Groundwater, biological treatment

Figure 26. Process diagram for revised groundwater and solvent wastes biological treatment system.

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. 

A permeable reactive barrier (PRB) is defined as an in situ method for remediating contaminated groundwater that combines a passive chemical or biological treatment zone with subsurface fluid flow management. Treatment media may include zero-valent iron, chelators, sorbents, and microbes to address a wide variety of groundwater contaminants, such as chlorinated solvents, other organics,... 

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. 

CPE XI returned to Cairo, Egypt in 1997, and papers and posters were presented on adsorption, analytical methods, chemical/biological/treatment, groundwater studies, ion exchange, modeling, risk assessment, waste minimization and treatment, and for the first time, ISO 14001, which focuses on environmental management and quality systems. 

The cost of pretreating contaminated groundwater on site, for discharge to a publicly owned treatment works is often the preferred alternative (provided the facility has the capacity and local regulations allow acceptance). Pretreatment is usually required to prevent explosive vapors in the sewers and disruption of the biological treatment at the plant. The most common pretreatment includes phase separation and reduction of dissolved contaminants to an assured safe concentration. At small sites, it is not unusual to use phase separation, air stripping, and activated charcoal filtration prior to discharge to a sanitary sewer. 

Alternative 1 consists of preliminary treatment for heavy metals removal with the primary concern being iron removal (Figure 8.3). The levels of iron observed in the groundwater at this site would be very detrimental to the downstream treatment processes. This pretreated water would then be used for cooling tower makeup water followed by biological treatment. This approach would be the easiest and cheapest alternative. This combined process should provide effective removal of BTEX. 

For the site of the trickling pond, a site-specific strategy for the remediation was established. Flighly contaminated hot spots were excavated to protect the groundwater. The applied biological treatment technology was tested in pilot scale on site. A feasibility study was done for the estimation of remediation time and TNT reduction which can be achieved by biological transformation. 

The technology is a slurry-phase biological treatment that, according to the vendor, has successfully treated soil, sludge, groundwater, and process water contaminated with volatile and semivolatile organic compounds (VOCs and SVOCs) such as toluene, naphthalene, fluoranthene, pentachlorophenol, and creosote. 

WaterSmart Environmental, Inc. (WaterSmart), has developed the Express process technology for simultaneous treatment of contaminated soil and groundwater. Express, a combination of soil washing/leaching and in situ biological treatment, is an acronym for EXPedited REmediation Site Strategy. 

U.S. Environmental Protect ion Agency (1991)- Biological Treatment of Wood Preserving Site Groundwater by BioTrol, Inc. EPA/540/A5-91/001. Washington, DC U.S. EPA. 

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