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Also of importance are those substances which cause problems of <br />taste and odor. Of particular concern are phenolic and related compounds, <br />minute concentrations of which cause repugiiwi1 Last-_ ra.ud odor in water <br />supplies. Pollution control programs are aimed at virtual elimination <br />of these substances in waters serving as a source of domestic supply. <br />Quality requirements for industrial water supply vary widely, <br />depending upon the type and nature of industry under consideration. Of <br />general concern are organic and biological constituents, toxic substances, <br />and properties of corrosion, encrustation, and slime formation. Waste <br />control measures contribute materially to improvement of water quality. <br />It is generally agreed that a minimum of 5.0 parts per million <br />(ppm.) of dissolved oxygen is necessary, in those streams of the South <br />Platte River Basin affording a suitable fishery habitat, for support of <br />a balanced aquatic life, and that a minimum of 6.0 ppm. is desirable for <br />trout streams. Because of limited dilution water during critical periods <br />of low flow, secondary treatment for removal of not less than 75 percent <br />of the Biochemical Oxygen Demand (B.O.D.), is required for most sources <br />of pollution in the Basin. A consistent B.O.D. removal approaching 85 <br />percent is possible with secondary treatment facilities properly designed <br />and well operated. <br />Water for recreational usage should be free from floating solids, <br />sludge banks, odors, and discoloration. Contamination of bathing waters <br />by sewage, especially that of recent origin, is particularly objection- <br />able. The Engineering Section, Missouri Basin Health Council, which in- <br />cludes representatives of the States of Colorado, Nebraska, and Wyoming, <br />recommend the following objectives for bacteriological quality of bathing <br />waters: "For bathing or swimming waters monthly arithmetical average <br />'most probable number' of coliform organisms should not exceed 1,000 per <br />100 ml. during any month of the recreational season; nor exceed this <br />number in more than 20 percent of the samples examined during any such <br />month; nor exceed 2,400 per 100 ml. on any day. For nonbathing or non- <br />swimming waters monthly arithmetical average 'most probable number' of <br />coliform organisms should not exceed 5,000 per 100 ml. in any month of <br />the recreational season, nor should exceed this number in more than 20 <br />percent of the samples examined during any such month." Sanitary sur- <br />veys must continue to play the major role in pollution control programs <br />as related to bathing waters. <br />The State water pollution control agencies of Colorado, Plebraska, <br />and Wyoming, recommend as bacterial objectives for irrigation water the <br />following: <br />(1) Sewage used for irrigation of forage crops should be given <br />treatment :insuring a consistent reduction in coliform bacteria of <br />not less than 90 percent. <br />(2) Sewage used for irrigation of human food crops should be <br />given treatment insuring a consistent reduction (a) in suspended solids <br />of not less than 75 percent, (b) in 5 -day 200C. B.O.D. of not less than <br />75 percent, and (c) in coliform bacteria of not less than 98 percent <br />unless discharged into a stream where the volume of dilution water, <br />36 <br />