AWWA Water Science Author Spotlight: Karl Zimmermann

Abstract

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

Design Considerations for Biological Ion Exchange Drinking Water Filters: Resin Selection, Backwash, and Regenerations

Karl Zimmermann, William Szu-Wei Chen, Jaycee Wright, and Madjid Mohseni

I recently completed my PhD with Madjid Mohseni at the University of British Columbia (Vancouver), and I’m now heading into the world of consulting engineering. My PhD focus was to understand biological ion exchange (BIEX), a strategy to operate IEX drinking water filters for the removal of natural organic matter. Typically, IEX filters are regenerated about once weekly with a salt brine to keep them in chloride mode. But at the point when most people regenerate their filters, it's true that they’ve run out of chloride, but what wasn’t understood was that organics removal could continue through ion-exchanging with sulphate. There's also biology going on. Our research looked at describing each of these three mechanisms for organics removal and their relative contributions to overall filter performance.

Karl Zimmermann's research focuses on biological ion exchange filters. Photo by Karl Zimmermann

Karl lives in Vancouver, B.C., with his wife, Bri, and their dog, Ossa. Photo by Karl Zimmermann

During COVID, I helped run a weekly seminar called WESTalks, which grew to be a worldwide event. I met and learned from dozens of water researchers and practitioners around the world, and I learned about the diverse range of water challenges facing society as well as the ways people are addressing these challenges. I became particularly interested in the WASH sector (WAter, Sanitation, Hygiene) and in water projects in developing communities.

Much of the research findings on biological ion exchange water filters come from long-term pilot tests. Here, Karl is taking a sample from a community-scale pilot system. Photo by Karl Zimmermann

In Rajasthan, India, Karl (center, facing away from camera) listens to stories about fluoride-infected waters from local health workers. Photo by Karl Zimmermann

We’re trying to understand more about how BIEX filters can be designed to fit into treatment trains. This article is our group's first attempt to inform the design of BIEX filters, building off our past works describing the underlying science. Now we can confidently move into more industry-relevant work to inform the design and operations of BIEX filters. We’re at a stage to engage further with water practitioners.

Our study was trying to load the BIEX filters totally with natural organic matter. But in the summer months, the river source's dissolved organic carbon would drop way down, which prolonged the time we needed to collect weekly water samples. We also had a huge washout after a November rainstorm one year that changed the shape of the river (and its water quality), and then of course we were shut down during COVID. All of these things affect a long-term water filter pilot, but you learn to roll with it and make the most of what you have.

With our better understanding of the science that allows BIEX filters to work so well, we’ve moved into more design-relevant research, like this article on resin selection and backwashing. Our next steps are to work more with the industry to collect pilot testing results from various water sources and operating conditions and to expand our knowledge of where BIEX filters do and don’t work well.

After spending two years traveling the world to learn from water leaders, I enjoy being home with my wife and our dog. We love getting out of the city for hikes, walks, camping, fishing, backcountry skiing, and other adventures. Bike rides with my cycling team and running are great ways to feel connected to the city.

The best part of being in the water sector is getting to listen to people's stories of how water is intertwined with their lives and their families. I feel privileged when people share what they perceive as their water challenges. When I get to listen and learn from these stories, I reflect on what I’ve learned through my water sector training, and from water stories I’ve heard elsewhere, to work with the person on options they can try out to meet their safe water goals.

To learn more about Karl's research, visit the article, available online at https://doi.org/10.1002/aws2.1356.