Date of Graduation

5-2012

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor

Julian L. Fairey

Committee Member

James C. Young

Second Committee Member

Wen Zhang

Keywords

Applied sciences; Earth sciences; Chlorine dioxide; Disinfection byproduct; Fluorescence

Abstract

Central Arkansas Water (CAW), the water utility for Little Rock, AR, draws their source water from Lake Maumelle and Lake Winona. To curb disinfection byproduct (DBP) formation, CAW has begun retrofitting their two plants to use chlorine dioxide as an alternative primary disinfectant followed by free chlorine secondary disinfection in the distribution system. In this study, fluorescence parallel factor (PARAFAC) analysis was combined with free chlorine simulated distribution system (SDS) tests and DBP formation potential (DBPFP) tests to study the benefit of chlorine dioxide primary disinfection (CDPD) with alum coagulation. Of the DBPs screened, trichloromethane (TCM) was formed in highest concentration in each source water and treatment scenario. In the DBPFP tests, TCM formation potential decreased on average by 30 and 42% after alum coagulation for Lake Maumelle and Lake Winona waters, respectively; after CDPD/alum coagulation, TCM formation potential decreased on average by 61 and 67%, indicating that CDPD was beneficial. Fluorescence-PARAFAC analysis identified four humic-like fluorophores with maximum intensity (FMAX) values that were linearly correlated (r2 values between 0.92-0.94) with the DBPFP of TCM; weaker linear correlations were found between TCM and chlorine demand (r2 = 0.41) and TCM and SUVA254 (r2 = 0.67). The strong correlations between DBPFP and FMAX indicate that fluorescence-PARAFAC analysis may be a useful screening tool to evaluate strategies (e.g., set chlorine dioxide and alum doses) to curb DBPs at CAW.

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