3o6 



SEWAGE AND ITS PURIFICATION 



n 



discharging on alternate sides when the hquid reaches a level 



which upsets their equilibrium. 



- Farrer's Automatic 



5 Distributor (Figs. 54, 



55, 56) is mainly suit- 

 able for smaller instal- 

 lations ; the largest at 

 present is on a bed 32 

 by 20 ft. Septic effluent 

 is discharged into a 

 tipper which supplies 

 distributing channels on 

 the beds, whence it 

 flows along troughs per- 

 forated on the lower 

 sides ; these being made 

 with a concave bottom, 

 clear themselves readily. 

 The maximum head re- 

 quired is stated to be 

 14" for small installa- 

 tions, increasing for 

 larger ones on account 

 of the section of the 

 tipper varying with the 

 greater volume. Con- 

 verging shoes under- 

 neath the tipper cause 

 equal quantities of 

 sewage to pass along 

 each distributing 



TIPPED 



P 



§ 



channel. 



Continuous and in- 

 termittent filtration, 

 % apart from the differ- 



-* ences between the re- 



J suits obtained, present 



a contrast both in the 

 mechanical arrangements and in the bacterial process itself 



In the case of contact beds, except when they are used in 

 series, there is no differentiation of the organisms in relation to 



