|Managing Water for Peace in the Middle East: Alternative Strategies (UNU, 1995, 309 pages)|
|4. Hydro-powered reverse-osmosis desalination in water-resources planning in Jordan|
Jordan, being semi-arid to arid, has a mean annual rainfall of only 114 mm. The potentially exploitable renewable water resources are further limited to about 900 million m³ per year, which will be fully exploited by the year 2000 owing to increasing demand especially in the population centres. As has been noted, however, the hydrology and hydrogeology of Jordan provide a wide range of alternative water sources such as rivers and streams, springs, flash floods in the wadis, renewable and non-renewable groundwater, the return flow of treated sewage effluents, and seawater. The non-conventional water sources are primarily the reclamation of urban waste water, brackish groundwater, and seawater, of which the present status and the future development plans are described in this section.
4.4.1 Reclamation of urban sewage waters
The Water Authority of Jordan has an ambitious ongoing sewage treatment programme, which not only will have positive environmental and health impacts but will also provide for the collection and treatment of sewage in a way that effectively lends itself to the reuse of treated effluents. Sewage collected in north Jordan is expected to increase from 29 million m³ in 1985 to 116 million m³ by 2004 and 165 million m³ by 2015, most of which will be reused in downstream irrigation in the Jordan valley. Ongoing sewage projects include construction of new sewage treatment plants in Baqa and Wadi Sir and extension of the existing plants in Salt and Jerash. These plants have priority because their effluents are discharged upstream of the Zarqa basin and will be reused in downstream irrigation through regulation by the King Talal reservoir.
4.4.2 Brackish groundwater
Brackish groundwater is generally stored in deep aquifers except in the southwest, where the Disi formation or Precambrian complex outcrops. The quality of the brackish groundwater ranges from 1,0002,000 mg of TDS per litre to 5,000-10,000 mg/l, which is good for neither domestic use nor irrigation. Brackish groundwater with salinity of less than 2,000-3,000 mg/l, can be used directly for some crop irrigation, depending on pervious or sandy soil conditions. Another potential use for brackish groundwater is for specific purposes in the mining industry such as for washing water. In general, brackish groundwater can be safely used after desalination or mixing with very fresh water.
Brackish groundwater has been found in some places in the Jordan valley, and has been accidentally detected in some deep sandstone aquifers such as the Kurnub formation on the uplands during either exploratory or exploitation Grillings, but no systematic study or investigation of brackish-water potential has been undertaken. However, a large storage potential for brackish groundwater is conceivable in the rather shallow aquifers of the eastern desert of Jordan, including the areas of Azraq, Sirhan, and Hamad. In these areas, the target aquifers will be the Amman-Wadi Sir (B2/A7) formation, which is underlain by the shallow aquifer unit of Rijam (B4). These brackish aquifers may exist at depths of 200-300 m and 500-700 m with l DS of 2,000-5,000 mg/l. From the scanty piezometric data, the depth to the water table from ground level is expected to be only 100-200 m in wadi depressions including the Azraq and Sirhan. This brackish groundwater potential is situated only 100150 km east of Amman, which suggests a potential source of water supply for the Amman municipalities if cost effective desalination is performed. The most important cost factor in such desalination is the energy cost, which can be controlled by introducing off-peak power operation, taking into account the dominant steam-power generation with high peak demand in Jordan. Recent innovative research in the high-molecular membrane industry could provide the necessary energy saving through the use of low-pressure reverse-osmosis modules for brackish water demineralization.
A large amount of exploitable brackish groundwater is conceivably stored in the deep sandstone aquifers in southern Jordan, such as the Kurnub and Khreim formations. A case study on their nature and potential use for desalination and water supply is provided in the following section.
Desalination of seawater for M&I water supply is the principal source of water in the oil-producing Gulf countries. Conventional distillation by the dominant multi-stage flash (MSF) method will be too expensive in Jordan, except for specific projects. Furthermore small-scale MSF desalination, for example to satisfy local water demand for the Aqaba municipal water supply, has a scale demerit to achieve the cost feasibility. Adding seawater desalination by reverse osmosis, however, may improve costs even for small- and medium-scale desalination plants. Thus the Aqaba steam-power station might be viable as a co-generation station either with MSF or RO. Hybrid desalination with MSF-RO and power will be a key element for regional water-resources planning in Aqaba district. Techno-political alternatives, including seawater pumped-storage hydro-powered RO desalination for co-generation, are described in section 5.6 in a case study on the inter-state Aqaba regional economic development plan for peace.