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<br /> 0 <br /> , ., <br /> .... <br /> w <br />-' ~ <br /> w <br /> <br />.' <br /> <br />,.' <br /> <br />Acid .vastes from coal and metal mines destroy the natural alka- <br />liJ.'lity of the water and increase its load of suspended matter. In addi- <br />tion, they increase the sulfate content of the water. Sulfates cannot <br />be removed by any practicable municipal vmter treatment process. <br /> <br />Untreated sffivage contributes vast numbers of bacteria to the re- <br />ceiving waters. SOl'le of these may be disease-producing organisms. This <br />is important from both a public water suppl;r and recreational use stand- <br />point. Se'~Ge, unless adequately treated, also places a heavy demand on <br />the oxygen resources of the stream. If the sewage load is too great, <br />oxygen levels may be reduced to a point where the stream can no longer <br />support fish life, <br /> <br />Unlike mineral pollution from chlorides and sulfates, putrescible <br />matter in sewage is gradually decomposed and rendered inoffensive by <br />natural stream purification processes. Just how far the effects of sewage <br />pollution are Significant below a point of sewage discharge depends upon <br />numerous factors such as dilution, strength of selvage, velocity of stream <br />now, turbulence, etc. <br /> <br />$-7 <br />