Document Type

Thesis

Date of Award

Fall 1-31-1997

Degree Name

Master of Science in Environmental Engineering - (M.S.)

Department

Civil and Environmental Engineering

First Advisor

Basil Baltzis

Second Advisor

Hsin Neng Hsieh

Third Advisor

Gordon Lewandowski

Abstract

This thesis deals with the conceptual design of an integrated air stripping/biofiltration process for cleaning aquifers contaminated with volatile organic pollutants. In this technology, the pollutant is transferred from the aquifer to an air stream which is subsequently treated in a biofilter. The work presented here is an effort to develop a design methodology for the integrated process and suggests a general, quantitative approach which can be used in preliminary technology evaluation. This methodology involves relatively simple equations for the stripping process and detailed (oftentimes complex) models for biofiltration under conditions of continuous variation of the properties of the polluted airstream which is fed to the biofilter. In this thesis, conventional biofilters were considered. These units have a porous organic support for the biofilms and do not involve supply of nutrients to the organisms through a liquid phase. The air stripping process was considered to be either under equilibrium distribution conditions for the pollutant between the aquifer and the air sparged through it, or under conditions deviating from equilibrium. This deviation was expressed through the use of a fraction of the Henry's constant.

The proposed methodology was applied to eight different situations (case studies). These involved differences in the equilibrium distribution of the pollutant, and the number and extent of the time periods in which the total remediation time is divided. This division is proposed for maintaining relatively constant pollutant concentrations to the inlet of the biofilter over an extended period of time.

Sample calculations have been performed assuming that a constant volume aquifer is contaminated with toluene. The results show that the integrated process can be designed based on predictive engineering models, and that the size of the required biofilter bed and the time frame for decontamination of the aquifer can be very reasonable.

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