What Is Turbidity in Water? Causes, Measurement & Treatment Methods

Water quality is influenced by many factors, and the presence of suspended particles is one of them. These particles can make the water turbid, which means it appears cloudy or slightly opaque due to the scattered particles of various types depending on the source. While visual observation can indicate that a change has occurred, it cannot provide a precise measure of turbidity.

For this reason, water turbidity measurement unit is an important part of monitoring water quality across drinking water, wastewater, and industrial applications. Measuring turbidity helps operators assess water conditions, monitor treatment performance, and identify changes that may require attention. Depending on the application, turbidity can be measured using portable meters for field testing or inline instruments for continuous monitoring.

What Causes Turbidity in Water?

The sources of turbidity can vary depending on where the water comes from and how it is treated or handled. Common sources include:

• Soil, clay, and sediment: Erosion, runoff, and disturbance of soil can introduce fine particles into surface water and other water sources.
• Organic matter and microorganisms: Algae, bacteria, and decomposing organic material can contribute to turbidity, particularly in natural water sources.
• Water treatment processes: Inadequate coagulation, flocculation, sedimentation, or filtration can allow more suspended particles to remain in treated water.
• Distribution systems: Changes in flow or pressure, maintenance work, and deposits within pipelines can temporarily increase the turbidity of tap water.
• Industrial and process activities: Manufacturing and other industrial operations may introduce suspended solids into process water or wastewater.

The concentration and characteristics of these particles can vary considerably. As a result, high turbidity in water can occur for different reasons, making measurement important for identifying changes in water quality and evaluating treatment performance.

Why Turbidity Monitoring Matters in Various Stages of Water Treatment?

Water quality can change as water moves through a treatment system, and hence turbidity needs to be monitored at different stages of the process. Regular water turbidity measurement unit provides operators with measurable information about changes in water quality and helps them determine whether treatment processes are working as intended.

Turbidity monitoring can be useful at several points throughout water treatment:

• Source water: Measuring turbidity in incoming water helps identify changes in the quality of the water entering the treatment system. Variations in turbidity may require adjustments to downstream treatment processes.
• Coagulation and sedimentation: Turbidity measurements help determine whether these treatment stages are effectively removing suspended particles from the water before it moves to filtration.
• Filtration: Monitoring turbidity after filtration provides an indication of filter performance. An unexpected increase in turbidity may indicate that the filter requires attention or that particles are passing through the filtration stage.
• Before disinfection: Turbidity is commonly monitored before disinfection because suspended particles can interfere with the effectiveness of some disinfection processes. Maintaining appropriate water clarity therefore supports effective downstream treatment.
• Finished water: Measuring turbidity in treated water provides a quantitative check on the quality of the water leaving the treatment process. This is particularly relevant when monitoring drinking water turbidity and confirming consistent treatment performance.

Distribution: Monitoring turbidity can also help identify changes after treatment, including those associated with changes in flow, pressure, maintenance activities, or disturbances within the distribution system.

What Affects the Accuracy of Turbidity Measurement Unit?

Accurate turbidity measurement depends on various factors more than the instrument itself. Following common factors can also affect measurement accuracy:

• Sample handling: Mixing, transferring, or shaking a sample can change the distribution of particles in the water and affect the measurement.
• Air bubbles: Bubbles can scatter light and produce artificially high turbidity readings. Hence, samples should be handled carefully to minimize trapped air.
• Particle settling: Larger or heavier particles may settle before the measurement is taken, resulting in a reading that does not represent the original sample.
• Cleanliness of the sample cell: Dirt, fingerprints, scratches, or residue on the measurement cell can interfere with the optical measurement.
• Sensor fouling: For inline instruments, deposits or buildup on optical surfaces can affect the amount of light reaching the detector and influence the reading.
• Improper calibration: Incorrect calibration, unsuitable calibration standards, or failure to follow the manufacturer's calibration procedure can result in inaccurate turbidity readings.
• Measurement range: The instrument should be suitable for the expected turbidity range. Using equipment outside its intended range can affect the reliability of the result.
• Flow conditions: For inline measurements, changes in flow conditions, bubbles, or an unsuitable installation can affect the measurement and should be considered during installation and operation.

Choosing the Right Turbidity Meter for Your Application

Selecting the right turbidity meter depends on the application, expected turbidity range, and monitoring requirements. Consider the following factors:

• Measurement range: Choose an instrument that covers the expected turbidity level. Use higher-range sensors for water with greater particle loading and ultra-low turbidity sensors where small changes in clear water need to be detected.
• Measurement format: Select portable meters for routine field testing and inline sensors or analyzers for continuous monitoring at specific points in a treatment or process system.
• Application: Select equipment based on whether you are monitoring drinking water, process water, wastewater, or another application, as water conditions and measurement requirements can vary.
• Measurement standard: Verify if the instrument uses the appropriate measurement method or standard, such as EPA 180.1 or ISO 7027, for the application.
• Connectivity and data needs: Look for features such as 4–20 mA output, RS-485/Modbus communication, data logging, and remote monitoring when turbidity data needs to be integrated into a control or monitoring system.
• Calibration and maintenance: Choose equipment that supports appropriate calibration procedures and allows practical cleaning and maintenance of the optical components.

How Is Turbidity in Water Reduced or Treated?

The treatment method used to reduce turbidity depends on the source and characteristics of the particles present in the water. Depending on the application, water treatment systems may use one or more processes to remove suspended and colloidal particles.

Common turbidity treatment methods include:

• Coagulation and flocculation: Coagulants are added to destabilize fine suspended and colloidal particles. During flocculation, these particles combine to form larger aggregates called flocs, which can be removed more easily in subsequent treatment stages.
• Sedimentation: After coagulation and flocculation, the water is held under controlled conditions to allow the formed flocs and other heavier suspended particles to settle by gravity. The clarified water can then move to the next treatment stage.
• Cartridge and Sediment Filtration: Cartridge and sediment filters can remove suspended particles that contribute to turbidity. They may be used as pretreatment to reduce the particle load before other treatment processes or as a polishing step to remove residual fine solids. Selecting an appropriate filter type and micron rating can improve water clarity and help maintain consistent turbidity levels.
• Centrifugal Separation: Centrifugal separation can reduce turbidity by removing heavier suspended solids such as grit, sand, and other dense particles. It is most effective when the particles have sufficient density and size for centrifugal separation. Removing these solids upstream can reduce the particle load entering subsequent treatment processes.
• Emulsion Breaking: Emulsion breaking can help reduce turbidity in wastewater containing finely dispersed oil droplets that make the water appear cloudy. By destabilizing stable oil-water emulsions, the droplets can coalesce and separate more readily, allowing subsequent separation processes to reduce turbidity associated with dispersed oil.
• Membrane filtration: Membrane processes use a semi-permeable barrier to separate particles and other contaminants from water. Depending on the membrane type and operating conditions, membrane filtration can remove very fine particles and provide a higher level of turbidity reduction.

Find the Right Turbidity Meters at Cannon Water Technology

The right measurement solution can help you obtain dependable data for your specific water-quality application. Whether you are evaluating drinking water turbidity, turbidity of tap water, or turbidity in an industrial process, selecting equipment suited to the measurement conditions is essential. Cannon Water Technology offers a range of filtration and water treatment solutions to reduce turbidity and various other parameters.