Turbidity

Turbidity

Why Does Turbidity Matter to Water Quality?

Turbidity is a simple indicator of water quality that can be measured with turbidity meters and sensors across a variety of applications. In almost all water supplies, high levels of suspended matter are unacceptable for aesthetic reasons and can interfere with chemical and biological tests.

The ability to accurately and reliably measure turbidity is an important component of understanding water quality for the following reasons:

Whether you are in the field or the laboratory, Hach® offers a variety of turbidity analyzers, meters, and sensors to ensure easy and accurate results.

In-Line Turbidity Meters and Turbidity Sensors

Turb Online

In drinking water and some wastewater treatment plants, it’s essential to monitor turbidity continuously to keep each step of the filtration process in check and avoid costly mishaps.

Process turbidity meters are simple, low-maintenance and accurate—perfect for an environment where they’re needed to provide readings at a moment’s notice.

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Portable Turbidity Analyzers for Remote Locations

Turb Portable

Setting up a lab at a construction site or near a river after a storm would be an unnecessary hassle. That’s where portable turbidity meters are most useful.

These handheld devices are durable, simple to use and able to conduct rapid tests in the field.

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Laboratory Benchtop Turbidity Meters

Turb Benchtop

Benchtop turbidity meters are perfect for measuring grab samples and conducting an array of tests on water from multiple sources.

They’re designed to be sensitive and precise for ultraaccurate measurements in controlled lab conditions.

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Why Measure Turbidity?

There are many reasons to measure the turbidity of water, but the primary one is to gauge its cleanliness—whether it’s source water, such as a lake in a state park, or potable water in a municipal water distribution system.

Turbidity was originally used as a qualitative measurement in the early 1900s to classify the aesthetic quality of drinking water.

Today’s process is similar in that it relies on qualitative observations but involves instruments that use light-scattering technology for more specific readings.

Quality & aesthetics, health and compliance are just a few reasons why measuring turbidity matters.

 

Which Applications and Processes Require Turbidity Monitoring?

Several industries require regular turbidity measurements in order to keep their day-to-day operations in check. While good water quality is essential, different processes reap additional benefits from measuring turbidity.

While regulatory compliance is important for municipal drinking water and water treatment plants, measuring turbidity can also help keep the cost of operations down. Taking regular turbidity measurements can optimize filter performance by establishing efficient filter backwash cycles. And in the case of filter breakthrough, turbidity readings can indicate a breach of particles before it becomes a costly problem requiring an appropriate regulatory response.

Ultimately, turbidity measurements are an important part of quality control in water treatment plants. They help operators achieve their most important goal: Making water safe for consumers to drink.

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Water treatment plants measure alkalinity since it acts as a pH buffer in coagulation.

How is Turbidity Measured?

There are three main ways for measuring turbidity, and each has benefits for different industries.

Secchi Disk

Taking an indirect measurement with a Secchi disk or tube can be helpful for gauging turbidity relative to water clarity in a body of surface water such as a lake or river.

Spectrophotometric Method

A spectrophotometer measures light transmittance of the water sample and the photons can be absorbed by the dissolved substances and scattered by suspended particles present in the sample. Both components contribute to the difference between the amount of light sent to the sample and coming out of it. This difference constitutes total light absorbance by the solution, and it is not easy to distinguish between the light truly absorbed by the components and the light lost to scattering by the particulate matter. The amount of scattered light can be captured by the instrument and translated into turbidity of the sample providing an additional reading besides absorbance. It adds to the design of such spectrophotometric instrumentation and makes it more complex.

Turbidimetry and the Nephelometric Method

Sensors dedicated to turbidity can measure a flow-through sample or be submerged in water to take more accurate readings using light-scattering techniques. Some turbidity meters can take readings on a sample without touching the liquid directly.

Turbidity meters are the most versatile devices for measuring turbidity, since they can be used in a wide variety of settings. Turbidity meters usually employ a beam of light, called incident light, which scatters off of suspended particles in the sample being measured.

The method of measuring scattered light at 90 degrees to the incident light beam is called nephelometry, and the turbidity meter used for this type of measurement is a nephelometer.

Nephelometers detect the amount of scattered light and compare it to a calibrated measurement standard that can be set by the user. If the water is more turbid, the light will scatter more. If it’s less turbid, the light will scatter less. Only nephelometric methods to measure turbidity are accepted for regulatory compliance and reporting in the US.

Different nephelometers and turbidity meters exist for different purposes, though their core principle of measurement remains the same—measure the portion of light scattered by the particles.

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