The U.S. Environmental Protection Agency’s new regulations are set to make this established technology more popular than ever
Regulations
governing water disinfection technologies are always in a state of review and approval in order to ensure the highest measure of safety in the U.S. water supply. The latest technology trend to come under the U.S. Environmental Protection Agency’s (USEPA) scrutiny is the use of ultraviolet (UV) disinfection as a viable primary disinfectant for municipal water treatment. Used for years to produce potable water in Europe, UV disinfection is used for only about one percent of the 40 billion gallons of drinking water produced daily by public utilities in the U.S. However, this figure is expected to skyrocket in the next 10 years as the USEPA’s regulations enable companies and municipalities to more accurately analyze the technology and measure its value.
In June 2003, the USEPA published the latest draft of its Ultraviolet Disinfection Guidance Manual (UVDGM) which, when finalized, will provide technical guidance on the application of ultraviolet light for the disinfection of drinking water by public water systems. Specifically, the USEPA developed the manual to support two upcoming drinking water regulations: the Long-Term 2 Enhanced Surface Water Treatment Rule, which requires certain systems to provide additional treatment for cryptosporidium; and the Stage 2 Disinfection Byproducts Rule, which will place more stringent limits on certain disinfection byproducts.
So, why is the USEPA suddenly focusing on this particular technology, and what do the new guidelines mean for municipalities and service providers? Improved technology, better analysis, and more widespread acceptance.
Shedding New Light on an Old Technology
Ultraviolet disinfection works by exposing waterborne microorganisms to UV light, in the germicidal range of 250 to 270 nm, at a specified intensity for a specified period of time. This exposure renders the microorganism "microbiologically dead" by penetrating the cell wall and affecting the DNA in such a way that it can no longer reproduce.
The highly effective germicidal properties of ultraviolet light have been known for more than 100 years. The first full-scale use of UV for wastewater disinfection was in 1910. The invention of neon tubes in the 1940s introduced the low-pressure mercury vapor lamp, which provided a practical and economical source of UV light. Convinced of the technology’s efficiency, a significant number of U.S. companies installed UV disinfection systems for the municipal wastewater market in the 1950s.
By the early 1980s, UV disinfection of wastewater had gained popularity due in part to the heightened regulatory requirements affecting the use of chlorine within the wastewater treatment process. The new regulations included the need to dechlorinate prior to discharge, the installation of chlorine scrubbers to protect against accidental release of chlorine gas, and the need to develop risk management plans in case of accidental chlorine release.
Because it effectively treats certain bacteria unaffected by traditional chlorine disinfection, and doesn’t present the same occupational hazards, UV disinfection became a popular alternative for the wastewater market. Recently, that popularity has expanded into the drinking water market as well. Chlorine use can lead to an overflow of strictly regulated disinfection byproducts (DBPs) that form when free chlorine reacts with organics in the water. These byproducts can cause taste and odor problems, and can also be carcinogenic. The use of UV disinfection does not create DBPs, therefore reducing or eliminating their presence in the distribution system.
UV disinfection is not only attractive as a primary purification technology; it is also a viable element of a multiple barrier approach to water treatment. UV disinfection can follow the use of a filtration treatment system as the finishing step to other disinfection approaches. UV disinfection leaves no residual and may require the addition of a disinfectant (such as chlorine) to achieve a residual.
Jump-Starting UV Disinfection Acceptance
The USEPA’s new UVDGM provides a consistent regulatory baseline for manufacturers to follow and offers a level playing field to maintain a competitive environment in UV disinfection technology. It also sets a basic standard that innovative systems must achieve before they can be introduced to the marketplace.
Once complete, the USEPA’s UVDGM will help further jump-start widespread acceptance of UV disinfection technology for municipal applications. The guidelines are especially attractive to technology manufacturers because they:
- Specify projects on a neutral base, which makes it more transparent for customers to compare different technologies
- Make customers more familiar – and, therefore, more comfortable – with UV technology
- Generate attention for UV disinfection technology on the whole
- Help to explain and quantify the science of UV disinfection
Until now, the biggest hurdle for the regulatory community has been measuring the effectiveness of UV in water systems. This is because there was no quick, analytical technology that showed whether or not a UV system was performing as claimed by the manufacturer. Now, the standards outlined by the UVDGM provide a base level of comparison from operational data gleaned from installed UV systems, enabling municipalities to more comfortably decide which system is the most efficient.
Ultimately, the USEPA’s manual demands that current UV sensor technology improve over time, allowing manufacturers to reduce the uncertainty in their systems while improving overall operational efficiency. The validation process, which requires manufacturers to stand behind their performance claims, will help to improve the quality and consistency of UV products in the marketplace. Steps may still need to be taken to reduce the costs of validations; this can be accomplished through competition among validation operations and increased validation site availability and capacity. The requirement to validate may be reduced as the standards evolve to model – and improve upon – validation results, and as the user community develops a comfort level with UV disinfection.
UV disinfection continues to gain momentum for use in potable water applications. It is an attractive alternative to other disinfection technologies because it has minimal safety and handling requirements when compared to other popular treatment technologies such as chlorination; it requires relatively low start-up and capital costs; it deals effectively with microbial contamination; and it’s simple to install and retrofit. Thanks to the USEPA’s new regulations, UV disinfection technology manufacturers can more effectively improve the technology’s efficiency and viability, and state regulators will increasingly view UV disinfection as a viable, attractive disinfection technology.