In part one of our series on desalination we gave a brief history of the process. In part two, we discussed the different methods of desalination. Part three discusses the implications of the process.
The energy needed for saltwater desalination is very high. The average energy you need for the process is about 3 kilowatts. To meet all of the United States domestic water needs through desalination would require an increase of over 10 percent of energy consumption through existing technology and methods.
One way to offset energy consumption is through cogeneration desalination. Cogeneration is the process that the United States Nuclear Aircraft Carriers and Submarines use. This is a process where they use energy or excess heat from an existing energy source for the desalination process. In the nuclear aircraft carriers and submarines, for example, the excess heat from the cooling water in the reactor heats pipes of saltwater, which evaporates the freshwater and condenses it to liquid form for human consumption.
Although cogeneration desalination plants are possible on land, they tend to utilize fossil fuels. This is ideal for places such as the Middle East, where freshwater is limited. However, fossil fuel is abundant and therefore a cost-effective solution. In countries like the United States, cogeneration plants are usually a hybrid of nuclear, solar power, or geothermal energy.
The biggest hurdle to desalination is the cost. It costs more money for infrastructure, maintenance, and energy to create freshwater from saltwater than it is to just filter and purify water from existing freshwater sources. Unfortunately, given the growth of the human population around the world, existing freshwater sources are stressed or may not be available in certain parts of the world, such as areas with arid climate or high elevation.
A big factor in the cost of desalination is the scope of the facility. The process on a small scale, such as for a ship, is in wide use and relatively affordable. These techniques, however, are used on a small scale and designed for a finite number of usage. To build the desalination infrastructure on a large scale to meet the freshwater needs for consumption and agriculture, it might not be economically viable, especially for countries that need it the most.
Desalination is not without environmental implications. The process of desalination of saltwater creates a byproduct called brine. Brine is the remaining liquid that has high concentrations of chemicals, minerals, and metals that are harmful to human consumption. Under current technology, the only way to get rid of brine is to dilute it with water and reintroduce it back into the ocean. Since brine is denser than freshwater or saltwater, it sinks to the bottom thus polluting the underwater ground-level habitat.
Another environmental concern of desalination is the intake of salt water. Desalination plants use h massive pipes to suck in seawater. The problem is that the pipe also sucks in marine life, such as fish and sea plants. The pipes, have the potential to harm or even kill that sea life.
Despite the concerns and costs associated with desalination, public polls have shown that people are generally in favor of the plants.