence on the total composition than on the leached amounts. Techniques are needed for creating undisturbed samples as well as testing them in the undisturbed conditions and new sampling techniques should be developed for volatile compounds at ¢eld sites. Finally, sample pretreatment methods should be harmonised and preser-
vation methods ( e.g. of leachates ) should be investigated. On-site characterisation ( e.g. identi¢cation of hot spots ) and compliance testing should be supported by ¢eld measurements and screening tests. This is not always applicable to waste-testing schemes: for solid phase, visual testing is applied but is not easy to perform; liquid phase may be studied through e.g. in-site leaching; ¢nally, several ¢eld-testing techniques exist for gas measurements. It is not necessary to obtain quantitative data from screening tests, i.e. a semi-quantitative response should be suf¢cient to decide whether or not analytical measurements need to be carried out ( e.g. upon detection of a contaminant ). Questions arose regarding the robustness of sensors which may give excellent results with simple ( calibrant ) solutions but may fail totally under ¢eld-test conditions; the production of sensors is costly but the low cost of the ¢nal instruments ( including disposable sensors ) makes it worth the effort of development, providing that this includes validation! Industry would be a potential user of sensors for rapid screening tests to map contaminated sites ( e.g. a battery of sensors providing `yes / no' responses ). It was, however, stressed that a number of sensors have already been developed ( many of them through EC-funded projects ) and that it would be timely to establish a compilation of the sensors available on the market in order to discuss their merits in relation to ¢eld applicability and validation. Such a document should be made available to industry and to regulators. In this way, a possible classi¢cation of sensors could be established on the basis of their applicability to real-case analyses and usefulness ( ease of handling ). Land¢ll test areas exist in different countries and they could be used for a large-scale validation of existing technologies; this would offer possibilities to compare methods used for leachate collection, to validate leaching tests and test sampling procedures for solid, liquid and gas phases in relation to different categories of wastes or contaminated soils. Industry needs to develop strategies to test written standards against results obtained by `rapid' techniques; land¢ll test areas could respond to these needs. In terms of development, rapid chemical methods should be adapted to waste analysis ( e.g. colourimetry, spectrometry ). Field measurements are closely dependent on the availability of miniaturised, portable, existing instruments ( e.g. XRF, MS, NIR ). For leachates, fast in-situ methods could focus on e.g. SFE procedures, slurry / microwave digestion, etc.
TRAC 2420 1-5-98
316
trends in analytical chemistry, vol. 17, no. 5, 1998
The development and use of ecotoxicological tests ( biological tests ) which may be used as con¢rmatory tests is on-going. However, these tests are seldom practical for screening owing to time-consuming and costly operating procedures. The group of experts recommended that a collection of available information on inorganic substances in leachates should be established, as well as a list of parameters to be measured at new ¢eld sites. In addition, an overview of the problems in the measurement and testing for organic compounds should be produced; methods for organic compounds are generally lacking and the possibilities of transforming methods for inorganic substances to organic compounds should be evaluated.
3. Rapid techniques for physicochemical characterisation The term `rapid' has different meanings for representatives of different organisations; for industry it should be ¢ve minutes; for research it means that analysis should be carried out immediately after sampling to obtain results within a maximum of ¢ve days. A correct de¢nition could be `the fastest way of measuring parameters'. The following levels of assessment were identi¢ed: e.g. ¢rst step to identify major à Characterisation, problems or to complete main analyses by screen-
à à
ing in the ¢eld. Short procedures (maximum 2^4 days), e.g. compliance tests. In-situ veri¢cation (less than one hour, cheap and simple tests), e.g. for quality control of material delivered for disposal or treatment.
It was agreed that short tests cannot replace characterisation for important decisions such as disposal routes or utilisation acceptance. Short procedures are generally used to check the consistency of the waste under consideration with the one which was previously characterised. One test is generally not suf¢cient; a combination of several short tests is recommended. Discussions concentrated on needs related to regulatory tests, quality control tests in production ( control of effectiveness of waste treatment ) and toxicity tests. For regulatory purposes, a number of different tests exist ( probably more than is necessary!); there is, however, a lack of clear guidance on limits of test
applicability ( conditions vary according to various matrix composition ) and it is felt that regulatory tests should be redesigned or limited to a few ( robust ) tests adapted to generic parameters. Rapid tests for quality control of waste treatment processes should be simple tests tailored to speci¢c parameters e.g. pH, nitrates ( e.g. on waste slurries ). Some speci¢c needs were identi¢ed: e.g. shorter permeability tests ( 4^5 days ) for waste characterisation; a rapid test could be developed on the basis of `pre-equilibrium' test, i.e. rapid analysis and extrapolation of results, which would require full automation, studies of grain size effect and studies of, e.g., shaking energy. It was stressed that the needs are not always for rapid tests but rather for economic ones. Models may be useful but they require a high degree of validation based on databanks and test veri¢cations. The main need at present is certainly the validation of existing tests in relation to de¢ned parameters ( grain size, contact time, etc. ) and the constitution of databanks. Toxicity tests are good complementary tests ( detection of risks not detected by chemical means ) e.g. use of daphnia or bacteria for ecosystems. In-vitro assays are used for evaluating risks for humans ( e.g. using rats, rabbits ). An alternative is to determine `stress enzymes' which are quite sensitive ( e.g. plant analysis ) but not rapid. Rapid toxicity tests should be developed and validated for the analysis of leachates to verify that waste will not inhibit bacteria used in waste treatment. The following priorities emerged from the discussions: of an European database of analytical and à Creation behavioural data on main waste streams and
à à à à
possibly contaminated soils; an Internet site could be a way to gather such information. Establishment of the state of the art of rapid techniques used for organic contaminants. Documenting the correlations between results from three levels of leaching tests, i.e. long ones (some months), short ones (some days) and very short ones (less than one hour), i.e. de¢ning and limiting the type/nature of information that can be correlated from one level to another. Study of the relations between quick solvent extraction, conventional trace organic analysis, and bio-availability. Development of a `Swiss Knife' type of tests (i.e. a compact set of short tests containing three or four
TRAC 2420 1-5-98
317
trends in analytical chemistry, vol. 17, no. 5, 1998
à
different extractions addressing the key parameters of behaviour). Improvement of use of tests and data interpretation by the establishment of a European Pro¢ciency testing scheme on waste analysis, involving control laboratories, industry and research organisations.
4. Elaborated measurement techniques The environmental impact assessment of solid wastes is very much dependent on the possible treatment and eventual utilisation of waste products; these issues cannot be discussed in a general framework without reference to speci¢c types of waste products and their characteristics. Discussions were hence limited to issues related to long term storage of waste products with special emphasis on contaminated soils and waste products such as sludges, dredging wastes and speci¢c industrial waste products ( mining or industrial wastes ), and contaminated soils associated with earlier land¢ll operations. Conclusions were reached with respect to various research needs, in particular to leaching experiments, measurements for waste characterisation and physical / analytical measurements. A summary is given below. A large mass of scienti¢c data and procedures is presently available for certain waste products but this information is not well enough disseminated to all concerned parties in Europe. It would be useful to collate the available information in a set of concise documents and possibly format them in the form of a schematic `decision tree'. For a number of essential issues either the information is not available, or a number of procedures have not been described, or methodological guidelines are sometimes not suf¢ciently clear and detailed; there is a need to de¢ne and collate missing information and possibly amend existing guidelines accordingly. Applied research should obviously be developed in collaboration with industry to study `real-world' problems. Fundamental research is also needed e.g. to establish `lifetimes' of a number of toxic organic compounds in waste deposits, to identify the transformation processes during storage and the movement in the waste, and ¢nally to determine the major physical and chemical factors controlling mobility of organic compounds. This research should be applied to a range of selected compounds, e.g. phenols, PCBs, PAHs and dioxins, as well as some organometallic species ( e.g. organotin compounds in dredging waste ).
Contaminated soils are considered an important area of study. Because of the wide variability in composition of European soils, proper care should be taken to select a limited number of soil types for detailed studies on leaching behaviours, which should be undertaken at the European level. It was stressed that the use of leaching procedures lacks coordination at the European level; there is a strong need to coordinate the development and use of tests which could lead to the de¢nition of set( s ) of standards for studying leaching of components from waste products. These tests should be de¢ned with the aim of providing information on the mobilisation of toxic compounds from wastes. There is a lack of suitable reference materials for testing and validating leaching tests, especially for the leaching of organic compounds; because of non-homogeneity and lack of suf¢cient large samples, existing materials are unsuitable for this type of work. The characterisation of the materials for study of waste products needs improvement. There are particular dif¢culties with the organic material, DOC being too generic a measurement for organic matter content of a waste product. Speci¢c organic products need to be determined directly in wastes used for leaching studies. Analytical methods such as gas chromatography / mass spectrometry and other hyphenated methods, combining chromatography with soft ionisation mass spectrometry, can be used for a more direct characterisation of organic matter. Here again, high organic reference materials are needed which could serve for studies of mobility of organic products and leaching studies in particular. In addition, further research should be devoted to the speciation of the elements in the eluates since chemical species are partly leached as natural complexes with organic complexing agents. Finally, the particular waste products could be characterised with microscopical methods of elemental and structural analysis (TEM, SEM, X-ray and electron diffraction ) in addition to the determination of the particle size. Ecotoxicity testing is an important additional activity and bioassays should be an integral part of detailed studies in the future, e.g. methods mimicking biological processes ( stress enzymes ). While leaching tests are considered to be important for short term assessment, long term behaviour cannot be safely determined from leaching experiments alone. Research should be devoted to other indirect measurement strategies for the determination of the mobility of toxic components in particular wastes. The problem should be addressed directly from well
TRAC 2420 1-5-98
318
trends in analytical chemistry, vol. 17, no. 5, 1998
characterised waste sites where measurements could be performed in a multidisciplinary approach. With respect to chemical measurements, analytical methodology developed for wastes is available for most of the required determinations. However, there is a clear lack of method validation and quality control in many cases which should encourage all parties ( 1 ) to develop simpler and more robust analytical methodologies that are easier to adapt to routine ¢eld exploitation, ( 2 ) to develop / validate more sophisticated techniques for detailed studies ( e.g. speciation ) such as SFE methods, microwave-based techniques, laserbased solid speciation, etc., and ( 3 ) to involve the analysts working in this particular ¢eld in training exercises, round-robin studies and user's networks to boost the accuracy and precision of the data. In all cases, the panel considered that the SMpT programme should continue to play a role as leading European organisation.
5. Modelling It was agreed that as part of the scenario of speci¢c assessment of environmental impact, modelling is an essential element of the overall evaluation. A number of different types of modelling can be considered: modelling (equilibrium condition). à Geochemical Water transport modelling. à Release modelling (dynamic and local equilibà rium). à Chemical interaction/transport modelling. Much can be achieved without developing models that are too sophisticated, i.e. those which are more readily assessed and more easily developed should be used. Models should include the behaviour of inorganic constituents, volatile substances and organic contaminants. Geochemical modelling can be subdivided into solubility controlled by speci¢c mineral phases, sorption onto active surfaces ( iron, manganese ) and complexation with particulate or dissolved organic matter. This type of modelling is primarily equilibrium based; it is a static assessment, i.e. it does not take time into account. Geochemical models can be used to provide information on speciation. Water transport modelling can deal with modelling of uptake, evaporation, reprecipitation, etc. This type of modelling should provide an estimate of timedependent changes in water throughput ( water bal-
ance ). This may be a surface phenomenon ( e.g. construction materials ) or percolation. Water transport models need also to take diffusion into account. Models should consider dry / wet periods as well. This is especially important for situations where the drying and wetting may change the chemistry of the system ( e.g. redox change at the surface of the materials ). Release modelling, e.g. diffusional transport or percolation, is dynamic and deals with changes with time in the contaminants released and the contaminants remaining in the source; such models will be an important part of waste characterisation for the identi¢cation of changes with time. Stability / degradation aspects need also to be considered for release modelling. The changes in systems caused by biological activity should not be disregarded. Modelling needs to take into account changes that occur with ageing ( oxidation, carbonation, remineralisation ). Other factors include changes resulting from temperature variations, freezing, degree of precipitation, geomorphology, ecology, etc. These factors vary with the geographical location of the European Member States. Geology has an effect on element migration. Modelling should consider both water transport and the consequences of contact with water such as weathering. This is particularly important with respect to matrices which are not durable in the long term ( e.g. expansive mineral formation ). Chemical interaction / transport modelling is related to time and spatial distribution; interface modelling also falls in this area. In order to obtain reliable data for models, there is a particular need to develop methods for the in-situ measurement of cation exchange capacity, permeability, organic carbon content, etc. General concern was expressed that models can become too complex; any model relating to more than one compound is already very complex. Models should not be created only from a database but should be developed in close cooperation between modellers and waste researchers who gather real data. There is a hierarchy of models, from simple to sophisticated, which are used regularly. A set of simple models can be developed relatively quickly; it is ¢rst necessary to identify the most important variables and to incorporate them into models. As not all variables are equally important in all situations, the maximum bene¢t can be achieved by identifying those which are important in a speci¢c situation. Many of the models or the components of the models already exist. It was strongly recommended that models addressing key variables should be connected together and developed as an integrated package, allowing predictions of environ-
TRAC 2420 1-5-98
319
trends in analytical chemistry, vol. 17, no. 5, 1998
mental impact. Society and regulators are now increasingly accepting modelling despite its limitations; it was emphasised that modelling is a useful tool and not just an academic exercise. Models can be used, with intelligent applications, as tools in decision-making, e.g. in regulations, treatment or reuse of waste, rapid initial assessment of environmental impact of a material in de¢ned circumstances, etc. It was recommended that selected examples be demonstrated of the intelligent application of models as valuable tools in decision-making. The validation of models and establishment of their limitations are vital issues. There are examples of where correlation is obtained between modelling and the ¢eld. It is recommended that models which are developed as suggested above should be run for well de¢ned ¢eld situations in order to validate them and to increase con¢dence in their application. Validation can only be carried out where it is possible for ¢eld data to be obtained over an appropriate time period. For very long term exposure, archaeological analogues can be used; it should be realised that comparison between prediction based on modelling and ¢eld veri¢cation has larger uncertainties as the time frame increases. Common sense must be used in the validation and application of models. It was emphasised that there cannot be a simple universal model in this complex ¢eld.
6. Expert systems The aspects of expert systems were not discussed in details. These systems are considered to be a useful tool but only displace the problem: the producer should analyse the waste! Expert systems should not be `black magic boxes' for decision-making; they will not replace human expertise based on data evolution. Such systems should only be considered as an aid for decision-making under strict control of experts. Participants felt that there is insuf¢cient state-of-the-art at this stage for developing expert systems, owing to the numerous interactions and parameters. Expert systems should be developed when the expertise warrants it and suf¢cient background information is available.
7. Databases Three different types of databases could be developed for thermodynamic constants ( geochemical models ), characterisation data: physical, chemical,
biological properties ( e.g. for soils, wastes, etc. ) and a database of models ( e.g. environmental assessment models, risk assessment models ). An ecotoxicological database with data on ecotoxicity of products was also identi¢ed as a valuable addition. Data properties can be a problem. Input is needed to improve the quality of data used in modelling. It was emphasised that data should be made available in an anonymous form in order to achieve the maximum bene¢t from the collective data. As the data do not need to be geo-referenced, data ownership may not be a problem. As discussed above, the group recommended as a priority the preparation of a database of existing information on characteristics of the common bulk waste streams in Europe. Such a database would allow workers to share the available information on these wastes and identify the key parameters and contaminants which need to be investigated. Such a database would allow available resources to be focused on obtaining site-speci¢c data rather than wasted on repeating the collection of information which is already available on well characterised materials. Participants take for granted the fact that data used in geochemical modelling is valid for the situation being modelled. Thermodynamic data are not available for several important contaminants relevant to wastes. Some of the data are not well de¢ned since they are derived from simple experimental situations. As discussed above, expansion and improvement of the existing data are needed and additional data are required to expand the range of chemicals, particularly with respect to trace organic compounds. It was recommended that a guidance document on how to establish databases for various purposes, validate data, etc. be prepared, including aspects of ¢eld tests, sampling selection of parameters, storage and within-laboratory quality control. Guidelines on onsite techniques for contaminated soils, including validation aspects, have been established in Scandinavian countries [ 1 ]; this document could perhaps serve as a basis for a comprehensive guidance document, covering aspects of sampling, storage, validation, reporting, databanking, etc. Education and training, in connection with these guidelines, should certainly not be disregarded.
Acknowledgements The scienti¢c committee was chaired by Prof. M. Astruc (Universiteè de Pau et des Pays de l'Adour,
TRAC 2420 1-5-98
320
trends in analytical chemistry, vol. 17, no. 5, 1998
France ) and was composed by Prof. C. Caèmara (Universidad Complutense, Madrid, Spain ), Dr. D. McGrath (Teagasc, Wexford, UK ), Dr. Ph. Quevauviller and Dr. H. van der Sloot ( ECN, Petten, the Netherlands ). The participants are gratefully acknowledged for their contribution to the success of this workshop. A special thank goes to the chairpersons and reporters who produced clear and concise minutes, enabling this summary to be written, namely O. Hjelmar, A.-M. Fallman, D. McGrath, L. Ebdon, R.
Morabito, J. Meèhu, M. Wahlstrom, C. Caèmara, L. Karstensen, F. Adams, H. van der Sloot, L. Heasman and O. Donard.
References [ 1 ] Nordic Guidelines for Chemical Analysis of Contaminated Soil Samples, NORDTEST Tech. Rep. 329, SINTEF Oslo, 1997.
TRAC 2420 1-5-98