Boron Removal from Desalinated Seawater for Irrigation with an On-Farm Reverse Osmosis System in Southeastern Spain

Alberto Imbernón-Mulero,Victoriano Martínez-Alvarez,Bernardo Martin-Gorriz,Belén Gallego-Elvira,Rubén Molina-Del-Toro,José F Maestre-Valero,Francisco J Jodar-Conesa

doi:10.3390/agronomy12030611

Alberto Imbernón-Mulero, Victoriano Martínez-Alvarez + Show 5 more

Open Access

https://doi.org/10.3390/agronomy12030611

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Abstract

Seawater desalination can provide water for irrigation in coastal regions where freshwater resources are scarce. Reverse osmosis (RO) is the most common technique to obtain desalinated seawater (DSW) worldwide. However, using DSW for irrigation may pose an agronomic risk as RO permeates have a boron concentration above the phytotoxicity thresholds of some sensitive crops, such as woody crops (0.5 to 1.0 mg/L). In this study, an on-farm RO system designed to reduce the boron concentration of DSW was evaluated from a technical and economic perspective. The impact of variations in the operating parameters feed water temperature, pressure, and pH, on the boron reduction process was assessed. The results showed that boron rejections close to 99% can be obtained by increasing the feed water pH to 11 with an operating pressure of 10 bar. Looking at the affordability of the system, a total production cost of 1.076 EUR/m3 was estimated for the 1.1 m3/h on-farm system used in the trial. However, this cost is expected to decrease to 0.307 EUR/m3 for a commercial RO plant (42 m3/h), highlighting the importance of the scale factor. Our results provide novel guidance on the feasibility of implementing on-farm boron removal RO systems, when DSW is provided by coastal plants with boron concentrations above the crop tolerance.

Highlights

Seawater desalination provides a steady water supply that overcomes climatological and hydrological constraints and mitigates drought risks in coastal regions where freshwater resources are scarce [1,2]
The results showed that boron rejections close to 99% can be obtained by increasing the feed water pH to 11 with an operating pressure of 10 bar
When comparing our results with previous research, we found even higher specific costs for reducing boron

Summary

Introduction

Seawater desalination provides a steady water supply that overcomes climatological and hydrological constraints and mitigates drought risks in coastal regions where freshwater resources are scarce [1,2]. In Spain, desalinated seawater (DSW) is being increasingly seen as a viable option to sustain both domestic and agricultural needs, since it is considered an inexhaustible resource [1,4]. One of the main limiting factors for its use in irrigation, in addition to the high associated energy consumption and production costs [1,2,4,8], is the high boron concentration of DSW (around 0.5–1.0 mg/L, depending on the treatment in the RO plant) that may imply toxicity risks and harmful effects for crop productivity in the medium term [4]. In Spain, the maximum boron concentration allowed by law in water for human consumption is 1 mg/L (Royal Decree 140/2003). In the absence of a specific regulation, the same value is adopted for irrigation water, unlike other countries such as Israel where the maximum boron concentration is below 0.5 mg/L, to prevent phytotoxicity issues [9]

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