The third and final installation of the "How to Test Water Quality?" blog posts outlines the ideal microbial test for water quality and efficient substitutes that exist now. The post suggests that the most practical solution is to test for an "indicator organism" which indicates fecal contamination. Three approaches to microbial water tests are presence-absense (P-A), most probable number (MPN), and membrane filtration. This blog lists additional resources concerning water quality monitoring.