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Aquionics’ UV disinfection systems are the first closed vessel, medium pressure systems in the world to be validated for wastewater reuse applications in accordance with AwwaRF/NWRI* guidelines. Having undergone third party validation testing by Carollo Engineers, they have now been formally approved for post-filtration and reverse osmosis applications by the California Department of Public Health (Title-22 validation).

Wastewater reuse has been practiced in various forms for decades, with the USA leading the way in reuse research. It is now a major issue, with large areas of the Western and Southern states experiencing chronic water shortages. The problem is becoming more acute with population growth, with many of the most arid states, such as Nevada and Arizona, experiencing rapid increases in their urban populations in recent years. Large-scale reuse projects are now also being considered in other water-poor regions of the world such as Australia, China and southern Europe.

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 with respect to pathogen inactivation, are driving the conversion from chlorine disinfection to other disinfection methods such as UV, which does not produce any significant 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 maintenance is minor. The only regular requirement is changing the UV lamps and wiper rings once a year, a straightforward operation that can be carried out by on-site personnel.

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. 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, fire fighting, foundation stabilization in the construction industry and artificial snow generation. In all these applications, reuse wastewater relieves the burden on existing municipal potable supplies.

“We are extremely pleased that we have achieved this important validation,” commented Aquionics’ President Bill Decker. “Our state-of-the-art technology uses UV sensors to actually measure how the UV systems are performing. This permits much greater control while saving energy, especially when compared to the existing methods of applying crude safety factors to systems that use high numbers of lamps or are unwiped.”

* National Water Research Institute (www.nwri-usa.org) / American Water Works Research Foundation (www.waterresearchfoundation.org)

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UV disinfection specialist Aquionics has appointed Oliver Lawal as its new Vice President. Having worked in the US, UK and Germany, Oliver has over ten years global knowledge of UV products and applications. In this new role he will work with existing product lines from Aquionics and its two sister companies, Berson UV-techniek in the Netherlands and Hanovia Limited in the United Kingdom, as well as overseeing the development of new product lines and applications.

He joins Aquionics from ITT-WEDECO, where he most recently served as Director of Engineering, responsible for new development. During his time with WEDECO he was responsible for project managing many large UV installations around the world, including the world’s largest UV wastewater treatment installation, in Manukau, New Zealand. 

Oliver holds a Bachelors Degree in Integrated Engineering Systems from Manchester University in the United Kingdom, is a Chartered Engineer and member of the Institution of Mechanical Engineers (UK). He also actively serves on a number of industry committees, including the International Ultraviolet Association, where he chairs the Manufacturers’ Council, the American Water Works Association UV Standards Committee, and the Water & Environment Federation’s Disinfection Committee.

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The need for disinfection

Cooling towers are used to dissipate heat produced by industrial processes such as power generation, oil refining and chemical processing. They generally work in two ways, either through the evaporation of water to remove heat and cool the process fluid, or relying solely on air to cool the fluid. Towers utilizing water evaporation are an ideal breeding ground for microorganisms – many of them pathogenic – which thrive in the warm, wet conditions, forming ‘biofilms’. Various species of Legionella bacteria, the cause of Legionnaires’ disease in humans, are commonly associated with cooling towers and must be controlled by law. In addition to the health risks for surrounding populations, biofilms also cause many mechanical problems with the cooling process, such as a reduction in heat transfer, microbial corrosion, interference with the effectiveness of corrosion inhibitors, and disruption of water flow.

There are several ways of controlling microbial infection, including biocides such as chlorine, chlorine dioxide, hypobromite and ozone. In addition, a non-chemical method that is gaining increasing acceptance is ultraviolet (UV) disinfection.

Whatever treatment method is used faces many demands and needs to meet the following criteria:

• it should be effective against all microorganisms
• it should work fast
• it should have a residual effect
• it should be cost effective
• it should be easy to use
• it should have minimal environmental impact

It is often recommended that two treatment methods are used simultaneously to control biofilms and Legionella. UV, in combination with another biocide, meets all of the above criteria, with much reduced reliance on the secondary biocide.

The advantages of disinfection using UV

UV disinfection, with secondary dosing using a suitable biocide, is in fact one of the most cost-effective and efficient methods of reducing biofilms in cooling tower water. UV works instantaneously against all water-borne microorganisms, including bacteria, viruses, molds, spores and protozoa – including those resistant to chlorine. UV systems are also very easy to use and can be effectively monitored and integrated with online process control systems.

The only other requirement is residual disinfection. Because UV has no residual effect it cannot reduce levels of bacteria colonizing pipework walls. To achieve this, dosing with a secondary biocide is therefore required. Even though residual disinfection is always required, UV dramatically reduces the required frequency and level of secondary dosing and therefore reduces the costs and safety issues associated with purchasing, handling and transporting chemicals.

UV disinfection systems are very compact, modular and easy to install into existing water treatment systems. In addition, secondary dosing does not require the complex monitoring equipment necessary if biocides are used as a primary disinfectant. In addition, UV does not cause the formation of chemical disinfection by-products, many of which can have undesired effects of their own.

How UV works

UV is the part of the electromagnetic spectrum between visible light and X-rays. The specific portion of the UV spectrum between 185-400nm (also known as UV-C) has a strong germicidal effect, with peak effectiveness at 265nm. At these wavelengths UV kills microorganisms by penetrating their cell membranes and damaging the DNA, making them unable to reproduce and effectively killing them.

A typical UV disinfection system consists of a UV lamp housed in a protective quartz sleeve which is mounted within a cylindrical stainless steel chamber. The water to be treated enters at one end and passes along the entire length of the chamber before exiting at the other end.

UV system design

UV systems for cooling water treatment should be installed post-filtration. The UV dose received by a microorganism is dependent on the energy output of the UV lamp, the flow rate of the water, the ability of the water to transmit UV (its transmittance value) and also the geometry of the treatment chamber. Proper design of the treatment chamber must take all of these factors into account. Transmittance is especially important and is a measure of the amount of UV light absorbed or scattered by suspended material in the water. This can vary considerably depending on the source of the water and its level of purity, so a transmittance test should always be carried out to determine correct UV system design.

As flow rates increase, chamber size and lamp power output can be increased as required. For larger flows, multiple chambers are used, in series or in parallel, until the required degree of disinfection is reached. The use of high intensity, medium pressure UV lamps is recommended to treat large flow rates, as these produce a high UV output without taking up valuable space.

Reliable disinfection requires that a constant UV dose is applied to the water. Power transformers are available to absorb fluctuations in power supply whilst maintaining constant power to the UV lamp(s). Power switching options are also available, adjusting the lamp power on-line as the water flow or the quality of the water changes. The power switching option maintains a constant, pre-determined UV dose level whilst ensuring maximum energy efficiency.

In most disinfection systems an instantaneous means of monitoring UV effectiveness is desirable. With chemical dosing techniques, disinfection is presumed to have been effective after a certain dose has been applied. Similarly with UV, if a minimum dose of UV energy, calculated from the maximum flow rate and taking into account the transmittance of the water, can be shown to have reached the outer surface of the treatment chamber (where the UV monitor is situated) then the necessary disinfection has taken place. The UV monitor can detect variations in the transmittance value of the water and helps to adjust the UV output accordingly, ensuring consistent UV disinfection at all times.

Conclusion

If used in conjunction with a secondary chemical biocide, UV disinfection is one of the most cost-effective methods of controlling biofilms in cooling tower water. UV is especially effective against the Legionella bacterium, a microorganism which thrives in the warm, wet, sheltered environment of a cooling tower. UV works instantly and is effective against all water-borne microorganisms, including those resistant to chlorine. The treatment systems are very compact and can usually be easily retrofitted to existing water treatment systems. In addition, secondary dosing does not require the complex monitoring equipment necessary if biocides are used as a primary disinfectant. All these factors add up to a simple, effective treatment process that saves the operator time and money while providing reliable protection against the spread of dangerous diseases.

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Aquionics technology replaces low pressure, multi-lamp system

A wastewater treatment plant (WWTP) in Richmond, BC, Canada, has opted to replace its existing low pressure UV disinfection system with a medium pressure UV system from Aquionics Inc. The WWTP serves the Riverport Sports and Entertainment Complex and surrounding residential areas in the City of Richmond, south of Vancouver.

The facility decided to switch to medium pressure UV because cleaning the low pressure system was proving to be very difficult. Each of the two disinfection chambers in the old system contained 24 low pressure lamps – automatic wiping is not an option with that number of lamps, so cleaning had to be done either manually or with chemicals. Both of these methods is extremely time consuming and requires the entire system to be shut down.

The operators therefore decided to look at other options, and medium pressure UV seemed an obvious alternative. While having a similar footprint, medium pressure systems utilise UV lamps with a much higher UV output than low pressure lamps. In fact, only two lamps per disinfection chamber are required for the same level of disinfection. Each of the medium pressure lamps is fitted with a mechanical wiper, which automatically moves up and down the lamp’s protective quartz sleeve, keeping it clean. This is simply not possible with multi-lamp, low pressure systems. Periodic chemical cleaning of the medium pressure lamps, if required, is simple and can be done by injecting the chemical into the treatment chamber where it cleans the lamps ‘in-line’, without the necessity of removing the lamps or shutting down the system.

How UV works

UV is the part of the electromagnetic spectrum between visible light and X-rays. The specific portion of the UV spectrum between 185-400nm has a strong ‘germicidal’ effect, disrupting the DNA of microorganisms, rendering them unable to reproduce. It is generally accepted that microbial DNA absorbs UV most effectively at 265nm, a wavelength that MP lamps produce in abundance. In addition to emitting UV at this optimum ‘peak’ wavelength,  medium pressure lamps also emit UV over a much broader range of wavelengths (between about 185 – 400nm) than low pressure lamps. This broad output, has been shown in independent tests to cause permanent inactivation of both pathogenic and non-pathogenic microorganisms such as E.coli  (references 1, 2, 3).

Low pressure UV lamps, on the other hand, produce just a single peak of UV output at 254nm. While also having a strong germicidal effect, the independent tests mentioned above showed that some microorganisms were able to repair or ‘reactivate’ themselves after exposure to UV from low pressure lamps, especially if they are subsequently exposed to sunlight (known as photoreactivation) – as is often the case in wastewater treatment facilities.

It is thought that the permanent damage caused by medium pressure UV may be a result of the UV at other wavelengths, such as 240nm and 280nm, having an effect on other intracellular molecules such as RNA and enzymes, which are unable to repair themselves.

The implications of the research into photoreactivation are far-reaching. For any industry where UV is used to disinfect water or wastewater, the operator needs to be sure that the treatment is permanent. This is especially the case when the treated liquid will subsequently be exposed to light and make its way back into the environment. Zimmer at al (reference 1) suggest that medium pressure UV could therefore provide better protection against photoreactivation if UV treatment occurs prior to any process units in which water is exposed to light for even a short time. According to their study, “Using low pressure UV in this type of situation should be avoided, since repair occurs rapidly following exposure to light.” A much larger research effort into the area of photoreactivation is still required, however, especially research involving real water and wastewater treatment plants.

The two Aquionics medium pressure units installed at the Riverport facility are situated after a Sequencing Batch Reactor and treat a combined flow of up to 2271 litres per minute (600 gallons per minute) of wastewater from the adjacent sports complex and residential areas. The disinfected wastewater is discharged into the Fraser River and meets all necessary quality standards for emission into watercourses.

Each of the two UV chambers is fitted with a UV monitor which measures actual UV intensity and dose from the two lamps. This provides real-time disinfection information which can be downloaded for record keeping. Operating the UV system is simple and, when lamps need replacing, it can easily be carried out by on-site staff.

The Riverport Sports and Entertainment Complex is a major development covering 14.5 hectares (36 acres) in southern Richmond, BC. It contains shops and restaurants, cinemas, bowling alleys, ice rinks swimming pools and spas. The WWTP is a private facility serving the complex and some surrounding residential areas. The complex is situated along a stretch of the Fraser River known as the Fraser River Port, which begins at the mouth of the river and extends 270 kilometres (168 miles) inland. 38.8 million tonnes of cargo are shipped through the port annually, making it the second largest in Canada.

References:

1. Zimmer, J. L., Slawson, R. M. & Huck, P.M. Potential repair of Escherichia coli DNA following exposure to UV radiation from both medium- and low-pressure UV sources used in drinking water treatment. Applied & Environmental Microbiology, Vol. 68 (2002), No. 7, 3293-3299.
2. Oguma, K., Katayama, H. & Ohgaki, S. Photoreactivation of Escherichia coli after Low- and Medium-Pressure UV Disinfection Determined by an Endonuclease Sensitivity Site Assay. Applied & Environmental Microbiology, Vol. 68 (2002), No. 12, 6029-6035.
3. Hu J. Y.,  Chu, S. N.,  Quek, P. H., Feng, Y. Y.,  and Tan, X. L. (2005). Repair and regrowth of Escherichia coli after low- and medium-pressure ultraviolet disinfection. Water Science and Technology: Water Supply, Vol. 5, No. 5, 101-108.

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UV disinfection specialist Aquionics will be showing its industrial UV disinfection systems at the 50th Annual InterBev Convention and Trade Show in Las Vegas, NV in September (booth 673 ).

Among the new products on show will be the AF3 industrial UV system. Capable of handling flows between 400 and 13,300 gallons per hour (1.5 and 51.0 m3 per hour) with lamp outputs ranging from 51 to 270 watts, the AF3 series uses low pressure amalgam UV lamps. The units have a small footprint and can easily be installed within existing pipework, vertically or horizontally, even in very restricted spaces. They can be fitted either with automatic wipers or quick release Tri-Clamps, both of which keep the quartz sleeves surrounding the UV lamps clean and clear of deposits, ensuring optimum UV output at all times.

A selection of Aquionics’ other UV systems will also be on display, including a transparent model showing the internal workings of a typical UV system. Experts will be on hand at all times to provide technical expertise and answer questions on the applications and advantages of UV in beverage manufacturing.

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UV disinfection specialist Aquionics will be showing its validated, medium pressure InLine+ UV system at this year’s WEFTEC Technical Exhibition & Conference in Chicago, Illinois. The InLine+, which is specially optimized to treat high volume water and wastewater flows, is validated under the German DVGW* standard for drinking water and is currently undergoing US EPA drinking water validation.

A selection of Aquionics’ other UV systems will also be on display, including a transparent model showing the internal workings of a UV system, such as the lamp wiper mechanism. Experts will be on hand at all times to provide technical expertise and answer questions.

WEFTEC Technical Exhibition & Conference
October 18-22, 2008
McCormick Place
Chicago, IL
Aquionics Booth No: 32109

* German Technical and Scientific Association for Gas and Water

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UV disinfection specialist Aquionics has appointed Bill Decker as its new President. Bill has extensive experience in the wastewater treatment industry, having spent 14 years with Ashbrook-Hartley Operations L.P., a company specializing in wastewater treatment technology. He held various positions with Ashbrook-Hartley, most recently Vice President of Biosolids. He also spent two years as an Operations Director at the company’s United Kingdom manufacturing facility.

Commenting on his appointment, Bill says, “Aquionics is a well respected company with proven, market leading technology. We were the first company to introduce the ‘InLine’ concept to UV wastewater treatment applications in the USA. My aim is to consolidate and build on our position as an industry leader by providing high quality UV systems and excellent customer support across the entire spectrum of water and wastewater treatment applications – both municipal and industrial, including high purity water.”

Bill has a BSc in Civil Engineering from the US Air Force Academy and is a member of both the Water Environment Federation (WEF) and the Water and Wastewater Equipment Manufacturers Association (WWEMA).

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UV disinfection specialist Aquionics exhibited its validated medium pressure InLine UV system at the ACE08 Annual Conference & Exposition in Atlanta, Georgia in June.

A selection of Aquionics’ other UV systems were also on display, including a transparent model showing the internal workings of a UV system, such as the lamp wiper mechanism. Experts were on hand at all times and answered many questions from visitors interested in UV technology for municipal water treatment applications.

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It is now almost five years since UV disinfection technology from Aquionics was selected to provide Cryptosporidium-free drinking water for the City of Henderson in Nevada. Henderson, the second largest city in Nevada, decided to upgrade and modernize its water treatment system in 2001 to enhance water quality and meet increasing demand. It was the first surface water plant in the USA to be specifically designed for Cryptosporidium inactivation with approval from the State and the USEPA.

“We were very proud to be the first plant in the USA to utilize this technology for Cryptosporidium inactivation,” says Mike Morine, Manager of Technical Services. “We take our commitment to the health and safety of our residents very seriously and we implemented this project to provide the best possible disinfection for our community. We saw UV as a cost-effective way of achieving this and since its installation almost seven years ago the Aquionics plant has helped us to exceed the USEPA’s water quality regulations. It has certainly exceeded our expectations.”

Treating 15 million gallons per day (mgd), the UV disinfection plant consists of four medium pressure UV chambers, each with an independently validated capacity of 5 mgd. Three chambers are in constant use, with the fourth on standby. The plant is completely automated with UV dose control, fail-safe features and reliable automatic cleaning for ease of maintenance. The water, which originates from Lake Mead, is coagulated with ferric chloride then flocculated and filtered before passing through the UV chambers prior to distribution. The Aquionics system provides at least 99 percent inactivation of Cryptosporidium oocysts, the infective stage of the organism which is resistant to chlorine.

Cryptosporidium is a single-celled parasite that invades the human digestive and respiratory systems, causing cryptosporidiosis. While the disease is often asymptomatic, intestinal cryptosporidiosis can cause severe diarrhea lasting two to four days in adults or up to four weeks in children.

UV disinfection is among only a few proven methods for rendering Cryptosporidium harmless, and it does so without the use of chemicals. UV light has been used successfully for disinfection of industrial process water and municipal effluent worldwide and for drinking water treatment for many years. Recent research documenting the effectiveness of UV disinfection against Cryptosporidium oocysts and Giardia cysts has made the technique a powerful and cost-effective alternative to ozone disinfection and other methods for water treatment.

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UV disinfection specialist Aquionics has appointed Kevin Shannon as its new Vice President of Sales and Marketing.

Kevin has considerable experience managing the sale of electrical equipment, lighting ballasts and specialty electronics. He joins Aquionics from Schneider Electric–Square D, where he was Senior Product Marketing Manager with responsibility for a portfolio of electrical equipment products. Prior to that he was Product Marketing Manager for Busway and Wire Management Products. Kevin has a B.S. in Industrial Engineering from Clarkson College of Technology, Potsdam, NY.

Aquionics is a market leader in the manufacture, application and development of UV technology for progressive, non-chemical disinfection and microbiological control. The company’s systems are used in a wide variety of applications including municipal water and wastewater treatment, high purity water treatment in the pharmaceutical, electronics and power generation industries, food and beverage processing, brewing, and aquaculture.

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