Date
Tuesday, September 10, 2024
Time
11:30 AM - 12:00 PM
Location Name
M108
Name
Parallel Design of KY’s Largest UV Disinfection Systems for Drinking Water
Track
Asset Management
Description

Kentucky American Water (KAW) is installing a UV disinfection system at two of its three water treatment plants (RRS and KRS2) to comply with the EPA’s Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). This rule was developed because of a 1996 amendment to the Safe Drinking Water Act requiring the EPA to develop rules to balance the risks between microbial pathogens and disinfection byproducts (DBPs). The purpose of LT2ESWTR is to reduce illness due to Cryptosporidium and other pathogenic microorganisms. LT2ESWTR builds upon earlier rules to address higher risk public water systems for protection measures beyond those required for existing regulations (US EPA Fact Sheet – Long Term 2 Enhanced Surface Water Treatment Rule). The rule applies to all public water systems that use surface water or groundwater under the direct influence of surface water. Based on source water monitoring, systems are placed into various bins that require differing levels of Cryptosporidium inactivation. KRS2 and RRS were placed into the Bin 2 classification, and as a result, are required to provide an additional 1.0 log inactivation of Cryptosporidium. Following evaluation of several alternatives, KAW elected to use UV disinfection to provide the additional Cryptosporidium inactivation. The target installation dates for KRS and RRS are Fall 2023 and Summer 2024, respectively. Given the proximity of these dates, KAW opted to proceed with concurrent preliminary designs for both facilities in order to accelerate the timeline and potentially procure the UV equipment simultaneously. This preliminary design phase included research and review of available technology as well as approximately 30% engineering for each facility. KRS2 has a rated capacity of 20 MGD (with the potential to increase to 30 MGD in the future) and RRS is rated for 25 MGD. The original concepts for these facilities were therefore very similar and envisioned three UV reactor trains (2 duty + 1 standby) to common suction and discharge headers between existing filters and clearwell. The preliminary design phase; however, yielded very different designs for each facility based on improved technology and an alternative configuration estimated to save approximately $3 million in construction costs by retrofitting the existing filter effluent piping with the UV reactors at RRS. Even with these changes and the divergent designs, the project team elected to procure the equipment for both facilities at the same time and from the same Vendor to expedite submittals, manufacture, and process integration with the existing control networks. Construction is expected to start in Late Spring/Early Summer 2023 at KRS2 with RRS following just behind. At KRS2, the proposed reactor – designed for maximum long-term flexibility in terms of UV dosage potential – will be the first ever installation for drinking water disinfection compliance. When complete, both facilities are anticipated to be the largest installations of UV disinfection to meet the LT2ESWTR in Kentucky.