Biotic Index Scale?
Biotic Index is a scale for showing the quality of an environment by indicating the types of organisms present in it. It is often used to assess the quality of water in rivers. It is measured from 1 to 10 and corresponds to the four basic water quality (Excellent, Good, Fair or Poor). The concept of the Biotic Index was developed by William M. Beck in an effort to provide a simple measurement of stream pollution and its effects on the biology of the stream. In this case, they would take some municipal waste, leave it in the water, and then test the water with the biotic index scale.