34 



LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



Disposal, the National Council for Stream Improvement and the Commit- 

 tee on Water Pollution, State of Wisconsin. 



The reaeration procedure, still going on, consists of pumping air under 

 pressure through carborundum diffusers located in the head and tail races 

 of Pixley Dam. This location — 6.3 miles from the pollutional source — 

 was selected as the point where dissolved oxygen approaches depletion. 



Fig. 1. Drainage area of Flambeau river. North Fork shown in black. 



Four summers of artificial reaeration study have shown the procedure to 

 be valuable in disposing of B.O.D. more rapidly, raising dissolved oxygen 

 levels and shortening the zone of critical conditions. That was the setting 

 under which a biological study was carried out during the summer of 1946. 

 The aims were three in number: (1) to determine the responses of 

 downstream biota to the presence of pollutants tributary to the river; (2) 

 to locate the stream level or levels of biological recovery, and (3) to deter- 

 mine if artificial reaeration visibly accelerates the biological recovery. 



