Water Treatment - Scale solution means cash back for supermarket06 December 2004

The Waitrose supermarket chain is generating savings on the maintenance, replacement and running costs of its water system, thanks to electronic treatment units which negate the effects of hard water.

David Upton, electrical services manager at Waitrose's head office in Bracknell, first became aware of Scalewatcher's Enigma product last summer after a recommendation from a colleague in the engineering department of Waitrose's parent company, the John Lewis Partnership. Following a demonstration of the technology in action at Southampton Geothermal Heating Company by the unit's supplier, Environmental Treatment Concepts (ETC), Upton agreed to installations in the store's Reading and Caversham branches.

ETC application engineers visited the sites to assess their needs and identify the best position to install the units. Both sites now use the Scalewatcher Enigma in their hot water systems, one linked to a purifier and the other in supporting a calorifier (used for the transfer of heat from the boiler system to the water needed for hand basins in the staff areas and behind fresh produce counters).

How does it work? Calcium carbonate (CaCO3), which comes from limestone or chalk, is converted to a soluble bicarbonate (Ca(HCO3)2) in mildly acidic water. Applying heat or pressure to the water drives out carbon dioxide, forming carbonate ions. Hard calcium carbonate crystals form on pipe walls or heating surfaces, and further precipitated crystals then seed onto this surface, accelerating the growth of a hard scale.

Scalewatcher Enigma generates a complex frequency modulated signal, which is applied by a coil around the outside of the pipe. ETC states: "The objective of applying these thousands of differing frequencies simultaneously is to induce a voltage in the water, match the resonant frequency of the dissolved ions and thereby give them sufficient energy to release the carbon dioxide and break their bond with the water molecules... This enforced precipitation results in a crystal forming, which seeds onto other ions in the water, such as zinc, iron, etc."

And Waitrose's experience? "After three months, we opened the calorifier to find that the interior surfaces were no longer coated with hard limescale. Instead there was just a soft powdery substance that would be flushed away in the normal use of the system," says Upton.

"This means that we no longer have to chip off limescale, which is difficult and time consuming, or replace parts so often. Importantly, less energy is needed to heat the water, which makes the whole process more environmentally friendly."

And Upton says he has been very pleased with the advice and support he has received from ETC so far: "The engineer has been working closely with us to ensure that Scalewatcher Enigma is working to its maximum capability. I have applied to Waitrose's chief engineer for this to be put onto our approved list of equipment for all future developments."

SOE

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