Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Environmental and Earth Sciences

Department

Geosciences

First Advisor

Soni M. Pradhanang

Abstract

High loads of natural organic matter (NOM) in source waters increase levels of toxic disinfection byproducts (DBPs) during treatment, including trihalomethanes (THMs) and haloacetic acids (HAAs), which are formed when NOM is chlorinated. Rates of NOM loading and, by extension, DBP formation potential vary spatially and temporally, and depend on land use within the watersheds. While non-chemical disinfection is typically based on mercury UV lamps, LED-based disinfection systems are being considered as an energy efficient alternative, since they require a fraction of the energy used by mercury lamps. This study explores the efficacy of a novel water treatment process for bacterial removal and DBP management that uses conventional NOM removal processes, and LED-based UVC and chlorine as primary and secondary disinfectants, respectively. Samples were collected from urban, agricultural, and forested watersheds during the summer and fall of 2018. Results show that LED-UVC with secondary chlorination results in the removal of all bacteria while producing 25% of the THMs and HAAs formed through conventional treatment during summer sampling, regardless of the land use. However, increased lignin-based plant matter during fall from defoliation inhibited conventional NOM removal, increasing turbidity and reducing UV transmittance. Additionally, due to the high concentration of NOM, DBP formation exceeded MCLs during the fall season. Therefore, consideration needs to be given to not only alternative disinfection strategies, but also to more efficient NOM removal processes that will reduce byproduct formation during disinfection and increase UV transmittance.

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