Remediation Of Hazardous Waste Sites Research Articles

Diffuse Double‐Layer Eqautions in SI Units

Clay particles are usually treated as lyophobic colloids and, thus, colloid chemistry provides a means for description of interactions in a clay-water-electrolyte system. The Stern-Gouy-Chapman theory of diffuse double layer has been applied to the behavior of clays with varying degrees of success. In most textbooks, the equations describing the diffuse double layer are given in electrostatic units. However, it is very confusing for researchers of different disciplines to communicate this way, as the existing equations are not even in compliance with the counterparts in electrical engineering. Moreover, it complicates double-layer computations when coupled flows are involved, i.e., one type of flow is induced by another type of force. These problems become apparent as the amount of research in hazardous waste management and site remediation grows. Hence, it is worthwhile to redevelop these equations using the SI system to eliminate these ambiguities and a redundant conversion factor. Moreover, it is shown...

A New Apparatus for the Evaluation of Electro-Kinetic Processes in Hazardous Waste Management

Abstract Possible uses of electro-kinetics for hazardous waste site remediation are being investigated. This paper describes a new apparatus which has been specifically designed, fabricated, and assembled to evaluate the viability, feasibility, practicality, and potential costs of these conceivable techniques experimentally. Results of studies on the existence of electro-osmotic flow in compacted clay and the electro-kinetic barrier to contaminant transport are used to illustrate the types of information that can be obtained by the apparatus.

Hazardous waste site remediation: The engineer's perspective, O'Brien & Gere Engineers, Inc., Robert Bellandi, Technical Editor, Van Nostrand Reinhold, New York, NY, 4 pages, U.S. List Price: $38.95 (1988)

Hazardous waste site remediation: The engineer's perspective, O'Brien & Gere Engineers, Inc., Robert Bellandi, Technical Editor, Van Nostrand Reinhold, New York, NY, 4 pages, U.S. List Price: $38.95 (1988)

Environmental biotechnology: biotechnology solutions for a global environmental problem, hazardous chemical wastes.

Biotechnology has a growing place in the remediation of hazardous waste sites throughout the world, and especially in Asia where population density is high and land and fresh water are scarce. In-situ bioremediation has been demonstrated already to be highly effective for petroleum hydrocarbons (alkanes, aromatics, polychlorophenols) and organophosphate pesticides in soils and for gasoline by-products (benzene, toluene, xylene) and chlorinated solvents (trichloroethylene) in groundwater. Heavy metals and PCBs are not suitable for bioremediation. Environmental biotechnology includes solid-phase and slurry-phase bioremediation for contaminated soils and site-specific bioreactors for contaminated groundwater. Specific examples are presented. From a policy point of view, accumulated wastes must be detoxified, preferably at sites where they already exist. We cannot continue to rely on their removal and disposal "elsewhere". For current waste streams, we must minimize the volumes and toxicity. Environmental biotechnology will play a key role.

Application of Observational Method to Hazardous Waste Engineering

Uncertainty is a key technical factor in hazardous waste site remediations. It can lead to unreasonable data gathering exercises if the point of diminishing information returns is not recognized. Engineering under uncertainty, however, is not unique to hazardous waste site remediation. Approaches have been used elsewhere to recognize and respond to substantial uncertainty. The observational method, traditionally applied in geotechnical engineering, has a number of key elements applicable to hazardous waste site remediation. The key contributions of the observational method are: (1) Remedial design based on most probable site conditions; (2) identification of reasonable deviations from those conditions; (3) identification of parameters to observe so as to detect deviations during remediation; and (4) preparation of contingency plans for each potential deviation. This paper describes an approach for incorporating the observational method into the current USEPA Superfund process and provides a detailed discussion of that process in the context of ground water remediation. Explicitly recognizing uncertainty in a proper application of the observational method offers the opportunity to reduce project time and costs as well as risks.

Application of Field Mobile EDXRF Analysis to Contaminated Soil Characterization

Effective assessment and remediation of hazardous waste sites dictates that analytical methodologies be developed which assist in the evaluation of site contamination and simultaneously make efficient use of sampling time and resources (1). Optimally, a technique would provide on-site personnel with immediate and accurate information concerning the identity and concentration of inorganic soil contaminants (2).

A proposed occupational exposure limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin.

One contaminant produced unintentionally during the manufacture of chlorophenols and phenoxy herbicides is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The resulting TCDD-containing wastes have been detected at many hazardous waste sites which in recent years have been in the process of remediation. Concerns about worker exposure to TCDD-contaminated soil (dust) during remediation of hazardous waste sites have produced a need for an occupational exposure limit (OEL) for TCDD. The animal toxicology data and human experience with TCDD are reviewed, and an occupational exposure limit for TCDD is proposed. The animal data support risk estimations which are based on TCDD as a nongenotoxic carcinogen. Studies on human populations have failed to demonstrate clearly any significant long-term health effects at levels to which humans have been exposed. The data indicate that an 8-hr time-weighted average limit of 2 ng/m3 is appropriate, and the associated risk would be consistent with other carcinogens at their corresponding OELs. A preliminary OEL of 0.2 ng/m3 (200 pg/m3) is recommended, however, in light of other sources of exposure because of TCDD's ubiquitousness in the environment, its unclear mechanism of action, and its rather long biological half-life in humans. This limit provides an ample margin of safety to prevent chloracne following repeated, acute exposure, and it addresses those chronic effects of TCDD observed in animal studies as well as those observed after accidental human exposure. The resulting body burden caused by chronic exposure to TCDD at the proposed OEL is examined. Its toxicological significance is compared with human tissue data and with other similarly persistent chemicals.(ABSTRACT TRUNCATED AT 250 WORDS)