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Show the 1880's. Today we have 9,000 such systems serving 75 million people. Sewer construction far outran provision for sewage treatment. The historical function of sewage treatment from the first has been to ex- tract the solid matter or sludge from the sewage and to discharge the remaining effluent in the form of a relatively disease- and nuisance-free waste, usually into the nearest water. Of the 9,000 sewer systems in operation today (compared with 16,000 waterworks) only 6,000 flow into a treatment plant. Nearly two-thirds of our population is served with a public water supply, and one-half with sewage collection facil- ities, but only a third of the population is served with sewage-treatment plants. In the pollution abatement efforts to date the emphasis has been placed on cure at the intake of urban water systems rather than on prevention at the outlet. Public health workers have long recognized that this was inadequate to meet the problem. Some years ago a U. S. Public Health Service Assistant Surgeon General described the progress in city sewer construction since 1880 as "a great sanitary achievement" but added soberly: "The direct consequence has been greatly to increase the pollution of watercourses; for the simplest and most obvious means of disposing of sewage is to discharge it directly into a convenient body of surface water, and this has been common practice." Nor was this the only weakness in our pollution policy in past days. Practically no thought was given to the possible use of the waste material, much less of the water itself. There was no con- ception of the large conservation possibilities in all sewer works, that transform an objectionable, unwanted waste material into valuable organic matter and usable water. The only desire was to get rid of the sewage and, if the river or other water dilution failed to make the waste harmless, the dangerous problem floated down to the com- munity below. There were sporadic protests, true, but the practice was not only prevalent but almost universally accepted. Today, the increas- ing use of modern kitchen equipment like garbage disposals throws an ever greater burden on the waste-carrying capacity of our rivers-and flushes away an ever larger quantity of organic material and minerals that should be returned to the soil. Industrial Wastes The attitude of factories toward the disposal of waste was at first identical with that of the cities. But before long, industry discovered that in some cases it was possible to recover part of its waste and convert it into valuable byproducts. More and more industrial managers have become alert to this opportunity. Nevertheless, and despite the sensitivity of industry to public good will, the industrial waste pollution problem today is greater and more crucial than the problem of our domestic sewage. Industrial waste is often as complex as indus- trial processes themselves; we do not know how to treat certain wastes, especially in the chemical industry, or how to eliminate mine drainage acid without great expense. Furthermore, techno- logical progress continually develops new ma- terials-such as coal-tar derivatives, cellulose compounds, and phenolic resins-producing new wastes whose effects on the water and whose treatment requirements are not yet known. Some industrial wastes are much more dele- terious than sewage. Aside from poisonous and corrosive characteristics-found in lead, arsenic, chromium, copper, and cyanide concentrations, sulfuric and other acids, and phenols (carbolic acid)-certain wastes destroy more of the normal oxygen content required by plant and animal life in the water than human wastes. The oxygen demand (or amount of oxygen required for the decomposition) of waste is one of the yardsticks for determining pollution in a lake or stream. Except for poisonous or corrosive qualities, this yardstick is the standard measurement for the pollutional effect of industrial waste compared with domestic waste. The oxygen demand for waste solids require 2*/2 times more, decomposing or "stabilizing" packinghouse waste is 10 times higher than sewage, while tannery 189 |
