18 



concentration of phosphate formed a top and bottom layer of 

 moderate quantity. Silicate was highest near the bottom, low 

 in the intermediate layers, and showed a moderate concentration 

 at the surface 



From the average profiles at the three outfall areas, it 

 is apparent that there is a great increase in the concentrations 

 of the nutrients in waters surrounding sewer outfalls. The 

 distance that high values persist from the outfall appears to 

 be determined by (1) the type of effluent (or treatment), 

 (2) the mode of discharge, (3) the depth of discharge, and 

 (4) the volume of discharge » (These conditions are not neces- 

 sarily in order of importance c) Concentrations are increased 

 measurably and sometimes appreciably as far as six miles from 

 the discharge pipe. 



Dissolved Oxygen 



The dissolved oxygen concentration around the three out- 

 falls was determined on each cast made for nutrient analyses. 

 The deficiency in per cent below the saturated value (deter- 

 mined from the concurrent chlorinity and temperature) is shown 

 in Figures 8 and 9, and was prepared by interpolation from 

 data by Harvey (1954). The oxygen demand of the organic matter, 

 ammonia, and BOD in the effluent is apparent at all outfalls 

 The pattern developed by immediate oxidation is especially 

 noticeable in the oxygen profile at Whites Point on February 

 12, 1956, where the bottom waters were moved to the surface 

 by the rising effluent and the minimal value of 2.82 ml/L 

 occurred (Figure 6), Pockets critically low in oxygen have 



