Water, the essence of all life on our planet, is becoming a scarce commodity. While the oceans provide an inexhaustible supply, only about 2.5% of the water on earth is fresh water. We rely on this small quantity of usable water for agriculture, industry, and domestic consumption.
Given the situation, it seems obvious that we should tap into the vast resources that our oceans provide. This requires desalination to remove the salt. This may be the best way of sustaining our way of life.
The answer seems simple, but is it really? Is desalination the solution to a pending water crisis?
Removing Salt from Seawater
Removing salt from seawater and other sources, like oil and gas operations, is not a new concept. Countries with limited freshwater reserves have been desalinating water for many years. In many arid regions, cities and farms depend on desalinated water for their survival.
While Desalination seems like a logical way of providing all our needs, only 1% of the fresh water that we use is obtained by desalination. This is because the process is not simple and requires large investments in technology and infrastructure.
The most common method of desalination is reverse osmosis, using a dense RO membrane to remove slats from water under pressure. Solar thermal evaporative water distillation is another, less common method as it can only be implemented in areas with sufficient sunlight.
Why is Desalination Not Used More?
For most of our history, fresh water from rivers, lakes, and wells have provided a cheap and easy supply of fresh water. As a result, there has been little motivation to find alternative water sources, except in areas where there simply isn’t enough fresh water.
As our global water needs have increased, subterranean water is threatened. We have to drill deeper into the ground to install wells. It will reach a point where wells are no longer feasible, and the environmental consequences will be severe. This places an even greater demand on rivers and lakes to supply our freshwater needs. These are also threatened by pollution and climate change.
It is obvious that we will need to find better ways of obtaining and using water as demand continues to increase. Desalination is an option, but growth in this market is slow because of numerous challenges:
To place these challenges in context, it comes down to one important consideration, what will be paying for desalinated water in our homes, farms, and businesses.
Is Desalination Expensive?
The US Department of Energy will be investing 21 million dollars in solar thermal desalination technologies. This means using solar heating energy instead of electricity, thereby saving on energy costs and CO₂ emissions.
How Much Does Desalination Cost?
According to the Department of Energy guidelines, the cost of desalination is around 50 cents per cubic meter, or 0.2 cents per gallon for sea water and $1.50 per cubic meter (0.6c/gallon) for water from oil and gas operations.
In Israel, one of the cheapest producers of desalinated water, the cost is relatively low, 41 cents per cubic meter, about 0.16c per gallon. Though project and operational costs in Israel are lower than in wealthier countries like the US. This makes the US Department of Energy cost estimate realistic for most developed countries.
This may seem very cheap on the face of things. However, this is only the cost of desalinating the water. It does not include water utility costs, like infrastructure and the electricity used to pump the water to the point of use.
Essentially, the cost of desalination will be added to what we are already paying for water. The average US household uses over 300 gallons per day. This means that desalinated water will cost the average American up to $1,800 extra per month.
This is quite reasonable for most of us, especially if we have no other option. The cost to industry is far higher. Factories that use thousands of gallons of water per day will be paying a lot more for desalinated water. This is a cost that will be transferred to the consumer. If water becomes more expensive, we will be paying more for most of the goods we buy in the stores.
The US uses 216 trillion gallons of water per year. When we look at it on this scale, an increase of 0.2 to 0.6c for a gallon of water will be a massive cost to the economy.
Desalination is, unfortunately, expensive when compared to natural freshwater sources. Yet, I still feel quite optimistic about the future potential that the water in our oceans have to offer. If it can become more affordable, we can be assured of an abundance of clean water. A lot is being invested in research and the supply of desalinated water is increasing. This should help to make it more affordable in the future.
Is Desalination a Viable Solution?
Over the last 100 years, demand for water has increased by 600%. This is a growth rate of about 1.8% per year. In 2018, the United Nations Water Development Report predicted that water scarcity will affect 5 billion people. Some areas face a greater threat than others.
In the middle east, where fresh water is incredibly scarce, desalination has been used to supplement the natural fresh water supply for many years. Saudi Arabia supplies about 50% of its fresh water from desalination plants. Israel obtains approximately 25% of its fresh water from desalination. However, China and the US will probably become the largest consumers of desalinated water in the future.
The market for desalinated water is expected to grow by almost 10% per year. Despite the costs involved, the decreasing availability of fresh water has resulted in an increase in the demand for desalinated water.
Apart from the reduction of fresh water sources because of pollution and over-exploitation of natural reserves, there are other challenges regarding global water security. Population growth obviously means that more people require water every year.
Developing countries are becoming more industrialized. Urbanization and increased wealth in these countries also results in a greater demand for agricultural products. All these factors increase the demand for fresh water.
Because of decreased supply and increased demand for fresh water, there is an urgent need for a solution. As a result, recycling wastewater and desalination have become a recognized necessity if we are going to meet future demand for a dwindling resource.
To ensure water security for our future needs, our options are:
Using water more efficiently will help reduce demand, which will lessen the burden on our freshwater reserves. Though we cannot ignore population growth.
While population growth has declined to around 1%, compared to 2% 50 years ago, the exponential effect of a larger population is enormous. With our global population currently at about 8 billion people, an increase of 1% is 80 million. If this trend continues, the following year will be 80.8 million, then 80.97 million, and will continue increase exponentially.
Regardless of how much water we are able to conserve through more responsible use of our resources, we will need to keep supplying more water for our growing population. This means that there is an urgent need to increase our water recycling and desalination capacity.
Cost for Desalination Vs Recycling Water
If we compare the cost of recycling water to that of desalination, there isn’t much difference. Water recycling costs about 0.33 cents per gallon, whereas desalination costs about 0.2c to 0.6c. In some instances, desalinated water may cheaper than recycling.
The debate around recycling vs desalination is bit more complicated than merely comparing the cost. It’s not possible to recycle all the water that we use. Only water from city wastewater facilities can be recycled.
Since about 85% of freshwater is used for agriculture, only 15% of all the water we use can be recycled. To meet global demand for water, it seems likely that both recycling and desalination will play equally important roles.
In areas where access to seawater is impractical, recycling may be the only option. Whereas desalination can be cheaper if the salt content of the water isn’t too high. The merits of desalination vs recycling need to be assessed according to practicality of either solution in a given area.
One fact remains indisputable, we need to value our water resources and use them responsibly. We also need to use technology, like reverse osmosis to make adequate use of the water that is available to us. Gaining global water security is achievable. However, it will come at a cost. The challenge is to make it as affordable as possible, especially in countries with limited financial resources.
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