Performing the bacteriological tests for potable water is based on 
   research , counting and discrimination of water pollution index (Coliform) .

          In these methods doing the tests needs some preparation before  
   sampling , during sampling and during transporting the samples to
   laboratory as well as during preparation of cultivation  environment. The
   above mentioned tasks require much equipment  and different  stages  of
   cultivation  .

          In this project , the Presence-Absence  method (P-A ), which examines 
   the presence or absence of pollution index in water  is compared to the
   multiple fermentation technique , which is being used in laboratories  all
   around the country at present, also the replacement of method is
   evaluated . This project was performed  during  3 months  and  263  samples 
   were  examined  by  both  methods  .

          The results demonstrate 7.01% more  sensitivity  for  P-A  method  to  the 
   other . Comparing quality and quantity of the two methods confirms more 
   benefits  for  P-A method  .