Forest Preserve District of Cook County, Illinois
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Stream Pollution
Nature Bulletin No. 401-A   January 9, 1971
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

The pollution of surface waters in the United States is one of man's most shameful and dangerous crimes against himself. It is ruining one of the nation's basic resources by rendering water unfit for human consumption and unsuitable for many industrial or domestic uses. Pollution is particularly alarming near most big cities, but, emptied into rivers and creeks, other communities may feel its effect a hundred or more miles downstream. Even in remote or rural regions, it originates as wastes from mines, paper mills, canneries and creameries .

A lot of the pleasure of living is taken away because our streams and lakes are fouled and spoiled for bathing, boating, fishing and other recreations. Further, the health hazard is very real. Unless such waters are boiled or chlorinated there is danger from typhoid, dysentery and many other diseases.

The most common and offensive effects of pollution arise from household sewage and wastes from the processing of foods: packing plants, canneries, distilleries and the like. This decaying organic matter, as it becomes putrid, stimulates an enormous multiplication of water bacteria and a host of other small plant and animal life which use it as food. Like other living things, most of these "breathe" and use up the oxygen dissolved in the water -- faster in warm weather, slower in winter -- often reducing it to the point where fish, for example, must retreat into cleaner water or suffocate.

Unfortunately, oxygen is but slightly soluble in water, reaching only 7 or 8 parts per million in summer and somewhat more in cold weather, even in clean water. At least half this amount is necessary for the survival of most kinds of gamefish and panfish, as well as for the minnows, crayfish, insect larvae and other animals on which they feed. Fish like carp, goldfish, buffaloes, bullheads and gars can live in polluted water so long as the oxygen does not go too low, but it may weaken them until even they fall prey to fish diseases. Among the small animal life there is also a wide range of tolerance to pollution: some very sensitive, others hardy. Even when the oxygen is completely exhausted, sludge worms (which look like miniature earthworms) may become so numerous that they look like red pile on a gray rug.

A clear fresh stream, receiving a heavy dosage of sewage, first becomes turbid and murky; then it bubbles, gives off foul odors and shows floating sludge; then if not further polluted, it slowly improves downstream -- finally becoming clear and fresh again. This process is called natural purification. Sewage treatment plants merely speed up this natural action and remove the sludge so that damage to streams and lakes is held to a minimum. This sludge, properly processed, can be used to improve the soil on lawns, gardens and fields. Pollution by oil wastes and by industrial wastes such as acids, cyanides, copper and arsenic, may poison aquatic life directly and make waters so unsafe for human use that they require special treatment.

Most cities and towns use about 100 gallons of water per person per day. This is in addition to industrial uses, which are much greater. It requires 55 gallons to make a pound of steel, 1000 gallons for a barrel of aviation gasoline and from 100 to 200 gallons for a pound of rayon. Water is truly a critical material in modern civilization and must be conserved for our very existence. Our health and our wealth depend upon clean waters.

Unlike the weather, something can be done about pollution. Let's do it.

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