Results of Coliform Tests

Unit 7 Exercise 2: 

  • To determine Q value: Match up the number of coliform colonies identified in the water sample to the graph next to the data table. (Estimation is okay).
  • For water quality description: Once you determine the Q value, use table 1 to obtain a water quality description. 
  • For EPA Standard: The United States Environmental Protection Agency (EPA) standard for drinking water is ZERO coliform bacteria. Type YES if locations meet the EPA standard for coliform bacteria; NO if locations DO NOT meet the EPA standard for coliform bacteria (Hint: 0 colonies = Yes; 1 or more colonies = No)
Q Value RangeWater Quality Description

 Water Quality can be determined by many other methods. We use this Water Quality Index for some other tests.   

Data Sheet: Results of Coliform tests                                                                                  Q-Value Graph               Table 1. Water Quality
Location of Water Sample# COLIFORM ColoniesQ ValueWater Quality DescriptionMeets EPA Standard?
Example     Tap Water0 coliform colonies100Excellent Yes
Fish Tank 
Santa Clara River – Valencia side 
Gilbert, AZ Riparian Preserve 
Bottled Water 
Ocean – Oxnard, CA 
Santa Clara River 12/26 
Riverside Pond (treated) 
Whitney Canyon