Producing drinking water from Seawater can be an affordable solution when no other reliable source of fresh water is available. The investment costs will in most cases the most important consideration.
Another thing to considerate will indeed be the costs of chemical, and electrical consumptions for the driving operating costs. The material (water) is free, but has considerable costs.
I was once, in the 80th, involved in a study regarding the construction of a Desalination plant, together with an old friend who had knowledge in nuclear energy. Our ideas never got to be realized, because of a negative and” misinformed” government. But the idea of converting seawater into irrigation resource and for human consumption, always kept my interest and have tried to keep myself updated in this field.
Its not easy to build a Desalination plant, but the basic idea seems to be simple, like this drawing.
Depending on the local energy costs, the choice of energy recovery device can be critical. The investment costs are higher with a pressure exchanger, but electrical costs will be much lower.
In countries where energy costs are expensive, typically islands with no energy resources, costs savings with a pressure exchanger, are more significative.
Thanks to Energy Recovery Devices, it is possible to reuse the energy from the concentrate flow. The concentrate is directed to the ERD, where it directly transfers its energy to part of the incoming feed water.
Before entering the seawater reverse osmosis membranes, clarified seawater is pressurized by the High-Pressure Pump typically between 55 and 85 bars, depending on the temperature and the salinity of the water.
In 2014, The Southern Seawater Desalination Plant in Perth Australia had been installed by SACYR.
The total cost of 750 million Euro! With a capacity of 305.000m3 per day and cover nearly 30% of the water consumption in Perth (2 million inhabitants). located approximately 1,300 meters inland from the coastline. It includes an 8-meter high verge that runs 1,100 meters around the perimeter to conceal the Plant from nearby residents and minimize sound and light pollution. The plant is also run using 100% renewable energy.
In the area of Axarquia, only 30 km east of Malaga (Spain), la Junta Andalucia have made a study of a desalinationplant project, that has been discussed for many years, has finally been put on the table (2023). The main problem in this area, after long period without rain, is the large consumption for the irrigating a good part of the 13,000 hectares of avocados and mangoes that are estimated to be in the eastern region.
In my opinion, this solution should have been handled by the Spanish government. Not declared as only general interest of the Autonomous Community. (Latest update; The government has decided to handel the project, 2024, but with an investment of onlt 100 MM € !)
I will follow with large interest the development of this project nearby and keep you updated.
Thanks for reading,
Windmush/Curt