UV Technology for Water System: The Benefits
How UV technology are used in water treatments
UV light is a physical, nonintrusive method of ensuring that organisms are unable to replicate, and with a typical life of only a few minutes, they are rendered harmless.
Correctly sized UV systems can also be used to de-chlorinate or de-ozonate process water and to assist in the removal of TOC and urea from ultra pure water. The level of a pathogens inactivation depends on the UV dose (UV intensity x exposure time) applied and the pathogens susceptibility to this UV dose and it varies for every pathogen.
UV technology does not affect the taste, colour, or pH of the fluid being disinfected and, as such, the technique is often used where conventional chlorine disinfection cannot be applied, such as within a brewery, soft drinks plant, pharmaceutical facility or fish farm.
Validations and Approval Testing
atg Evoqua are committed to providing Ultraviolet disinfection systems that deliver the required amount of UV for a given application. This has become paramount as pressure increases on facilities to provide sufficient treatment. With this in mind, atg have invested in Bio Dose Testing on selected product ranges, enabling atg to offer “Validated” systems.
atg Evoqua have a large number of validated UV systems to ensure UV disinfection performance. Our validation testing has been carried out in accordance with the United States Environmental Protection Agencies (US EPA), Ultraviolet Disinfection Guidance Manual (UVDGM).
The EPA method is one of the most modern and rigorous testing regimes in the world, offering a number of benefits over other existing validation standards, such as an increased flexible operation for validated equipment.
The US EPA UVDGM 2006 uses the mandate of the Safe Drinking Water Act to monitor emerging contaminants, under the Unregulated Contaminant Monitoring Regulation (UCMR2).
Aimed at water supplies originating from lakes, reservoirs, groundwater aquifers and rivers, the purpose of the US EPA UVDGM legislation is to ensure populations are kept safe from emerging pathogens, such as Giardia and Cryptosporidium.
These pathogens are among 17 such species of microorganisms that are resistant to conventional disinfectants, such as chlorine. There are no microorganisms that are resistant to Ultraviolet disinfection.
As an industry leader with considerable experience in supplying US EPA Validated UV systems for Cryptosporidium protection, atg Evoqua are well placed to support and advise all water companies on the application of the validated units into water disinfection strategies.
These include: log reduction, RED Dose, installation into existing infrastructures, upgrades and retrofits, ongoing industry regulation and future product development.
atg Evoqua have designed and developed a large range of fully compliant UV systems, specifically for municipal drinking water and waste water applications.
Additionally, our experience in the US pools market has placed atg Evoqua as an industry leader for validated uv disinfection system for swimming pools. For instance, thanks to atg Evoqua’s close work with the New York Department of Health, it is now compulsory in New York State (US) to fit UV on spray-pad type aquatic features.
UV Dose & System Selection
UV light output at 254 nanometres is known as UVC light (germicidal region). UVC light has the ability to inactivate all known microorganisms, bacteria, pathogens, virus and moulds, including chemically resistant organisms, such as Cryptosporidium and Giardia. UV dose (fluence) is calculated from intensity (UV Power) and time (flow rate) and is typically measured in mJ/cm2.
UV Systems are typically sized in two ways:
- To provide a minimum level of UV intensity. This sizing ensures that the UV intensity at all points with the UV chamber, including the points furthest away from the UV lamp (UVC light source) receives a minimum dose set point e.g. 30 mJ/cm². This UV dose is often referred to as wall dose, due to the chamber wall typically being the furthest point from the UV lamp.
- An average UV dose calculation takes into account the wall dose (furthest distance from the UV lamp) and the area immediately in front of the UV lamp where the UV output is greatest. The sizing method calculates an average dose for the whole UV chamber.
- Validated RED Dose. The term RED – Reduction Equivalent Dose is used for validated UV systems that have undergone independent, 3rd party bioassay testing. The testing uses live surrogate microorganisms e.g. MS2 and T1 to physically test and ascertain ‘real world’ reactor performance. Validated RED doses take into account UV chamber design, hydraulic flow efficiencies, lamp positioning and intensity zones to guarantee the performance of a UV system at achieving bacterial log reductions of microorganisms e.g. a 40 RED will achieve 99.99% reduction. Safety factors such as lamp aging and quartz fouling factors are also included in the UV dose equation to provide a conservative and guaranteed performance.
For more information about UV dose and system selection, read our guide here.