Date of Award

Spring 1-1-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Fernando L. Rosario-Ortiz

Second Advisor

R. Scott Summers

Third Advisor

Diane M. McKnight

Abstract

The water quality of lakes and reservoirs can significantly influence the formation of disinfection byproducts (DBPs) upon treatment. Specifically, increased nutrient loads and enhanced algal growth can lead to changed quantity and character of dissolved organic matter (DOM), the primary precursor for DBPs. In this thesis, water quality characteristics, including chlorophyll-a, total organic carbon (TOC), total phosphorus (TP), total nitrogen (TN), and total organic nitrogen (TON), were examined in order to evaluate their effects on the formation of DBPs. Trihalomethane (TTHM), haloacetic acid (HAA5), and haloacetonitrile (HAN) formation were measured. Surface waters located throughout the state of Colorado were studied, and relationships between nutrients, algae, DOM, and carbonaceous and nitrogenous DBPs were explored. Spectrophotometric methods including ultraviolet absorbance and fluorescence were also employed in order to better characterize DOM, and predict DBP formation.

For 10 municipal reservoirs, nutrient and chlorophyll-a relationships were developed, which support the assumption that increased sources of nutrients in surface waters can lead to enhanced algal growth. Chlorophyll-a was further related to TTHM and HAA5 formation; however these relationships are indirect, with an interdependent variable of DOM. A relationship between specific ultraviolet absorbance (SUVA) and C-DBP yield was also developed.

The influences of algal derived organic matter (AOM) and effluent organic matter (EfOM) on DOM character and subsequent DBP formation in 38 Colorado surface waters was assessed. Relationships to haloacetonitrile (HAN) formation were evaluated, and fluorescence analysis was utilized. Sites heavily influenced by wastewater were found to yield the highest levels of HAN and the lowest levels of TTHM and HAA5. The fluorescence index (FI) proved a useful indicator for AOM, organic nitrogen enrichment, and the level of wastewater influence. The FI was also found to indicate DBP reactivity, however DBP species must be taken into consideration as C-DBP and brominated HAN showed opposite trends. Results presented in this thesis suggest that controlling nutrient loadings to drinking water sources could aid in minimization of DOM, and thus presents an approach to DBP control. Results also showed how EfOM and AOM both play an important role in HAN formation.

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