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

Abstract

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.

Leveraging Sustainable Irrigated Agriculture via Desalination: Evidence from a Macro-Data Case Study in Israel

“…In 2012 only 4 of 26 crops were found to have lower Na than US standards and more than half had concentrations of Na more than double the standards. The move to desalination is expected to be particularly influential on Mg in agricultural systems [13,14]. This is supported by the data of Mg in edible products and its comparison with USA standards (Figure 3A,B).…”

“…Management of desalinated water for irrigation proved to come with its own set of challenges though, most particularly following the realization for need to supply minerals such as calcium (Ca), magnesium (Mg), and sulfate (SO 4 ) that had traditionally been components of delivered water but are not present in the desalinated water [13]. An additional important ramification of the desalination of municipal water supply was the decreased salinity in the wastewater stream and significant lowering of salts in recycled effluent used for irrigation [14].…”

Using Desalinated Water for Irrigation: Its Effect on Field Scale Water Flow and Contaminant Transport under Cropped Conditions

“…Half of the irrigation water in Israel is treated wastewater. The relatively low content of calcium and magnesium in desalinated water and the high addition of sodium in household use has raised concerns about the high sodium adsorption ratio (SAR) in wastewater originating from desalinated seawater [13].In contrast to the aforementioned concerns, the change towards lower salinity irrigation water may be regarded as an opportunity. Higher yields or smaller irrigation rates for the same yield and reduced leaching of salts below the roots are expected benefits of using more desalinated water for irrigation [14,15].…”

“…Half of the irrigation water in Israel is treated wastewater. The relatively low content of calcium and magnesium in desalinated water and the high addition of sodium in household use has raised concerns about the high sodium adsorption ratio (SAR) in wastewater originating from desalinated seawater [13].…”

Establishment of the Underlying Rationale and Description of a Cheap Nanofiltration-Based Method for Supplementing Desalinated Water with Magnesium Ions

“…Finally, it is noted that in arid areas of the world, such as Israel and parts of Spain and Australia, a considerable portion of treated wastewater is reused for agricultural irrigation. Thus, low Mg(II) concentration in drinking water eventually leads to low Mg(II) concentration in irrigation water [17].…”