138 



Water 



superimposing local ones on the general 

 coastal current. This occurs because large 

 local discharges of warm water of low salinity 

 form lenses that float atop the sea water of 

 the shelf or mix with sea water to form 

 lenses of mixed water. The light water tends, 

 of course, to drain radially outward down the 

 sides of the lenses, but owing to Coriole's 

 force the water follows an outward spiral in 

 a clockwise direction. Chief of these sources 

 of warm dilute water are large sewage out- 

 falls. For example, when at capacity the 

 planned Hyperion outfall will discharge 

 420,000,000 gallons of Los Angeles sewage 

 per day. If the discharge were to reach 

 steady-state conditions such that one day's 

 discharge remained in a conical lense of 

 5-km radius, its thickness at the middle 

 would be 6 cm. At isostatic equilibrium the 

 center of the cone would then reach about 

 0.15 cm above normal water level. Such a 

 slope of 0.03 cm/km is large enough to pro- 

 duce a current of about 0.1 knot. Where 

 the lens is close to shore, the clockwise 

 movement of water probably tends to pile 

 water against the shore. Such an explana- 

 tion may well account for observed higher 

 bacterial counts on the beach north of the 

 old Hyperion outfall than south of it. 



The amount of heat contributed to the 

 ocean from sewage and cooling systems 

 of steam plants designed for generat- 

 ing electricity is also large, as shown by 

 Gunnerson (1956, \95Sb). The temperature 

 of the sewage is higher than that of the 

 ocean, usually by about 9°C during both 

 winter and summer. This high temperature 

 means a contribution of about 3.4 x 10' kg- 

 cal of heat per million gallons of sewage. 

 Additional heat is liberated on further oxi- 

 dation of the organic matter after it is dis- 

 charged from the outfall, amounting to about 

 6 kg-cal per gram of sewage solids. For the 

 concentration of suspended solids at Hype- 

 rion outfall, the heat of oxidation is equal to 

 about 0.6 X 10^ kg-cal per million gallons. 

 When at its capacity discharge of about 

 420,000,000 gallons per day, the heat con- 

 tributed will be (3.4 + 0.6) 10' x 420 = 

 1.7 X 10'° kg-cal/day. To this must be 

 added 2.8 x 10'° kg-cal/day from the cool- 



ing systems of the Redondo, El Segundo, 

 and Scattergood steam plants, assuming that 

 average output is 65 per cent of the rated 

 total capacity of about 2800 megawatts/day 

 (contemplated for about 1960) and that 

 cooling losses are 0.83 x lO*' kg-cal/hr/Mw. 

 The combined heating from sewage and 

 cooling systems is then 4.5 x 10'° kg-cal/day 

 in Santa Monica Bay alone. This corres- 

 ponds to the amount of solar energy falling 

 on an area of 8 sq km in a summer day. 

 Other sewage outfalls and steam plants 

 along the coast perform similar but smaller 

 contributions of heat to the ocean. 



Sewage also contains about 1000 times 

 the concentration of inorganic nitrogen and 

 phosphate present in surface sea water, 

 leading to considerable local enrichment of 

 the water. If phytoplankton could grow be- 

 fore the nutrient-rich water became diffused, 

 there would be great blooms near the out- 

 falls. Since experience in southern Cali- 

 fornia shows that this does not occur (Steven- 

 son and Grady, 1956), evidently the growth 

 rate of phytoplankton is too slow at least 

 under most conditions. Nearly all the in- 

 organic nitrogen in sewage is in the form of 

 ammonia, which slowly becomes oxidized to 

 nitrate after it is discharged from outfalls. 

 Oxidation of the ammonia and of suspended 

 organic matter tends to deplete the oxygen 

 content of the sea water receiving the sew- 

 age; however, in the open sea diffusion and 

 currents are sufficiently great to renew the 

 water before oxygen becomes exhausted. 

 Only in narrow restricted bays where waste 

 discharge is great and circulation is slow, 

 such as the inner Los Angeles Harbor, is the 

 oxygen content of the water sometimes 

 brought to zero with consequent formation 

 of hydrogen sulfide (Los Angeles-Long 

 Beach Harbor Pollution Control Committee, 

 1956). In larger bays or in areas receiving 

 relatively small amounts of wastes the oxy- 

 gen content is reduced but not brought to 

 zero; examples are San Diego Bay (Miller 

 and Nusbaum, 1952), Newport Bay (Depart- 

 ment of Fish and Game, 1953), Alamitos 

 Bay (Reish and Winter, 1954), and the 

 lower San Gabriel River (Reish, 1956). 



