Probiotics and Prebiotics

Construction of groundwater desalination plants in arid and semi-arid areas is increasing. Already in Israel, millions of cubic meters of brine are produced each year and more are expected shortly. This brine may be used as a new water source for aquaculture, and draws high interest by Israeli inland fish farmers, due to its low cost, constant temperature and pathogen-free characteristics, as well as the opportunity of growing marine species inland. The experience in using groundwater desalination brine for aquaculture is, however, very limited. In unpublished experience, scale formed on essential organs and led to fish mortality. In the current study, sea-bass survival in brine that was pretreated by aeration to reduce calcium concentrations (“softening”) was investigated. Kinetics of the softening process were also studied to assess design criteria for commercial application. Results suggested that under very low water exchange rates, fish can survive even in untreated brine. Over 70% of calcium can be removed in the process, at a hydraulic retention time of several hours. CaCO3 was found to be the dominant precipitant, at up to 1.5kg m-3. The aeration rate was found to have a much stronger effect on kinetics, compared with seed concentration. It was concluded that fish rearing in desalination brine may be feasible and economic, although care must be taken about the exchange rate and biofiltration. A pilot system is planned to operate during 2019 near Kfar Massarik desalination plant in northern Israel.