The importance of monitoring the conductivity of your water lies in identifying sudden changes in concentration of various dissolved materials in the water. An unexpected increase in organic compounds may be an indicator of a problem with your influent.
How can conductivity help identify sudden changes?
Because conductivity in a water body is generally stable, sudden changes in it represent an abnormality in its total dissolved solids (TDS) concentration. This may indicate a breakage or an unusual spill.
In water, conductivity is the concentration of charged cation and anion ions that allow the transport of electrical charges. For this reason, ultrapure water, which is free of polyvalent and monovalent ions, is generally referred to as having a resistivity level rather than a conductivity level. In other words, the absence of ions in water can block the transfer of electrical energy since they act as conductors for energy transfer.
It is important to note that some organic compounds are not good conductors. This means that a high concentration of these compounds, oil for example, does not greatly affect the conductivity of water. In addition, the temperature of water significantly affects its conductivity; an increase in temperature is proportional to its conductivity since heat accelerates the reactions of ions.
Understanding and measuring the conductivity of water?
First, to measure the conductivity of water, it is important to have access to a conductivity meter. Although there are several different models, they work in a similar way. Generally, to operate, conductivity meters apply an alternating current between two electrodes contained in the conductivity cell. While the anions move to the positive electrode, the cations move to the negative electrode. This allows the instrument to calculate the ion concentration in the sample being tested.
The unit of measurement used to express the conductivity of a water sample is Siemens per centimeter (S/cm) or microsiemens per centimeter (µs/cm). The expression µs/cm can be expressed in ppm to make it easier to understand. In fact, some conductivity meters calculate this automatically. To put things in perspective, a microsiemens represents the electrical conductivity equal to 1/1,000,000 of Siemens.
The Siemens is a unit of measurement in the international system of units. When expressed in terms of alternating current, the Siemens represents the reciprocal relationship between impedance and ohms. Whereas for direct current, the Siemens represents the reciprocal relationship between resistance and ohms.
To summarize
Conductivity in water represents its ability to transfer electrical energy through the ions in it. Expressed in microsiemens and being an indicator of the concentration of total dissolved solids present in a water sample, conductivity is a key parameter in identifying the proper functioning of a system.