What are the environmental hazards of desalination? Describe 3 environmental impacts of desalination plants.

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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Desalination is being used as an option for obtaining clean water from the oceans and seas by removing salt from marine water. This option is most commonly exercised by large industries in coastal areas or regions that have no source of fresh water (for example, countries in the Middle East Asia: Israel, Saudi Arabia).

There are a number of environmental hazards associated with the desalination of ocean water, including excess energy consumption, detrimental effects on marine biodiversity at both inlet and outlet points, etc. Desalination uses about 12,000-18,000 kWh of energy per million gallons of water produced, as compared to about 1500 kWh of energy per million gallons for recycled water after tertiary treatment. Most of this energy is supplied by power plants based on fossil fuels. Thus, desalination causes higher consumption of fossil fuels, increases the concentration of greenhouse gases in the atmosphere, and leads to global warming. 

The intake pipes of the desalination plant operate on suction (created by pumps), resulting in the deaths of fish larvae, eggs, planktons, etc. These biological materials forms the base layer of the marine food chain and thus these deaths affect the entire food chain. Serious environmental damage is caused by the exhaust from these desalination units as the discharge has a high temperature, low dissolved oxygen, high salinity and a high concentration of metals. These impurities adversely affect marine life and the lack of life forms in the regions adjacent to the discharge outlet can directly be attributed to the desalination process.

Environmental impacts of desalination plants

Desalination plants cause environmental damage by their location and operation. 

The construction of a desalination plant and energy supply infrastructure disturbs the natural environment, especially when located near population centers and protected or sensitive regions. The environmental impacts are the noise generated at the plant, air pollutants generated during energy production to satisfy the energy requirements of the plant, and chemical usage in the desalination plant.

The feedwater pipe or intake pipe, as mentioned above, sucks the water from the ocean and in the process kills millions of lifeforms that form the base layer of the marine food chain. 

As mentioned above, the discharge from the desalination plants has an elevated temperature, high salinity, a high chlorine concentration, low dissolved oxygen and a high concentration of metals. The high temperature causes gas solubility issues. High salinity increases the salinity in the region surrounding the discharge and acts as shock load to the marine life forms. Low dissolved oxygen is hazardous to the survival and functional of life forms. Chlorine is a known disinfectant and residual amounts can cause the death of marine species. 

Thus, the desalination process should only be used as a last resort and care should be taken so as to minimize the environmental damage.