WATER 53 



Deep well waters when uncontaminated contain but few 

 bacilli and no B. coli or other indicator organisms. In waters of 

 this class therefore a considerable increase in the number of 

 organisms and in particular the presence of B. coli, with or with- 

 out streptococci, must indicate pollution with surface water or 

 other undesirable material and much higher standards of require- 

 ments are reasonable. It is justifiable to maintain an attitude 

 of great suspicion towards any water from such sources which 

 contains B. coli in 100 c.c. or less. 



To ascertain the precise source of contamination and to 

 measure and assess its danger often requires a very careful study 

 of topographical and geological conditions and the making of a 

 series of subsidiary bacteriological examinations. 



One important cause of bad bacteriological results from deep 

 water supplies, which it is important to eliminate or confirm at 

 the outset, is contamination of the supply at the surface outcrop. 



Frequently a spring runs some distance on the surface before 

 it is collected and utilised, and samples taken at a point on the 

 distribution side may entirely owe their bad bacteriological results 

 to surface contamination of an otherwise pure deep water supply. 



It is important to realize how frequently such surface con- 

 tamination occurs and is allowed to exist owing to the care- 

 lessness or want of knowledge on the part of those entrusted 

 with the care of the water supply. The following is a striking 

 illustration of such contamination and its influence upon the 

 bacteriological examination results. 



Samples were received in November 1912 from three separate 

 springs in connection with a proposed new water supply. All 

 three springs were from the same formation and indeed from the 

 same hill. No. 2 was satisfactory while No. I and No. 3 showed 

 evidence of contamination. A careful examination of the local 

 conditions was recommended. At first it seemed difficult to 

 account for any difference in quality since the three springs were 

 obviously coming from the same strata and in each case were 

 piped for about 100 yards from the springs, glazed open-jointed 

 earthenware pipes being used. Further examination however 

 disclosed the fact that in springs I and 3 the pipes had been 

 covered with a layer of bracken by the workmen employed 



