Wastewater engineers across the world aim to safeguard human health and alleviate environmental pressure.
The widespread use of UV disinfection technology for global wastewater treatment is evidence, if needed, that it is no longer an ’emerging’ technology. Indeed, it is now an accepted, mainstream disinfection method used routinely by water and wastewater engineers worldwide to safeguard human health and alleviate environmental pressures.
UV is particularly useful when it comes to reuse. The USA has led the way in reusing wastewater in various forms for decades. It is now a major issue in the southern USA, southern Europe, the Middle East, Australia, and many parts of Asia, where chronic water shortages drive investment in reuse technology. UV is now playing its part.
Using computational fluid dynamics (CFD) modeling has vastly improved UV equipment manufacturers’ ability to confidently predict the level of treatment required for wastewater using their proprietary equipment. All manufacturers now use this tool to optimize the dose delivery of their reactors and minimize energy costs. Also, as manufacturers develop and improve optimized UV reactors, they will soon be able to validate the designs using recognized validation protocols.
Conventional UV lamp technology has improved significantly over recent years, with medium-pressure lamps continuing to see gains in energy efficiency, lamp life, and power density, and quartz coating techniques extending lamp life to well over 12,000 hours.
New mercury-free UV-LED systems are now also appearing. These small systems are ideal for low-flow applications and easily integrated into treatment applications. In addition, a brand new LED-based UV transmittance monitor, the BersonSense – the first in the world to use UV-LED technology – provides highly accurate UV transmittance readings in all conditions over an extended lifetime, ensuring highly accurate UV dosing.
Finally, a new range of low-pressure, high-output (LPHO) multi-lamp UV systems are being developed. Two versions are available: a ‘U’ configuration with a smaller footprint for lower UV Transmittance (UVT) applications where higher doses are required (such as wastewater reuse or virus removal); and an ‘L’ configuration for higher UVT and lower dose requirements (for example drinking water applications). Both configurations create a rotational liquid flow, ensuring extensive fluid mixing and optimal disinfection performance while minimizing head loss.
The most common method of wastewater disinfection for reuse has long been chlorination. Despite chlorine’s impressive track record, concerns regarding disinfection by-products (DBPs) and, more recently, disinfection performance concerning pathogen inactivation, are driving the conversion from chlorine disinfection to other disinfection methods such as UV, which does not produce any DBPs.
Closed vessel UV systems are easy to install within existing pipework, so there is minimal disruption to plant operation. Day-to-day operation is simple, and only minor maintenance is needed. The only regular requirement is changing the UV lamps and wiper rings once a year, a straightforward operation that on-site personnel can carry out.
UV systems for wastewater reuse are also validated to much higher doses than drinking water systems, according to protocols established by the National Water Research Institute (NWRI) in the USA. Drinking water-type product validation will emerge as the dominant method of assessing suitability for these critical applications. The ability to prevent photo repair will also emerge as a key.
Potential applications for wastewater reuse are extremely wide-ranging and include any instance where water is needed for non-potable use. The most popular and widespread use is for agricultural irrigation, with California and Florida leading the way in the USA and several Australian states also making significant progress. Other irrigation uses include landscape and recreational applications such as golf courses, parks, and lawns.
Reclaimed wastewater is also used for groundwater recharge applications such as aquifer storage and recovery or preventing saltwater intrusion in coastal aquifers. Other uses include toilet and urinal flushing, firefighting, foundation stabilization in the construction industry, and artificial snow generation. In all these applications, reuse wastewater relieves the burden on existing municipal potable supplies.
The UV industry has experienced considerable maturation over the past decade, and the world’s major water technology companies now regulate and dominate it. Various applications have field-tested conventional UV technologies, and they now boast significant track records. UV’s acceptance is expected to grow rapidly over the next 20 years, with decreased uncertainties surrounding regulations, royalties, technology, and engineering. CFD has greatly aided conventional UV designs, and future designs will use it as a routine sizing tool. The addition of UV-LED technology is also opening up many new markets for UV disinfection.
The wastewater reuse market is now poised for dramatic growth, particularly as increasing populations add even more pressure to already overstretched water resources in many world regions. Tighter limitations on pollution discharge will also play an important role in developing this technology.
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Nuvonic is the innovator in sustainable UV technology for water, air and surface disinfection on a global scale. Our mission is to support nature’s purity with science by protecting people and processes from harmful contamination.
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