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UV dechlorination saves on maintenance

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article image Maintenance workers at Proctor & Gamble's Carolina plant.

SINCE installing Hanovia ultraviolet (UV) dechlorination equipment, available in Australia from Fluidquip , Procter & Gamble USA has significantly reduced the cost of maintaining the reverse osmosis (RO) membranes at its North Carolina manufacturing plant.

The number of shutdowns for RO membrane maintenance has also been significantly reduced.

"We are very pleased with the UV system," utilities process engineer Kurt Loughlan said.

"Not only have we saved money since it was installed, but the disruption caused by plant shutdowns as a result of RO membrane fouling has also been significantly reduced. UV provides a high standard of dechlorination without any of the drawbacks of using chemicals or GAC filters."

Chlorine is widely used for water disinfection in many different process industries. Because of its properties, however, it can damage delicate process equipment like RO membranes and deionisation (DI) resin units and must be removed once it has performed its disinfection function.

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 bisulfite.

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 bisulfite, 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 underdosing due to human error.

An increasingly popular dechlorination technology, with none of the above drawbacks, is UV treatment.

High intensity, broad-spectrum UV systems dissociate both free chlorine and chloramine compounds (mono-, di- and tri-) into easily-removed byproducts.

UV has the added benefit of providing both high levels of microbial disinfection and also total organic carbon (TOC) destruction.

At Procter & Gamble's facility, the Hanovia UV dechlorination unit was installed before two banks of RO membranes; prior to this dechlorination was achieved using sodium bisulfite.

Trials run soon after the UV system's installation showed a dramatic reduction in the RO membrane wash frequency - down from an average of eight cleanings a month to only two a month - amounting to annual savings of $US70,000.

Hanovia is a market leader in UV technology for progressive, non-chemical disinfection and contamination control.

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