MadSci Network: Environment & Ecology

Re: What organismslive in our drinking water? How do you identify them?

Date: Tue Dec 19 16:51:55 2000
Posted By: Steven Korenstein, Grad student, Environmental/Occupational Health, Cal. State Un. Northridge
Area of science: Environment & Ecology
ID: 977162331.En


Your question asks what type of organisms live in drinking water.  The 
answer really depends. Water that is not treated before it is sent to 
peoples houses can have all sorts of microrganisms in it.  Such as 
bacteria, viruses, protozoans ,worms and algae.  Some of these can be seem 
with a regular microscope. Usually the treatment process removes the larger 
organisms like the worms , the protozoans and the algae and we won't see 
them in drinking water.  The drinking water in most cities in the United 
States goes through a process (called treatment) that removes almost all of 
the micro-organisms that can make us sick.  But, it is impossible to get 
every single cell out of the water.  Usually there are still some bacteria 
left over, even after it is treated.  Since there are so few bacteria in 
drinking water and since they are so small, it is very hard to see them 
under a regular microscope.  Usually, to tell if there are any bacteria in 
drinking water, we have to try to grow them so there are enough for us to 
see.  We can do this by putting a sample of the water onto a jell-o like 
substance called agar.  If there are any bacteria in the water, they will 
eat the jell-o and reproduce themselves until there are millions and 
millions more then in the water.  When there are so many, we can see them 
with just our eyes.  We can tell what type of bacteria they are by the 
diffect colors they make on the agar, and sometimes by using different 
types of agar.  There are many kinds of bacteria that we might find.  Water 
testers usually look for a group called Coliform Bacteria, because some of 
them can make us sick.

Good Luck

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