Biodegradation groundwater systems

Lu, C.J. (1994). Effects of hydrogen peroxide on the in situ biodegradation of organic chemicals in a simulated groundwater system. In Hydrocarbon Bioremediation, ed. R. E. Hinchee et al., pp. 140-7. Boca Raton, FL CRC Press. 

Mass-balance considerations, in particular the observed consumption of contaminants, were useful in showing the importance of biodegradation processes for limiting the mobility of petroleum hydrocarbons in groundwater systems. The mass-balance approach also contributed to our understanding of the environmental fate of chlorinated solvents in groundwater systems. In the 1980s, the observed behavior of chlorinated... 

A simple use of mass-balance considerations that shows this net transformation of chlorinated ethenes is the observed accumulation of chloride in contaminant plumes. For example, in a study of a large plume of TCE-contaminated groundwater at Dover Air Force Base, Delaware, Witt et al. (2002) showed that the concentration of chloride increased as TCE concentrations decreased, suggesting the net transformation of the chlorine in TCE to chloride. This chloride tracer of chlorinated ethene biodegradation is of use for mass-balance calculations to demonstrate biodegradation processes in the held. These held observations formed the basis of experimental studies under controlled laboratory conditions that documented the many and varied microbial processes that transform and destroy chlorinated ethenes in groundwater systems. 

A full-scale cleanup was performed using in situ bioremediation to treat MTBE and BTEX at a service station in Massachusetts. Soil at the site consists of a layer of sand and gravel underlain by peat, silt, and clay. The in situ bioremediation system consisted of 12 injection wells and two butane injection panels used to stimulate cometabolic aerobic biodegradation of the contaminants in groundwater. The system was operated between October 2000 and January 2001. MTBE concentrations were reduced from 370 to 12 pg/L and BTEX contamination in groundwater was reduced by approximately two orders of magnitude during the 4-month period.74... 

Microbes are ubiquitous in the subsurface environment and as such may play an important role in groundwater solute behavior. Microbes in the subsurface can influence pollutants by solubility enhancement, precipitation, or transformation (biodegradation) of the pollutant species. Microbes in the groundwater can act as colloids or participate in the processes of colloid formation. Bacterial attachment to granular media can be reversible or irreversible and it has been suggested that extracellular enzymes are present in the system. Extracellular exudates (slimes) can be sloughed-off and act to transport sorbed materials [122]. The stimulation of bacterial growth in the subsurface maybe considered as in situ formation of colloids. 

Cresols are widely distributed natural compounds. As discussed above, they are formed as metabolites of microbial activity and are excreted in the urine of mammals (Fiege and Bayer 1987) and humans (Needham et al. 1984). Cresols from human urine are probably biodegraded at municipal sewage treatment facilities prior to release to ambient waters. However, for combined septic and storm sewage systems, cresols may be released to surface waters during periods of precipitation when influent volumes exceed treatment plant capacities. Also, in rural and suburban areas where septic tanks are used (o- and m-cresols can resist anaerobic digestion), human excrement may be a nonpoint source release of cresols to groundwater. 

The results of the EPA SITE demonstration also showed that the cost of methane necessary to support trichloroethylene biodegradation is not excessive in relation to the costs of other technologies available for the removal of trichloroethylene from water. Thus, the Biotrol system may prove to be a cost-effective alternative to more traditional groundwater remediation technologies. 

OXY I is an oxygen injection system for remediation of organics-contaminated groundwater. The oxygen enhances biodegradation of the contaminants, particularly methyl tertiary butyl ether... 

The PetroClean bioremediation system treats biodegradable contaminants (i.e., gasoline, diesel fuel, aviation fuel, solvents, polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), total petroleum hydrocarbons (TPH), and other organic compounds in soils and groundwater. 

The Biodrain system is a patented, commercially available, in situ technology for the collection and treatment of biodegradable contaminants in soil and groundwater. The Biodrain system... 

Advantages of microbial barriers over conventional pump-and-treat systems are that barriers can eliminate the need for additional treatment, and they do not disrupt the namral flow of groundwater. Furthermore, if contaminants can be volatilized or biodegraded throughout the impacted portion of an aquifer, there is no need for surface treatment systems, discharges,... 

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