~The following was in response to a suggestion by a reader of an Australian Newspaper.~ Let me see if I understand the donut in a big dry salt lake concept. We dig around the parameter to a few meters below sea level, using the salty soil to construct a mountain size donut in the center of the dry salt lake. We fill the deep part with a meter or two of ocean water and grow algae on the surface of this salty lake. Now we fill the center with toxic water from the mines to a water level perhaps 100 meters higher than the algae growing lake. The toxins are removed from the water as it oozes though the salty dirt donut shaped dam. This provides non toxic (to the algae) make up water for the algae lake, as evaporation will other wise concentrate the salt until it is too salty for any kind of algae. The only living thing in Utah's Great Salt Lake is a type of brine shrimp. To keep the carbon dioxide content high we bubble the exhaust gas from cement kilns into the algae lake. The flue gases from coal fired electric plants would likely poison the algae, but perhaps we can bubble it into the toxic water at the center of the donut. Insoluble carbonates would precipitate out in the toxic lake, but perhaps enough carbon dioxide would make it though the donut shaped earth dam to nourish the algae. How much sodium and potassium carbonate can algae tolerate, as these are soluble in water? Please correct if I have this wrong and suggest improvements. ~Neil~