What is Turbidity? Turbidity Meters & How They Work

In this blog, we will:

• Explain what turbidity means
• Why turbidity matters in environmental and water testing
• Give you expert insight into the best practices for accurate and repeatable measurement readings

Turbidity plays a key role in tracking ecosystem health, spotting microbial contamination, and identifying protein clumping. Understanding how it’s measured and applying the right best practices makes it easier to catch these issues early.  

Water treatment is one of the clearest examples. Turbidity meters give operators greater confidence in the quality of treated water and can provide early warning of filter breakthroughs, well before problems become visible.

But it’s not just water treatment; those working in laboratory environments face their own turbidity challenges too. Let’s get started.

What is Turbidity?

Turbidity means the level of cloudiness in water. This cloudiness is typically caused by particles that get into the water system. Each of these particles is then suspended in the water and often too small to be seen. If there are multiple particles, such as oil, proteins, bacteria, or dirt, in large numbers, they can make water appear cloudy.

Why Does Turbidity Matter in Water & Environmental Testing? 

Turbidity is a critical measurement for professionals in environmental testing and laboratory work, with implications spanning public safety, ecological impact, and industrial process control.

We’ve broken down the importance of turbidity across each profession for you, from environmental testing to laboratories.

Environmental Testing

Monitoring turbidity is vital for environmental stewardship and safeguarding water quality. Key areas of impact include:

• Ecosystem Health: Excessive turbidity blocks sunlight, hindering photosynthesis and reducing the food and oxygen aquatic life depends on. 
• Water Temperature: Suspended particles absorb heat, warming the water and reducing the oxygen levels critical for aquatic life.
• Runoff Management: Storms and construction runoff often introduce sediment, creating spikes in turbidity that need to be monitored.

Laboratory Testing

For laboratory testing, measuring turbidity levels provides critical insight into sample purity, reaction progress, and quality control across various applications. 

• Measuring Cell Growth: Life sciences researchers use optical density and turbidity to monitor bacterial and cell growth in liquid cultures.
• Checking Purity: Laboratories measure sample cloudiness to detect microbial contamination or protein aggregation early.
• Purging Groundwater Wells: Environmental labs verify low-turbidity conditions during well purging to ensure representative groundwater sampling.

How to Choose a Turbidity Meter?

Choosing the right turbidity meter for your needs depends on your application and range, your calibration and regulatory standards, and your operational setup. Choosing the wrong turbidity meter can lead to inaccurate data, regulatory compliance failures, and higher operational costs.

To support your choice, we’ve broken it down into three main factors.

Determine Application & Range

Depending on your application, you’ll want to choose a turbidity meter that suits your challenges.

For example, if you are working with drinking water or clean water compliance, you need a turbidity meter that monitors White Light (Tungsten). While this method offers high sensitivity to small particles, it can be easily skewed by sample colour. 

For precise measurements in the Low Range (0 to 10 NTU), you will specifically require high-sensitivity Nephelometric (90-degree) detection.

For industrial processes and chemical blends, consider using meters that handle high turbidity and sample tinting better than standard models by utilizing multiple detectors.

Use attenuation-based detection, reported in FAU (Formazin Attenuation Units), to prioritize concentration sensitivity, or ratio-based detection, reported in NTRU (Nephelometric Turbidity Ratio Units), to correct for sample colour.

But how does this affect your choice of regulatory standards depending on your process?

Identify The Regulatory Standards Required For Each Process

For industrial processes, standards are often plant-specific or process-driven. 

Unlike clean water compliance, which must strictly adhere to external guidelines such as EPA Method 180.1, industrial applications frequently rely on customized internal or proprietary quality control criteria. 

These tailored benchmarks ensure product consistency, maintain operational efficiency, and address the specific chemical characteristics or production requirements of the facility.

Choose Operational Setup

When making your decision, consider where and how the meter will be deployed.

For applications requiring maximum regulatory precision, benchtop or laboratory units are ideal because they minimize vibration-induced measurement errors.

In contrast, field technicians, such as those conducting environmental testing, often rely on sealed calibration standards to maintain and verify accuracy on site.

After defining your turbidity meter specifications and standards, review our recommended best practices to ensure consistent and accurate measurements.

Best Practices for Accurate & Repeatable Readings

To achieve accurate, repeatable turbidity measurements, you must manage the optical environment of the sample. Turbidimeters measure scattered light; minor imperfections such as dust, fingerprints, or tiny air bubbles can skew your turbidity reading.

We want to ensure that you are getting the most accurate and repeatable readings; that’s why we’ve compiled our tips for good practices below.

Sample Collection & Preparation

To ensure accurate and repeatable measurements, start by eliminating microbubbles, as tiny air bubbles can reflect light and artificially spike your readings. Avoid condensation or fogging by ensuring your sample is at ambient temperature; cold water in a warm room creates moisture on the outside of the glass that blinds the meter. 

Finally, mix your sample gently but thoroughly by inverting the container several times to resuspend any settled solids, and be sure to read your results immediately.

Vial & Glassware Care

Take care of the glass sample vial as it’s part of the meter's optical path. Avoid scratches and keep vials clean. To ensure there is no cross-contamination that can lead to inaccurate readings, you should index your vials. 

Instrument Operation & Environment

Maintaining an optimal operational environment requires consistent daily verification, physical stability, and light control. Start each shift by verifying calibration against a secondary standard; if the measurement strays beyond a ±5% tolerance range, perform a full recalibration. 

Next, ensure your instrument is set up for stability by placing laboratory and benchtop meters on heavy, vibration-isolated surfaces well away from centrifuges, pumps, or shakers, as physical movement ripples the sample surface and causes display fluctuations. 

Finally, make sure the sample compartment lid closes tightly to completely block ambient room light or direct sunlight from interfering with internal photodetectors and corrupting your readings.

Read: How Accurate is an Analytical Balance? Understanding Uncertainty

Turbidity Measurements Made Easy

Now that you have the information, you can implement our advice and get accurate, reliable data. Our collection of turbidity meters includes advanced devices with dual optic paths and dual detectors from brands such as OHAUS. 

If you’re ready to explore our range of turbidity meters, you can discover more here. Or you can speak to one of our experts today.