Evaluation of a nanofiltration desalination unit: Combined production of strawberries irrigated with desalinated water and Salicornia irrigated with the desalination concentrate
Vegetablesתחום או ענף אגרוטכנולוגיה; ירקות; תבלינים
תאריך עדכון 14/3/2012
Evaluation of a nanofiltration desalination unit: Combined production of strawberries irrigated with desalinated water and Salicornia irrigated with the desalination concentrate
Andrea Ghermandi, Rami Messalem – Ben-Gurion University of the Negev, Zuckerberg Inst. for Water Research, Desalination & Water Treatment, Israel
Rivka Offenbach, Shabtai Cohen – Central and Northern Arava Research and Development, M.P. Arava, Sapir, Israel
E-mail address for correspondence: sab@inter.net.il
Abstract
The quality of irrigation water, specifically its high salinity, is a limiting factor for the expansion of the range of crops grown in the Arava. During the 2010/11 growing season, an experimental apparatus (model) was used at the Yair Station in the Arava to improve the local water using a principle similar to that used in reverse-osmosis systems. This involved the use of sophisticated membranes that allow for the selective penetration of ions, in contrast to the membranes used in reverse-osmosis systems, which “clean out” all of the salts from the water that passes through the system. That water then needs to be supplemented with calcium, magnesium, sulfur and bicarbonate before it can be used for agriculture. The use of a nanofiltration system will improve this situation, so that some of the elements are passed through to the final product (including limited amounts of chloride compounds and sodium). The nanofiltration system also provides a significant energy savings, specifically a 50% energy savings when compared with conventional reverse-osmosis systems, because the pressure levels necessary for its use are relatively low, making it possible to power the system with solar cells.
This experiment was designed to investigate the use of nanofiltration for desalination and the intelligent use of water for producing strawberry crops for export in raised/artificial beds that are irrigated with high qualtiy water, with the goal of expanding the variety of crops grown in the Arava for export, in combination with the production of halophytes, such as Salicornia for the export market, that are irrigated with the brine that is a side-product of the desalination process.
The experiment was conducted in a 350-m2 greenhouse at the Yair Experimental Station. The greenhouse was equipped with hanging beds that were hung 1.7 m above the soil surface. The growth medium was coconut in growth bags. The coconut was tightly compressed and when it was saturated with water it expanded to fill the plastic growth bags. In each plastic sack, there were 12 holes to allow for the stand density desired in this type of system. The distance between drainpipes was 0.6 m. Transplanting was carried out on 26 September 2010. The greenhouse was equipped with a fan and pad evaporative cooling system and a climate-control system, in order to keep temperatures relatively low during the first stages of the crop’s growth. High-quality water with an electrical conductivity of 0.8 dS/m was used to irrigate the strawberries and to operate the cooling system. Two-thirds of the greenhouse was used for strawberry production. We evaluated the cv. Tamir, which was developed by Nir Dai at the Vegetable Department at Beit Dagan, and the cv. Yuval, which was developed by the Fertiseeds company. A hive of honey bees was put into the greenhouse and when that did not bring the expected results, a hive of bumblebees was added as well.
The remaining third of the greenhouse was used to grow Salicornia. The Salicornia was planted on 20 December 2011. The halophyte was irrigated with the brine produced in the desalination process, which had an electrical conductivity of 4.5 dS/m, mixed with table salt (NaCl) that was dissolved in water at a rate of 6 kg/m3, in order to bring the electrical conductivity of the irrigation water to the optimal level for Salicornia production (15 dS/m).
Strawberry yield. Both strawberry cultivars began to bear fruit in November, but the yield from cv. Tamir was almost double that of cv. Yuval (0.81 kg/m2). This was surprising, since cv. Yuval is considered to be the earlier-bearing cultivar. This yield advantage persisted until February. During this period, the accumulated yield for cv. Tamir was 4.58 kg/m2 and the accumulated yield for Yuval was 3.47 kg/m2. During the month of December, there was almost no marketable yield due to fruiting problems related to the beehive situation. The fruiting period of strawberry has great economic importance. During November, strawberries sell for 20 to 25 shekels/kg, as compared to only 5 shekels/kg at the end of the season. We recommend the continued evaluation of production methods and additonal cultivars, in order to maximize yield per unit area.
Salicornia yield. Salicornia harvesting began in the middle of April. Over the course of 50 days of harvesting, we collected a yield with a fresh weight of 5 kg/m2. Ninety percent of this yield was of export quality. The combination of crops modeled in this study was found to be feasible. We recommend continuing research in this area and evaluating other crop combinations, in order to increase the profitability per unit area of crops irrigated with desalinated water.
Acknowledgements
We would like to thank the JCA Charitable Foundation for their financial support of this project, Avi Osherovitz and Dorit Hashmonai from the staff of the Yair Station (Arava R&D) for their dedicated work on this project and Ramat HaNegev R&D for supplying the Salicornia seed that made this project possible.
שפה English
AUTHORS Andrea Ghermandi, Rami Messalem, Rivka Offenbach, Shabtai Cohen,
שנה 2011
שייכות yzvieli
תאריך יצירה 14/3/2012
תאריך עדכון 14/3/2012