The Concept of Evaporation Ponds Fitted with Fresnel Lenses for Brine Disposal

The high salt concentration in the brine which is produced as a result of desalination processes are either returned to the sea or disposed inland. This brine has TDS as high as 36,000 mg/L. Most impacts on the marine environment arise as a consequence of this brine disposal. This increase in salt concentration, which raises the density of waters, can lead to increase of turbidity, disrupt the photosynthesis process. On the other hand, improper land disposal of brine has the potential for polluting the groundwater resources and can have a profound impact on subsurface soil properties.

If this brine is sent to evaporation pond instead, the water will get evaporated leaving behind salts which can be used for various other purposes thus eliminating the need to dispose it to sea or inland. Thus, leading to cleaner and safer environment. But the rate of evaporation is very low as compared to the output of brine of the desalination plants, and hence there is a need for a very large space to accommodate all the rejected brine.

By increasing the rate of evaporation we can decrease the space required by these evaporation ponds. The rate can be increased by using multiple fresnel lenses fitted in a grid. Fresnel lenses are thin lenses which can be as big as 1 m² in area. These lenses can reach a temperature of about 2000 K thus significantly increasing the evaporation rate.

This evaporation pond should be constructed of glass in semi-cylindrical shape, fitted with suction pumps on both of its semi-cylindrical bases. The floor of this pond should be constructed with high thermal conductive material such as copper for higher heat transfer. During the day, these fresnel lenses will concentrate the sun's energy and evaporate the water which is removed by the suction pumps, leaving behind the salts. In the night when it becomes non-functional, the scales and deposition of salts are removed thus maintaining the efficiency.

Keywords: brine disposal, fresnel lens, evaporation ponds