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Description
The use of saline water resources in agriculture is becoming a common practice in semi-arid and arid regions such as the Mediterranean. The joint EU-PRIMA research project “SmaCuMed” aims at developing and testing an all-in-one smart irrigation cube system for smart-sensor controlled irrigation and the energy-autonomous treatment of brackish groundwater. This study focused on the testing and comparison of two desalination technologies: (1) low-pressure reverse osmosis (LPRO) and (2) membrane capacitive deionization (MCDI)— for the first time at pilot scale.
Both desalination units MCDI and LPRO were integrated in a “Smart Cube” as a holistic technological solution. In this study, both units were used in parallel to desalinate groundwater of different salinites. The Smart Cube as tested at two typical Mediterranean locations in Morocco (each over one full year) with different hydrogeological conditions. Location 1 was situated in Douar Foulouste, a rural municipality Sidi Kaouki, Essaouira, Morocco) for the irrigatation of argan trees (Argania spinosa). Groundwater here had a salinity of TDS = 2.8 g/L. Location 2 was situated in in Efoud, Errachidia in cooperation with a cooperative and association of Aoufouss for irrigation of Date palms. Groundwater here had a salinity of TDS = 5 g/L. The desalination technologies were compared at each location for 33% and 66% salt removal, respectively.
Concentrate disposal was carried out in evaporation ponds, thereby reducing leaching of brine salts and the environmental impact. During the pilot trials, approximately 145 m³ of brine was discharged into the evaporation basins, adding to a total of 550 kg of salt. Salts obtained from the basins could have potential indwustrial uses. However, salt was contaminated by dirt and sand and no economically feasible use was possible.
Results of desalination showed that MCDI had 40-70% lower specific energy consumption (SEC) and 10-20% higher water recovery. In general, the MCDI showed a better performance than LPRO when at lower desalination rates (33%). However, the throughput of LPRO (2.9 m3/h) was up to 1.5 times higher than that of MCDI. In addition, both technologies were successfully powered by PV solar energy with total water costs ranging from €0.60 to €1.34 per m³. Specific water costs of LPRO were significantly lower at higher desalination rates (66%). However, to evaluate both technologies, additional criteria such as environmental criteria, ease of use and operability, and brine disposal need to be considered.
