Over 90% of the water supplied in the coastal region in Israel in 2013 (600 Mm3 y−1) will be from desalination plants. The wastewater generated from this water (>400 Mm3 y−1) is planned, after proper treatment, to be reused for agricultural irrigation, making this low-salinity water the main agricultural-sector future water source. In this respect both the Mg2 + concentration and the Sodium Adsorption Ratio value of the water are of concern. We show that the typical Na+ concentration addition to wastewater (between ∼100 and ∼165 mg L−1) is much higher than the combined addition of Ca2 + and Mg2 + (between 0 and several mg L−1). Since desalinated water is typically supplied with low Ca2 + and Mg2 + concentrations (∼35 and 0 mg L−1 respectively), the treated wastewater is characterized by very low Mg2 + concentrations, low salinity and very high SAR values, typically >6 and up to 10 (meq L−1)0.5. SAR values can be lowered by adding either Ca2 + or Mg2 + to desalinated water. Adding Mg2 + is preferable from both health (minimizing cardiovascular disease hazards) and agriculture (inexpensive Mg fertilization) aspects. The low cost of Mg2 + addition at the post-treatment stage of desalination plants corroborates the request for Mg2 + addition in regions where treated wastewater from desalinated water origin is planned to be reused for irrigation.
Potential drawbacks associated with agricultural irrigation with treated wastewaters from desalinated water origin and possible remedies
Ori Lahav, Malka Kochva, Jorge Tarchitzky; Potential drawbacks associated with agricultural irrigation with treated wastewaters from desalinated water origin and possible remedies. Water Sci Technol 1 May 2010; 61 (10): 2451–2460. doi: https://doi.org/10.2166/wst.2010.157
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