CHAPTER VIII 

 AMOUNT OF SEWAGE PER CAPITA 



THE probable future population of the city for whose use 

 the sewers are designed being determined, it remains to assume 

 a daily sewage-flow per capita, with such variations from hour 

 to hour from the average flow as may be found to be usual. 

 The amount of sewage contributed per head per day is a 

 quantity variable in different parts of the country and in 

 different cities, depending on the variation in the water-supply, 

 and it has been customary in this country to assume that the 

 daily water-supply of a place is all converted into sewage, 

 and that a determination of the amount of sewage is made 

 when the amount of water-supply is found. This undoubtedly 

 approaches the truth, although it is more in accordance with 

 sewer-gagings to say that the hourly and daily variation in 

 flow of sewage corresponds closely to that of the water-supply, 

 while the actual amount of sewage is something less. That 

 the records show the volume of sewage always less than that 

 of the water used is partly due to the fact that the houses 

 supplied by city water-works generally exceed in number those 

 connected with the sewers. And, further, since the water- 

 connections precede the sewer-connections, there can never be, 

 as long as connections with either water- or sewer-pipes are 

 being made, an equal flow of water and sewage. Nor can there 

 be any fixed relation between the two volumes until the final 

 number of houses and buildings in a city are supplied with both 

 connections. 



Fig. 24 * shows the pumping records of the water-supply, 

 and the relation between the two volumes, at Atlantic City, 

 N. J., for the several months of the year 1892, with the water- 



* From Engineering News, Vol. XXIX, p. 124. 



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