Anaerobicaerobic Fixed Film Biological System For Groundwater Decontamination

Another ex situ bioremediation process introduced here is an anaerobic-aerobic fixed film biological groundwater treatment system (Fig. 9) commercially known as the immobilized cell bioreactor biotreatment system. It is designed to remove organic contaminants (including nitrogen-containing compounds and toxic chlorinated solvents) from contaminated ground-water, and other heavily polluted aqueous streams. This groundwater decontamination system offers improved treatment efficiency by using (a) a unique reactor medium that maximizes biological activity in the reactor, and (b) a bioreactor design that maximizes contact between the biofilm and the contaminants.

This anaerobic-aerobic fixed film biological groundwater treatment system has a completely enclosed headspace, eliminating the possibility of air stripping of volatile organics or intermediates. These features result in quick, complete degradation of target contaminants to carbon dioxide, water, and biomass. Additional advantages include (a) high treatment capacity, (b) compact and mobile system design suitable for site remediation, and (c) reduced operations and maintenance costs resulting from simplified operation and low sludge production.

Basic system components of the anaerobic-aerobic fixed film biological groundwater treatment system include the bioreactors, media, mixing tanks and pumps, feed pump, recirculation pump, and a blower to provide air to the aerobic bioreactor. Depending on the specifics of the influent groundwater streams, some standard pretreatments, such as pH adjustment or oil and water separation, may be required. Effluent clarification is not required for the system to operate, but may be required to meet specific discharge requirements. The system is designed to treat 10 million gallons per day of contaminated groundwater streams, and has been successfully applied to groundwater containing contaminants including polynuclear aromatic hydrocarbons (PAH), phenols, gasoline, chlorinated solvents, diesel fuel, and chlorobenzene.

Figure 9 Dual anaerobic/aerobic immobilized cell bioreactor system diagram. (Courtesy of USEPA.)

The readers are referred to the USEPA Risk Reduction Engineering Laboratory, Cincinnati, OH, for more detailed information regarding this process system.

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