Brackish water desalination for greenhouse agriculture: Comparing the costs of RO, CCRO, EDR, and monovalent-selective EDR

Abstract

Greenhouses are a rapidly growing agricultural sector that uses desalination systems. However, the desalination requirements of the greenhouse industry and an economic evaluation of desalination technologies for greenhouses have not been reported previously. Several greenhouse operators in North America using desalination systems were interviewed to identify key design specifications. A detailed cost comparison was conducted for key technologies: reverse osmosis (RO), closed circuit RO (CCRO), electrodialysis reversal (EDR) and monovalent selective EDR (MS-EDR). Capital, energy and membrane replacement costs, savings in feedwater costs from operating at higher recovery, and potential savings in fertilizer from using MS-EDR, were calculated. For <10-hectare greenhouses, RO was the most cost-effective technology. For >10-hectare greenhouses, alternatives can be considered. MS-EDR is economically competitive if it can retain at least 20% of the calcium and magnesium needed for growing and if membranes last 7 years.

Brackish water desalination for greenhouses: Improving groundwater quality for irrigation using monovalent selective electrodialysis reversal

“…Of the 28,000 brackish groundwater samples, 5069 Table 7. We ensure that the final sodium concentration remains below 100 ppm [33].…”

“…These two trends suggest that larger farms would benefit more from MSED-R and are better initial adopters of this technology. We consider the RO 7 and MSED-R 8 capital and operating costs for a 10 hectare farm treating groundwater containing 850 ppm of TDS [33]. Each hectare under greenhouse cultivation is assumed to require a desalination sys-525 tem with a capacity of 60 m 3 /day operated without supervision for 12 hr/day annually at a 90% capacity factor.…”

How to Close the Gap of Desalinated Seawater for Agricultural Irrigation? Confronting Attitudes between Managers and Farmers in Alicante and Murcia (Spain)

“…The incorporation of desalinated water to agriculture can produce quite different agronomic effects, depending on the quality of the irrigation water that is replaced [16,17]. One of the main concerns about the quality of desalinated water is the lack of essential nutrients and its effect on plant growth, which requires higher fertilization requirements, since is of central importance to greenhouse producers [18]. In addition to its low mineralisation, desalinated water is characterised by a chemical composition quite different from that of conventional water sources that could promote the degradation of the soil structure due to soil sodicity, which highly affects crop yield, and concerns about potential crop toxicity related to high levels of boron and chloride [19].…”

Water Treatment and Desalination

“…Electrodialysis desalination process is in some way similar to "ion exchange" treatment process, but it differs in utilizing both cation and anion selective membranes to separate charged ions as shown in Figure 3. Improvements to ED process, an electrodialysis reversal process, were introduced where it utilizes regular automatic polarity reversal, which helps in decreasing fouling process [30][31][32].…”