UV takes the lead in non-chemical disinfection systems

Paul Boughton

The advantages of UV disinfection have been known about for years - and, reports Sean Ottewell, the process industries are at the forefront of making the most of them today.

As part of its environmentally conscious approach to brewing, Korea's Hite Brewery Company has recently installed 25 Hanovia UV water disinfection systems at its Massan and Gangwan plants.

The ultra violet (UV) systems ensure water used in the production processes remains free from microbial contamination, ensuring a high quality, pure final product. Seven units are installed at Massan and 18 at Gangwan.

In Massan the UV is used to treat clean-in-place (CIP) water (three units), cooling water-injected after the CIP (three units), and activated carbon-filtered water (one unit). At the Gangwan plant three UV units are used to treat water after deaeration and the remaining 15 units treat activated carbon-filtered water.

CIP is used for cleaning the interior surfaces of pipework, vessels, filters and other process equipment. CIP water must be completely free from microbial contamination, otherwise it could infect the whole system. As CIP uses very hot water, pipework and vessels need to be cooled down afterwards and before beer production can recommence. Cooling water also helps flush out the remaining CIP water, which contains acid and caustic soda. The purity of the cooling water is therefore extremely important to prevent any residual contamination.

Activated carbon is commonly used in water treatment for decolouring and deodorisation, due to its strong adsorption properties. This adsorption can also remove residual chlorine from the water, leaving the post-filter water vulnerable to microbial contamination. UV therefore plays a vital role in ensuring the post-filter water is adequately disinfected.

Deaeration removes dissolved oxygen from water prior to the addition of yeast, a key part of the brewing process. Any contamination of the deaeration water could kill the yeast, meaning the whole batch would have to be destroyed. UV is ideal for this step as it is quick acting and effective without producing any unwanted disinfection by-products which could affect the yeast.

"When Hite was considering UV for the first time it looked at a number of UV system suppliers," commented Ying Xu, Hanovia's Asia Pacific sales manager. "We were selected as our UV systems not only produced the highest microbial reduction rates, but we also offer a comprehensive and cost-effective spare parts and maintenance service. Hite now uses over 45 Hanovia UV systems in its breweries across Korea, including the latest project at Massan and Gangwan."

"According to the company it also needs to do CIP less frequently, it uses less preservative in the finished product, and the final water has no unwanted residuals, so the taste and colour is not altered in any way. This all adds up to a cleaner, greener process and product," she added.

According to Hanovia, meeting the increasingly rigorous hygiene standards required in the brewing and beverage industries is a real challenge. If improvements need to be made to plant and equipment, they need to bring quick returns on the investment and measurable improvements in product quality.

For manufacturers seeking to improve the quality of the end product, UV is an economic, realistic option, says the company. It is an established method of disinfecting drinking water throughout the world, and is also widely used for high purity applications such as pharmaceutical processing and microchip manufacturing, where water of the highest quality is essential (Fig.1).

There are no microorganisms known to be resistant to UV - this includes pathogenic bacteria such as Listeria, Legionella and Cryptosporidium (and its spores, which are resistant to chlorination).

Overall, says Hanovia, UV disinfection systems are also easy to install, with minimum disruption to the plant. They need very little maintenance, the only requirement being replacement of the UV lamps every 9-12 months, depending on use. This is a simple operation that takes only a few minutes and can be carried out by general maintenance staff.

Swedish drinking water

Xylem has won a contract to provide UV drinking water treatment solutions to the largest UV disinfection project ever undertaken in Sweden. The Xylem solutions will help deliver clean, treated drinking water to 900,000 people across 16municipalities. The facility will have the capacity to handle a potential 25 per cent increase in water volume to support future population growth.

The company will provide four WEDECO K-series UV disinfection systems to upgrade the Sydvatten waterworks in the Scania region in southern Sweden. Xylem's UV systems were chosen for their flexible and innovative design, low lifecycle costs, negligible environmental impact and ability to handle large volumes of water in the most efficient manner possible, while catering to potential future plant expansion.

The Sydvatten waterworks drinking water treatment plant has been in operation since 1966. Xylem's UV systems will complemaent existing traditional treatment methods to eliminate bacteria, viruses and parasites.

In a separate move, Xylem has expanded its offering of WEDECO UV disinfection solutions specifically developed for the tank-based aquaculture industry. Xylem's new closed-vessel WEDECO BX and Quadron series UV systems are designed for inactivating fish pathogens.

The systems are contained in duplex stainless steel reactors capable of resisting the corrosive effect of saltwater.

The new WEDECO units will enable customers to efficiently handle pressurised flows ranging from 10 to more than 4000m3/h.

Large-scale fish farms in European countries such as Norway, a country with some of the longest established and most advanced aquaculture industries, rely on Xylem's disinfection equipment to protect their aquatic livestock from the spread of diseases and to ensure clean, safe water for their aquaculture businesses. Xylem's aquaculture UV solutions are approved by the Norwegian Veterinary Institute (NVI) and validated according to the United States Environmental Protection Agency (EPA) standards.

For its part Siemens Water Technologies offers a complete range of UV disinfection solutions for industrial, commercial, aquatic and high-purity applications.

"UV irradiation can be used for multiple purposes in water treatment, but is primarily employed as a disinfection process that inactivates waterborne pathogens without chemicals. For other applications, UV is used for the removal of organic and inorganic chemicals, including chlorine, chloramines, ozone and total organic carbon (TOC).

When combined with oxidants such as ozone or hydrogen peroxide, or semiconductors such as titanium dioxide, UV can be used for the oxidation of refractory chemicals such as chlorinated solvents, taste and odour compounds, and other emerging contaminants," notes the company.

While the advantages of UV disinfection have been realised and the technology successfully employed worldwide for decades, Siemens says that the primary advantage of being able to effectively control all types of microorganisms, including those which are chlorine-resistant, without chemicals has numerous benefits for municipal, industrial, commercial and aquatics customers. In addition to disinfection, UV is also very effective for TOC removal, destruction of chlorine, chloramines and ozone.

So, overall, UV: improves disinfection efficacy; reduces environmental, health and safety risks; eliminates formation of disinfection by-products; does not alter the aesthetic qualities of the water; and eliminates any concerns about 'over dosing'.

Lenntechs complete UV solutions

According to Lenntech, increasingly stringent industry regulations coupled with the emergence of resistant strains of bacteria are two of the major driving forces behind the growth of interest in UV systems. Consequently the company offers complete UV systems for high technology industries such as pharmaceutical, chemical, semiconductor, soft drinks, water treatment, potable water and offshore platforms. At the other end of the spectrum, its low-cost domestic systems have been successfully solving individual water quality problems for many years.

Today the company supplies medium pressure, low pressure and low pressure amalgam disinfection systems - along with special ultraviolet systems that offer clients an individually tailored service to solve the most complex of disinfection problems.

For example, for a water treatment company, Lenntech has completed a project that treats effluent flow based on a flow through open channel arrangement. This is incorporated in stainless steel channels and concrete channels. The effluent system uses medium pressure UV mercury discharge lamps, which enables variable lamp power output to be included, extending lamp life and increasing energy efficiency by means of UV dose control. Each system features banks of medium pressure UV lamps, divided into independently removable lamp support racks that can be removed without necessitating system shut down.

Lenntech has also designed and delivered an ozone/UV installation for an unnamed pharmaceutical company. In this system softened water is disinfected and biofilm formation is prevented by the use of a duplex ozone system. The water is de-ozonised before use in the process by a quadruple UV system. The system is PLC controlled and the quality of environment and water is controlled via a variety of control systems.

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