IOWA ACADEMY OF SCIENCES. 81 



tity of organic matter which may be present in the sewage 

 and not in a decomposing state. In order to obtain a 

 result which will indicate the action of the permanganate 

 on the organic matter that is not in a more or less decom- 

 posing state a method must be used where the conditions 

 are more favorable for the oxidizing agent, and for this 

 reason the association method is used to complete the series 

 of determinations. 



The effluent naturally is high in nitrogen as nitrates yet 

 it is not as bad as the water furnished by some shallow 

 wells and which is sometimes used for household purposes. 

 For comparison the following analysis of water from a 

 shallow well may be of interest. The analysis is from a 

 recent investigation : * 



PARTS PER MILLION. 



Free ammonia 104 



Albuminoid ammon'a _086 



Solids on evaporation 874 . 



Solids at 180° 714 . 



Solids on ignition 50g_ 



Nitrogen as nitrites 15 



Nitrogen as nitrates 40. 



Oxygen consumed in 15 minutes 64 



Oxygen consumed in 4 hours .96 



Chlorine as Chlorides 26 . 



The results of the investigation of the College Sewage 

 Plant indicates that the purification of the sewage from the 

 towns and cities by the bacterial method is possible under 

 the conditions present in the state. The fact that the 

 sewage is more concentrated than that of many other local- 

 ities does not prevent the production of an effluent which 

 will meet any reasonable standard for purity. 



»A study of a contaminated water supply. Weems and Brown. Proceedings of the 

 Iowa Academy of Sciences. Vol. 7, p. 91. 



