What microorganisms are in water?

CYSTS: Every water system should remove protozoan cysts since they are present in most waer sources. Their relatively large size makes them easy to filter but their protective shell strongly resist chemical treatment. Example: Giardia, Cryptosporidium

BACTERIA: Bacteria is a common threat in untreated water. Most quality water microfilters remove bacteria from outdoor water.

VIRUSES: Viruses are the least common microorganism in outdoor water, however thay can also be a serious health risk. Viruses are typically too small to be removed by a water microfilter.

What microorganisms are in water?
What microorganisms are in water?