AWWA Water Science Author Spotlight: Kyle Shimabuku

Abstract

Having recently published an article in AWWA Water Science, Kyle Shimabuku answered questions from the publication's editor-in-chief, Kenneth L. Mercer, about the research.

Modeling Chloramine Stability and Disinfection Byproduct Formation in Groundwater High in Bromide

Kyle Shimabuku, Tarrah Henrie, David Schultise, and Sunil Pillai

Kyle Shimabuku (left) and his wife take a photo after surfing together at Faria Beach in Ventura, Calif.

I earned a BS degree in civil engineering from San Diego State University and an MS degree and PhD from the University of Colorado Boulder. Between my undergraduate and graduate studies, I had the opportunity to work on water projects in remote villages of Southern Sudan, where I developed a passion for protecting public health through the provision of safe drinking water. I also worked briefly in my hometown of Ventura, Calif., in the Environmental and Water Resources Department. My first research experience was at Cal Poly San Luis Obispo, where I studied wastewater treatment using high-rate algal ponds. I later explored the efficacy of widely used water and wastewater disinfectants in deactivating antibiotic-resistant genes at the University of Washington. My PhD research focused on using biochar to control organic contaminants in stormwater. After completing my PhD, I worked at Corona Environmental Consulting, primarily on groundwater treatment projects.

Providing safe and reliable water requires implementing multiple barriers to contamination, including source protection, treatment, and distribution system management. Some of my research has focused on protecting water sources by treating stormwater runoff to prevent harmful chemicals from reaching drinking water supplies and understanding how wildfires may affect water source quality. The majority of my work, however, has concentrated on improving the efficiency and cost-effectiveness of contaminant removal during the treatment process. I have also developed tools to help water providers quickly and reliably verify in real time that their treatment systems are functioning as intended.

Maintaining safe water quality in distribution systems is particularly challenging. Operators must balance maintaining detectable levels of chlorine to prevent disease-causing organisms from growing or surviving, even in the event of accidental contamination, while minimizing the formation of toxic disinfection byproducts. The AWWA Water Science article addresses this complex challenge, particularly when bromide is present. Bromide complicates this balancing act by accelerating disinfectant breakdown and promoting the formation of toxic disinfection byproducts.

Working with two students for their senior design project, Kyle (left) demonstrates the process for leaching substances from burned soils post-wildfire using a jar test apparatus.

Kyle (third from right) and others explore the water infrastructure and windmills used to pump water in the Netherlands as part of a study-abroad course.

While we mostly used standard colorimetric methods to measure oxidants, this study represents, to our knowledge, the first use of DPD (N,N-diethyl-p-phenylendediamine)- and indophenol-based analytical techniques to evaluate the presence of bromamine. Further research is needed to confirm that differences in chlorine residuals measured by these methods can reliably indicate the concentration of total brominated oxidants in chloraminated systems. One of the strengths of this study is that it offers a new interpretation of analytical methods that are already widely used by water systems, potentially enhancing their utility in monitoring and managing water quality.

We were most surprised by how well models developed in laboratory clean water were able to fit some of the data collected in a complex groundwater matrix. The main challenge in completing this project was interpreting the role of dissolved organic matter in causing deviations between the model predictions and the experimental data.

In future research, it would be valuable to validate the effectiveness of our colorimetric method for estimating bromamine levels by pairing it with more advanced analytical techniques, such as membrane introduction mass spectrometry. Additionally, investigating the role of dissolved organic matter characteristics in its reactivity with bromaminated oxidants is a largely unexplored area. This research could improve predictions of how chloramines decay or form disinfection byproducts in various chloraminated systems that use different water sources.

I love spending time outdoors skiing, mountain biking, river rafting, and, most of all, surfing when I’m back home visiting family in Ventura. My wife and I also enjoy sharing our passion for these activities with our young kids.

I am most excited by the process of learning—whether it's revisiting concepts from water treatment textbooks, discovering firsthand how chemical and biological phenomena influence our ability to provide safe water, or sharing this learning journey with students through courses or their own research. I am also excited by the prospect of performing research and educating future water engineers that will have a positive impact on public health and environmental resources.

To learn more about Kyle's research, visit the article, available online at https://doi.org/10.1002/aws2.1365.