Potential drawbacks associated with agricultural irrigation with treated wastewaters from desalinated water origin and possible remedies

摘要

Over 90% of the water supplied in the coastal region in Israel in 2013 (600Mm3 y21) will be fromndesalination plants. The wastewater generated from this water (.400Mm3 y21) is planned, afternproper treatment, to be reused for agricultural irrigation, making this low-salinity water the mainnagricultural-sector future water source. In this respect both the Mg2+ concentration and thenSodium Adsorption Ratio value of the water are of concern. We show that the typical Na+nconcentration addition to wastewater (between ,100 and ,165mgL21) is much higher than thencombined addition of Ca2+ and Mg2+ (between 0 and several mgL21). Since desalinated water isntypically supplied with low Ca2+ and Mg2+ concentrations (,35 and 0mg L21 respectively), thentreated wastewater is characterized by very low Mg2+ concentrations, low salinity and very highnSAR values, typically .6 and up to 10 (meq L21)0.5. SAR values can be lowered by adding eithernCa2+ or Mg2+ to desalinated water. Adding Mg2+ is preferable from both health (minimizingncardiovascular disease hazards) and agriculture (inexpensive Mg fertilization) aspects. The lowncost of Mg2+ addition at the post-treatment stage of desalination plants corroborates the requestnfor Mg2+ addition in regions where treated wastewater from desalinated water origin is plannednto be reused for irrigation.