Dr. Karl Linden is an Environmental Engineering Professor at the University of Colorado Boulder. He has researched and developed UV technology since the early 1990s. Dr. Linden currently holds the Helen and Huber Croft Professorship, and has decades of experience in the use of UV for water and wastewater treatment.

When he was a young boy living in New York City, Dr. Linden remembers, "I wanted to do something to help protect the environment but I did not just want to talk about it. I actually wanted to learn how to physically do something about it." He had the opportunity to engage this interest when he participated in an environmental cluster in 7th and 8th grades. Dr. Linden’s early teachers had an impact on his career path. "After attending the Bronx High School of Science in New York City, I was accepted into the Environmental Engineering Program at Cornell University," he recalled.

While taking a break from his undergraduate studies at Cornell, Linden read an article in the New York Times about an engineering method used to clean up sewage water using an anaerobic process to produce methane and wetland plants to polish the water. The project was overseen by William Jewell, a professor at Cornell University. Linden returned to Cornell and asked permission to join the graduate level course Jewell was teaching. After acing this class as the only undergrad among graduate students, he was hired as a member of Jewell’s research team. Later, "I applied for a National Science Foundation Research Experience for Undergraduates program and received a summer scholarship to work in Professor Jewell’s lab on my own project," he remembered. This experience "got me hooked on research and teaching as a way to make a big difference in the world both for people and the environment," said Dr. Linden.

Dr. Linden chose University of California at Davis for his graduate studies. There he worked closely with leaders in the field of UV disinfection of water and wastewater. Dr. Linden recalled his years as a graduate student, "At Davis I worked with Dr. George Tchobanoglous and Dr. Jeannie Darby. They presented me with a project on disinfecting wastewater with ultraviolet light. I was lucky to have two excellent mentors to guide me through my research. I quickly became one of the UV experts in this young field and have continued building on this knowledge, tackling new problems, ever since."

Fundamental discoveries in UV technology research coupled with practical applications are the characteristics of Dr. Linden’ work. Dr. Linden and his team are working on UV disinfection exposure responses to Adenovirus, which was previously thought to be very UV resistant, resulting in high regulatory UV doses. He said, "We are showing that with polychromatic UV light (such as that from medium pressure UV lamps) the inactivation of adenoviruses is mush faster than with the UV 254 wavelengths. I hope this helps to improve the acceptance of UV for small systems looking to use it for virus inactivation credit." Dr. Linden’s team also significantly contributed to the research showing "UV photolysis was very effective for destruction of the chemical contaminant NDMA." NDMA was resistant to treatment by conventional means, but "UV happens to be very effective," added Dr. Linden.

Dr. Linden is widely known for a publication he co-authored with Jim Bolton, one of the founding members of the International Ultraviolet Association. The paper standardizes bench scale testing for UV disinfection. It is currently the gold standard for performing UV dose-response studies and is cited widely in the water industry.

UV water disinfection technology is embraced worldwide. It is an excellent choice for developing countries for several reasons. "It’s on-demand, fast, does not require storage or long contact times and does not add any strange taste to the water," said Dr. Linden. Currently his team is working with Manna Energy in Rwanda to bring UV systems to communities there. These are powered by solar energy and have built in remote monitoring for maintenance and operations. "We are also working on a UV household system based on low cost UV lights and hope to pilot that system in Rwanda in the coming year, pending funding," added Dr. Linden.

Along with major advances in UV technology also comes challenges. "Being able to translate a very interesting and technical process like UV to the general public and even to professionals in the water industry to help them understand how UV works and its effectiveness is important," said Dr. Linden. UV technology is viewed as green technology because it does not require harmful chemical additions to water to work well. Many industry leaders are working to reduce the carbon footprint and energy usage of UV disinfection equipment. "Recent improvements in lamp design and efficiency are welcome," observed Dr. Linden, "and, the future holds a lot of promise for new technologies like LEDs.

In 2013, Dr. Linden will become the President of the International Ultraviolet Association (IUVA), based in Washington D.C. The IUVA’s mission is to advance the science, engineering and applications of ultraviolet technologies to enhance the quality of human life and to protect the environment. This non-profit organization has more than 500 members in 35 countries. IUVA is recognized as the leading knowledge-base and voice for UV technologies through its varied conferences and programs.

With many years of experience in researching and developing UV technologies and implementing its usage worldwide, Dr. Linden will be an excellent leader for the IUVA. His impact on Environmental Engineering students will continue at University of Colorado Boulder. Dr. Linden has achieved his childhood goals to protect the environment and water supplies through study, research, teaching and action.