Anaerobic Degradation of Chlorinated Solvents


Book Description

The symposium included 600 presentations in 50 sessions on bioremediation and supporting technologies used for a wide range of contaminants already in, or poised to invade, soil, groundwater, and sediment. Three hundred and fifty-two papers were selected and organized into ten volumes. Volume seven's articles examine the use of enhanced anaerobic biotransformation processes for treatment of chlorinated solvents in soil and groundwater. Electron donors used to stimulate reductive dechlorination processes in lab- and field-scale demonstrations are also presented. Articles average eight pages, and contain abstracts and references. Annotation copyrighted by Book News Inc., Portland, OR.







Bioremediation of Chlorinated Solvents


Book Description

Soil and groundwater contamination stemming from the release of various chlorinated compounds into the environment is a significant and difficult site remediation challenge. The articles in this collection discuss the use of aerobic and anaerobic biological degradation to dehalogenate sites contaminated with pesticides and chlorinated solvents such as trichloroethylene, tetrachloroethene, tetrachloromethene, perchloroethylene, carbon tetrachloride, pentachlorophenol, and chlorinated benzene. Bench- and field-scale studies of the biological processes associated with in situ dechlorination of soil and aquifers are described. Discussed are the uses of microcosm studies and numerical simulation of dechlorination to manage system operation. Site characteristics (e.g., hydraulic properties, temperature, nitrogen availability) and their effect on the stability of the methanotrophic community are examined. Methods discussed include the use of air venting, alternative electron donors, biofilm reactors, surfactants, municipal digester sludge, iron enhancement, and sulfate reduction to improve conditions for the microbial consortia that effect dechlorination.













In Situ Remediation of Chlorinated Solvent Plumes


Book Description

In the late 1970s and early 1980s, our nation began to grapple with the legacy of past disposal practices for toxic chemicals. With the passage in 1980 of the Comprehensive Envir- mental Response, Compensation, and Liability Act (CERCLA), commonly known as Sup- fund, it became the law of the land to remediate these sites. The U. S. Department of Defense (DoD), the nation’s largest industrial organization, also recognized that it too had a legacy of contaminated sites. Historic operations at Army, Navy, Air Force, and Marine Corps facilities, ranges, manufacturing sites, shipyards, and depots had resulted in widespread contamination of soil, groundwater, and sediment. While Superfund began in 1980 to focus on remediation of heavily contaminated sites largely abandoned or neglected by the private sector, the DoD had already initiated its Installation Restoration Program in the mid-1970s. In 1984, the DoD began the Defense Environmental Restoration Program (DERP) for contaminated site assessment and remediation. Two years later, the U. S. Congress codified the DERP and directed the Secretary of Defense to carry out a concurrent program of research, development, and demonstration of innovative remediation technologies. As chronicled in the 1994 National Research Council report, “Ranking Hazardous-Waste Sites for Remedial Action,” our early estimates on the cost and suitability of existing techn- ogies for cleaning up contaminated sites were wildly optimistic. Original estimates, in 1980, projected an average Superfund cleanup cost of a mere $3.




Anaerobic Biodegradation of Mixtures of Chlorinated Solvents


Book Description

The widespread contamination of groundwater with mixtures of chlorinated hydrocarbons poses a health threat and an obligation to the landowner to remediate this threat. Organic solvents such as tetrachloroethene (PCE) and carbon tetrachloride (CT) are frequently found on contaminated sites and as suspected carcinogens must be removed from the environment. The objective of this study was to determine the susceptibility of mixtures of PCE and CT to biological reductive dechlorination. Using microcosms and a continuous column the impact of CT degradation on the degradation of a PCE was examined. Using an ethanol/PCE enrichment culture the effect of CT and its degradation products, chloroform (CF) and dichloromethane (DCM), on the degradation of PCE was examined. In microcosms 5 mg/L CT totally inhibited the degradation of PCE. Full PCE degradation to cis-DCE did occur after the bottles were purged with nitrogen and PCE was applied in the absence of CT. In the column studies the addition of 0.5 mg/L CT totally suspended PCE degradation for 24 days. The biodegradation of organic solvents can be an effective way to eliminate possible human health threats, however extra care must be taken when dealing with mixtures of organic solvents. (Abstract shortened by UMI.).







Biodegradation of Chlorinated Solvents


Book Description

The anaerobic biodegradation of chlorinated solvents is of great interest both for natural attenuation and for engineered remediation of these hazardous contaminants in groundwater. Compounds to be studied are carbon tetrachloride (CT) and the chlorinated ethenes, tetrachloroethene (PCE), trichloroethene (TCE) cis-1,2-dichloroethene (cDCE), and vinyl chloride (VC). The chlorinated solvents often are present as dense non-aqueous-phase liquids (DNAPLs), which are difficult to remove. Biodegradation of DNAPLs was previously thought not possible because of toxicity, but recent evidence indicates that under the right conditions, biodegradation is possible. Anaerobic biodegradation of DNAPLs is the major subject of this research. The specific objectives of this multi-investigator effort are: (1) Evaluate the potential for chlorinated solvent biodegradation near DNAPLs, (2) Provide a molecular understanding of the biological mechanisms involved, (3) Determine cellular components involved in carbon tetrachloride transformation by Pseudomonas stutzeri strain KC without chloroform formation.