As a leading testing and validation protocol, the United States Environmental Protection Agency (US EPA) Ultraviolet Disinfection Guidance Manual (UVDGM) 2006 provides an advanced testing and validation method for guaranteeing UV disinfection performance for a large range of operating conditions, such as flow rate and water quality measured in UVT% (Ultraviolet Transmittance).
Advantages of the US EPA UVDGM Validation
Using the protocols established in the US EPA Ultraviolet Disinfection Guidance Manual (Long Term 2 Enhanced Surface Water Treatment Rule), atg UV Technology systems are rigorously biometrically tested using live surrogate microorganisms (T1 and MS2). This provides guaranteed UV disinfection performance against a range of microorganisms, such as Cryptosporidium, Adenovirus and other waterborne pathogens.
Unlike alternative validation methods, such as the DVGW and ONORM, which only test to a single UV dose set point of 40 mJ/cm2 RED, the US EPA UVDGM validation allows for the selection of multiple data points. The result is a highly flexible UV performance validation that allows for guaranteed UV doses between 10 mJ/cm2 RED and 120 mJ/cm2 RED.
This is of particular importance when aiming for a log reduction of Cryptosporidium, Giardia, E-Coli and Adenovirus. By adopting the US EPA UVDGM Validation, UV systems can be sized to provide the correct UV intensity in direct relation to the specified UV Transmittance e.g. 90% UVT. See table below.
|UVT%||US EPA UVDGM VALIDATION||ONORM VALIDATION||DVGW VALIDATION|
|95% UVT||16.56 RED||40 RED||40 RED|
|90% UVT||20.76 RED||40 RED||40 RED|
|85% UVT||24.12 RED||40 RED||40 RED|
|80% UVT||26.64 RED||40 RED||40 RED|
|75% UVT||28.32 RED||40 RED||40 RED|
|70% UVT||30.06 RED||40 RED||40 RED|
(Table 1 is based on the log reduction tables for a 3 log reduction of Cryptosporidium: 12 RED x required RED Bias in relation to known UVT% value)
As illustrated above, in the case of UVT% values higher than 90% UVT, using the USEPA UVDGM validation method typically provides a 50% saving in power and system size when compared to the DVGW and ONORM solutions, which can ONLY offer a UV dose of 40 mJ/cm2.