1) While water covers the majority of our planet, freshwater scarcity is already a huge issue in many regions of the world. Arid areas particularly suffer for the most, and they have a lack of freshwater resources in the form of surface water. Underground water resources are turning into more brackish due to relentless extraction from the aquifers. We use freshwater to drink, bathe in, irrigate our farm fields, but only 3% of the total water is qualified as freshwater. Within 3% of the water, two-thirds of it is stored in frozen glaciers, so we only use the remaining one percent as freshwater.
Approximately 1.1 billion people in the world lack access to water, and inadequate sanitation causes diseases such as cholera, typhoid fever, and other water-borne illnesses. Each year, two million people die from diarrheal diseases alone. Climate change alters patterns of weathers and water in the world, which led to shortage and droughts. Under the current trajectory, two-thirds of the world’s population is expected to face water shortage problems.
2) Desalination is considered as one of the possible solutions to provide sufficient water quantity and quality against population growth and climate change. Desalination refers to the water treatment process that converts sea or brackish water into potable water. Among various methods, Reverse Osmosis is the most advanced desalination system in the world that accounts for 60% of the world’s facilities. This technology uses a high pressure pump to dissolve salts up to 99%+ including colloids, organics, bacteria, and pyrogens. When high concentration salt water receives pressure, the water flows in a reverse direction through the semipermeable membrane and leaves the salt behind. In sume, it starts with a pre-treatment system and uses high-pressure pumps. Afterwards, it utilizes membrane systems and completes the process with post-treatment.
The desalination process demands a huge amount of energy, and is very expensive. Depending on the location, labor and energy costs, monetizing the value of the process varies. Under the currency technology, it is more economical to purchase local freshwater. Moreover, sea life sometimes gets sucked into desalination plants. When the separated salt water is returned into the ocean, it also gives a negative impact on aquatic life. Minimizing the negative impact is possible, but it costs even more.
“Desalination of Water”, Manish Thimmaraju et al, 3/5/2018
“Why don’t we get our drinking water from the ocean by taking the salt out of seawater?”, Peter Gleick,7/23/2008
- All citizens of the planet particularly in arid regions.
- Vulnerable population who are exposed to water related diseases
- Energy companies like ACWA power that wants to combine renewable energy and desalination technology to create extra synergy
4) Three steps of deploying the technology
- Takes the seawater through a semipermeable membrane
- Filters smaller particles through pretreatment filters. Remove salt from seawater through a high pressure through reverse osmosis membranes.
- Returns seawater to the water and store drinking water
3 thoughts on “Salt Water Desalination”
Good summary. We (humans) need to make this work. I read before that Israel is very advanced in using this technology. The government of Singapore is also very active in this area. Both nations have very limited fresh water resources. As scale increases, cost comes down as well. If we were to price in all the externalities of using water the way we do today, that cost difference is for sure to be narrower.
Thanks for this thorough summary of desalination, Byungchul. Zhongmin, you make a good point about economies of scale and pricing externalities of current freshwater harvesting practices. However, negative environmental externalities also exist with desalination, and I’d like to dive deeper into Byungchul’s point about the adverse impacts that desalination plants have on aquatic life. There is currently a heated debate in LA about a proposed desalination plant in Huntington Beach (see: https://www.latimes.com/environment/story/2021-04-28/questions-linger-about-environmental-impact-of-poseidon-plant; https://www.latimes.com/environment/story/2021-02-23/newsom-pushes-poseidon-seawater-desalination; https://www.latimes.com/environment/story/2021-04-29/poseidon-wins-key-seawater-desalination-permit). Opposition not only revolves around the high cost of the water – and lack of contracted purchaser of the 50 million gpd of expensive desalinated water – but also around the environmental impacts of the plant. State scientists predict that the plant will kill nearly 300,000 microscopic organisms a day, which will have a significant impact on algae, plankton and fish larvae that make up the base of the marine food web. The current plans do not take measures to avoid these impacts because the developer was able to take advantage of a provision stating that environmentally harmful open ocean intakes are permissible when less harmful alternatives are not economically feasible. LA’s drought problem is severe, and diversifying water sources is increasingly necessary, but we must ensure that innovations are implemented responsibly and don’t cause negative environmental impacts (in this instance to marine life as well as impacts from polluting power producers if the high electricity demand from the plant is not supplied via renewable generation).
One of the negative externalities of water desalination is the byproduct of highly concentrated salt water, which currently finds its way back into the ocean. There is also a high cost for the desalinated water. It seems like there is a missed opportunity here, to sell the byproduct, to salt producers, and potentially help reduce cost for the clean water. The salt would not need to be edible, despite the fact that people do seek out sea salt for consumption. Could potentially be used for other purposes, such as salting roads before snow, etc.