Finding the energy to heal

On Irish swimmers, high densities, and the silver bullet to solve water pollution once it happens

An Irish swimmer may have been the last Olympic victim of the dirty water in the Seine, going to the hospital after competing in a 10-kilometer open water swim -- instead of getting to be a flag bearer at the closing ceremonies. He certainly didn't want anything to do with the river again.

■ The whole Seine debacle highlights the enormous role that energy plays in water quality. Would it be theoretically possible to treat all of the water that flows down the Seine? Perhaps. The same could plausibly be done with any river; it's all a matter of scale.

■ But there's no getting around this: Healing polluted water takes a large amount of energy. Water is dense: A single cubic foot of water contains just shy of 7.5 gallons, and every gallon weighs 8.34 pounds. That means a cubic foot of water weighs more than 62 lbs.

■ Every time water is lifted, pumped, clarified, filtered, or aerated, at least some of it has to be displaced. That comes at a high cost of mechanical energy, and that almost entirely involves passing energy through electric motors.

■ In the long term, the best thing that can be done for the good of reducing water pollution (other than preventing that pollution in the first place) is to generate enormous quantities of cheap, non-polluting electricity. With enough of that energy, almost any sick water can be healed. And healing the water is preferable to healing humans who get sick because of it.