3-91 



Changes in Dissolved Oxygen Concentration 



The solubility of oxygen in sea water is a function of temp- 

 erature), salinity and |iressurc. Solubility dexrrcascs with ijicrcasiuq 

 temi'craturc and salinity, but increases with increasing prc.-.ssure. 



The New Haven Harbor Generating Station changes the oxygen 

 solubility by mixing water properties at intake and increasing the 

 temperature of the water by 15 F. The effect that the change in solu- 

 bility has on the actual amount of dissolved oxygen contained in the 

 harbor waters depends on the percent saturation of the discharged water 

 and the pressure. When water with a percent saturation over 100% reaches 

 depths where the pressure is not great enough to keep the oxygen dis- 

 solved, oxygen may bubble out and be lost to the atmosphere. The poten- 

 tial for this occurrence in New Haven Harbor can be demonstrated for 

 winter conditions. 



Table 3-7 gives the properties of a hypothetical water column 

 which are typical of that at Station 4 during the winter. The dissolved 

 oxygen content of the water was determined by assuming 100% saturation. 



If the water column was quickly and completely mixed at the 

 intake to the generating station, the water would have a temperature of 

 1.9 C, a salinity of 17.6 ppt, and a dissolved oxygen concentration of 

 12.2 mg/1. At the discharge, the temperature of the water would'be 10.2 C. 

 The solubility of oxygen in water of 10.2 C and 17.6 ppt is 6.87 ml/1 

 (9.8 mg/1 at 1 atm) , thus the percent saturation of the discharge is 

 124%. The 12.2 mg/1 of oxygen does not have a volume of 6.87 ml/1 until 

 it reaches a depth of 4 m below the surface, by which time it has been 

 mixed with the ambient water in a ratio of approximately 3 to 1. 

 Ass\iming that the ambient water in the region of the discharge has a 

 salinity of 24 ppt, a temperature of 3 C, and is 100% saturated with 

 dissolved oxygen (concentration of 11.3 mg/1), the plume water at the 



The percent saturation of oxygen in sea water is defined as one hundred 

 times the observed concentration of dissolved oxygen divided by its 

 solubility in water at the same temperature and salinity under a 

 pressure of 1 atm. 



