Date of Award

Summer 2019

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

James P Malley

Second Advisor

Emmanuelle Prest

Third Advisor

Johan C Kruithof

Abstract

Application of chlorine-based disinfection to drinking water and wastewater leads to the formation of disinfection by-products that are harmful to human health. This paper presents research performed on the formation mechanisms of trihalomethanes (THMs) and nitrosamines (specifically NDMA) from chlorine-based disinfection practices. The formation of THMs and nitrosamines was investigated under a range of water matrices and disinfection conditions by developing a set of laboratory prepared water matrices containing natural organic matter (NOM), bromide and ammonium. In addition, two pretreated surface waters and one secondary treated wastewater effluent were selected to link experimental results to practice. THMs and nitrosamines were measured under a range of chlorine doses along the chlorination breakpoint curve to investigate the effects of chlorine dose, NOM, bromide and ammonium on DBP formation.

The formation of NDMA was mainly observed at chlorine doses causing the presence of dichloramine, suggesting that critical NDMA formation pathways involve dichloramine. The highest NDMA concentrations were measured in wastewater effluent, suggesting that the complex NOM composition from wastewater contains many NDMA precursors. THMs were primarily of concern during free chlorine disinfection. Results showed that complex organic matter, specifically humic substances, were primary THM precursors. Humic acids contained fast and slow reacting precursors that were reactive with bromide and chlorine resulting in high THM concentrations. Alternatively, fulvic acids contained slow reacting precursors that were reactive primarily with bromide, resulting in lower overall THM formation with higher bromine incorporation. The results of this research provide professionals in the water industry with a better understanding of THM and NDMA formation and the impact of chlorination practices and water quality on DBP formation.

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