70 IOWA ACADEMY OF SCIENCES. 



Class I. Waters of Great Organic Purity. All waters in which the oxy- 

 gen absorbed does not exceed .5 parts per million 



ClaFS II. Waters of Medium Purity. Waters in wh'ch the oxygen 

 absorbed ranges from .5 to 1.5 parts per million. 



Class III. Waters of Doubtful Purity. Waters in which the oxygen 

 absorbed ranges from 1.5 to 2.2 parts per million. 



Class IV. Impure Waters. Waters in which the oxygen absorbed exceeds 

 2.2 parts per million. 



The Michigan standard is that water should not require 

 over 2.2 parts of oxygen per million. 



It is of interest to note that some of the deep well waters 

 come within the first class of waters according to Tidy's 

 classification and the larger number within the Michigan 

 standard. The application of any standard to the sanitary 

 analysis of the deep well waters is unsatisfactory and mis- 

 leading in many ways. The most important results, that 

 of albuminoid aaimonia and nitrogen as nitrites and 

 nitrates show conclusively that the waters are not contam- 

 inated in any manner. The oxygen absorption is valuable 

 in many respects, but the other results vary to such a 

 degree that no standard can be selected which could be 

 applied to the deep well waters as can be done for the 

 waters from shallow wells. 



THE CHEMICAL COMPOSITION OF SEWAGE OF THE 

 IOWA STATE COLLEGE SEWAGE PLANT. 



BY J. B. WEEMS, J. C. BROWN AND E. C. MYERS. 



The sewage plant of the college was constructed in 1S9S 

 from the designs and under the supervision of Prof. A. 

 Marston, the co lege engineer. The plans and a short 

 description of the work of the plant have been recently 

 published* and only the chemical investigations will be 

 considered in this paper. 



♦The Iowa State College Sewage Disposal Plant and Investigations. Marston, Wcems 

 and Pammel. Proceedings Iowa Engineering Society, 1900. 



