With the shortage of fresh water resources becoming a global crisis, more and more countries realize that fresh water, as a limited resource, should be consumed on the paid basis. We analyze the cost of seawater desalination as the following:

Operation cost and Maintenance cost

The cost of seawater desalination water production consists of Operation cost and Maintenance cost, which include management fee, staff salary, energy consumption (including electricity, oil, or other energy spending), dosing chemicals and other consumables, annual repair (usually 1.5% of equipment cost), and financial costs such as interests. Please check Factors Affecting Desalination Plant Cost. If by Reverse Osmosis method we also need to consider the membrane replacement costs. The calculation formula is shown below:

Annual recovery share of investment on seawater desalination = total investment amount × annual investment reimbursement rate for water production cost per ton of fresh water per year = (annual operation cost + maintenance cost + annual investment recovery share) / annual total freshwater production.

Energy consumption

For seawater desalination cost, energy consumption is the key factor to determine the cost of seawater desalination. For more than 40 years, with the development of technology, the energy consumption index of seawater desalination has been reduced dramatically by 90% (from 26.4kwh/m3 to 2.9kwh/m3), with a result of the cost being greatly reduced. At present, the cost of seawater desalination in China has dropped to USD0.60-1.06/m3, and the desalination cost of brackish water has fallen to USD0.30-0.60/m3. If the desalination of brine water is used to make salt and extract chemicals, the overall desalination cost can be greatly reduced even further.

SWRO product water has the cost advantage in the field of industrial application. For the water to be applied in industrial field such as the boiler feed water, the quality requirement is high thus it is also expensive for processing the municipal water to reach the applicable standard. The cost is actually much higher than desalinated seawater. In this aspect, seawater desalination or brackish water desalination especially is a competitive solution for industrial water application if neglecting the government subsidies on the water processing.

Comparing the unit costs for several acquisition methods of fresh water :

Seawater desalination: USD0.60-1.06/m3 (comprehensive cost)
Brackish water: USD0.30-0.60/m3 (comprehensive cost)

With the increasingly serious shortage of fresh water resources, water prices have been increasing all the time and all around the world, plus various ways of limitations on water consumption being applied. It can be predicted that on one hand, the cost of desalination will continue to decrease in the near future due to technology innovations. And on the other hand, the price of tap water will continue to rise. And these two figures will be closer and closer. The price of tap water will even be higher than the cost of brackish water desalination in the near future. The cost problem of seawater desalination will finally be solved and its commercial application is widely promoted soon.

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