Below is a diagram of a zero liquid discharge system. As you can see, there is a lot that goes into making an energy efficient system like this, and there is an estimated cost between 100 and 200 million dollars being put into ZLD systems every year. "Nobody puts in a ZLD unless they have to, because it's very expensive, says Tim Cornish, marketing manager for HPD. "It's driven by discharge regulations. Zero Liquid Discharge System Components .
Another form of water use that few people consider is the production of energy. The Virginia water resources research center analyzed 11 sources of energy such as coal, fuel ethanol, natural gas, and oil. Out of all the studied energy sources, natural gasses and fuel produced through coal gasification are the most water efficient and the least water efficient are energy sources produced by fuel ethanol and biodiesel. For energy production to continue at the most water sustaining rate, energy production needs to continue research in the areas of these natural gasses and coal gasification methods. .
Two of the researchers at the research center, Tamin Younos and Rachel Hill, conducted a study analyzing how many gallons of water are used from single light bulbs throughout the year. At 12 hours a day, a single incandescent bulb used between 3 and 6 thousand gallons of water in a year. On the other hand, using a compact fluorescent bulb would use between 1 and 2 thousand gallons for the year. With this staggering amount of water used, it seems that all homes should be required to use florescent bulbs and the production of the outdated incandescent bulb should be retired from production. .
Below are some charts from Virginia's center for water research showing the amount of water used for different types of fuel: looking at the above chart on the right, the efficiency of power generation technologies are shown. The most efficient of these is hydroelectric power generation, which is advantageous because it is currently the most widely used renewable energy source in the world.
