Methodologies for technology selection

The selection of pre-treatment, processing, storage and disposal technolo­gies is necessarily bound up with the overall strategy for the management of the waste under consideration, and this is turn may be part of a larger scheme embracing many waste types. To achieve a satisfactory waste man­agement strategy, waste management components must be complementary and compatible with each other [1]. Many aspects have to be addressed, the challenge being to achieve the optimal solution in a logical, structured and justified way. An existing IAEA publication has already reviewed most important factors affecting the selection and implementation of waste man­agement technologies [48] . In any case, it is important to ensure that all three basic waste management routes (e. g., clearance, discharge or regu­lated disposal) are taken into account and evaluated in defining waste management strategies. It is important to consider strategies for all waste streams generated at facilities or sites rather than selecting options for individual waste streams. In addition, most national regulators now demand an impact assessment of proposed technologies and a justification for the selected technology.

The process of selecting a waste management technology typically starts by collecting and assessing available data, by considering all potentially influencing factors such as applicable regulations, waste properties, waste routes and associated good practice indicators. A set of possible technologi­cal options is then devised together with a preliminary waste management plan for implementing each option. These plans can be relatively brief at this stage but still sufficiently well defined, so that the associated major hazards and risks can be visualized.

The next step is to perform technology selection studies. During this process, formal decision-aiding techniques and ‘workshop’ discussion ses­sions can be employed. Selection of a preferred or optimized waste process­ing technology is best achieved through the evaluation of the general criteria and constraints in terms of their attributes for a specific waste stream or facility (Table 4.1).

This evaluation can benefit from the use of formal decision-aiding tech­niques that address the influencing factors and associated good practice indicators. When evaluating the various influencing factors for a specific technology option, a simple ‘decision-tree’ approach could be adopted, in which the various factors are evaluated. The limitations of a linear approach are that influencing factors may only be considered one at a time, and in descending order of priority. Project selection decisions require multiple, generally non-linear, objectives to be simultaneously optimized. In addition, factors that are mutually influential cannot be considered in combination. An example of the simplified decision-tree approach for the selection of a suitable technology for a particular waste stream is given in Fig. 4.2, although not all criteria and constraints are accounted for.

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