Cheaper, cleaner water - and faster
developed a more efficient, less costly method of disinfecting
water used in food processing. The new Advanced Disinfection
Technology System relies on ultraviolet (UV) radiation to eliminate
moulds, viruses and bacteria, but handles water more efficiently
than existing systems using the same technology.
Researchers from the Georgia Institute of Technology claim to have developed a more efficient, less costly method of disinfecting water used in food processing.
Like current technologies the new Advanced Disinfection Technology System relies on ultraviolet (UV) radiation to eliminate moulds, viruses and bacteria. But the new system handles water more efficiently and thus improves the overall effectiveness of the disinfection process, say the researchers.
Preliminary work with the new lab-scale UV disinfection device shows a reduction in the concentration of viable pathogens by a factor of more than 200, compared to existing technology with the same UV dosage, according to Carolyn Goodridge, a visiting postdoctoral fellow and member of the research team.
In the US, as in Europe, regulations require the disinfection of water used in food processing before it can be reused. The researchers found, however, that in many cases the lack of cost-effective disinfection means water is used only once and then discarded. When a disinfection system is used, the process is not always effective, they say.
Most existing systems pump water through pipes lined with dozens of UV lamps. The lamps tend to get dirty quickly, reducing their effectiveness and requiring ongoing cleaning and replacement. Furthermore, UV light has little penetrating power - just about an inch - so used water must be run through long pipes to increase the likelihood that UV light will contact enough of the liquid to affect the micro-organisms it carries.
"Water right up against the lamp gets treated, and water farther away gets treated less - or maybe not treated at all," explained John Pierson, a senior research engineer at the Georgia Tech Research Institute and co-principal investigator.
"We're creating a mixing pattern to ensure that every particle of water is equally exposed to the (UV) lamp," said Pierson. "By doing a better job of mixing the water, you get better disinfection."
The heart of the new advanced system is a pair of cylinders, one inside the other. The smaller cylinder rotates inside the stationary outer cylinder while water is pumped through the gap separating the two. Inside the gap, the cylinder rotation causes water to churn and tumble in a phenomenon called a Taylor vortex.
This vortex comprises a number of vortices, which mix water with light shining from four UV lamps embedded in the outside cylinder wall. UV light penetrates the water thoroughly, so no additional cycles through the system are necessary, explain the researchers. And as fewer UV lights are required compared to conventional systems, it saves energy.
"Even if the fluid absorbs radiation, which would normally limit light penetration and thus the effectiveness of conventional UV reactors, the vortex motion in the new design continuously exposes fresh fluid to the radiation surface," explained Larry Forney, project director and an associate professor of chemical engineering at Georgia Tech. "You bring the fluid in contact with just a few lamps in a repetitive basis."
Other advantages claimed by the researchers are that the vortex motion also keeps the lamps free of material build up and that the device is mechanically simple. "Its low rate of revolution - about one cycle per second - means no bearings or special seals are required," added Forney.
Although the process was designed for recycling water from fruit and vegetable washing at food-processing plants, the researchers believe that it could be applied in other industrial processes.
"We think it could be useful for a number of water-treatment situations ranging from storm-water runoff to bottle washing to certain industrial-process water recycling applications," Pierson continued. "It fits any application where you could use disinfected water rather than potable water, which would cut down on water use generally and conserve potable water in particular."
"We're also beginning to work with certain kinds of fluids, such as fruit juices, that absorb lots of radiation to see what effect our device has on the inactivation of pathogens in that kind of environment," said Forney.
He went on to explain that virtually anything that flows can run through the system, thus allowing for applications in the soft drink industry, brewing, dairy products and fruit juice processing - useful for any kind of fluid for which there are concerns about the existence of pathogens. As a non-thermal procedure, he believes that it has the potential to even supplant pasteurisation, which he says is expensive, changes the taste and consumes a lot of energy.
