Code
The US EPA Ultraviolet Disinfectant Guidance Manual shall be considered a recognized national STANDARD in the MAHC.
Annex
Validation is a process by which any UV unit is tested against a surrogate microorganism in order to determine its performance. Validation is required because there is no on-line test of a UV unit’s ability to disinfect and, due to the relatively short contact time, it is impossible to size units accurately based on just calculations.
It is important to note that evidence of testing is not the same as validation.
Validation must adhere to the following criteria:
* Follow one of the approved validation systems, preferably the USEPA DGM 2006,
* Have been carried out be a genuine third party, and
* Include all the required validation factors and RED bias.
The validated performance is based on the flow and transmissivity of the water to be treated. Therefore it is essential that the system is used within its validated performance range. A system operated outside its validated range is NOT acceptable.
Validation Factor
The validation factor is used to account for statistical variations in the recorded data during third party testing. The validation factor is required to ensure that the equipment’s actual performance will always be equal to or better than it’s validated performance. This figure can be between 15% and 35% depending on the quality of the testing and must be included in any validated performance curve.
Transmissivity (Transmission)
The transmissivity (often called transmission) of the water to be treated is an important design factor in sizing a UV system. The transmissivity is normally quoted as a % value in either a 1 cm, 4 cm, or 5 cm cell. It is measured in a UV Spectrophotometer.
In many water treatment applications, this value will vary considerably but AQUATIC VENUES are for the most part consistent, due to the bleaching effect of the CHLORINE used as a residual disinfectant.
Typically AQUATIC VENUES will have a transmission of between 94% and 95% in a 1 cm cell, with splash pads and other INTERACTIVE WATER PLAY VENUES between 92% and 94%.
The installation of a UV unit itself will increase the transmission by perhaps 2% due to the improvement in the POOL water quality so the values noted above refer to a situation where a UV unit is installed and operational.
Design transmissions over 94% are not recommended, and exceptionally heavily loaded AQUATIC VENUES may consider using a lower number as a design basis.
It is also important to understand that as transmission is reduced, the performance of the equipment is reduced and the RED bias increases, requiring the UV to deliver more performance. For this reason, the performance difference between any equipment’s validated performance at 98% transmissivity and actual field performance at 94% transmissivity can be 40% lower. When presented with validated performance data at 98% transmission, operators should therefore be aware that the equipment may only deliver half the performance when installed.
Validation Range
A validated system will have different performance levels at different water qualities and flows. The relationship between these is traditionally represented as a performance curve where the performance can be noted at any point on this curve. However the lowest transmission test point and the highest flow tested are normally considered the extents of the validated range. This means that any UV unit tested at 95% and above is NOT validated at transmissions lower than 95%. For the same reason, a unit tested at a maximum flow of 500 gpm is NOT validated for any flow over 500 gpm.
Validation factors can reduce equipment validated performance by 30%, so it is essential that systems without validation factors built into performance curves are not considered validated.
The performance of a UV system in the field is measured by a combination of flow and intensity readings from the UV sensors. Performance in the field can be verified on inspection by regulators who will compare actual sensor readings with those indicated on the performance charts, so these charts must be retained at the AQUATIC FACILITY for each validated system.
UV equipment is utilized for its ability to disinfect CHLORINE-tolerant pathogens and for its ability to reduce combined CHLORINES in the POOL water. For the latter, typically a calculated dose of 60mJ/cm2 is utilized based on the total UV-C and UV-B spectrum. This is similar to the validated dose requirements of the SECONDARY DISINFECTION SYSTEMS.
Where UV is fitted as a SUPPLEMENTAL TREATMENT SYSTEM the CODE allows some operational and equipment concessions. Operators should note that the regulations as stated represent BEST PRACTICE; but where specific circumstances dictate, then the equipment specifications may be reduced.
For a SUPPLEMENTAL TREATMENT SYSTEM, the operator may consider reducing the dose applied to the process. This will reduce performance accordingly and operators should consider carefully such reduction in performance, and assure themselves that the equipment will still provide a beneficial level of performance.