Seawater you can drink!
The Problem: We need more and more clean water, while we have access to less and less of it.
The Fix: Large-scale desalination
Summary: Water is one of the most important resources for humans and most other life on the planet, unfortunately, due to climate changes, there is less of it in some places where we have built up large cities, not to mention the fact that these cities are growing beyond their means and water usage growing twice as fast as population , causing problems even without climate changes. This causes a need for creating more water, which has been done for centuries on ships and submarines through desalination, the removal of salt and other minerals from sea water.
General Information
Attempting to find a cost-effective large scale way to implement desalination has been a primary concern for many areas of the world. Large-scale desalination typically requires large amounts of energy and expensive infrastructure, making it a very expensive process, monetarily and with regards to carbon emissions. This should obviously be a last-case scenario, but sometimes fresh water from rivers or the ground are not available, and so the options are for entire cities to get up and move, or to go through this process. The best thing to do to avoid desalination is to conserve and use water efficiently, but once that has peaked, desalination is better than using water reclaimed from irrigation and industrial use. It is already a very common practice in Middle Eastern countries, where, in mid-2007, 75% of the world's desalination was occurring. This is because the Middle East is relatively water-poor, but energy-rich.
Monetary Costs
Depending on the technology used and local energy prices, 1,000 gallons of desalinated water can cost between $3 and 4, which, although not very much, is much more than it costs to pump water out of the ground. The price difference will probably narrow, however, as climate change causes more intense droughts in some areas and populations and water usage continue to grow. This website has costs from different types of plants in California, including capital, operating, and maintenance costs. Costs for RO plants tend to be lower than distillation plants. These cost estimates assume a 20-30 year lifetime, although if a plant is assumed to be run only part time or for a short period of time, the costs increase.
Energy Costs
Energy use for desalination are quite high and are used to produce electricity and heat. It depends on the salinity and temperature of the feedwater, the quality of water produced, and the desalting technology used. Estimates for electricity and heat usage are listed on this website. One way to reduce energy usage is through cogeneration plants to produce both electricity and heat.