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The sight of rainwater flowing through streets and open areas on its way to the sea, or evaporating before it can get there, is common in many Israeli cities. But a trial project in Kfar Sava will soon attempt to prevent such losses by harvesting urban rainwater, treating it biologically and allowing it to percolate back into the ground, where it may become a renewed source of useable water.

Staffers of the Jewish National Fund in Australia, in cooperation with the Kfar Sava municipality, will test the effectiveness of what is known as a biofilter, which absorbs rain runoff and purifies it via biodegradable means.

Afterward, the processed runoff is returned to the ground water.

The biofilter was developed by a research group from Monash University in Australia, with the participation of Israeli Yaron Zinger. They are working to apply the green technology in Israel with Dr. Avi Gafni of the Jewish National Fund.

The biofilter has already proved successful in Melbourne, and according to Zinger, the Australian city intends to make broader use of it in the near future.

"The biofilter may be installed near sidewalks, traffic islands and in any open area," Zinger said. "It consists of layers of soil and plants with deep roots. A bacterial population develops, which then breaks down polluted matter in the runoff."

In the first stage, the water flows into the filter, its quality is examined and it continues into a drainage system. Later, after the water is purified, it is returned to the aquifer.

"If we get permission from the water department to return the processed water, we also drill afterward to check its quality," Zinger said. "There have been attempts in the past to return runoff water to the ground, but because they contained pollutants and other matter, wells were blocked."

The amount of runoff in the developed areas of Kfar Sava is estimated at 3 million cubic meters a year. A biofilter system in the city could save a large portion, and recharge the ground water with it.

Zinger points out that the effectiveness of biofilters is greatest in areas which are in planning stages.

"In existing neighborhoods, it is complicated to find suitable sites, but in neighborhoods that are being planned, space can be allocated for this use," he said.