The Evolution of UV Disinfection in Indianapolis: Balancing Between USEPA Guidance and Other Regulatory Frameworks

UV disinfection has been implemented as a disinfection barrier to provide Cryptosporidium and Giardia inactivation at four surface water treatment facilities serving the City of Indianapolis and surrounding communities. The first UV systems installed in Indianapolis were designed in accordance with the 10 State Standards having the disinfection capacity to provide a MS2 reduction equivalent dose of 40 mJ/cm2, with operation based on the recommended approaches of the EPA's UV Disinfection Guidance Manual (UVDGM) to attain compliance with Federal regulations. As more UV systems were installed in Indianapolis and throughout Indiana, the increased experience and confidence in UV disinfection resulted in a shift in UV system design requirements, with the Indiana Department of Environmental Management moving away from 10 State Standards and towards the recommended procedures of the UVDGM. This evolution in UV system design and operation requirements in Indiana has resulted in significant savings in capital costs, energy usage and maintenance requirements at several facilities, all while operating with robust monitoring strategies ensuring the full protection of the public health.