288 MICROBIOLOGY OF WATER AND SEWAGE 



ranging from one to five parts per million of available chlorine (25. to 

 125 pounds of bleaching powder per miUion gallons), will produce a 

 bacterial removal amounting to 98 or 99 per cent. This disinfectant 

 is the most efficient of the known germicides, cost being considered. 

 By this means it is possible to practically eUminate the bacteria, good 

 and bad, from an effluent and it is no longer necessary nor desirable 

 to seek high bacterial removals in the purification process proper. 

 By thus dividing the work of purification into its component parts 

 each part can be carried out at a maximum of efficiency and economy. 



