BACTEKIOLOGY OF SEWAGE 239 



contact eflBuents. Septic sewage, on the other hand, 

 required large amounts of chlorine to produce a rea- 

 sonable bacterial reduction. The table on page 240 

 shows the results obtained at Marion, Ohio. 



In Germany, on the other hand, Schumacher (1905), 

 Kranepuhl (1907), and Kurpjuweit (1907) found larger 

 amounts of chlorine necessary, in the neighborhood of 

 60 parts per million parts of sewage. Their tests 

 were somewhat severe, however, the criterion of success 

 being the absence of B. coli in a large proportion of 

 liter samples. 



Standards for Sewage Effluents. The science of sew- 

 age bacteriology is in its infancy; and it is d ifficult to 

 give any general rules for the interpretation of bac- 

 teriological examinations designed to indicate whether 

 disposal plants are successful or not. Houston stated 

 provisionally that the 20° count should be under 100,000 

 and the 37° count under 10,000, while B. coli should 

 be absent from .001 c.c. and B. sporogenes from .1 c.c. 

 (Houston, 1902^). This standard seems to us far too 

 lenient. Either organic purity alone is necessary, as 

 at many sewage disposal plants, or a higher grade of 

 purity than this should be attained. It seems wisest" 

 at the present time to avoid fixing any general standards 

 of purity for sewage effluents. Each case should 

 be judged intelligently on its own merits. In general, 

 however, where bacterial purification is indicated at all, 

 it seems fair to demand that the effluent should be 

 of such a quality as not to increase materially the 

 bacterial content of the body of water into which it 

 is discharged. 



