INDUSTRY FOCUS FOOD & BEVERAGE CHEMICAL-FREE DISINFECTION


Duncan Ockenden, of atg UV Technology, explains how Ultraviolet disinfection can improve reverse osmosis water treatment plant performance


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everse osmosis is now the technology of choice for water purification in the food and beverage industries. The process uses a membrane to remove dissolved salts from the water and, because the pores in the membrane are very small (about 0.001µm), it acts as a very good filter to remove bacteria and organic matter. This ability to remove bacteria by filtration is one of reverse osmosis’ strengths, but also a weakness. Although the reverse osmosis permeate is essentially bacteria-free, viable bacteria that are filtered out of the raw water can colonise the membrane surface. Once established, the bacteria proliferate and many species excrete extracellular polymeric substances (EPS) which stick the cells together to form adherent slimes or biofilms causing blockage of the membrane’s pores. This “biofouling” reduces the membrane flux, which increases operating pressures and energy consumption and also causes membrane degradation and reduced life. In other words, higher operating costs. The traditional approach to solving the


biofouling problem is to apply a dose of biocide as part of the pre-treatment process. Because of human toxicity issues, these disinfectants are normally oxidising biocides such as chlorine (or sodium hypochlorite), chlorine dioxide or ozone. Oxidising agents, even at low concentrations, cause deterioration of membranes so residual traces of the biocides have to be removed – usually by sodium bisulphite dosing – upstream of the reverse osmosis plant. There are further issues with these biocides. The first is immunity. Natural


genetic variation in bacterial cells means that some are naturally immune to specific chemicals. Bacteria multiply at alarming rate – given the right conditions they will double in number every twenty minutes – and this makes them fiendishly adaptive. This is not a problem if the disinfected water is going to be used but, if the bacteria are retained on the membrane, the resistant cell strain will continue to multiply. The second problem


INC WA AT IN COMING


WATER (MAINS/ BOREHOLE)


Validated systems such as the ECF offer operators a compact solution


DECHLORINA O OR


CARBON FILTRATION


CARBON FILTRAT


DECHLORINATION


STORAGE TANK


STORAGE TANK


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MICRO FILTRATION


FILTRATIONT


DE AERAT


DEAERATION


PACKAGING CKA


BOTTLING


BLEND TANK


TANK WA WASHING CIP OR O CARBONATI ONTCARBONATION STORA


FINAL SYRUP


STORA TANK


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ORAGE TANK


SUGAR SYRUP


RECIRCULATE B ACK TO TA OR BATCH PROCESS


RECIRCULATE B CK TO T FOR BATCH PROCE


LAT FLA LAV


TANK CONCENTRAT


FLAVOR & ONCENTRA


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is disinfection by-products. In the presence of organic matter, even at low concentrations, chlorine based chemicals can produce a range of potentially carcinogenic by-products including


A typical beverage processing plant diagram. A UV disinfection system is simple to install and has low operating and maintenance costs – only a few pence per cubic metre of water depending on the bacteria reduction required – and it can give operational and economic benefits


A leading soft drink manufacturer has installed a high purity drinking water package


SAFE PROCESSING OPTIONS FOR FOOD ALLERGENS


Food processors now have safe processing options for a number of foods containing allergens thanks to Hosokawa Micron’s specialist toll processing service which features segregated hygienic processing suites and a rigorously controlled food safety and quality programme in conjunction with an allergen control plan. Kathryn Hipkins, Technical Centre manager, Hosokawa Micron, said: ‘We always know what products are arriving at our site. The materials that are processed in our food processing suites are sourced from accredited sites that are free from or control allergens. We regularly retrieve information from our clients regarding allergen policies and assess the accreditation and grade of the raw material supplier. “We have two food processing areas that are fully segregated and have dedicated PPE and colour coded


clothing. One is for the production of allergens and the other is for the production of allergen and gluten free materials. This has been positively received by those companies who do not have the capability or required accreditation for segregation and allergen management, which we can provide through a rigorous HACCP programme which involves 3rd party laboratory swab testing and validation of our toll processing suite and its equipment.” Hosokawa Micron


www.hosokawa.co.uk


trihalomethanes (THMs), haloacetic acids (HAAs) and nitrosodimethylamine (NDMA), whilst ozone can generate bromates from bromide in the raw water. All of these by-products will pass through the membrane into the permeate. This is where UV scores as a disinfectant: there are no chemical oxidation reactions so no by-products. Ultraviolet radiation in the UV-C band has a wavelength around 250nm which is close to the absorbance wavelength of the amino acid bases which form the “rungs” of the DNA double helix. UV radiation fuses adjacent amino acid groups making it impossible for the molecule to divide and replicate. This means that bacteria exposed to UV radiation are not killed but cannot reproduce – as far as disinfection is concerned that is the same thing – and cannot then produce a resistant strain. UV can inactivate a range of micro-organisms, and the technique, which is used in drinking water treatment, pharmaceutical manufacturing and healthcare water systems, is chemical-free with no health and safety or environmental issues. All it needs is an electricity supply. As water flows through a reaction chamber housing lamps which generate UV-C radiation, it is exposed to a UV effective dose (or “fluence”) in mJ/cm2


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Different microorganisms have a different sensitivity to UV-C light. Most bacteria require a relatively low dose whilst protozoans, moulds and yeasts need a higher dose but, typically, a single pass through a UV system generating a fluence of 40mJ/cm2


will achieve a 3 log to 5 log


(99.9% to 99.999%) reduction of most microorganisms. The hydraulic design of the reaction chamber ensures that all the water is exposed to equal intensity of radiation with no short circuiting. This should always be validated by a third party to a recognised test protocol, such as that set out in the US EPA 2006 Ultraviolet Disinfection Guidance Manual, and reputable suppliers will have validation certificates for their products.


atg UV Technology www.atguv.com


40 JULY/AUGUST 2017 | PROCESS & CONTROL / PROCESS&CONTROL


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