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Now that Israel is desalinating seawater, researchers at the Technion - Israel Institute of Technology are experimenting with the desalination of purified sewage, in an effort to expand its use in agriculture. Up until now its use was limited due to its poor quality.

Last month, staff at the Technion's Grand Water Research Institute began desalinating wastewater on an experimental basis in the Nir Etzion area, south of Haifa. The experimental facility pumps wastewater from the regional sewage treatment plant and further purifies it so that it is more suitable for agricultural use. Israel is a leader in the use of wastewater for irrigation.

Nonetheless, Josef Hagin of the Grand Water Research Institute said sewage treatment plants in Israel produce wastewater which still contains a level of contaminants and high levels of salt which harm agricultural produce and raise the salinity of ground water. "We examined the effects of purified wastewater on a grove of almond trees in the Negev Desert," he said, "and the trees simply died when they were irrigated with treated wastewater."

Ilan Katz, who planned the desalination project, noted that production of avocados grown around Acre declined with the use of purified wastewater, due to the presence of contaminants and the water's level of salinity.

The Nir Etzion facility was set up to overcome these effects by further purifying wastewater with a membrane material, similar to what is used in seawater desalination plants. The membranes filter out salt and other contaminants, including bacteria and viruses. Carlos Dosoretz of the Technion's water institute said: "Based on tests that we have conducted, the facility will be able ultimately to supply wastewater of the quality of drinking water."

Katz noted that because the level of salinity of the wastewater coming into the experimental facility is much lower than seawater, less energy is expended to purify it. The researchers acknowledge, however, that the additional treatment does add substantially to the cost of sewage treatment. Katz pointed out that in measuring the feasibility of the facility, the agricultural benefits and the substantial improvement in the quality of water resources should also be taken into account.

The Israeli treatment plant and similar facilities in Jordan and the Palestinian Authority are being funded by a U.S. governmental aide program and by the Peres Center for Peace.