M.Sc Thesis


M.Sc StudentRom Idan
SubjectAquaculture in Groundwater Desalination Brine
DepartmentDepartment of Civil and Environmental Engineering
Supervisors ASSOCIATE PROF. Youri Gendel
DR. Sivan Klas


Abstract

The brine produced by groundwater desalination plants can be an attractive water source for fish farming due to potential cultivation of valuable marine species, all year-round warm temperature and low price. However, this water source usually contains high concentration of dissolved inorganic carbon and calcium that can precipitate on the fish as CaCO3 and lead to their death. The solution proposed in this work is to soften the brine before entering the fishponds. The selected softening method relied on CO2 stripping and heterogenous nucleation. Two continuous reactor configurations were examined to establish optimal reactor design and operational parameters such as hydraulic retention time, aeration flow rate and seed concentration. The Effect the of feed water quality on the survival, health and growth rate of European Seabass, was assessed in a flow-through system. The results suggested that under the experimental conditions, fish can grow both in softened and raw brine, though the latter led to some minor precipitation on the fish gills and major scaling on the equipment, which is expected to demand intensive maintenance and produce large quantities of solid waste. Removal of calcium increased with aeration rate, seed concentration and HRT. Two continuous reactor configurations showed similar performance, however the novel design of one of the configurations can simplify operation. Removal of 1.2 g/l CaCO3, corresponding to 75% of maximal removal at equilibrium was achieved at HRT of 80 min, enabling the construction of a reasonable size full scale softening reactor. A relatively low energy consumption of 1.47 kWh to aerate each m3 under aeration rate of 0.25 LPM per l of reactor at HRT of 1.33 h Was estimated. Average diameter of the particles crystalized in the reactor was found to be 70-100 µm, which indicates simple gravitational solid separation. The precipitates contained > 92% CaCO3, which may be recovered as a commercial product to reduce overall costs and make the process more attractive for fish cultivation and brine desalination.