ALGAE IN RELATION TO OXIDATION PROCESSES IN NATURAL WATERS 



Alfred F. Bartsch 



Water Supply and Water Pollution Research 



Robert A. Taft Sanitary Engineering Center 



of the 



United States Public Health Service 



Cincinnati, Ohio 



Agencies concerned with management of water 

 quality are especially interested in the following 

 oxidation processes that occur in natural waters: 

 (a) stabilization by microorganisms of natural or in- 

 troduced organic matter, (b) respiration by the 

 aquatic biota, and (c) direct oxygen demand of 

 chemical substances. Each process to some ex- 

 tent draws upon the oxygen resources of the water 

 so that replenishment must occur to prevent serious 

 and lasting oxygen depletion. Replenishment oc- 

 curs chiefly by reaeration from the atmosphere and 

 through photosynthesis in algae and other aquatic 

 plants. As will be shown, algae are involved in 

 several ways in both the oxidation processes and 

 the broader oxygen relations in natural waters . 



Direct Algal Oxidation of Organic Matter 



Algae have direct as well as indirect effects 

 upon oxidation processes . It has been shown that 

 a number of algae are able to use organic sub- 

 stances directly for energy and growth (Samejima 

 and Meyers, 1958; Eny, 1951; Wilson and Danforth, 

 1958) . A recent summary by Saunders (1957) lists 

 32 species of phytoplankton that possess this ca- 

 pability. Also listed is a wide variety of the or- 

 ganic substances known to be used, grouped as 

 carbohydrates, aldehydes, ketones, alcohols, es- 

 ters, fatty acids, organic acids, amino acids, and 

 related compounds . 



Raw and treated sewages have not generally 

 been analyzed thoroughly for their content of or- 

 ganic compounds of the groups cited above. The 

 origin and history of domestic sewage leave little 

 doubt, however, that many if not all of these or- 

 ganics are present, along with others not men- 

 tioned. Presumably, select members of the phyto- 

 plankton in natural waters utilize some of these or- 

 ganics if they are present. When such organics in 

 polluted waters are utilized by phytoplankton, the 

 resulting reduction in their concentration would be 

 beneficial to water quality in the same sense that 

 bacterial oxidation is beneficial. In this sense the 

 phytoplankton participate directly in the oxidation 

 processes that occur in natural waters, although 

 the extent of such action has not been determined . 

 From casual observation it would appear that the 

 over-all effect of this type of algal activity upon 

 both the dissolved organics content and the 

 stream's oxygen resources would be of little con- 



sequence . The algae would be merely competing 

 with and perhaps to some extent displacing the ox- 

 idation activities of the customary assemblage of 

 heterotrophic organisms that stabilize such pol- 

 lutants . 



Shallow waste stabilization ponds are becom- 

 ing popular for treating municipal sewage and some 

 industrial wastes and have recently received con- 

 siderable study (Gotaas , Oswald andLudwig, 1954; 

 Oswald and Gotaas, 1955; Hermann and Gloyna, 1955; 

 Gloyna and Herman, 1956; Anon . , 1957; Bartsch and 

 Allum, 1957) . Successful operation depends es- 

 sentially on bacterial decomposition of the waste 

 organics and algal photosynthesis to provide dis- 

 solved oxygen for the aerobic processes. Obser- 

 vations on many sewage stabilization ponds have 

 shown that ability to reduce organic matter, as 

 measured by the B.O.D. test, is not seriously im- 

 paired during winter in spite of cold weather con- 

 ditions that generally impede biochemical proces- 

 ses . B.O.D. reduction persists at 70% or more, 

 in spite of anaerobic conditions under semiopaque 

 ice cover 9 to 30 inches thick. Undoubtedly, a 

 combination of processes makes possible this con- 

 tinued reduction . Much of the phytoplankton 

 gathers on the bottom, but appreciable quantities 

 of Scenedesmus dimorphus , S. quadricauda , 

 Chlorella sp . , Euqlena sp . , Phacus longicauda , 

 and other algae have been observed suspended in 

 the water, motile if flagellated, and obviously ac- 

 tive. With extremely low light intensity below the 

 ice, the presence and active condition of these 

 algae raise the question of heterotrophic use of or- 

 ganic substances as a contribution to the stabiliza- 

 tion performance. Interestingly, these algae are 

 still active in the prolonged absence of dissolved 

 oxygen as shown by the Winkler procedure and by 

 the presence of sulfides up to 117 ppm. Such ac- 

 tivity of Chlorella , Chlamydomonas , and Euglena 

 in the presence of hydrogen sulfide has been ob- 

 served also by Abbott (1951). The full significance 

 of these observations is not presently apparent, 

 and further study is needed to establish clearly the 

 role of algae along with other more obvious proces- 

 ses in the winter performance of waste stabiliza- 

 tion ponds . 



Along this same line, studies are in progress 

 at the Sanitary Engineering Center to determine the 

 ability of specific algae to utilize sugars in spent 

 sulfite liquor. The study was designed to explore 

 possibilities that algae may serve in treating this 



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