Aquifers, treatment

This chemistry has been investigated and implemented for wastewater minerahza-tion by oxidizing the organic pollutants. The process is very efficient, not selective and, as a consequence, almost all carbon matter can be removed. Topical areas also include soil and aquifer treatments, sometimes in combination with a secondary biotic process [145]. 

Mansell J., J. Drewes, and T. Rauch (2004). Removal mechatusm of endocrine dismpting compounds (steroids) during soil aquifer treatment. Water Science and Technology 50 229-234. 

Montgomery-Brown J., J.E. Drewes, R Fox, and M. Reinhard (2003). Behavior of alkylphenol polyethoxylate metabolites during soil aquifer treatment. Water Research 37 3672-3681. 

Possible water sources for injection are sea water, fresh surface water, produced water or aquifer water (not from the producing reservoir). Once it has been established that there is enough water to meet demand (not an issue in the case of sea water), it is important to determine what type of treatment is required to make the water suitable for injection. This is investigated by performing laboratory tests on representative water samples. 

Bioremediation is also an option when spills of such compounds contaminate groundwater. For example, bioremediation seems a feasible treatment for aquifers contaminated with alkylpyridines (72) and phenol (73). 

Actual water treatment challenges are multicomponent. For example, contamination of groundwater by creosote [8021-39-4], a wood (qv) preservative, is a recurring problem in the vicinity of wood-preserving faciUties. Creosote is a complex mixture of 85 wt % polycycHc aromatic hydrocarbons (PAHs) 10 wt % phenohc compounds, including methylated phenols and the remaining 5 wt % N—, S—, and O— heterocycHcs (38). Aqueous solutions of creosote are therefore, in many ways, typical of the multicomponent samples found in polluted aquifers. 

Detailed sampling can include, but is not limited to, the installation of monitoring well networks. After the wells have been installed, aquifer tests are typically performed. Once the aquifer tests are performed and the aquifer characteristics are determined, time series sampling for a given contaminant, or a surrogate, is undertaken. The combined results of these efforts provide the basis for development of a treatment strategy. Modeling can be used as part of this effort to help determine the best technical and most cost-effective techniques to be used at a site. 

Nyer, E.K. Innovative Biological Treatment of Contaminated Groundwater. In First National Outdoor Action Conference on Aquifer Restoration, Groundwater Monitoring, and Geophysical Methods, May, 1987. 

Tse KKC, S-L Lo, JWH Wang (2001) Pilot study of in-situ thermal treatment for the remediation of pentachlorophenol-contaminated aquifers. Environ Sci Technol 35 4910-4915. 

To recondition the pots, the potliner is dug out and discarded Prior to discovery of the Spokane aquifer contamination, the procedure had been to remove the pot to an outdoor concrete slab where the pot was filled with water and allowed to soak for a few days to fracture and soften the cathode The contaminated water was presumably reused for soaking and not discharged to the industrial waste treatment system because of the cyanide content The pots were Jack-hammered and the potliner dumped on the slab The potliner was transfered by a front-end loader to an unprotected pile next to the slab ... 

Groundwater samples collected over the last 10 years from monitoring and private water wells in the offpost area of RMA have provided data regarding the extent of diisopropyl methylphosphonate. The data indicate that diisopropyl methylphosphonate in the alluvial aquifer extends from the RMA northwest to the South Platte River. In the 1995 sampling event, diisopropyl methylphosphonate concentrations ranged from less than 0.392 g/L, the detection limit, to just over 600 g/L in this area. The highest reported concentrations were present upstream of the Peoria Street Treatment Plant. The lowest or non-... 

CW systems can provide treatment inside the well, in the aquifer, or a combination of both. For effective in-well treatment, the contaminants must be adequately soluble and mobile so they can be transported by the circulating groundwater. Because C W systems provide a wide range of treatment options, they provide some degree of flexibility to a remediation effort. 

The pump-and-treat method is comparable to soil flushing. In fact, the pump-and-treat method can treat both groundwater and aquifer soil at the same time, and can also be directly applied to unsaturated soil zones. The soil flushing method is mainly considered as a treatment in unsaturated zones. 

The main advantage of in situ thermal methods is that they allow soil to be treated without being excavated and transported, resulting in significant cost savings however, in situ treatment generally requires longer time periods than ex situ treatment, and there is less certainty about the uniformity of treatment because of the variability in soil and aquifer characteristics and because the efficacy of the process is more difficult to verify. 

For in situ soil flushing, large volumes of water, at times supplemented with surfactants, cosolvents, or treatment compounds, are applied to the soil or injected into the groundwater to raise the water table into the contaminated soil zone. Injected water and treatment agents are isolated within the underlying aquifer and recovered together with flushed contaminants.50-52,85... 

Other factors affecting performance include the presence of toxic material, the redox potential, salinity of the groundwater, light intensity, hydraulic conductivity of the soil, and osmotic potential. The rate of biological treatment is higher for more permeable soils or aquifers. Bioremediation is not applicable to soils with very low permeability, because it would take a long time for the cleanup process unless many more wells were installed, thus raising the cost. 

This system consists of an in situ polyethylene tank, an application system, and a bottom water recovery system.65 An underlying, permeable, water-bearing zone facilitates the creation of ingradient water flow conditions. The tank defines the treatment area, minimizes the potential for release of bacterial cultures to the aquifer, and maintains contaminant concentration levels that facilitate treatment. The ingradient conditions facilitate reverse leaching or soil washing and minimize the potential for outmigration of contaminants. 

May be difficult to implement in low-permeability aquifers Reinjection wells or infiltration galleries may require permits or may be prohibited Biodegradation pathways may be site-specific, potentially requiring pilot testing or treatability studies A relatively large amount of oxidant may be needed for treatment of large contaminant mass... 

Since 1995, the sparks solvent/fuel site located in Sparks, Nevada, a remediation system consisting of MPE, air sparging, and SVE, has been operational. The treatment system consists of 29 MPE wells, an oil-water separator, and a fluidized bed bioreactor, with an influent flow rate of 23.3 L/s (370 gpm) and a retention time of 8 min. Vapors are sent through a condenser, followed by a thermal oxidizer, before its release to the atmosphere. Condensate is sent back through the oil-water separator. Performance data, available for the first 650 days of site operation, showed a reduction in MTBE concentration across the bioreactor from 2400 to 55 pg/L. No data were provided for reduction of MTBE concentrations in the aquifer.51... 

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