Rivers Overwhelmed by Man's Wastes

…Why have so many of America's rivers become casualties as the country grew? Shortsightedness? Not at first. When only a few settlements dotted a river's banks, the sewage that poured in caused little harm. The organic wastes were recycled into nutrients that nourished the tiny forms of life that fed the fish. The river purified itself before it reached the next settlement.

What village could resist using such a convenient disposal system? Pour sewage in, and it disappeared downstream.

Then villages grew into towns. The river reeked a bit on hot summer days, but towns-people knew that the tainted water soon would be disappearing into the "boundless" sea. The answer to pollution was dilution.

Most towns today remove at least some of the sewage before pouring the wastes into the rivers. Primary plants settle out about a third of the solid matter. More-sophisticated treatment plants add a second step, using bacteria to convert the remaining organic material into inorganic nitrates and phosphates.

But even this disrupts the river's cycle. The "purified" water is too rich in these nutrients. Detergent wastes add more, and so do the fertilizers that wash in from farmland.

Nitrates and phosphates are food for the water plants such as algae. In the overnourished river, too many algae grow. But algae need sunlight to live. When the algae layer becomes too thick for light to penetrate, the deeper-lying algae die and sink to the river bottom in a thick brown soup. Oxygen is consumed by the decaying algae, making the water uninhabitable by fish.

Thermal pollution, too, afflicts our rivers. When power plants gulp water to cool their steam generators, they return it warmer than before. A temperature rise of just a few degrees can disrupt the breeding habits of fish, "cook" some of the oxygen out of the water, and increase algal growth.

Industrial chemicals pour into rivers. Pesticides wash in from farm fields. Petroleum products from marine engines and industrial spillage coat the surface, inhibiting the river's oxygen intake. Ohio's oily Cuyahoga River actually caught fire last year and burned two railroad bridges.

Lakes can be even more vulnerable than rivers. Witness Lake Erie, second smallest (after Ontario) and shallowest of the five Great Lakes. No body of fresh water in the country has received more attention than Erie, a lake dying of too much nourishment.

"Lake Erie is suffering from eutrophication," I was told by Francis T. Mayo, Great Lakes Regional Director of the Federal Water Quality Administration. "That word comes from the Greek eutrophos, meaning 'well nourished.' A lake becomes overnourished as part of its normal aging process, but man accelerates the process tremendously by pouring in nutrients and industrial chemicals."

When I asked if Lake Erie could be saved, he nodded. "It has to be saved. Nobody can afford to write it off."

But salvation comes hard, I learned. Many industrial plants and municipalities around the lake must change their ways. The tributaries that flow into the lake must be cleaned up—including the inflammable Cuyahoga River. Sewage plants must be upgraded, and agricultural runoff must be controlled.

"Nitrates are very difficult to remove from sewage water," Mr. Mayo said. "About 80 percent of the phosphorus can be taken out chemically, though, and that should hold down algae. Once the pollution stops, Erie should begin to clean itself. Its flushing time is only three to five years—that's the time it takes to replace all its water."

If three to five years seems long, consider Lake Michigan's flushing time: one century! The lake's only outlets are the slow-moving Chicago River and the Straits of Mackinac. Thus Michigan rates special concern from Mr. Mayo and his associates. The lake's pollution load is light—by Erie standards, at least—but any pollution is bound to be there for a long, long time.