86 proceedings: chemical society 



tions to stream pollution, the older scheme of sewage analysis has failed 

 to yield results commensurate with the labor involved. In place of the 

 nitrogen cycle of water chemistry we are substituting a carbon cycle with 

 special reference to the oxygen relations. The difficulty of dealing an- 

 alyticalty with the reactions that are involved in the oxidation of sewage 

 under artificial or natural conditions makes it necessary to employ indi- 

 rect methods for this purpose. 



"The oxygen requirement" of a sewage or effluent is defined as the 

 amount of oxygen which Avill be eventually consumed by the organic 

 matter when that sewage or effluent is brought into equilibrium with 

 oxygen-saturated water. The ''relative stability" of a given effluent 

 or polluted stream is similarly defined as the relation between the avail- 

 able oxygen in the mixture in the form of free dissolved oxygen, nitrites, 

 and nitrates, and the total oxygen requirement of the organic matter as 

 defined above. This establishes a practical working method for the 

 determination of the degree of purification of a sewage or of the degree 

 of pollution of a stream. 



The actual determination of relative stability is made by the use of 

 methylene blue as an indicator for the oxygen-zero point. By the appli- 

 cation of the methods of physical chemistry the reaction has been shown 

 to be of the first order and from the time required to decolorize methyl- 

 ene blue one determines the relative stability ratio. A more direct 

 and generally applicable method is the actual determination of dissolved 

 oxygen before and after a period of incubation. These data give directly 

 the velocity of the reaction and its probable future course. By the ap- 

 plication of these newer methods the study of stream pollution is being 

 placed upon a quantitative scientific basis (Author's abstract). 



Discussion: In reply to inquiries by Sullivan, Gore, S. T. Powell, 

 and Bunzel, the following points were brought out: The deficiency in 

 oxygen is the factor which harms fish in streams. The effect of sewage 

 on oysters is entirely a -hygienic, not a chemical question. "Available 

 oxygen" includes free oxygen, nitrites, and nitrates, but no other sources 

 of oxygen. Acidity ancl alkahnity also enter as factors in the rate of 

 reaction. 



Medical Director Ames, U.S.N. , who was a visitor at the meeting, 

 discussed the question of cooperation between municipal chemists and 

 sanitarians and manufacturers whose byproducts pollute streams, as 

 well as various projects for utilization of sewage. Professor Phelps 

 stated that our present knowledge of methods is in advance of our prac- 

 tice, because of the great expense of sewage disposal. The question of 

 saving the sewage for agricultural purposes was discussed by Ames, 

 Schreiner, Sullivan and Yoder. It was shown that the great dilution 

 of modern American city sewage makes it almost impossible to utilize 

 it for fertilizer, and that the concentrated sludge obtained by certain 

 methods of concentration is also not utilizable; in China the sewage is 

 very largely utilized, and in Hong Kong its disposal is a source of revenue 

 to the city. 



