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Written by: Gunvinder Bhogal, EngineerLive

“Ultraviolet (UV) technology was originally used to ensure the adequate disinfection of municipal drinking water. Since its introduction over 40 years’ ago it is now applied globally for disinfection, of water in many different industries, including food and beverage industries, pharmaceutical manufacturing, aquaculture and shipping.

UV kills all known spoilage microorganisms, including bacteria, viruses, yeasts and moulds (and their spores). It is a low maintenance, environmentally friendly technology which eliminates the need for chemical treatment while ensuring high levels of disinfection.

 

How UV disinfection 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 (known as UV-C) has a strong germicidal effect, with peak effectiveness at 265nm. At these wavelengths UV eliminates 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 and mounted within a cylindrical stainless steel chamber. The liquid to be treated enters at one end and passes along the entire length of the chamber before exiting at the other end. Virtually any liquid can be effectively treated with UV, including water, sugar syrups, beverages and effluent.

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). The UV dose necessary for deactivation varies from one species to another and is measured in millijoules per square centimetre (mJ/cm2). Values for specific microorganisms have been experimentally established and are used to determine the type and size of UV system required.

The dose received by an organism in a UV treatment system is dependent on four main factors:

1. The energy output of the UV source

2. The flow rate of the fluid through the treatment chamber

3. The transmission value (ability to transmit UV light) of the fluid being treated

4. The geometry of the treatment chamber

By optimising these criteria, a UV system can be tailored to effectively treat large or small flows, as well as viscous fluids or those containing dissolved solids and high levels of starch or sugar compounds.

There are two main types of UV technology based on the type of UV lamps used: low pressure and medium pressure. Low pressure lamps have a monochromatic UV output (limited to a single wavelength at 254nm), whereas medium pressure lamps have a polychromatic UV output (with an output between 185-400nm).

 

Benefits of UV disinfection

UV disinfection has many advantages over alternative methods. Unlike chemical treatment, UV does not introduce toxins or residues into process water and does not alter the chemical composition, taste, odour or pH of the fluid being disinfected.

UV treatment can be used for primary water disinfection or as a back-up for other water purification methods such as carbon filtration, reverse osmosis or pasteurisation. Since UV disinfection does not rely on a chemical residual, the location(s) of the units should be carefully considered for optimum performance.

Food, beverage and brewing industries

Disinfection of direct contact water: Although municipal water supplies are normally free from harmful or pathogenic microorganisms, this should not be assumed. In addition, water from private sources such as natural springs could also be contaminated. Any water used as an ingredient, or coming in direct contact with the product, can therefore be a source of contamination. UV disinfects this water without chemicals or pasteurisation. It also allows the re-use of process water, saving money and improving productivity without risking the quality of the product.

CIP (Clean-in-Place) rinse water: It is essential that the CIP final rinse water used to flush out foreign matter and disinfecting solutions is microbiologically safe. Fully automated UV disinfection systems can be integrated with CIP rinse cycles to ensure final rinse water does not reintroduce microbiological contaminants. Because of their high energy density, MP lamps are less affected by any sudden changes in the temperature of the CIP water than a LP lamp.

Filter disinfection: Reverse osmosis (RO) and granular activated carbon (GAC) are often used to filter process water, but can be a breeding ground for bacteria. UV is an effective way of disinfecting both stored RO and GAC filtered water and has been used in the process industries for many years.

Cooling media and chiller disinfection: Some meat and dairy products are subject to contamination after heat treatment or cooking. UV provides an excellent way to protect foods from contamination by contact-cooling fluids.

Sugar syrups: Sugar syrups can be a prime breeding ground for microorganisms. Although syrups with very high sugar content do not support microbial growth, any dormant spores may become active after the syrup has been diluted. Treating the syrup and dilution water with UV prior to use will ensure any dormant microorganisms are deactivated.

De-aerated liquor: De-aerated liquor is added as part of a high gravity brewing process, often in the packaging operation. This liquor is added directly to the beer so needs to be kept free from contamination by gram negative bacteria, which can cause off-flavours and acidity.

Yeast preparation: The problems associated with yeast preparation in breweries are well recognised and include hazes, altered fermentation and surface membranes on packaged beer. A single cell of Sacchoromyces (var. Turbidans) in 16 million cells of pitching yeast will cause detectable hazes. UV destroys all known yeasts and their spores.

Wastewater: As part of a multi-barrier process, including filtration, UV can destroy microorganisms in the effluent from food and beverage facilities prior to discharge. As UV reduces reliance on hazardous chemicals, it also ensures all discharges meet with local environmental regulations.

UV as an alternative to ozonation

Nongfu Spring Co. Ltd., one of China’s leading producers of bottled water and beverages, has recently opted to use UV for its production plants across China. This is a major milestone in the bottled water industry – particularly in China – because presently in that country virtually all bottled water is disinfected using ozone. And around the world ozone is still the disinfection method of choice for many producers.

The decision by Nongfu Spring to opt for UV was driven by a number of reasons, not least of which was concerns about ozonation by-products such as bromate. In fact, Hanovia has noticed that more and more bottled water and soft drinks producers are now looking for ozone alternatives, and enquiries about UV are on the increase.

Bromide ions occur naturally in many spring waters and on their own pose no problem. However, the presence of ozone can cause conversion of bromide into bromate, with the consequent potential for consumer health problems. The World Health Organization (WHO) lists bromate as a carcinogenic substance and recommends its maximum limit in mineral water be set at 0.01mg/l (10ppb). In July 2008 the Chinese General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ), recommended in a revised draft national standard for drinking water and mineral water that a maximum limit for bromate in bottled water be in line the WHO guidelines. This limit has now been in force since October 2009.

Pharmaceutical industry

Disinfection: As in the food and beverage industries, UV is used to disinfect water used in the manufacturing process, whether it is for direct product make-up or for rinsing and washing process equipment.

TOC reduction: Short UV wavelengths (below 200nm) are highly effective at breaking down organic molecules present in water, especially low molecular weight contaminants. The process works in two ways: the first method is by direct photolysis, when energy from the UV actually breaks down chemical bonds within the organics; the second method is by the photolysis of water molecules, splitting them to create charged OH- radicals, which also attack the organics.

Dechlorination: To date, the two most commonly used methods of chlorine removal have been granular activated carbon (GAC) filters or the addition of neutralising chemicals such as sodium bisulphite and sodium metabisulphite. Both of these methods have their advantages, but they also have a number of significant drawbacks. GAC filters, because of their porous structure and nutrient-rich environment, can become a breeding ground for bacteria. Dechlorination chemicals such as sodium bisulphite, which are usually injected just in front of RO membranes, can also act as incubators for bacteria, causing biofouling of the membranes. In addition, these chemicals are hazardous to handle and there is a danger of over- or under-dosing due to human error.

UV is now becoming increasingly popular as an effective alternative method of dechlorination. It has none of the drawbacks of GAC or neutralising chemicals, while effectively reducing both free chlorine and combined chlorine compounds (chloramines) into easily removed by-products.

Aquaculture

Increased water extraction and lowered water quality can result in increased outbreaks of viral and bacterial fish diseases in the aquaculture industry. Due to the intensive nature of fish farming, fish stock is also highly susceptible to infection from natural fish populations in the water feeding the farm. To break the infection cycle between fish farms and natural fish populations, a disinfection system is needed to treat water entering and circulating within fish farms.

UV is ideally suited for these applications as it uses no chemicals and does not create by-products which would harm the fish stock, or other aquatic life, on discharge. Unlike other treatment methods, UV avoids the expense of complex monitoring systems involved in adding and removing chemicals before the water reaches the fish. In addition, it does not alter the pH of the water. Indeed, UV is the most economical disinfection technique that can be used in fish aquaculture. Applications include treatment of water in hatcheries, shell-fish purging tanks and fry rearing tanks, and recirculation water in marine parks and aquaria.

Swimming pools and spas

UV is now a well-established method of swimming pool water treatment, from hydrotherapy spas to full-sized competition pools. This growth in popularity has been largely due to UV’s reliability and ease of use. Another major factor is the reduced reliance on traditional chemical treatments it affords, particularly chlorine. UV is also highly effective at destroying chlorine-resistant microorganisms like Cryptosporidium andGiardia.

Some of the more unpleasant by-products of chlorination are chloramines, formed when chlorine reacts with sweat or urine in pool water. Trichloramines in particular are powerful irritants which are responsible for eye and respiratory complaints and the unpleasant smells commonly associated with indoor public pools. They are also corrosive and in time can lead to damage to pool buildings and structures such as ventilation ducts.

Another major benefit of UV is that it significantly reduces the need for backwashing and dilution, saving hundreds of pounds a month for pool operators.

Link between chloramines and asthma

A recent study found an increased incidence of asthma in children who swam regularly in chlorinated pools. In some cases the damage was equivalent to that found in heavy smokers. Even people sitting at the sides of pools, such as lifeguards and instructors, were found to be at risk.

The symptoms are caused, the researchers believe, by chloramines – particularly trichloramines. The problem is potentially so serious that the study’s authors suggested pool operators should seriously consider alternatives to chlorine-based disinfection. They also recommended better ventilation to help remove chloramine-laden air from pool surroundings, improved hygiene practices by bathers themselves – such as showering before swimming – and the regular renewal of pool water.

While further research is needed, these findings add further credence to the importance of reducing chloramines as much as possible.

Other UV applications

Ship Ballast Water: All ocean-going vessels take on water to provide ballast and stability. It is usually taken on in coastal port areas and transported to the next port of call, where it may be discharged. The IMO (International Maritime Organisation) sets tough standards to treat all ballast water prior to discharge, and UV disinfection – in conjunction with filtration – is now one of the accepted methods of treatment.

Conclusion

Meeting the increasingly rigorous hygiene standards required in the production of food, beverages and pharmaceuticals, as well water quality concerns in the leisure, aquaculture, shipping and oil drilling 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. It is an established method of disinfecting drinking water throughout the world, and is now finding applications in many other industries.

UV disinfection systems are 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.”

Source: Bhogal, Guvindar. “UV Disinfection Technology – the Applications Just Keep on Growing.” Engineer Live. N.p., n.d. Web. 15 Sept. 2016.

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Particles to be filtered usually fall into one of two categories:

Non-deformable particles that under normal conditions (temperatures) do not deform. In some instances, non-deformable particles can become deformable with a temperature or chemistry change—an example of this would is a particle of resin, which at ambient temperatures may be solid, but at elevated temperatures turns liquid.
Deformable particles (frequently called gels) that deform when put under pressure. The amount of pressure needed to deform gels varies depending on the specific gel/particle. With deformable particles, if enough pressure is applied, the gel will deform, push out through the filter, and frequently re-agglomerate on the downstream side of the filter. Sometimes, when the particle re-agglomerates, it is larger than could be seen on the upstream side due to coalescence that may have occurred in the filter. In some instances, deformable particles can become non-deformable due to changes in temperature, chemistry, or other conditions.

Copyright 2008 Barney Corporation, Inc… www.Filters.com… Info@Filters.com…1.614.274.9069

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Each page in the “drinkable book” is printed with instructions in local languages. (Brian Gartside/Courtesy of pAge Drinking Paper)

Imagine a book that has pages you can tear out and use to turn raw sewage into drinking water. Each page is implanted with silver or copper nanoparticles that kill bacteria when water passes through them. And each page is printed with a message in your local language: “The water in your village may contain deadly diseases. But each page of this book is a paper water filter that will make it safe to drink.”

That’s exactly what one postdoctoral researcher at Carnegie Mellon University says she’s created. She calls it the “drinkable book.”

“I originally starting working on it to help the environment — by using greener chemistry, and it’s evolved to have the noble goal of helping others,” Theresa Dankovich, who has been working on the product over the past several years, told The Washington Post in an e-mail.

The new water filtration system has been shown to eliminate 99 percent of bacteria in water during its first field trials at 25 contaminated water sources in South Africa, Ghana, Kenya, Haiti and Bangladesh, according to the researchers. The researchers, working with charities WATERisLIFE and iDE-Bangladesh, pulled pages from the book, put them into a holder and poured water from rivers and streams on top, straining away the bacteria. The findings were presented earlier this week at the 250th annual American Chemical Society conference in Boston.

“In Africa, we wanted to see if the filters would work on ‘real water,’ not water purposely contaminated in the lab,” Dankovich told the American Chemical Society. “One day, while we were filtering lightly contaminated water from an irrigation canal, nearby workers directed us to a ditch next to an elementary school where raw sewage had been dumped. We found millions of bacteria; it was a challenging sample.

“But even with highly contaminated water sources like that one, we can achieve 99.9 percent purity with our silver- and copper-nanoparticle paper, bringing bacteria levels comparable to those of U.S. drinking water.”

The pages are put into a holding device that allows water to pass through. (Brian Gartside/Courtesy of pAge Drinking Paper)

How does it work?

Dankovich said the microbes are killed when they absorb the silver or copper ions from the nanoparticles in the paper. “Only a few milligrams of silver are needed to be highly antibacterial,” she told The Post. Each filter can be used to purify 100 liters of liquid, meaning each page could last for weeks and each book could last for about a year, according to the researchers.

Some metal particles do seep through the paper, Dankovich said, but the amount is still “well below” the limits set by the Environmental Protection Agency and World Health Organization.

Silver or copper ions from the nanopartricles in the paper kill bacteria in the water. (Brian Gartside/Courtesy of pAge Drinking Paper)

Kyle Doudrick, who studies sustainable water treatment at Notre Dame’s College of Engineering, told BBC News that although the science is important, the key is making sure people understand how to use the filters and when to replace them.

It’s also unclear whether the nanoparticles would kill other disease-causing microorganisms, including viruses.

“Overall, out of all the technologies that are available — ceramic filters, UV sterilization and so on — this is a promising one because it’s cheap and it’s a catchy idea that people can get hold of and understand,” Doudrick said.

Dankovich came up with the idea while working at McGill University in Montreal and developed it later at the University of Virginia.

The book is still in the development phase and will require many more laboratory tests and field trials over the next year, Dankovich said, but within the next couple years, Dankovich, working with students from Carnegie Mellon, hopes to have the product on the market. She said her goal is to provide each filter for less than 10 cents a piece.

“I hope that these filters will one day help improve the health of millions of people around the world,” she said.

Source:Washington Post August 19, 2015 

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“Membranes are selectively permeable barriers that can provide a filter for a range of processes, from removing salt from sea water in desalination plants, to filtering the blood of kidney patients in dialysis machines. Filtration processes using membranes could potentially reduce energy consumption compared to other separation methods.

 

Membrane

 

The membrane is very thin, yet extremely strong

However, many industries use evaporation and distillation techniques rather than membranes, because membranes can be costly to scale up and they are not resistant to the organic solvents used in many industrial refining and chemical processes.

Now, researchers from Imperial College London have developed a prototype crumpled membrane that has the potential to be used widely across industry. The prototype is extremely thin – it would take a stack of ten thousand membranes to match the diameter of a human hair – making it very permeable. It is also strong, and is able to filter organic liquids at pressures of around 50 bar, which is the equivalent to the pressure at around 500 metres below the ocean’s surface. The membrane is durable and resistant in a range of organic solvents.

In a study detailed in the journal Science, the team created a membrane with nanoscale crumples and established that this provides an increased surface area for filtering substances that remains strong and does not buckle, even under extreme pressures. The prototype is 80 millimetres in diameter, but the team is confident that it can be scaled up to industrial areas.

Ultimately, the researchers believe that their prototype membrane could be used to improve or completely replace industrial processes that process organic solvents, which currently rely on evaporation and distillation techniques. Approximately 30 per cent of the world’s energy is currently used by industry, with a substantial fraction of that being used in evaporation and distillation processes. These industries could potentially make major energy savings if they used the membranes, with consequent reductions in carbon dioxide emissions.

Professor Andrew Livingston, co-author of the study from the Department of Chemical Engineering at Imperial College London, said: “Membranes are currently used for a range of important tasks such as making water drinkable and life-saving kidney filtering. The drawback has been that industry hasn’t been able to use membranes in organic liquid systems more widely because they’ve had cost and design limitations. Our research suggests that we can overcome these challenges, which could make these membranes useful for industries ranging from pharmaceutical companies to oil refining. The energy and environmental benefits could be massive.”

Dr Santanu Karan, co-author also from the Department of Chemical Engineering at Imperial College London, added: “I am really excited about this research breakthrough. We now want to work even more closely with industry to further refine our membranes so that they can meet their needs. We hope our work will lead to new collaborations and ultimately, improvements in the way industries use separation processes.”

To test the effectiveness of the membrane in the lab, they team mixed together a solution containing a solvent, alcohol, and dyed molecules of different colours and sizes. They then made the solution percolate through the membrane at high pressures, using a device called a dead-end cell, to see if they could filter out everything apart from the alcohol. The team observed the process using an absorption spectroscopy device, which uses light at different wavelengths to determine what molecules are passing through the membrane. They determined that the membrane was completely effective, with only the alcohol passing through.

The researchers then compared the crumpled membrane to a conventional membrane, carrying out the same experiment. Their aim was to determine how fast their membrane could purify and concentrate the solution compared to the conventional model. They found that the crumpled membrane could separate substances 400 times faster than the conventional membrane.

The team is now planning to further develop and optimise the membrane technology so that it can be scaled up for use in industries such as pharmaceuticals, manufacturing and oil refining.

The research was funded by the Engineering and Physical Sciences Research Council (EPSRC) and the BP International Centre for Advanced Materials.”

 

Written by Colin Smith 

Source: http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_18-6-2015-14-9-44

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