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Accepta Newsletter: Issue 3

A message from the editor: Welcome to our third newsletter. If you'd like to comment on any of the issues raised, make suggestions for future articles or suggest ways in which we can improve this service please contact me

Articles in issue 3:

• Innovation: Ultrasound cleaning of ceramic filters could aid water treatment.
• Product review: solvent impregnated wipes.
• Escherichia Coli O157 (E Coli) and drinking water.

Ultrasound Cleaning of Ceramic Filters could Aid Water Treatment

Engineers at Ohio State University claim to have discovered how to clean high-tech ceramic water filters at low cost using ultrasound.

Although the research is still in its early stages, they claim the technology may one day allow water treatment plants to purify water with ceramic membrane filters instead of traditional water treatment chemicals.

Harold Walker, assistant professor of civil and environmental engineering and geodetic science at Ohio State University said "If water treatment plants could clean water with membrane filters, they could minimize the cost, safety and disposal issues associated with the use of harsh chemicals,"

Researchers are currently studying ceramic membrane filters, honeycomb networks of micro-channels separated by thin ceramic membranes. As water passes through the micro-channels, the ceramic membranes act to filter contaminants including clay, iron oxide, bacteria and viruses. However, over time these membranes become clogged and require cleaning.

Walker took note of recent research involving ultrasound and bubbles. The idea, most recently reported by scientists at Oak Ridge National Laboratory and their colleagues, is that sound waves can form and collapse bubbles inside a liquid, releasing heat and energy.

To test whether collapsing bubbles could clean a ceramic filter, the engineers submerged a filter in water that contained latex and silica particles. They used particles in a range of sizes to mimic the contaminants found in water treatment.

They used an ultrasonic probe to vibrate the water at 20 Kilohertz, a low frequency that is easily obtainable with typical ultrasound equipment. For example, the fetal ultrasound tests that women undergo during pregnancy employ much higher frequencies, in the order of 10 Megahertz. But that doesn't mean a 20 Kilohertz probe is less powerful, Linda Weavers, also assistant professor of civil and environmental engineering and geodetic science at Ohio State University, explained.

"Frequency has nothing to do with power. Think of it as bass sounds versus soprano sounds. Both can be louder or softer. Whether a sound is bass or soprano depends on frequency, whereas loudness and softness depend on power," she said.

The 20 Kilohertz vibrations caused bubbles to form and collapse, and kept the ceramic filter clean.

"The bubbles seemed to scour the surface of the filter," Weavers said. "Where the bubbles collapsed, tiny water jets formed and flushed away the contaminants."

Though the engineers are still not certain exactly how the process works, Weavers suspects that the jets sprang from vibrational nodes, locations along the surface of the filter where ultrasonic waves merge together and magnify each other.

With ultrasound as a cleaning method, water treatment plants wouldn't have to remove filters from use to clean them, Walker said. Loosened contaminants would wash away in an exhaust flow separate from the clean water.

"If you left the ultrasound running, you could clean a filter while it was still in use, and keep it from ever getting clogged in the first place," Weavers added.

If all goes well, Walker said, the technology may be ready for full-scale testing in a water treatment plant within the next few years.

Extracted from an article originally written by Pam Frost Gorder

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Accepta Launch a Range of Versatile Impregnated Wipes

This month we profile Accepta's range of solvent based wipes, suitable for applications involved with the manufacture or use of oils, grease, resins, adhesives, elastomers, mastics, plastics and paints etc.

Solvent Based Wipes

Whatever your work within industry, there is a constant need to clean equipment, components and personnel. Accepta's innovative solution to this problem, their solvent impregnated wipes are not only convenient and easy to use, providing exactly the right quantity of solvent in each wipe, they also offer excellent economy.

Accepta's solvent based wipes have been well received by industry in general and have proved particularly suitable for critical application and have already been approved by the UK's aerospace and defence industries.

Accepta's wipes also take account of three important regulatory issues, ozone depletion, Health & Safety and volatile organic chemical (VOC) emissions.

Ozone Depletion

The depletion of the ozone layer has been reliably associated, at least in part, with the catalytic breakdown of ozone by some chlorinated and chloro-fluorinated hydrocarbons accumulating in the upper atmosphere in the presence of incoming radiant energy.

Whilst the main culprits appear to be those highly volatile and mobile "CFCs" employed as aerosol propellants and refrigerants, the generally heavier and less mobile species employed as cleaning and degreasing agents have also been implicated.

The Montreal Protocol (1987) was signed by around 40 countries and sought to limit the use of ozone depleting compounds by 50% before 1999. The EEC Directive (1989 and subsequent amendments) seeks to act even more quickly and has targeted the cessation of production of ozone depleting species by the mid 1990s.

Health & Safety

The control of substances hazardous to health (COSHH) regulations require the user of hazardous substances to review and document procedures involving such materials and to adopt less hazardous materials and/or processes where possible, such that the hazard is diminished.

Certainly it is implicit in the act that the operator of a process may not replace it directly with an alternative process wherein the overall hazard (comprising both material and method) is increased. The manner in which two totally unrelated hazards, i.e. fire hazard versus chronic dermal irritance, are to be compared is not evident since no absolute index of severity exists and legal precedent is far from clear.

It is, however, self evident that the obligations enshrined in COSHH regulations must be carefully weighed in any scheme devised to supplant the use of ozone depleting cleaning processes.

Volatile Organic Chemical (VOC) Emissions

The volatile organic chemical emissions regulations form part of the Environmental Protection Act (1991). The regulations place limits upon the tonnage of solvent vapours exhausted into the atmosphere from industrial premises engaged in nominated processes - including solvent degreasing and cleaning. The numerical limits are time-related and include, additionally, those VOC's arising from all nominated processes. So the combined emissions from degreasing, cleaning and painting operations will be considered as a single entity.

A solvent-based paint must ultimately dry and therefore contribute a fixed finite emission. The emission of VOC from cleaning and degreasing processes in unit time can, in contrast, be managed by the careful selection of the degreasing solvent in order to minimise its volatility and hence its loss at atmosphere.

Typical Wipe Applications

If you are involved with the manufacture or use of oils, grease, resins, adhesives, elastomers, mastics, plastics and paints etc. you will require a cleaning product that takes into account those important regulatory issues and also removes soils effectively, economically and easily.

Accepta 5304: An odourless cosmetic grade solvent cleaner intended as a specialised replacement for 1,1,1-Tricholoroethane and other chlorinated and fluoro-chlorinated solvents where the latter are scheduled for discontinuation under the Montreal Protocol. Superb solvency towards oils and greases. High flash point, low toxicity and moderate evaporation rate.

Accepta 5305: Solvency and activity - as Accepta 5304, though with a moderate flash point, low toxicity and an enhanced evaporation rate.

Accepta 5306: High boiling safety solvents - designed to give good solvency with low toxicity and controlled evaporation required to meet the increasingly stringent Health and Safety and Environmental regulations now being imposed on industry. Accepta 5306 has a low odour and low vapour pressure, together with a high flash point. Ideal for removing those really stubborn paints, resins, adhesives and elastomers as well as graffiti.

Accepta 5307: Accepta 5307is similar to Accepta 5306, it is a high boiling safety solvent blend that is particularly effective against complex modern polymers and adhesives.

Accepta 5308: Functionally similar to Accepta 5307, but offers a pleasant citrus aroma.

Other Products

Accepta's range of 'wipe' products also includes several alchol based products suitable for office, hospital, clean room and other applications. For further details please contact us.

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Escherichia Coli O157 (E Coli) and Drinking Water

Escherichia coli or E coli are bacteria that normally live in the intestines of humans and animals. Although, most strains of these bacteria are harmless, several are known to produce toxins that can cause diarrhea. One particular E Coli strain called O157 can cause severe diarrhea and kidney damage.

Escherichia coli O157 (E Coli)

Why this note?

There have been a number of media reports on outbreaks of diarrhoeal illnesses caused by the the E Coli O157 bacteria, including reports from North America involving water supplies. The purpose of this note is to provide reassurance about the safety of public water supplies in England and Wales.

Why the concern?

In contrast to the harmless E Coli strains normally found in the gut of all warm-blooded animals, the O157 strain produces a potent toxin. This causes severe diarrhoea and in some cases renal failure and death. Toxigenic E Coli, including O157 and other strains, are carried by 10-15% of healthy ruminants, including cattle, sheep, goats and deer. The bacteria may be transmitted to humans by consumption of raw or undercooked meats, or by faecal contamination of foodstuffs or water supplies.

How does this affect drinking water?

Because E Coli are always present in human and animal faeces in very high numbers, they are used as an indicator of faecal pollution in the microbiological surveillance of drinking water. On very rare occasions, low numbers of E.coli are detected in drinking water. This does not indicate that O157 is present, or that there is an immediate risk to health. Detection of E Coli does however necessitate an immediate investigation of the water supply system in order to identify and eliminate the source of pollution.

How is E coli dealt with?

All E Coli bacteria are rapidly inactivated by chlorine and other disinfectants used in the treatment of public water supplies. Drinking water related cases of infection are invariably associated with unchlorinated supplies or with systems where there is poor maintenance or operation of disinfection systems. In the UK, no O157 infections have been associated with public water supplies. Some cases have occurred where consumers use private water supplies that are not disinfected.

Reproduced courtesy of the Drinking Water Inspectorate
dwi_enquiries@detr.gov.uk
© Crown copyright 2001

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