Why Desalination Is Important?
We are staring at a global water crisis. By 2025 half of the world’s population will be living in the water-stressed zone. Our planet is made up of 72% water. We have a limited amount of potable water. Remember the line “Water-Water everywhere, not a drop to drink”? That is what we are facing right now. But what if we could tap into that vast water resource known as the sea and ocean and convert that saline water into potable water? Wouldn’t that be great? It could solve the world’s water crisis.
Desalination refers to the removal of salts and minerals from a target source or in other words, Desalination can be defined as a process of removing saline from seawater. Desalination is not something new. It has been part of mankind throughout history. Sailors have been using various desalination methods for a long time to meet their water demand on ships. But in recent years, as the water demands increase and water resources begin depleting. Desalination has gained popularity.
Many Middle Eastern countries like Saudi Arabia, UAE, Dubai, and Israel have already switched to desalination to meet a large part of their water demand. Israel meets more than 50% of its water demand via desalination. Even countries like the USA, which has many alternate sources of water, have started using desalination plants. Currently, the USA can generate 1 million gallons of water/per day via the desalination process. It is not only municipalities and authorities who are using these processes, but many industries and private institutes have also started using Desalination plants to meet their water demands.
There are various methods through which one can perform desalination like solar distillation or complex methods like electrodialysis membrane. Below is a list of common desalination methods used today:
- Solar Distillation: Solar desalination is one of the oldest and simplest kinds of desalination methods. In this, the seawater is first evaporated using sunlight. The vapors are captured and condensed onto a cool surface, from which freshwater is collected.
- Multi-Stage Distillation: in this type of plant, saline water is heated and condensed multiple times, until a desired level of purity is reached. The water can be heated either by using solar energy or some other source of heat.
- Graphite Oxide sieve: Graphene filters provide an alternative to the current desalination process, developed by scientists from the University of Manchester (United Kingdom). The process uses nano filters made from Graphite Oxide which allows water to pass through it but retains salt. It is a relatively new material and is still some years away from becoming a true solution
- Reverse Osmosis (RO): Many people don’t realize that, but their household RO systems are very efficient desalination devices that work by using a semi-permeable membrane passing water under osmotic pressure to remove all the salts and minerals from the water. RO systems are highly efficient but scaled-up RO plants are costly and have high energy demand.
- Forward Osmosis (FO): FO is a relatively new commercial desalting process. In FO, the flow of water is in the opposite direction to that of RO. FO uses a semi-permeable membrane and the natural energy of osmotic pressure to separate water from dissolved solutes. It has an advantage over RO as it doesn’t have energy demand.
- ElectroDialysis: It is an electrochemical process in which ion transfer separates salt from water. The process is driven by direct current (DC) in which ions (as opposed to water in pressure-driven processes) flow through ion-selective membranes to electrodes of opposite charge. It is effective only for substances that can be ionized (like common salt) and is usually used for water having low TDS
Drawbacks of Desalination
Many countries like Saudi Arabia, Kuwait, UAE, and Israel have started to rely heavily on desalination water. But if you look carefully, the one thing common in all these countries is the fact that they lack any other alternate freshwater sources. They have no option but to switch to desalination water. Most countries, still do not consider desalination as a sustainable water source because of the following drawbacks
- High cost: Currently desalination processes are hugely expensive as compared to other sources. Most of the desalination process requires high energy input and specialized materials as well as a large amount of land for plant setup, making its overall cost very high.
- Secondary Emission: Desalination requires high energy input. As a result, it has the potential to increase fossil fuel dependence, increase greenhouse gas emissions, and exacerbate climate change if renewable energy sources are not used for freshwater production
- Threat to the marine ecosystem: Desalination surface water intakes are a huge threat to marine life. Mature fish, larvae, and other marine life can be significantly injured or killed when they become trapped or sucked into open water surface intake pipes.
- Disposal of Brine: Desalination plant creates a large quantity of wastewater in the form of brine (1.5 liters of brine for every 1 liter of freshwater). This brine water can accumulate in and around disposal areas and can deplete the oxygen level of water, and increase salinity as well as water temperature, which can destroy bottom-dwelling species and significantly alter coastal ecosystems.
Desalination of seawater has shown huge potential as an alternate water source. Although currently, desalination is not a popular alternative for most countries due to its high cost, huge energy demand as well as various negative environments, that doesn’t mean it has no future. People have realized that the only way desalination can be a good option for solving the water crisis is if renewable energy is used, costs are lowered, and environmental protections are put in place for marine life too. And keeping this in mind, many scientists, institutes, as well as nations, are already working to make desalination a viable sustainable alternative to meet our future water demands.