New Water Softener Provides Alternative to Ion Exchange

01.05.1994

You are here

Prof. Kedem  Ben-Dror. Soft water without salt

Novel water-softening equipment based on Institute technology is being manufactured by EcoSoft, a new company in the Kiryat Weizmann Industrial Park, adjacent to the campus. This equipment is designed to soften water without polluting underground aquifers with salt.

Established by Crecor B.V. of the Netherlands and Israeli paint manufacturer Tambour Ltd., EcoSoft will exploit the innovative "cake" filtration method for water softening developed by Weizmann Institute's Prof. Ora Kedem and EcoSoft's Jonathan Ben-Dror.

Many industries, laundries, hotels, municipal waterworks and private households soften their water by removing calcium salts in order to reduce the need for detergents and prevent the scaling of pipes and heating elements.

At present, the most commonly used method of removing calcium is ion exchange, in which the mineral is extracted in purifying columns that are regenerated for future use with the help of salty water. Yet this seemingly clean process leads to invisible pollution caused by the dumping of tons of sodium-rich effluent, which finds its way into the aquifers. Therefore, pressure has been mounting throughout the world to ban the ion-exchange method.

Ion exchange was introduced to replace the age-old method of lime softening, which consists of adding lime to hard water so as to cause precipitation of calcium carbonate. However, lime softening is hardly used today because it requires vast ponds to allow the precipitate to settle, takes about 24 hours and creates enormous pools of sludge.

The new cake filtration method is based on similar chemistry: caustic soda solution is added to hard water in order to induce the precipitation of calcium carbonate. However, the passage of the alkaline water -- supersaturated with calcium carbonate -- through a filter cake leads to complete precipitation within seconds. Rapid crystal growth and formation of new crystals produce a readily disposable, and even useful precipitate instead of sludge.

The installations required for cake filtration are only one-tenth the size of those needed for lime softening.

Cake filtration technology was patented by the Yeda Research & Development Co., which facilitates commercial exploitation of Institute research.

Prof. Ora Kedem of the Department of Membrane Research and Biophysics holds the M. Myer Cyker Chair of Membrane Research.
 

Share