Uv, A Bright Future For The Water Industry
atg UV Technology's Technical Director Tony Leigh looks in detail at the advancements and future for Ultraviolet disinfection systems for the municipal industry in an increasingly water stressed world.
Ultra Violet light was discovered in 1801. It took over 100 years to develop lamps and power supplies on a commercial scale, and a 0.2MGD drinking water plant in Marseilles, France briefly used UV light in 1910. Chlorine was the disinfectant of choice, and UV was really only used in municipal context where chlorine could not be used, or where the distribution main was itself being used as a contact vessel and the first consumers lived adjacent to the point of injection. UV light was used successfully throughout industry with brewers, pharmaceutical plants and fish farmers adopting the technology quickly.
UV gained prominence in applications where the water was itself used as the product, (bottled waters, beer, carbonated soft drinks), or where the water has a process application (wafer rises by ultra pure water, Clean in Place applications, product rise and chase applications, Ballast Water, well field injection).
As the customer base expanded, so did the process application. UV was now being used break specific chemical bonds, sometimes by direct photolysis, but more often by the creation of highly reactive hydroxyl (OH-) radicals. Photolysis applications now include dechlorination, de-ozonation, the removal of TOC from ultra pure rise water in the semiconductor industry, and recently as a barrier to counter the threats caused by the endocrine disruptors and both metabolized and un-metabolised pharmaceutical compounds found in wastewater.
By the year 2000 several key drivers had led to the technology being routinely incorporated into wastewater processes; a flight from chemical regimes, a desire to avoid potentially carcinogenic disinfection by-products, increasing attention to the discharge of chlorine as an active substance into a receiving watershed, and the growing re-use of tertiary treated effluent.
The early applications for re-use were limited to golf course irrigation, however applications have expanded to use the reclaimed waste water for Aquifer Storage and Recovery (ASR), and broad non potable industrial uses. The ASR applications are popular in coastal regions where aggressive water abstraction has led to brackish, saline water permeating into the water table from the sea. The ASR processes injects highly polished reclaimed effluent as a buffer between the water table and the ocean.
How does UV work? UV light between 250nm and 270nm is absorbed by the DNA in all living matter, or RNA in the case of a virus. The light causes cross bonds within the DNA structure to vibrate to the point of rupture. The UV light breaks the cross bonds in the DNA, and forms dimers. Once these bonds are broken, normal cell function quickly ceases. Replication, assimilation of food and respiration are all permanently interrupted, resulting in non viability of the organism.
Lamp technology is based around either Amalgam or Medium Pressure lamps. Both lamp types are used by the leading companies, and each type has specific strengths and weaknesses. Model performance is predicted using Computational Fluid Dynamics (CFD), and usually off the shelf software is customised by the manufacturer to accurately gauge performance.
UV systems destined for drinking water applications are validated using a third party test house to demonstrate system capability, and usually a non pathogenic surrogate such as MS 2 phage or Bacillus Subtilis is used to verify actual system performance. atg UV have verified the performance of a number of reactors in the USA, in each case iteratively improving the predictive models.
The Future: All the water that will ever be is, right now. (National Geographic) The world is quickly running out of drinking water. Critically the drivers are accelerating; population growth, a warming climate, drought, urban sprawls, waste and excess. According to the World Bank, water usage has increased by 600% since 1900, as the worlds' population has increased by 200%.
Water demand doubles every 21 years. The worlds' population is forecast to increase again by 50% to 9 Billion people, causing 80 countries to face shortages of water by 2050. Agricultural use of water accounts for more than 70% of treated water use, and rising standards of living (meat, not grain in diets) will accelerate this trend.
Therefore it is logical to use reclaimed waste water ("re-use") for applications such as crop irrigation, and the application of UV ensures that the water is free from pathogens such as e-Coli, Legionella and Cryptosporidium.
The era of cheap water is now drawing to a close, and price increases are inevitable to fund the repair or rehabilitation of aged infrastructure. Increasingly water conservation will become the norm, and wastewater, once seen as a nuisance to be dumped will be seen as a valuable resource. A non-chemical disinfection process such as UV will play a key role as the planet realizes how valuable clean water actually is.
atg UV Technology have vast experience in providing Validated UV systems to the municipal industry worldwide, using the mandate of the US EPA Ultraviolet Disinfection Guidance Manual 2006 (UVDGM - The world's strictest validation standard). atg UV have designed and developed a large range of UV systems specifically for municipal applications that are fully compliant with the requirements of the US EPA, and have been independently validated to demonstrate performance under a variety of operating conditions.
atg UV Technology's in-depth working knowledge of the US EPA, and the UK's DWI UV Disinfection Guidelines, together with vast experience in supplying validated systems to drinking water and waste water companies worldwide uniquely places atg UV as an industry expert on UV disinfection for municipal applications, including validation, log reduction, RED Dose, installation into existing infrastructures and ongoing industry regulation.
atg UV's product range offers fully validated systems that deliver a 1 - 5 log reduction of Cryptosporidium for flows as small as 10 m3/hr to over 2000 m3/hr within a single high output, small footprint, system. For larger flows, systems are offered as packages, utilising units placed in either series or parallel configurations.
For more information on UV systems please contact atg UV Technical Sales on: +44(0) 1942 216161 or visit www.atguv.com
For further information please email atg UV Technology