The Dan Metropolitan Region, Israel, consists of about 1 million inhabitants, about 50% of whom live in the city of Tel Aviv and the rest in surrounding communities.

The industrial, economic, and commercial growth of this region has been rapid in recent years and the effluent

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forecast in 1980 is estimated at more than 100,000 cu m (80,000 acre-ft) per year, and 175,000 cu m (140,000 acre-ft) in the year 2000.

The sewage-reclamation recharge project was conceived to solve both environmental hazards and water-resources management problems and consists of 2 phases, sewage reclamation and recharge of the reclaimed sewage.

The project provides for treatment of the sewage in a series of oxidation ponds and pumping to nearby spreading grounds after detention in the terminal pond. Recharge operations will begin in 1973 with the recharge of 7,500 cu m/year; the scope of these operations is to be stepped up gradually to reach 50,000 cu m by 1980. The spreading grounds cover an area of 250 acres and are about 0.7 mi from the oxidation ponds.

The area occupied by the spreading grounds consists of sand dunes, overlying, for the most part, calcareous sandstones. These formations constitute the main aquifer of the region. The reclaimed sewage will be spread alternately to allow the grounds to be dried and cultivated between recharge operations in order to remove the surficial crust and increase infiltration. It is estimated that the rate of percolation will be about 6 in./day.

An array of 30 production wells--drilled for the specific purpose of exploiting the recharged water--surrounds the spreading grounds at a distance of 0.3 mi from its perimeter. The quality of the recharged water is satisfactory from the content of nitrogen compounds (less than 10 ppm), phosphates (less than 1 ppm), and bacteria and virus. As an additional precaution, the water will be held in the subsurface for a period of 400 days, during which it will undergo natural filtration and mixing with existing groundwater. Furthermore, the recharge operations will allow regulation of supply and demand according to existing conditions.

Following its subsurface movement and mixing, the reclaimed water will be pumped and conveyed to the National Water Carrier for transfer to the southern area of the country for supplementing irrigation requirements.

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