78 



L. BARRIETY 



A 



C 



ilh5 i-_h2 ^EM3 



3^ drain 



Figure 1. — Filtering system — side view above, top view below : A, concrete tank ; B, filter chamber ; 

 C, storage compartment ; Z), heat exchanger ; E, centrifugal pump. 1, 2, 3, Jf, and 5 are gate 

 valves. 



device is the filter. It consists essentially 

 of a rectangular basin of reinforced con- 

 crete from which the flow may be inter- 

 rupted by means of a gate valve (1). 

 The dirty water arrives from the tank in 

 the lower compartment of the filter {B') ; 

 the abrupt loss of speed of the water, 

 which flows from the pipe into a much 

 larger vessel, causes a rapid deposition of 

 the largest impurities. The bottom is at 

 a 10-percent incline, with a gate valve {2) 

 at its lowest point; this permits easy 

 evacuation of the slush formed. From this 



lower compartment the water passes 

 through a perforated slab and reaches the 

 filter proper {h) which consists first of a 

 layer of oyster shells designed to fix the 

 nitrites, and then of beds of gravel of 

 gradually decreasing size ranging from 

 5-7 cm. to 1-1.5 cm. The water in the 

 upper part of this filter is sufficiently trans- 

 parent to be reused in the exhibition tank. 

 The water is caught once more by a 

 tube which conveys it into a last storage 

 compartment {C) where it may still lose, 

 by gravity, a few elements that might have 



