Process Engineering for Pollution Control and Waste Minimization_12

Các khái niệm và mô hình của chemodynamics được cung cấp chi tiết đáng kể bởi Thibodeaux (5), và Reible và Choi (6). Theo mục đích của cuộc thảo luận này, nó được giả định rằng các mô hình thích hợp của số phận và vận chuyển chất gây ô nhiễm đối với trường hợp được biết, ước tính, hoặc có sẵn trong một số thời trang.
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Process Engineering for Pollution Control and Waste Minimization_12 material and energy balances many be found in a number of chemical engineering texts, such as Felder and Rousseau (4) and others. 3 ADDITION OF CHEMODYNAMICS In order to take LCA beyond its usual scope to assess a waste site remedy, we need not only to include the mass and energy balances for environmental compartments, but also the models and mechanisms of inter- and intramedia transport. The concepts and models of chemodynamics are provided in significant detail by Thibodeaux (5), and by Reible and Choi (6). For the purposes of this discussion, it is assumed that appropriate models of the fate and transport of contaminants for a case are known, estimated, or available in some fashion. Since the objective of the LCA in remediation is to assess the burden being placed on the environment by various remedies, the application of realistic and appropriate models is essential and found in references above (5,6) for certain cases. 4 APPLICATION With the objective being assessment of the environmental (eco- and human health) burden from various remedies in a waste site problem, we may employ, as with LCA, risk assessment in the reverse, following the methodology of Hwang (7) as extended by Constant et al. (8). The exposure is summed from different routes to get total exposure, Et, which, to have an acceptable risk, should not exceed the reference dose level (RL). Exposures are calculated as in any other assessment, based on concentration, time, body weight, etc. Key here is the concentration at the exposure point (receptor), which is a function of the concen- tration in the soil or other medium. This function is the subject of much modeling work as described above, as it is essential to have accurate representations of the fate and transport of the contaminants in and across media under investigation. Thus, one may apply the above exposure method for an acceptable risk, combined with LCA, as follows (8). First, land use or other resource needs are established, followed by assuming a chemical management or remediation scheme or treat- ment train concept. Then, incorporating regulations, laws, and liabilities, chemi- cals are traced from “cradle to grave” throughout the process as in a typical LCA. Next, risk is assessed for the scheme (7) with all material and energy balances incorporated, along with eco-risk as appropriate. With these balances completed including appropriate fate and transport models, economics of the process(es) being considered are established. If the economics are acceptable, then the technology or waste processing is appropriate for the present level of available technology considered (or assumed) in the first step. If the economics are unfavorable, another treatment, manufacturing, or remediation scheme should beCopyright 2002 by Marcel Dekker, Inc. All Rights Reserved. applied to this integrated management methodology for comparison to the first attempt. Thus, methods can be evaluated for risk-based remediation or manufac- turing as in LCA for the most economical approach. It should be noted here that technology is on a moving time line, and what is successful and economical today will need to be reassessed several times in the future as chemical fate and transport modeling, our understanding of the environment, technologies, and regulations all change. In this manner, “new” technologies such as monitored natural attenuation (MNA) can be assessed alongside and with active remedies as described in the example below. 5 EXAMPLE OF ASSESSMENT The Petro Processors, Inc. (PPI), site is one of the most significant Superfund sites in the United States. While it is not directly under Superfund, due to agreement among the parties and existing consent decree in the U.S. District Court, Middle District of LA, it provides an excellent example, via hindsight, of the utility of LCA for risk-based remediation methodology as described by Constant et al. (8). Details of the site(s), being named Brooklawn and S ...