What is Turbidity?

Turbidity is a crucial parameter in water quality, used to measure the reflection of light from suspended particles in water. These particles encompass a wide range of substances such as proteins, minerals, algae, bubbles, dirt, bacteria, and hydrocarbons. While these particles may not be individually visible, they become noticeable as they aggregate or as they clump together.

The turbidity of water increases as the concentration of suspended particles rises, resulting in cloudier water. Turbidity serves as a reliable and well-established indicator of water quality, and it has been extensively employed in monitoring drinking water for over a century. Elevated turbidity levels can pose challenges to chemical dosing, leading to inefficiencies in the treatment process. Furthermore, high turbidity can significantly interfere with the accuracy and reliability of sensors and laboratory-based tests.

In many cases, high turbidity indicates the presence of high levels of suspended solids or Total Suspended Solids (TSS). In extreme scenarios where the particle concentration is exceptionally high, a turbidity probe may not provide accurate readings, necessitating the use of a TSS probe instead.

Optical Turbidity Probe

 The measure of clarity or cloudiness of water and an indicator of the quality of water.

A turbidity probe or turbidity sensor, is a device used to measure the turbidity of water. It is specifically designed to assess the clarity or cloudiness of water by quantifying the amount of light scattered or absorbed by suspended particles in the water.

The probe consists of a light source that emits light into the water sample and a detector that measures the intensity of light scattered or transmitted through the sample. The amount of light scattered or absorbed is directly related to the concentration and size of suspended particles in the water. This information is then displayed as value of Turbidity, usually expressed in units of Nephelometric Turbidity Units (NTU).

Turbidity probes are commonly used in various applications, including environmental monitoring, water treatment processes, wastewater management, and research. They provide a quick and reliable measurement of turbidity, allowing for the assessment of water quality, the detection of changes in water clarity, and the monitoring of treatment efficiency.

Turbidity probes used in combination with UV254 probes offer a comprehensive scope for all optical water quality parameters, used with a Photonic Measurements controller allows presentable, trendable and digestible data.

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Benefits of Turbidity Measurements

Early indication of water with high particulate levels can:

• Minimise wear on pumps, pump systems and valves reducing repair and replacement costs

• Alerts to corrosive grit in system  

• Detection of changes at inlet i.e. a weather event occurring. Allowing for predictive maintenance 

• Savings on Dosing and Flocculation (DAF) processes, knowing turbidity levels can allow feed-forward control 

• Testing filtration system integrity. Measuring turbidity post-filtration will alert operators to filter failure and allow for scheduled replacement or maintenance.

• Data for site optimisation
• Ensure quality by measuring final effluent 

A modern UV254 Chemical Oxygen demand analyser


Lisburn BT28 2GN, GB

About us

Photonic Measurements is:
Incorporated in N.Ireland (NI622996) 
VAT registered in UK (GB192976846)
VAT registered in N.Ireland (XI192976846000)

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