Numerical study of brine plumes discharged from a desalination plant at different depths in the coastal waters of the Caspian Sea

Document Type : Research Article


1 Department of Space Physics, Institute of Geophysics, University of Tehran, Tehran, Iran. E-mail:

2 Corresponding Author, Department of Space Physics, Institute of Geophysics, University of Tehran, Tehran, Iran. E-mail:

3 Department of Space Physics, Institute of Geophysics, University of Tehran, Tehran, Iran. E-mail:


In Reverse Osmosis (RO) desalination plants, the most important problem is the increase of salinity near the outfall. In this study, different scenarios of brine waste dispersion discharge of a desalination plant in terms of the depths of outlet system positions and physical properties of discharge system that meet the standard criteria of the Department of Environment of Iran are investigated.
In this work, the effect of the desalination effluent discharge site in terms of the depth of discharge location and emission of pollutants on a Caspian Sea coastal area (Neka) has been investigated and various scenarios have been implemented and proposed. Here the effectiveness of desalination effluent discharge depths of different scenarios, using a numerical model, have been considered. The model simulates unsteady 3D flows, by taking into account density variations, currents and other hydrographic conditions. The model has a dynamical nesting facility which gives a possibility of making an increase in resolution in areas of special interest. For increasing numerical efficiency, structured nested grids with three sizes of 90, 30, and 10 meters and uniform vertical mesh size equals to 0.5 meters have been used. In comparison with other common works, in this research, using a 3D non-hydrostatic (fully hydrodynamic) mathematical model to simulate the dispersion of saline water effluent, is an important feature. The effective density variation between the effluent and the receiving environment and generation of vertical flows resulting from this density variation, cannot be simulated using simplified mathematical models as they may face serious errors. Lack of the rapid diffusion and ideal conditions for plume development, illustrates that the worst condition for brine dispersion is a calm sea with minimum currents in coastal areas. So, the effects of the sea waves have been neglected and longshore wind induced current has been assumed to be a minimum of approximate value of 0.03 m/s.
The mean salinity in in the southern Caspian Sea is about 12.5 gr/lit and the desalination brine salinity has been considered as 25 gr/lit and the rate of fresh water and brine waste water production is about 6 m3/s. With these assumptions for rate of effluent discharge and sea conditions, different scenarios have been investigated using a 3D numerical model including different velocities and directions of a pair of jet fluxes in outlet system and outlet installation Reverse Osmosis (RO) desalination plants salinity near the outfall. In this study, depths of outlet system positions and physical properties of discharge system are mainly investigated.
The results show that in acceptable scenarios (with higher jet discharge speed and vertical direction of 30˚ to the vertical axis), the receiving environment has high brine concentrated area with a radius less than 200 meters. The results of different scenarios of discharge depths show that regarding the depths of discharge studied in this work (5, 10 and 15 meters), when the jet injection is closer to the horizontal direction, there is no significant difference between the results of different depths. But, in selected conditions, i.e. conditions where the angle of the effluent discharge jet is closer to the vertical axis (vertical direction of the jets is 30˚ to the vertical axis), deeper dischages create better conditions in terms of salinity propagation horizontally in the environment.


Main Subjects

Baluchi, S., Mohammad Mehdizadeh, M., & Pakhereh Zan, M. (2014). Modeling the effect of desalination on marine pollution (Case study of desalination in Bandar Abbas). The 7th National Conference and Specialized Environmental Exhibition.
Berkün, M. (2016). Coastal environmental impact overview of desalination plants.
Bohluly, A., Esfahani, F. S., Namin, M. M., & Chegini, F. (2018). Evaluation of wind induced currents modeling along the Southern Caspian Sea. Continental Shelf Research, 153, 50-63.
Danish, D.R., Mudgal, B.V., Dhinesh, G., Ramanamurthy, M.V. (2015). Mathematical Model Study of the Effluent Disposal from a Desalination Plant in the Marine Environment at Tuticorin, India. InRecent Progress in Desalination, Environmental and Marine Outfall Systems 2015, Springer, Cham. 333-347.
Korotenko, K. A., Mamedov, R. M., & Mooers, C. N. K. (2001). Prediction of the transport and dispersal of oil in the south Caspian Sea resulting from Blowouts. Environmental Fluid Mechanics, 1, 383-414.
Latteman, S. (2010). Devlopment of an environmental impact assessment and decision support system for seawater desalination plants. CRC press.
Le, N. L., & Nunes, S. P. (2016). Materials and membrane technologies for water and energy sustainability. Sustainable Materials and Technologies, 7, 1-28.
Mohamed, K. A. (2009). Environmental impact of desalination plants on the environment. In Thirteenth International Water Technology Conference, IWTC, 13(2009), 951-964.
Monfared, A., & Hamzeei, P. (2016). Simulation of the best point of the sea for dewatering and disposal of desalination effluent in Bushehr (Iran) using Mike software. The first conference on marine regions, development and water resources of the coastal areas of the Persian Gulf
Malcangio, D., and Petrillo, A. F. (2010). Modeling of brine outfall at the planning stage of desalination plants. Desalination, 254(1-3), 114-125.
Patel, Y. B., Nimbalkar, P. T., Nagendra, T., & Shukla, V. K. (2016). Numerical Modelling of Brine Dispersion In Shallow Coastal Waters. International Journal of Civil Engineering and Technology, 7(3).
Rucevska, I., & Simonett, O. (2011). Vital Caspian Graphics 2. Opportunities, Aspirations and Challenges. Arendal.
Zaker, N. H., Ghaffari, P., Jamshidi, S., & Nouranian, M. (2011). Currents on the southern continental shelf of the Caspian Sea off Babolsar, Mazandaran, Iran. Journal of Coastal Research, 1989-1997.