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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Final Progress Reports: University of Arizona: Enhanced Bioventing with Gas-Phase Nutrient Amendments

Superfund Research Program

Enhanced Bioventing with Gas-Phase Nutrient Amendments

Project Leader: Roberto Guzman
Grant Number: P42ES004940
Funding Period: 1995 - 2000

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Final Progress Reports

Year:   1999 

During this year researchers have worked and contributed in two fundamental areas of remediation technology. The first is a mathematical model that can be of great utility in remediation of vadose zone sediments containing water-soluble organic contaminants (eg., trichloroethylene). The second is the development of an adsorptive technique to remove specifically arsenic contaminants to below 5 ppb, the new MCL established by the USA EPA. In the first contribution project investigators formulated a mathematical model for remediation of chlorinated solvents in unsaturated soils that takes into account the effect of pore-scale water distribution on contaminant transport. The model considers the already established observations that diffusional limitations in the liquid phase play an important role in modeling these processes. Using this model it has been shown that diffusion in the liquid phase is a limiting rate process in soil venting of soluble contaminants from the vadose zone. The results suggest that the mathematical model developed in this work can be used to represent soil venting processes without adjustable parameters if a realistic pore-scale liquid distribution is available. This model can be extended to cometabolic bioventing, for which diffusional limitations in the liquid phase might be even more critical if the microorganisms form biofilms covered by liquid phase. The second contribution of this research involves the development and application of new adsorbents based on solid phase polymer chemistry to remove arsenic from contaminated waters. In this method specific polymers grafted on gels are used to bind metal ions of strong arsenic affinities. These immobilized metal ions in turn (which need not to be removed in the regeneration process) function as adsorption sites for arsenate and arsenite very effectively.

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