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Electrical Conductivity and Water Purity

Our first environmental engineering lab was concerning one method of water quality assessment called electrical conductivity. The theory behind this technique is based on the fact that pure water is not a good conductor of electricity. As the amount of inorganic, ionic elements or compounds in the water increases, the conductivity also increases. Conductivity also increases with temperature, therefore most results are standardized at 25 degrees Celsius. With this understanding we can make comparative analysis of conductivity values to assess the purity of the water. Conductivity in this context is usually in units of microsiemens per centimeter. In the lab we utilized a handheld electrical conductivity meter like the one above. Below is a table we were given of the typical value range found in different types of water.

The reason for the high conductivity in seawater is the high salt content and thus a high number of sodium and chloride ions in this aqueous solution. If you are interested in additional information, I found a good EPA website concerning water quality monitoring and electrical conductivity.