TrojanUV systems can be utilized as a primary disinfection barrier to viruses at drinking water plants treating both surface water and groundwater.
The United States Environmental Protection Agency’s Long Term 2 Enhanced Surface Water Treatment Rule (LT2) defined UV dose requirements for inactivation of viruses based on a relatively resistant virus: adenovirus.
The UV dose required to accomplish a 4-log (99.99%) inactivation of viruses is 186 mJ/cm2, as seen in the USEPA UV Disinfection Guidance Manual. The LT2 Rule requires 4-log virus treatment for public water systems using surface water and groundwater under direct influence (GUDI) of surface water. Furthermore, the USEPA’s Ground Water Rule requires that non-GUDI groundwater systems also provide 4-log inactivation of viruses if fecal indicators are detected during monitoring. However, some regions mandate 4-log virus treatment regardless of monitoring results.
In Pennsylvania, the Department of Environmental Protection mandated all groundwater providers obtain 4-log virus treatment credits regardless of monitoring results from their wells under the Ground Water Rule (GWR). Affected facilities needing to enhance their disinfection practices often do so with modified chlorine dosing. However, the Hall Road Well Station was a unique installation in that its existing chlorine dose capabilities would have required an impractical amount of additional pipe in order to establish the necessary disinfection contact time. UV technology, on the other hand, provided a favorable lower footprint alternative.
A UV dose of 186 mJ/cm2 is required by the USEPA for 4-log treatment of viruses. Traditional surrogates used for validations, such as MS2, aren’t resistant enough for UV to demonstrate inactivation of 4-log virus. To overcome this challenge, we used a high-resistance surrogate to validate four TrojanUVSwiftSC units to the doses required for 4-log virus inactivation. Our third-party-witnessed validation meets all the recommendations of the USEPA UV Guidance Manual, and, for the first time, allows water providers to implement a fully EPA-compliant UV solution for 4-log treatment of viruses with a single unit.
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