S54 
Purification  of  Water  Supplies. 
I  A  m.  Jour.  Pharm 
1   December,  1904. 
the  situation  was  complicated  by  the  fact  that  absolutely  no  efficient 
remedy  for  the  condition  was  known.  The  plants  responsible  for 
this  bad  odor  and  taste  in  the  water  are  for  the  most  part  confined 
to  a  group  known  as  the  Algae,  and  are  among  those  forms  popularly 
known  as  "  pond  scum,"  "  green  scum,"  etc.,  which  occur  so 
abundantly  in  stagnant  pools  during  the  warmer  months  of  the 
year.  While  in  some  instances  the  disagreeable  odor  is  due  to  the 
death  of  these  organisms  and  consequent  decomposition,  this  is  by 
no  means  the  only  way  in  which  these  plants  affect  the  water. 
Very  many  of  the  blue-green  algae,  together  with  certain  other  more 
or  less  closely  related  forms,  have  the  power  of  liberating  an  oil 
which  is  comparable  to  one  of  the  aromatic  series,  a  very  small 
quantity  being  sufficient  to  affect  a  large  amount  of  water.  The 
odor  and  taste  of  these  oils  is  variously  described  by  different  con- 
sumers, but  in  no  case  is  it  any  addition  to  a  drinking  water,  and  at 
times  the  odor  becomes  so  strong  as  to  make  it  almost  impossible  to 
use  the  water  for  sprinkling  the  streets  and  lawns,  to  say  nothing  of 
domestic  use.  Up  to  the  present  time  only  the  most  general  methods 
have  been  resorted  to  to  prevent  the  growth  of  these  algae  in 
water  supplies.  The  problem  has  been  one  which  frequently  con- 
fronted the  water  engineer,  but,  although  many  costly  experiments 
have  been  carried  on,  the  results  in  almost  every  instance  have 
failed  to  accomplish  what  was  desired.  One  of  the  favorite  recom- 
mendations made  to  water  companies  for  difficulty  with  algae  was 
to  cover  the  reservoirs.  Since  most  of  the  algae  require  light  for 
their  development,  this  was  a  very  logical  recommendation,  but 
unfortunately  the  expense  and  inconvenience  of  constructing  a 
permanent  cover  for  most  reservoirs  is  almost  prohibitive,  and  there 
have  been  very  few  water  companies  in  this  country  which  have 
even  made  the  attempt  to  exclude  the  algae  in  this  way.  Another 
precaution  which  of  late  years  has  been  almost  universally  practised 
in  endeavoring  to  keep  the  source  of  supply  and  reservoir  free  from 
algal  growth  is  to  carefully  remove  as  much  of  the  organic  matter 
as  possible,  which  will  in  time  be  in  contact  with  the  water.  Nat- 
urally, when  new  reservoirs  are  being  constructed  every  precaution 
should  be  taken  to  prevent  the  presence  of  any  more  organic  matter 
than  is  necessary,  as  this  only  serves  to  increase  the  nutritive  value 
of  the  water,  and  consequently  the  algae  flourish  more  readily.  In 
this  connection  it  should  be  borne  in  mind  that  even  though  reser- 
