257 



Municipal waste discharge have four important effects on receiving- 

 water quality: 



(1) The decomposable organic matter of municipal Vt^aste dis- 

 charge exerts a demand on the oxygen resources of the receiving 

 water. This demand can result in depletion of dissolved oxygen 

 to the point where desirable biota cannot tolerate the environ- 

 ment ; they disappear or are killed. Complete depletion can result 

 in noxious odors with destruction of esthetic values. 



(2) Municipal wastes may contain pathogenic organisms dan- 

 gerous to human beings. The colif orm bacteria measurement is an 

 index of the possible presence of pathogens. The basic premise is 

 that if fecal indicator organisms are present, there is a high prob- 

 ability of pathogens being present; this condition is a public 

 health hazard for anyone ingesting or contacting the water. There 

 are many documented cases of waterborne epidemics and water- 

 transmitted diseases to support the health hazard premise. 



(3) The sett] cable material in municipal wastes may be de- 

 posited on the bottom, resulting in large sludge banks of organic 

 content. These sludge banks can also deplete the oxygen resources 

 through biochemical reactions. The suspended materials, if suffi- 

 cient in quantity, can reduce the depth to which sunlight pene- 

 trates, altering that portion of the ecosystem dependent upon 

 photosynthetic activity. 



(4) Dissolved salts can make the water less desirable for other 

 uses and the fertilizer or nutrient portions are sometimes impli- 

 cated in stimulating nuisance growths of algae and other aquatic 

 plants. These aquatic growths in an enriched stream can cause 

 severe fluctuations in dissolved oxygen concentrations and can 

 interfere with other legitimate uses. 



Table IV.5.5 summarizes municipal waste discharge volumes into 

 the biophysical regions. While the Middle Atlantic region has by far 

 the largest volume of municipal waste discharge, the potential impact 

 on the estuarine zone is greatest in both the Pacific Southwest and in 

 the Pacific islands because of the small estuarine water areas in these 

 two regions. This potential impact is lessened by the ability to use deep 

 ocean outfalls, an approach made practicable by the narrow Conti- 

 nental Shelf in these regions. 



TABLE IV.5.5— MUNICIPAL WASTE DISCHARGES IN THE ESTUARINE ZONE 



Biophysical region 



North Atlantic 



Middle Atlantic 



Chesapeake Bay _ _ 



South Atlantic ._. 



Caribbean 



Gulf of Mexico.-- _ 



Pacific Southwest 



Pacific Northwest 



Alaska - --- 



Pacific Islands (Hawaii only) - - 



Total - - -, 8,300 50 180,000 



^ Based on 150 gallons per capita per day of total population in standard metropolitan statistical areas, 1965. 

 2 Data from USDI, FWPCA, "Cost of Clean Water, 1969." 

 ^ Not available. 



