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The desalination process's energy consumption depends on the water's salinity. Brackish water desalination requires less energy than seawater desalination. [82] The energy intensity of seawater desalination has improved: It is now about 3 kWh/m 3 (in 2018), down by a factor of 10 from 20-30 kWh/m 3 in 1970.
The process goes through the following steps: When the plant is operating in steady state, feed water at the cold inlet temperature flows, or is pumped, through the heat exchangers in the stages and warms up. When it reaches the brine heater it already has nearly the maximum temperature. In the heater, an amount of additional heat is added.
The first and last stages need external heating and cooling respectively. The amount of heat removed from the last stage must nearly equal the amount of heat supplied to the first stage. For sea water desalination, even the first and warmest stage is typically operated at a temperature below 70-75 °C, to avoid scale formation. [3]
The LTD process is most suitable for high saline feedwaters starting from typical concentrations of sea water to concentrated wastewater solutions from various industrial processes. [10] One possible application is the capacity duplication of RO based desalination systems by further treatment of the evolving effluents to the precipitation of salts.
Low-temperature thermal desalination (LTTD) is a desalination technique which takes advantage of the fact that water evaporates at lower temperatures at low pressures, even as low as ambient temperature. The system uses vacuum pumps to create a low pressure, low-temperature environment in which water evaporates even at a temperature difference ...
And then there is the brine — the salty, sludgy byproduct of desalination that typically gets released back into the ocean at the end of the process. A global survey of desalination in 2019 ...
Vapor-compression desalination (VC) refers to a distillation process where the evaporation of sea or saline water is obtained by the application of heat delivered by compressed vapor. Overview [ edit ]
Sea-water RO (SWRO) desalination requires around 3 kWh/m 3, much higher than those required for other forms of water supply, including RO treatment of wastewater, at 0.1 to 1 kWh/m 3. Up to 50% of the seawater input can be recovered as fresh water, though lower recovery rates may reduce membrane fouling and energy consumption.