Home >> Science & Nature >> Science

How to Use Resistivity to Determine Microbiological Contamination

Microbes emit carbon dioxide (CO2) as they live and grow. Electrical conductivity and resistivity is a measure of a liquid̵7;s ability to conduct or resist an electric current. Electrical current is transported through water utilizing dissolved ions. Carbon dioxide can be detected at very low concentrations by using resistivity meters. As the level of CO2 increases, a correlation with microbial contamination concentration can be made.

Things You'll Need

High sensitivity resistivity/conductivity meter
Pure water
Water with three known and different microbial contamination levels
Water sample with unknown level of microbial contamination

Instructions

- 1
  Determine the baseline resistivity value of pure water. This is done using the resistivity meter in the pure water. The reading should be zero or very close to zero.
- 2
  Test the water with the first known level of microbial contamination and record that baseline. Record the reading as representative of the microbe contamination concentration. Repeat this for the other two known levels of contamination.
- 3
  Draw a graph using the three known contamination levels with concentration on the bottom axis and resistivity on the left side axis. Connect the three points to produce a curve.
- 4
  Test the unknown concentration level sample and record the resistivity. Find the value on the graph and determine the microbial contamination in the sample.

Science