THE AQUARIUM BUILDING 



21 



to five days and is at best haphazard. Sodium thiosul- 

 fate (0.05 gms. per gallon of water for 7 p.p.m. chlo- 

 rine) is widely used for chlorine removal but it fre- 

 quently breaks down and results in a drastic drop in 

 pH. If sodium thiosulfate is used, overtreatment must 

 be avoided and calcium carbonate should also be 

 added. A number of commercial chlorine-neutralizing 

 preparations are also available but are much more 

 expensive than thiosulfate. 



SILT turbidity: Water from lakes and streams 

 is frequently very turbid. This problem can be over- 

 come by use of a sand filter ( Figure 2 ) . The principal 

 requirements are a bed of sand and a back-flushing sys- 



tem. 



FLOAT SWITCH FOR PUMP SUPPLY OR 

 FLOAT VALVE FOR ORAVITY SUPPLY.. 



APPROXIMXTE R/TE OP PILTR/(noi4 

 2&RM.PER SaFOOT 



-.2 FT 8 AND.;' 



\o,i X nuu.: 



'/IFT^FlfJE GRAVEL 



BACKFUISHING REQUtREMCNTSt 

 ISeeM. PER SO. FOOT 

 40-60 BS.L 



BACK-FLUSH 

 CONNECTION 



z 



SQUARE HOLLOW / 

 CLAY TILES i-Z' STEEL 



PIPE 



2. Sand filter for removal of silt and other fine matter. 



