By Troy Smith
Today we see a wider array of ultraviolet (UV) options than ever before. New players are entering the field; mature manufacturers have merged and new methods to deliver UV are being designed and brought to market. Once relatively unknown and identified by the generic ‘other disinfection methods’, it is quite clear that the UV industry has matured.
Throughout North America, many drinking water and wastewater systems use chlorine gas as primary and secondary disinfection; UV light is used to combat certain disinfection byproducts (DBPs) and inactivate organisms resistant to chlorination, such as Cryptosporidium. UV (as a means of disinfecting water) has been around since 1955; it became increasingly popular as a main means of disinfection throughout the 1980s and 90s, with the number of users rising annually.
Understanding UV
There are four main types of UV technology currently on the market: low pressure/low intensity (LPLI), low-pressure/high-output (LPHO), medium pressure (MP) and pulsed UV (PUV).
The most common type of UV system on the market is LPLI. Lamp size here varies from 35 to 75 watts; the strength of this lamp is the concentration of energy at the 254 nm wavelength. The benefit of LPLI is the strength of the lamp to produce energy at 45 to 80 watts of energy with the highest energy output at 253.7 nanometers; however, these systems have a disadvantage in that a large number of lamps may be required to produce the desired energy needed for disinfection. Despite that requirement, LPLI remains one of the most widely used system types, largely due to the amount of equipment already in the field.
LPHO systems are the next generation to LPLI systems; these use a lamp that is typically four times the output of its predecessor. This is achieved through amalgam lamp power or high-output/low-pressure lamps. A typical LPHO system will require far fewer lamps, while maintaining high lamp power with a concentration of energy at the 254 nm wavelength.
MP systems feature a single lamp and are used in many applications to treat greater volumes of water. The MP lamp type is a high-pressure gas lamp that produces a large multi-spectrum of energy. It is used as a competitive model to the LP systems in many cases and has a small footprint with single- to two-lamp configurations.
PUV uses capacitance to store and create energy in pulse form. Significantly more expensive than the aforementioned systems, it is not widely used at this time.
Assessing the situation
Once we understand what system you have, it is important to understand how it was designed to your application and how the system measures and quantifies performance. Finally, the most important part of any UV system is to understand the “How, What and When” of maintaining it!
How
Engineering design and maintainence are the two critical factors for attaining quality system performance. From the US EPA, the International Ultra Violet Association (IUVA) and other recognized national and international associations, we now have standards of engineering design. The US EPA Guidance Manual for Surface Water Treatment, 2006, provides standards from design to suggested service; however, it is still the owners’ responsibility to maintain a properly working system that will meet application-specific requirements. Third party service groups (such as Radiant Industrial Solutions, Nalco and Siemens) work with the end-user base to establish site-specific working standards.
To design a system correctly, focused on-site visits are performed. Water quality is tested to understand the challenges to the UV system. Each UV system is designed to a(n) UVT (ultraviolet transmittance) level that is determined by the application process. A further definition of water quality is knowing the answer to the important question, “What is in the water?” will tell us how to maintain the system: whether wipers are needed, how often to clean the quartz, sensor and where to expect the actual UV intensity to measure.
With an understanding of the equipment, application and environment, we can now get into using the system, but first, we should understand the precaution(s) appended to the various UV items on the market.
As with any developing technology, UV has gone through many changes over the past two decades. For example, thanks to the availability of long-life lamps at reasonable prices, we now operate lamps longer than ever before. The precaution necessary here is that the rest of the system may not be comprised of long life components. When using such lamps, it becomes imperative to understand your system from the inside out. While each environment and/or application is different, in some instances owners will need to clean the quartz sleeves periodically in order to get the full use of this longer-lasting lamp type.
Take the time to truly understand the system and you can keep the unit running for many years regardless of what type of system it is. You can accomplish this through measurement: of performance, UV intensity, lamp operation and of any variables present that affect your system. This can be accomplished through several simple steps:
What
…within the system needs to be maintained? Lamps, quartz, sensors, temperature, water quality feed and internal chamber conditions. With an understanding of what in your system affects its performance, we can now measure how the system is working with an understanding of what action to take for process failures, as well as preventive maintenance.
When
We will use this knowledge with the application specific data of UVT and sitespecific conditions to determine when to service equipment. Using equipment standards for guidance, we will look at the system daily, monthly and annually, as follows:
Daily: Ensure the unit is performing correctly without failures or water leaks Monthly: Verify the unit is performing to the expected intensity value above the low acceptable level of intensity output.
Annually: Review system controls, interlocks, output, lamp performance, quartz performance and overall unit output to expected design.
As we get deeper into the UV system, we now turn our attention to the methods of performing service or maintenance on equipment. One of the major concerns with any UV system is lack of service. The equipment is built to run for a minimum of 8,500 hours on LP systems and 5,000 hours on MP systems. With this in mind, it is not uncommon for users in the field to only look at their systems when it is time for lamp change.
A common question when looking at a UV system is how to determine if it is functioning correctly. Service providers answer this through UVT measurement, equipment operation signals (such as all lamps on), mechanical inspections (no leaks), UV intensity measurements (equipment metering) and a review of performance logs (date of lamp change). Each of these factors can be measured and used to better understand the system and, more importantly, to control the system’s performance.
Metering
Metering is the one item within a UV system that is always discussed. This is the ‘tattler’ of the system. A good metering device within a UV system gives the ability to log data that may affect the performance of UV disinfection (remember, this is the whole purpose!). One can measure and record all of the variables of the system and, at a glance, know the UV intensity, lamp age, water flow, UVT and water temperature—at present and over time. It is not uncommon for a change in one of these factors to throw a system into low-UV.
Most systems in the field today will allow owners the ability to meter one or two of these factors; there are only a few systems that actually record this data, thus leaving the end-user to record the data by hand. Advancements in the field are changing this; now there is metering that can record some or all of these factors automatically.
A good meter will have the ability to verify the UV intensity and that the system is working correctly and to preset levels. Such a meter effectively enables users to prevent failures caused by unknown variables affecting the system.
With deeper understanding comes enhanced comprehension of the factors that attribute to problematic conditions and the need to quantify performance. It is this ‘need-to-know’ that is driving new equipment development, especially new metering devices. There is a change occurring in the UV market which is bonding the ‘need-to-know’ to metering control. This information is being used to understand the UV system and to control performance as required by the regulations at hand—and those yet to come.
Through these efforts, we get better control of system performance in the field, which allows the manufacturer or service provider to understand what action to take when reviewing any concern related to UV performance. The UV marketplace is continuing to evolve and the equipment in the field, both new and old, is changing as well. User understanding increases with better controls.
About the author
Troy Smith is the President of Radiant Industrial Solutions. Over the past 19 years, he has personally been involved with the development of new lamp technology, new applications, new metering devices and many other advances within the industry. Reach him at Radiant Industrial Solutions, Inc. 4248 Bluebonnet Drive, Stafford, TX 77477; telephone (713) 972-0196 extension 223 or by email, [email protected]
About the company
A leader in UV applications, Radiant provides UV equipment, products and services for water, air and surface UV applications. Radiant works with distribution and end-users to understand and control UV performance. Radiant metering products arm the end-user with the knowledge to accomplish preventive maintenance at never-before-seen levels. The PinPoint Metering system by Radiant, along with all the company’s products for commercial and industrial UV users, can be seen at www.radiantuv.com