Page 5 - Demo

University of Minnesota College of Science and Engineering | DEPARTMENT OF CIVIL, ENVIRONMENTAL, AND GEO- ENGINEERING 5Opportunity within the CrisisThe Grand Rapids situation presented an opportunity for a natural full-scale experiment. Water distribution systems are complex with many variables: water source, location, temperature, disinfection method, and water storage differences, including the use of large storage towers, to name a few. It is difficult to compare systems with so many variables. A unique aspect of the Grand Rapids situation was that a Legionnaires%u2019 disease outbreak was attributed to a system that obtained its water from groundwater. Groundwater sources are generally considered cleaner than surface water sources because the water is naturally filtered through layers of gravel and soil. Federal regulations do not require disinfection for water systems that use groundwater, as long as the drinking water regularly tests free of coliform bacteria%u2014indicating that there is no contamination from fecal matter. Hence, the Grand Rapids water system was not using disinfection prior to or during the outbreak. The Grand Rapids site presented Hozalski and his team the chance to study an active system in a wide-scale crisis, to recommend a solution, and to assess the impact of the intervention. Hozalski was also able to leverage a large, existing research project to provide the data to help.An Existing Research Study Provides SerendipityDisinfection stifles pathogens that can harm humans, but adding disinfectants to drinking water can also carry risks by creating so-called disinfection byproducts that might also be harmful to human health. When he received the call from Grand Rapids, Hozalski was leading a large USEPAsponsored project to study the complex interactions and tradeoffs involved when disinfecting drinking water. Hozalski%u2019s