Date of Award

Spring 1-1-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

R. Scott Summers

Second Advisor

JoAnn Silverstein

Third Advisor

Fernando L. Rosario-Ortiz

Fourth Advisor

Kevin M. McCabe

Fifth Advisor

M. Robin Collins

Abstract

The occurrence of trace organic contaminants in drinking water sources concerns utilities since the human health risk is often unknown for many of the contaminants and their occurrence in mixtures complicates the health risk uncertainty. Drinking water treatment facilities are looking for technologies that remove trace organic contaminants to lower this potential risk. Biological filtration (biofiltration) can be an effective treatment process to reduce trace organic contaminants at little extra cost to most surface water treatment plants.

The objectives of this thesis were to evaluate and model the effects of biological filter (biofilter) design and operation on trace organic contaminant removal. The long-term removals of 34 trace organic contaminants were evaluated at a constant influent concentration. The contaminants included pesticides, pharmaceuticals, and personal care products, some of which are endocrine disrupting chemicals, and represented a wide range of uses, chemical structures, adsorbabilities, and biodegradabilities. Contaminant removal ranged from no measurable removal to near-complete removal with effluent concentrations below the detection limit. Contaminant removals followed one of four trends: steady state removal throughout, increasing removal to steady state (acclimation), deceasing removal, and no removal (recalcitrant). Acclimation occurred at different rates depending on the contaminant and the community structure of the biofilter. Contaminant removals followed pseudo-first-order kinetics in drinking water biofilters and were modeled using a biomass based pseudo-first-order rate constant model. When a biofilter was intermittently exposed to a trace organic contaminant, the biofilter retained its biodegradation capacity for non-exposure events less than five months. Granular activated carbon (GAC) biofilters provided more stable removals under variable influent conditions (attenuation) as compared to a non-adsorptive media. The performance of trace organic contaminant removal in biological GAC (BAC) was a function of the adsorption affinity and biodegradability of a contaminant and the acclimation state of the biofilter. The framework for a biofiltration treatment technique for the control of trace organic contaminants was developed from the models and behaviors observed.

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