Gongol.com Archives: August 2024
August 7, 2024
France's folly with the River Seine continues, with another river swim being cancelled over high levels of bacteria in the water. On one hand, the distant observer has to admire the ambition of the Olympic organizers who thought they could clean up the river in time. On the other hand, it's hard not to wonder how they managed to so severely underestimate the scale of the problem. ■ The best way to keep water clean is to keep contaminants out in the first place. It's much better to prevent pollution at the source -- which often means addressing what we know as non-point-source pollution, which mostly consists of runoff from agricultural and other diffuse sources. ■ Non-point-source pollution is a classic case of the tragedy of the commons; while it's easy to point to a factory discharging polluted water from a pipe into a sewer or a nearby creek and order them to clean up their act, it's much harder to tell lots of farmers, ranchers, homeowners, and businesses to stop doing damage by the acre. ■ Thus, the farmer who over-applies some fertilizer over here, the homeowner who blows some grass clippings into the street over there, and the store that over-salts its parking lot in the wintertime down the way each contributes a little bit to a pollution problem which, in the aggregate, devastates the water quality in the next river downstream. ■ The Seine could, in theory, be cleaned through the state-of-the-art technologies already widely known to the field of civil engineering. But the flow rate of the river is considerable -- at some times, higher than 500 cubic meters per second. That's almost half a billion gallons of water per hour -- or 11.4 billion gallons per day. ■ To clean all of it to a swimmable standard would mean treating something like 38 times the typical daily flow through the water reclamation facility that serves Washington, DC, which is one of the largest in the US, or about eight times the peak flow through Chicago's Stickney Water Reclamation Plant, which is widely regarded as the largest in the world. ■ For many years, the prevailing belief was summed up in the phrase, "Dilution is the solution to pollution". That was short-sighted and incomplete. In the long run, even diluted pollutants have a way of becoming concentrated (see, for instance, the problem with mercury levels found in tuna). Taking pollutants out is possible -- but it requires an enormous scale of investment and energy. It's far better to keep out the unwanted stuff in the first place.
