There are more than 14,000 desalination facilities spread around the globe today. The highest-density region of desalination plants is by far and away the Middle East, where other methods of obtaining drinking water are scarce. Desalination is the only climate-independent source of water purification available, so it can be quite necessary in certain parts of the world. Thermal desalination is one of the techniques used to desalinate water, and it has some measured pros and cons. Here are some fast facts on how thermal desalination affects the water and the environment.
1. The salt is recycled
Salt from the desalination process becomes part of a brine solution, which is discarded back into the ocean to be diluted back out naturally. Since the ocean is so vast and contains such a large quantity of water, this highly concentrated brine solution should theoretically dilute easily. Due to the process involved, it would be incredibly hard and expensive to actually recover the salt for use, so it is typically never recovered.
2. Thermal desalination contributes to global warming
Thermal desalination has been shown to contribute significant amounts of greenhouse gases to the environment. A rather sizable power input is required to desalinate water, and that input likely translates into sizable greenhouse emissions, as most power plants, especially those in the Middle East, produce carbon waste byproducts.
3. It can disrupt marine ecosystems
Marine ecosystems may be threatened if desalination becomes more widespread. Due to the large vacuums that suck seawater into the system, many small aquatic creatures are inadvertently sucked into the system and killed. This and the global warming impacts introduced in the previous point are why most environmentalists oppose thermal desalination except where absolutely necessary such as in desert climates.
4. The output water is completely pure
The high point of thermal desalination is that the output is pure, distilled water. The water is free from all contaminants and completely safe to drink. It’s the same kind of distilled water you can buy in a gallon jug at your local store.
5. The brine solution…not so much
Due to the treatments that the water undergoes to prevent damage to the machinery and aid in the distillation process. These chemicals are often still present in the brine solution that returns to the sea, and thus they do contribute pollution to the seawater. Among these potentially harmful chemicals could be acids, antifoaming agents (like polyglycols), cleaning chemicals, and oxygen scavengers. Some researchers also claim that the increased salinity and temperature of the brine solution can have an adverse impact on certain benthic communities (clams, crabs, sponges, lobsters, etc.) in the water.