Conductivity in Water Chemistry and Molecular Science

Conductivity is a basic water quality measurement that directly measures how capable water is of conducting an electrical current. This measurement is commonly used to determine what has dissolved in a sample or body of water. If conductivity readings are high, this indicates that the water is comprised of a high concentration of contaminants. Low readings mean that the water is relatively clean.

Conductivity testing is regularly used to gather data pertaining to ionic concentrations, which extend to dissolved compounds found in aqueous solutions. The standard applications that conductivity sensors are used for include identifying the concentration amounts in various solutions and water purification.

Conductivity is a highly important measurement for water chemistry as well as molecular science. This measurement tells industries and municipal facilities if the water is of sufficient quality. In fact, conductivity is one of the few measurements that gives you the ability to directly determine if water is clean enough to drink or needs to be treated.

Conductivity is typically measured as micro-Siemens per centimeter or milli-Siemens per centimeter. By gathering baseline readings, you can continuously check the quality of the water to ensure that proper conductivity levels are maintained. This article provides a closer look at conductivity and how it’s used in water chemistry.

Electrical Conductivity and Water

Water and electricity don’t usually go well together. For instance, if water gets too close to an electrical socket, the outlet would likely stop working altogether. It’s even possible for sparks to fly and cause a fire. However, pure water that is free of all contaminants is considered to be a fantastic insulator, which means that it doesn’t conduct electricity. Since there are no impurities, there aren’t any ions from which to conduct electricity.

In reality, pure water is difficult to come by since water dissolves practically anything. Whether water comes from a swimming pool or a kitchen faucet, it likely has a considerable amount of dissolved substances, chemicals, and minerals within it. These solutes dissolve in water and will cause conductivity readings to increase. Removing these chemicals through filtration will result in conductivity readings dropping.

Free Ions in Water Conduct Electricity

Water is no longer a great insulator when it begins to dissolve substances. In this scenario, free ions are created. The substances that are typically dissolved in water are salts, which are ionic compounds that consist of cations and anions. Cations are positively charged ions, while anions are negatively charged ions.

When used in a solution, these ions cancel each other out, which results in the solution being electrically neutral. If only a small concentration of ions are present in a water solution, the solution is then able to conduct electricity. For instance, putting salt into bathwater while a thunderstorm is taking place outside makes it more likely that a lightning strike would occur. Electricity invariably looks for oppositely charged ions that are present in water.

When water is comprised of a high amount of ions and solutes, the water will become a highly efficient conductor of electricity. In this scenario, an electrical current that passes through the water could ignore anything that’s in the water. If a person is standing in water that consists of high amounts of solutes and ions, they might not be in danger of electrocution in the event of a lightning strike. This is why the risk of electrocution when out at sea is relatively low.

Is Conductivity a Physical or Chemical Property?

Before you begin to measure conductivity, you might want to know if conductivity is considered to be a physical or chemical property. A physical property is one where matter is able to be observed or measured without the chemical components needing to be altered in any way. The most common examples of physical properties include:

• Molecular weight
• Volume
• Color
• Hardness
• Density
• Melting point
• Boiling point

It’s only when the chemical identity of a substance changes that a chemical property is able to be seen, which means that you must perform some kind of chemical reaction to effectively view a chemical property. The most common examples of chemical properties include:

• Flammability
• Reactivity
• Acidity
• Toxicity
• Heat of combustion

Electrical conductivity is considered to be a physical property since the identity of this substance isn’t changed. There’s no alteration of a chemical composition. All that occurs is the transmittance of energy, which could be heat or electricity.

How Does Conductivity Affect Water Quality?

Conductivity directly affects water quality by identifying the concentration of dissolved salts in the sample of water. Any inorganic chemicals in the water will also increase conductivity. When salinity levels in the water rise, the same will occur with conductivity readings. Since high salinity indicates that the water is contaminated, conductivity measurements are direct indicators of water quality.

How Do You Measure Conductivity in Water?

If you want to measure the conductivity of water, you can do so with a specific conductance measurement, which can be performed with any conductivity sensor. Specific conductance measures how well water is able to conduct electrical currents.

As touched upon previously, conductivity will increase when the concentration and mobility of ions increases. These ions come from the dissolving of compounds. They conduct electricity since they are positively or negatively charged once dissolved in water.

Which Conductivity Changes Indicate Poor Water Quality?

There are multiple different sources for conductivity changes in water quality. If these changes are substantial enough, they might point towards changes in the quality of water. If pollution is increasing in a sample of water, conductivity readings will increase while water quality drops.

Salinity

Salinity is one of the primary drivers of conductivity readings in water. If water is pure and doesn’t contain any salinity, the body of water won’t conduct electricity. Even though salinity and conductivity are highly correlated with one another, conductivity is considered to be easier to measure, which is why these measurements are used to estimate the concentration of salinity in a sample of water.

Total Dissolved Solids

Total dissolved solids are any salts, metals, or minerals that have been dissolved in water. In most cases, TDS involves inorganic salts like:

• Magnesium
• Sodium
• Potassium
• Calcium
• Chlorides
• Sulfates
• Bicarbonates

If water has a high concentration of total dissolved solids, cells may shrink, which affects the ability organisms have to move in this water. In this scenario, the organisms that are affected could sink or float well beyond their standard range.

Temperature

Temperature can also affect conductivity in water. Warmer water tends to cause the conductivity of water to increase, which means that a drop in water temperature will cause a drop in conductivity readings.

How Monitoring Conductivity Can Help Protect Water Quality

If you want to protect water quality, it’s highly recommended that you regularly monitor conductivity by performing conductivity measurements. As mentioned previously, there are numerous conductivity sensors that can provide you with precise readings. When it comes to conductivity, it’s essential that the measurements you perform are extra accurate.

If you need to make sure that the quality of water is above set parameters, inaccurate readings could result in you using water that isn’t as clean and filtered as it should be. Measuring conductivity tells you the concentration of total dissolved solids and chemicals in water. If conductivity increases, the water will contain more impurities. In this situation, there must be something that’s causing the water to worsen in quality.

There are two types of conductivity sensors at your disposal, which include contacting conductivity sensors and toroidal conductivity sensors. Both sensor types offer accurate readings. However, toroidal sensors are designed to be used in exceedingly contaminated waters. Even if the sensor becomes covered in dirt and other contaminants, it should still be operational. Conductivity toroidal sensors consist of:

• A single circuit that provides a continuous waveform within the transmission coil
• The alternating magnetic field in the transmission coil creates a voltage within the medium
• The anions and cations in the medium generate what’s known as an alternating current
• The current will then produce another current that flows within the reception coil
• The conductivity and intensity of the current increases when there are a high number of free ions present in the medium

Whether you’re testing water quality in a municipal facility or at your home, among the most effective measurements is conductivity, which gives you an accurate idea of how many contaminants are present in the water. Too many contaminants means that conductivity readings will be high. Low readings indicate that you shouldn’t have an issue with unclean water.