MIT makes some bold claims for a cheap, small scale desalination system.

The researchers estimate that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters of drinking water per hour and last several years before requiring replacement parts. At this scale and performance, the system could produce drinking water at a rate and price that is cheaper than tap water.

MIT

If it works for salt water, I wonder if it could work for any type of water. Decentralized treatment is a worthy goal – if we could easily and safely reuse water from our rooftops, showers, dishwashers, etc., that would be a lot less water to be sucking out of the environment and moving around in pipes, and a lot less energy and chemicals than we use to run our water systems now. Toilets? People don’t like to hear this, but if we get desperate enough we might be open to it. For the water industry, it could be a “killer app” akin to the digital camera or cellular phone. Don’t expect the water industry to go quietly though.