384 Report S.A.A. Advancement of vScience. 



The effluent from the filter bed can be used for watering the 

 garden. A cubic yard of filter is required for 15 persons; where 

 the drainage from stables is taken in, it is usual to allow one horse 

 equal to five persons. 



The bacterial system is very adaptable for native compounds, 

 a great saving being effected in the annual cost, compared with the 

 pail system. 



The initial cost of an installation and drainage varies from 

 17/6 to 20/- per native; this includes drainage, building of latrine, 

 and purification works. 



In the latrine troughs containing water are provided ; two troughs 

 are allowed for a thousand boys, but six will be sufficient for four 

 thousand. These latrines are each about 22ft. 6in. long, and contain 

 6in. of standing water. At regular intervals these are flushed out 

 by a discharge of water by automatic cisterns of 100 gallons each, all 

 the contents being washed into the drains. Urinals are also provided. 

 The floors of the building are laid with granolithic pavement, which 

 can be easily washed down, so that perfect cleanliness is obtained. 



The drains conduct the sewage to the Septic Tank ; after pass- 

 ing through the tanks the effluent is distributed on to the filter beds. 

 The distribution is effected by revolving sprinklers, of which there 

 are various types on the market. Fixed sprinklers are also used, 

 which spray over the bed ; these are good when the flow is constant, 

 and sufficient head of water is obtainable. 



If the filtrate is required to be very clear, and the water returned 

 to be used over again in the latrines, it is advisable to have straining 

 beds. These are filled with sand, in which the liquid is filtered 

 through at a constant head. Any flocculent matter is thus caught, and 

 on the flow becoming too slow the bed must be drained off, and the 

 film formed on the top of the sand raked off and thrown on one 

 side. The filter will then be ready for work again. 



The working cost of this system is very small, as after the first 

 charge of water, which must be at least 15 gallons per head of 

 population, only a small amount is required per diem for freshening 

 purposes. This is often obtained from the washing out of the kitchens 

 and that used in the cooking, so that the only direct charge is the 

 pumping back of the water. 



The purification effected bv the filter in an intallation of this 

 kind is shown by the following table : — 



For the information of those who are unfamiliar with analytical 

 methods, it may be mentioned that the reduction of organic ammonia 

 in the filter, compared with the tank effluent, affords a very good 



