03/08/2022 | Industrial Water Treatment | 9 MINUTE READ

Conducting Water Analysis with Sensors in Water Treatment Plants

aeration wastewater treatment tanks

Water analysis is a core component in many different industrial settings, the primary of which are water treatment plants. In many cases, industrial processes require precise water quality control, which makes it necessary to conduct regular water analysis. The only way to obtain a quality water supply is to first determine what the current water quality is. The right water equipment and instrumentation allow you to monitor everything from nitrate content to organic carbon content. Once you have the necessary measurements, you will be able to treat the water and get rid of any contaminants that are found within.

Industrial facilities use water analysis for numerous applications. Along with making sure that the water is distilled enough for various processes, it’s also necessary to perform water analysis when treating wastewater. During such industrial processes as dairy processing, power generation, mining, food production, and chemical production, an ample amount of wastewater will be produced. The EPA requires a majority of industries to treat any wastewater they produce on site before the water is discharged into a sewer or river.

The only issue with treating wastewater is that the exact treatment you use depends on the types and amounts of contaminants that are present in the water. It’s possible to properly identify contaminant levels with water analysis tools, which include everything from pH sensors to conductivity sensors. The following takes an in-depth look at how to conduct water analysis and the different sensors you can use.

Water treatment plant

Water Analysis and the Effects on Industrial & Environmental Systems

Water analysis is essential for industrial settings of all types. Many industrial processes require water to be either fully purified or nearly free of contaminants. Performing water analysis on a consistent basis provides these facilities with the ability to determine if the water needs to be treated and the amount of treatment that needs to be performed.

Nearly every facility must also contend with water quality standards that will need to be met before wastewater can be reused or discharged into the environment. The methods of treatment that are commonly used to get rid of contaminants include neutralization, precipitation, and chemical immobilization. If an industrial facility discharges wastewater without properly treating it, they could be fined or face severe penalties by the EPA and similar agencies.

No matter the reason for analyzing the quality of water, it’s necessary to have the appropriate tools for precise measurements. If the sensor that you use is even slightly off, the treatment you deploy to rid the water of contaminants may not produce the results you’re looking for.

Keep in mind that effectively analyzing water can also be highly beneficial when it comes to the industrial systems that you use. The systems that are used in everything from smelting facility to food production facilities could begin to worsen in efficacy if your facility is using contaminated water. For instance, scale buildup can occur in boilers and similar systems if water doesn’t have the right balance. The development of scale can lead to worse system efficiency, which will increase your operational costs until the scale has been removed and the water properly treated.

Since a lack of water analysis can cause system efficiency to worsen and costs to increase, it’s common for efficiency to improve and costs to be reduced when water analysis is performed on a regular basis. Conducting water analysis is also highly beneficial to the environment since you’ll be able to effectively treat the water before it gets sent out into the environment. When water contains ample amounts of contaminants, it can damage the environment substantially.

Chemical analysis

Measuring Physical Properties in Water Analysis

Measuring the physical properties of water is an integral aspect of water analysis that allows water treatment plants to identify contaminant concentration and determine the next steps that should be used to rid the water of contaminants and reach the accepted EPA levels for water reuse or drinking water. There are many different measurements that can be taken with the appropriate water sensor, which include everything from oxidation reduction potential to conductivity.


The pH of water is a basic measurement that’s used to identify how acidic or alkaline a sample of water is. When making this measurement, it’s possible to receive readings that range from 0-14. Anything below 7.0 is considered to be acidic, while any measurement above 7.0 is known to be alkaline. Filtered water typically has a pH of 6.5-7.5. If water contains a considerable number of contaminants, it’s likely that the water is acidic, which means that treatment would be necessary.

A pH sensor provides water treatment plants with a quick pH reading, after which the plant can take the necessary steps to treat the water. This sensor will likely be used again once treatment has been applied. These measurements are commonly used in environmental monitoring, odor scrubbers, water pre-treatment, and cooling tower control.

Oxidation Reduction Potential (ORP)

Oxidation reduction potential measures the ability that a molecule has to reduce or oxidize another molecule. Reduction refers to the gain of electrons, while oxidation refers to the overall loss of electrons. When you use an ORP sensor, this particular measurement is displayed in millivolts. A reducer will have a negative ORP value. On the other hand, an oxidizer will have a positive ORP value.

ORP measurements have proven to be a cost-effective technique to monitor ozone disinfection or chlorine disinfection. When a wastewater treatment plant is trying to determine if their treatment methods are effective, an ORP sensor can provide them with the answer they seek.


Conductivity refers to the ability that water has to conduct an electric current. This measurement is displayed as micro-Siemens per centimeter. Many industrial facilities have begun to use total dissolved solids (TDS) to determine the contaminant levels of a solution. TDS is shown as PPM and can be calculated with a conductivity sensor. When the TDS readings are high, this indicates that the water is contaminated, which means that it’s highly conductive. On the other hand, purified water is a poor conductor of electricity.


As mentioned previously, alkalinity is a pH reading that shows if the water is able to resist acidification. While it’s usually better for water to be alkaline as opposed to acidic, high alkalinity can be dangerous for drinking water. Toothpaste can have alkalinity readings of 8-9. In comparison, household bleach has alkalinity readings of 12-13. While pH readings in water treatment plants are typically more acidic, highly alkaline water must also be treated to ensure that the water doesn’t damage the environment.


Turbidity is the measurement of the clarity of water. If high levels of dissolved particles can be found in a sample of water, light will be scattered, which is what makes the water appear to be cloudy or hazy. High turbidity readings indicate that the water needs to be treated before reuse. If the turbidity readings are low, the water should be practically clear. It’s possible to measure turbidity with a turbidity tube or an electronic turbidity meter.

Measuring Organic Properties in Water Analysis

It’s relatively common for water treatment plants to measure organic properties while performing water analysis. These properties include everything from dissolved oxygen to biological oxygen demand.

Dissolved Oxygen

Dissolved oxygen is the total amount of oxygen that has been dissolved in a sample of water. Oxygen can get into water as a result of plants producing waste via photosynthesis, aeration, or diffusion with surrounding air. The DO levels of water are most important for aquaculture reasons. If the DO levels drop too low, the fish in the water won’t have access to the oxygen they need to survive, which means that a lack of dissolved oxygen could result in many of the fish dying.

In water treatment plants, bacteria is used to decompose any solids in the water. In the event that the DO levels are low, this indicates that the beneficial bacteria will die off, which means that the decomposition process will stop. High DO levels mean that energy is being wasted. By monitoring DO content with a dissolved oxygen sensor, the water treatment facility will be able to determine if additional oxygen needs to be added to the water to facilitate more effective treatments.

Biological Oxygen Demand

Another reading that’s tied into dissolved oxygen is biological oxygen demand (BOD). This kind of measurement tells you how much oxygen bacteria and other microorganisms consume during the decomposition process. If you want to identify if your water treatment solutions are working as intended, biological oxygen demand readings should be used in conjunction with the dissolved oxygen readings you obtain.

Biological oxygen demand is obtained by measuring how DO levels differ throughout a five-day period. Higher readings indicate that there isn’t enough dissolved oxygen in the water, which means that the water continues to be contaminated. You can be confident that your water treatment was effective if your BOD readings are low. This means that the bacteria in the water no longer requires dissolved oxygen since there are hardly any contaminants that need to be decomposed.

Future Considerations for Water Analysis

Water analysis is and will continue to be important to the water treatment industry as well as a wide range of additional industries and applications. When you perform water analysis, it’s possible to measure everything from the pH of water to the conductivity of water. These readings will give you the information you need to identify if additional treatment is necessary or if the water is distilled enough to be used reused or sent into the environment. Make sure that you have the right sensors at your disposal if you want to conduct water analysis that provides you with accurate readings.

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Posted by Dominic O'Donnell on March 8, 2022

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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