Potential drawbacks associated with agricultural irrigation with treated wastewaters from desalinated water origin and possible remedies.
Over 90% of the water supplied in the coastal region in Israel in 2013 (600 Mm(3) y(-1)) will be from desalination plants. The wastewater generated from this water (>400 Mm(3) 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 Mg(2 + ) concentration and the Sodium Adsorption Ratio value of the water are of concern. We show that the typical Na(+) concentration addition to wastewater (between approximately 100 and approximately 165 mg L(-1)) is much higher than the combined addition of Ca(2 + ) and Mg(2 + ) (between 0 and several mg L(-1)). Since desalinated water is typically supplied with low Ca(2 + ) and Mg(2 + ) concentrations ( approximately 35 and 0 mg L(-1) respectively), the treated wastewater is characterized by very low Mg(2 + ) 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 Ca(2 + ) or Mg(2 + ) to desalinated water. Adding Mg(2 + ) is preferable from both health (minimizing cardiovascular disease hazards) and agriculture (inexpensive Mg fertilization) aspects. The low cost of Mg(2 + ) addition at the post-treatment stage of desalination plants corroborates the request for Mg(2 + ) addition in regions where treated wastewater from desalinated water origin is planned to be reused for irrigation.
Lahav
Ori
O
Faculty of Civil and Environmental Engineering, Technion, Haifa, Israel. agori@tx.technion.ac.il
Kochva
Malka
M
Tarchitzky
Jorge
J
D000327:Adsorption; D000383:Agriculture / Q000379:methods*; D002118:Calcium / Q000032:analysis; D005308:Fertilizers; D007557:Israel; D008274:Magnesium / Q000032:analysis; D011188:Potassium / Q000032:analysis; D054712:Salinity; D012964:Sodium / Q000032:analysis; D013431:Sulfates / Q000032:analysis; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
D005308:Fertilizers; D013431:Sulfates; D014874:Water Pollutants, Chemical; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium