What is turbidity?

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What is turbidity?

Turbidity measures the relative clarity of a water sample. It is determined by the amount of scattering that occurs when a light source is shined through a water sample. Light scattering is caused by increased concentrations of suspended particles in water that are not individually visible to the naked eye, which can give the water a cloudy appearance.

This parameter is used as a general indicator of the quality of water, along with colour and odour. A large concentration of particles in drinking water is undesirable as it causes an unpleasant taste and appearance. It also reduces the ability of chemicals and radiation to neutralize disease-causing bacteria and viruses. Turbidity that is not removed during treatment can also provide shelter for these pathogens, promoting their re-growth throughout the distribution system. In natural water sources, this can result in loss of habitat quality, recreational value, and lakes being filled in.

Turbidity is an optical parameter, measured in nephelometric turbidity units (NTU) when a white light source is used, following Standard Methods 2130 B, ASTM D1889 and EPA 180.1. It is measured in nephelometric formazin units (NFU) for an infrared light source, following ISO 7027 and EN 27027. Use of an infrared light source can eliminate bias introduced by coloration of a water sample. Turbidity meters typically consist of a light source, which shines through either a static or dynamic (flowing) sample cell. A detector around the cell measures the amount of scattered light to determine the turbidity value of the solution within the cell. The traditional method measures scattered light at 90 degrees from the incident beam. Alternative measures of turbidity use ratios of scattering from different angles to eliminate certain biases.

MANTECH offers an automated turbidity add-on to the MT-Series Automated Titration & Multi-Parameter Systems. The unique flow-through cell design allows for accurate measurement of turbidity in water and wastewater samples within the range of 0.5 to 2000 NTU, with a method MDL of 0.1 NTU. The method is very stable, utilizing MANTECH’s Intellirinse™, which ensures the cell is thoroughly rinsed until the meter reading reaches a defined value, allowing for calibrations to be valid for 1-3 months with Quality Control check verifications. The method is also non-invasive, allowing for a large portion of the sample volume to be returned to the sample vessel to run additional analyses on the same sample aliquot. MANTECH systems have increased efficiency and productivity in commercial and industrial laboratories around the world.

Read the application abstract here.


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