l8o PHARMACEUTICAL BACTERIOLOGY 



3. The human habitations near the supply. 



4. The source of the water. 



5. The available amount of the supply. Cubic contents, or 

 volume of flow per hour. 



6. All possible sources of contamination and the nature of the 

 contamination. 



A microscopical examination should be made of the shore and bottom 

 mud and ooze at the points of most likely contamination and a record made 

 of the microscopic flora and fauna of the shore. If the body of water 

 is small and is highly contaminated by cattle, horses, or hogs, it must be 

 abandoned for drinking purposes, or the water first purified by the use of 

 some coagulant, by filtration and by boiling. If the body of water is 

 large and the shore is contaminated by animals the water must be taken 

 from a middle point and either boiled or treated with hypochlorites, or 

 other chemicals. Samples should be taken by means of suitable sampling 

 bottles and some of the water thus collected should be centrifuged and 

 the sediment examined microscopically and the findings recorded. 



After the completion of the topographical survey, the organoleptic 

 tests, and the microscopical examination, the analyst is then in position 

 to make a definite recommendation as to what is to be done regarding 

 the water in question. His recommendations will be along the following 

 lines. 



1. Unfit for drinking purposes and impossible or impracticable to 

 render it potable. 



2. Suitable for drinking purposes in the raw state. Safe. No treat- 

 ment required. 



3. Suitable for drinking purposes, after filtering through sand filter. 



4. Suitable for drinking purposes, after coagulating and filtering. 

 Sand-alum filtration. Sedimentation and filtration. 



5. Suitable for drinking purposes after adding calcium hypochlorite. 

 Hypochlorous acid sterilization of suspicious water supplies. 



Additional methods for purifying water supplies are. 



1. The use of Pasteur-Chamberland pressure filters. These are im- 

 practicable for large volumes of water. May be applicable in homes, 

 public buildings and hospitals. 



2. Use of gravity porous clay filters and coolers. Often quite satis- 

 factory where the quantities of water used are comparatively small, as in 

 private homes, stores, schools, etc. 



3. Distilling the water. Rather impracticable for large volumes. 

 Used on board ships. 



