Date of Award

Summer 2023

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Susan D. Richardson

Abstract

The disinfection of water has been hailed as one of the most important triumphs for public health in the 20th century. Drinking water treatment plants produce safe drinking water by inactivating microorganisms through the use of disinfectants, including chlorine, chloramine, chlorine dioxide, UV irradiation, and ozone. However, these disinfectants also produce toxic disinfection by-products (DBPs), through reactions with natural organic matter and anthropogenic pollutants, as well as bromide and iodide present in source waters. The presence of bromide and iodide results in the formation of bromo- and iodo-DBPs which are much more toxic than DBPs containing chlorine. DBPs are always present in our drinking water, usually in parts per billion (ppb) level. Currently only eleven DBPs are regulated by the U.S. Environmental Protection Agency; however, more than 700 DBPs have been identified to date. Many unregulated DBPs are more toxic than those regulated. DBPs are important because epidemiologic studies show that they are linked to adverse health effects such as bladder and colorectal cancer, birth defects, and miscarriage. Thus, understanding the formation and more comprehensively identifying DBPs is crucial to uncovering the toxicity drivers in disinfected drinking water, and ultimately improving drinking water safety. The studies discussed here used highly sensitive analytical techniques and instruments to measure DBPs from drinking water and assessed the impacts of harmful algal blooms (HABs) on DBP formation and drinking water safety. Moreover, the third and final study revealed the identity of 6 novel and highly toxic DBPs from chlorinated and chloraminated drinking water. The ultimate goal of this research is to uncover these risks so that new strategies can be applied to improve the safety of drinking water. Study 1 discussed the impacts of harmful algal blooms from Microseira wollei (also known as Lyngbya wollei) and Phormidium on drinking water safety with regard to DBP formation during chlorination. Study 2 discussed the effect of chloramination in reducing DBP concentrations in algae-impacted drinking water. Both of the studies discussed the effects of bromide and iodide ions in the formation of more toxic bromo- and iodo-DBPs. The third study finds 6 novel DBPs (trichlorocyclopentadiene, 1,2,3,4-tetrachloro-1,3-cyclopentadiene, 1,2,3,4,5-pentachloro-1,3-cyclopentadiene, 1,2,3,4,5,5-hexachloro-1,3-cyclopentadiene, tetrachloro-bromo-cyclopentadiene, and pentachloro-bromo-cyclopentadiene) from chlorinated and chloraminated drinking waters. Overall, results from these studies reveal that harmful algal blooms can directly impact drinking water safety, and higher levels of DBPs and more toxic nitrogenous DBPs are formed from algae-impacted drinking water. Also, the novel halocyclopentadiene DBPs identified are much more toxic and bioaccumulative than the 11 DBPs currently regulated in the United States.

Rights

© 2023, Md. Tareq Aziz

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