-12 — 



lU 



BCD OF SUSPENDED MATTER AND ALGAE 



BOD OF SOLUBLE MATTER 



EXCESS D.O. PRODUCED IN CONTINUOUS LIGHT 



1. SAMPLE AS RECEIVED; INCUBATED IN DARK 



2. SAMPLE CENTRIFUGED; INCUBATED IN DARK 



3. SAMPLE AS RECEIVED; INCUBATED IN LIGHT 



6 

 TIME 



8 

 DAYS 



lU 



EFFECT OF NATURALLY OCCURRING PHYTOPLANKTON ON RATE OF 



OXIDATION IN A FOX RIVER SAMPLE 



STATI ON C. JULY 25. 195G 



Fiqure 6 

 Modified from Wisniewski, 1958 



volume, or some other expression. Toward this 

 end the Sanitary Engineering Center is continuing 

 to study photosynthetic oxygen production in rivers 

 and sewage stabilization ponds and also is co- 

 operating with the Tennessee Valley Authority on 

 similar studies on rivers immediately below large 

 impoundments . 



Costs of Dissolved Oxygen 

 from Algal Photosynthesis 



Oxygen production by algae is not a free ben- 

 efit to the aquatic habitat. At times, in fact, it is 



probable that the benefits do not outweigh the 

 costs . 



Stimulation of algal production by nutrients 

 derived from sewage, other organic wastes, and 

 their decomposition products can lead to formation 

 of a mass of organic matter greater than that of the 

 original waste (Renn, 1954) . This result is demon- 

 strable in the laboratory. It was also observed by 

 Renn at two study stations on the Potomac River 

 that, during the bright light period, rise and fall of 

 B.O.D. concentrations were parallel with rise and 

 fall of dissolved oxygen. This observation was 

 interpreted to indicate accelerated production of 

 algae that became a part of the total B.O.D. 



62 



