By Ismail Gobulukoglu, Ph.D., Gary Vander Laan and Yang-jen Chen, Ph.D.
Bottled water products are produced utilizing a multi-barrier approach, from source to finished product, that helps prevent possible harmful microorganisms or chemicals from contaminating the finished product or storage, production and transportation equipment. Measures in a multi-barrier approach may include source protection, source monitoring, RO, distillation, filtration, ozonation or UV light. Many of the steps in a multi-barrier system may be effective in safeguarding bottled water from microbiological, chemical and other contamination. Piping in and out of plants (as well as storage silos and water tankers) is also maintained through daily sanitation procedures. In addition, bottled water products are manufactured in a controlled, sanitary environment to prevent contamination during the filling operation.1
When the main product ingredient is water, its quality is essential. Beverage formulations typically contain more than 95-percent water, and almost nothing affects product taste like its primary ingredient. Therefore, it is critical to use water as pure and natural as possible. However, even pure and natural waters have varying taste, and treatment can bring consistency to soft drink and bottled water products. UV disinfection is a flexible, safe and cost-effective technology that effectively inactivates pathogenic bacteria, spores, viruses and protozoa (including Cryptosporidium oocysts and Giardia cysts). The use of UV technology for water treatment has several inherent advantages. UV light does not add anything to the water stream, such as undesirable color, odor, chemicals, taste, pH or flavor, nor does it generate harmful byproducts. It is fast, effective, efficient and environmentally friendly, when used in accordance with manufacturer’s guidelines. UV systems have small footprints and they can be key components of water treatment process trains. Therefore, many bottled water and soft drink producers around the globe rely on UV to provide microbial-free, pure water and ingredients, which help protect the ‘brand’, the flavor, and extend shelf life.
In 2006, several US EPA activities were completed, including the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR),2 the UV Design Guidance Manual (UVDGM)3 and the Ground Water Rule (GWR).4 These activities culminated over an extensive period of time, intended to improve disinfection practices and protect public health. Two significant developments resulted from this work; codification that the validated UV dose for four-log inactivation of virus would be 186 mJ/cm2 and that this would be specifically based on Adenovirus.
In addition to the regulatory impact on community water supplies, non-community water supplies (such as bottled water producers) retail water facilities and/or bulk-water haulers that draw from groundwater sources may also be impacted by regulations promulgated in 2006. This is particularly true with respect to the GWR. As states adopt the GWR, the potential exists for interpretation of the rule by primacy agencies to require a four-log virus inactivation for public, non-community water supplies. These non-community water supplies may not be able to meet the four-log virus inactivation by way of chemical disinfectant use due to limitations on chemical addition and therefore, such a requirement would present a significant compliance challenge that may be alleviated by the use of UV disinfection technology.
The UVDGM is the tool that outlines the requirements for compliance when considering the use of UV for meeting the disinfection requirements codified in the GWR. The UV system will be independently tested by a recognized, accredited agency. The goal of the testing is to identify the window of operating conditions in which the UV unit may run in which it delivers the required four-log inactivation of Adenovirus. A UV system having undergone testing will have an independent validation report that has been prepared for it. The report identifies the operating window in which the specific system can be used, and is provided to the customer at the time of sale. The UVDGM also outlines what reporting capabilities the UV system must include in order to to report ‘off-spec’ water, water which has not been adequately disinfected.
Water treatment applications
High-temperature, steam-sterilizable, compact UV water treatment systems provide an economical means of water disinfection and can be used in many applications (see Figure 1). There are six primary types of applications for UV systems in the beverage industry. The first involves the use of UV light protecting a source water at the spring site, before water is transferred to a bulk tanker en route to the bottling plant. Today, many bottlers at spring sites select UV water disinfection technology as an alternative disinfection method when loading tankers, in order to reduce sanitation frequency and also mitigate the risk of bromate formation (in case bromide shows up in spring source water). The second application involves disinfection of bulk-tanker water supplies. Water flows from tankers through the UV system, prior to entering the storage tank at the bottling plant. The third application is liquid sugar or syrup. UV is more cost effective and simpler in operation and maintenance than the conventional boiling process. For this application, thin-film UV reactor design is required to ensure disinfection efficiency. The fourth application is wastewater and reclaim-water disinfection that can be used as general water in the plant. The fifth application is designed for ozone destruction, as ozonated water leaves the storage tank before entering the bottling lines (see Figure 2). This method also provides the added benefit of secondary water disinfection after the ozone system. Water can be re-circulated from the storage tank back through the UV system in order to maintain bacteria reduction if ozone is not used. The sixth application is for chlorine destruction in the incoming city water before membrane filtration (see Figure 3).
The absorption of UV energy by microbes results in photochemical damage to nucleic acids (DNA and RNA). Nucleic acid damage interferes with normal cell processes, such as protein synthesis and cell division. Since UV irradiated pathogens cannot replicate, they cannot overwhelm the host’s immunological system, and the pathogens eventually die or are destroyed by the host’s defenses. Absorption of ultraviolet energy by RNA and DNA is wavelength dependent; similarly, the inactivation of individual organisms is a function of wavelength (see Figure 4). The germicidal effectiveness of the monochromatic low- pressure lamps (wavelength 254 nm) has a close correlation with the absorption peak for nucleic acid (265 nm) and with the inactivation peak of E.coli (near 260 nm). The amount of cell damage depends on the dose of UV energy absorbed by the microorganisms and their resistance to UV. UV dose is a product of UV intensity and exposure time, and is expressed as milliJoules per square centimeter (mJ/cm2) or milliWatt seconds per square centimeter (mWs/cm2) or microWatt seconds per square centimeter (µWs/cm2). Growth and infectivity assay methods are used to assess the degree of disinfection achieved. UV is effective against a wide variety of pathogenic viruses, bacteria and protozoa. Animal and tissue assay methods have demonstrated that low doses of UV inactivate Giardia cysts and Cryptosporidium oocysts by several orders of magnitude. These low doses are a fraction of the design dose currently specified in most UV disinfection applications, indicating that UV is extremely effective against these waterborne protozoa.5 UV water treatment systems designed to deliver a UV dose greater than 90 mJ/cm2 can provide more than three-log inactivation to the pathogenic microorganisms in water, as shown in Table 1. UV design with low-pressure/ high-output or low-pressure/high-output amalgam lamps is more effective in this application than low-pressure/standard output lamp design (see Figure 5). Medium-pressure UV lamp systems are also used, requiring disinfection of high flow rates in a small footprint, and for high UV doses requiring chlorine destruction applications (see Figure 6).
Activated carbon beds may be necessary to scrub out organics exceeding the primary maximum contaminant levels (MCL) established by the US EPA.
Ozone is an effective oxidizer and in specific water treatment applications, ozone is applied to the water stream to oxidize trace organics, or to disinfect the process water, piping and distribution system in water-bottling manufacturing plants. But residual ozone is often left behind and must then be removed using UV at a wavelength of 254 nm in order to help insure the integrity of the process and the product. Ozone absorbs the 254-nm light emitted by UV lamps within the reactor, and UV ozone destruction systems add sufficient UV dose to residual ozone, decomposing the O3 molecule into harmless oxygen via UV photolysis. UV ozone destruction systems are located immediately downstream of the water storage tanks, and the water must pass through the UV reactor to ensure the ozone is destroyed prior to being distributed to the points of use (see Figure 2).
In some source waters, bromide can be present and if ozone is used as disinfectant at favorable concentrations and contact times, then ozone and bromide ions react together, resulting in generation of bromates to levels exceeding the primary MCL established by US EPA. One way to control bromate levels is by reducing ozone concentrations to a low enough level so that bromate generation is kept to a minimum, and by incorporating UV disinfection to the treatment train to enhance lost disinfection capacity due to reduced ozone levels.
Chlorine and chloramines are two common chemicals added by municipalities to provide residual bacterial disinfection; their removal from a water stream is necessary if it affects a downstream product or equipment. The two most common methods for re- moving chlorine and chloramines utilize a sodium metabisulfite injection or carbon bed. Organics that tend to concentrate in the carbon bed, however, are trapped within the bed and provide an excellent food source for bacteria, which may cause biofouling of any downstream membrane. On the other hand, sodium meta- bisulfite is a food source of sulfur-reducing bacteria (SRB), which cause microbiologically induced corrosion, attacking downstream piping, tanks and valves. UV light may be a preferred method, due to the detrimental nature of the other two. UV light’s powerful energy can be successfully harnessed to destroy trace amounts of residual chlorine present in city feed water. This non-chemical and environmentally friendly method offers significant inherent advantages and benefits compared to conventional dechlorination technologies utilized thus far by the industry (see Figure 3). Substitution of UV for these technologies, however, may be subject to contaminant, site and regulatory variables.
The beverage industry requires clean, pure, natural and microbial-free water for manufacturing bottled water products. UV is an effective method for treating bottled water products without compromising their ingredients. UV disinfection systems deliver UV doses in a few seconds without creating byproducts. A properly sized and maintained UV system can be effective against most microorganisms commonly found in water. Residual ozone and chlorine can readily and reliably be removed from water systems by the irradiative action of ultraviolet light.
UV technology has served the industry well for more than 60 years, keeping pathogenic microorganisms at bay. Effective use of UV located at strategic points in the process such as at spring source water, before tanker loading, after transportation, before unloading to storage tank, after liquid syrup storage tank before mixing with product formula and water, can protect the overall integrity of the end product, lower maintenance costs by decreasing the microbial load, and reduce some CIP sanitation frequencies and related maintenance on the equipment.
- Bottled water is a safe, healthy packaged beverage choice, Position Statement, International Bottled Water Association (IBWA), March 10, 2008.
- EPA 40-CFR Parts 9, 141 and 142 – National Primary Drinking Water Regulations: Long Term 2 Enhanced Surface Water Treatment Rule; Final Rule, 654. Federal Register/Vol. 71, No. 3/Thursday, January 5, 2006.
- EPA 815-R-06-007. Ultraviolet Disinfection Guidance Manual, November 2006.
- EPA 40-CFR Parts 9, 141 and 142. National Primary Drinking Water Regulations: Ground Water Rule: Final Rule, 65574. Federal Register/Vol. 71, No. 216/Wednesday, November 8, 2006.
- The mechanism of ultraviolet disinfection, Trojan Technical Bulletin # 60, Trojan Technologies, March 2000.
- UV Sensitivity of Pathogenic Microorganisms in Water, Table A.2, EPA 815-D-03-007. Ultraviolet Disinfection Guidance Manual, June 2003.
About the authors
Dr. Ismail Gobulukoglu joined Aquafine Corporation–A Trojan Technologies Company in 2002 as Chief Scientist. Previously, he served as Director of Research and as an Electron Microscopy Facility Manager. After completing his undergraduate degree in physics from Marmara University (Istanbul), Gobulukoglu earned a Master’s Degree in physics and a Ph.D. Degree in chemical and materials engineering, both from the University of Nebraska-Lincoln. He has 13 years experience in technical engineering, applied research, business and product development, sales and customer support, and more than eight years experience in UV water treatment applications. Gobulukoglu is the author/co-author of more than 15 publications and a member of IUVA, ISPE, AWWA, IWA, WEF and ASHRAE.
Gary Vander Laan, Market Manager for Aquafine Corporation, has over 18 years of industry experience in the application of UV technology. Prior to becoming a part of Aquafine, Vander Laan worked in the industrial sales department at Trojan Technologies.
Dr. Yang-jen Chen is Director of International Sales at Aquafine Corporation. He received his Ph.D. in physics at Louisiana State University in 1976. Since that time, Chen has worked in R&D, product development, engineering and management in the power, energy and environmental- control technology fields. For the last 10 years, he has devoted his efforts to developments, sales and marketing of UV technologies in various applications, especially for industrial processes.