How to Test the Turbidity in Water

A liquid’s appearance and appeal to consumers are based on optical qualities like turbidity. Learn more about the meaning of turbidity and our turbidity test procedure with a spectrophotometer.

What Is Turbidity?

Turbidity is the measure of the clarity of a liquid to indicate the presence of suspended particles. It’s a visual feature that can be seen with the naked eye and calculated with turbidity measurement methods. Highly turbid liquid has an opaque, cloudy appearance, and low-turbid liquid is clear and transparent.

What Causes Turbidity?

Turbidity is caused by materials like:

  • Microscopic organisms
  • Minerals
  • Sand
  • Clay
  • Algae
  • Proteins
  • Dissolved colored organic compounds
  • Silt
  • Oils
  • Microscopic organic and inorganic matter
  • Bacteria
  • Plankton
  • Dirt

When a body of water has low flow, it is clear and has low turbidity. Movement through water, such as a rainstorm, washes particles from the land into it. The flow speed also stirs up material from the bed. As a result, this water is cloudy and highly turbid.

Why Does Turbidity Matter?

In nature, bodies of water with high particulate concentration affect the environment. Highly turbid water reduces recreational value, lowers ecological productivity, fills in faster and decreases habitat quality. Pollutants like metals and bacteria can attach to the particles, contaminating the water and harming aquatic life.

Turbid water is also concerning for human health. Pathogens can live on and feed off the particles, which protect microbes from exposure to disinfectants. Highly turbid water can grow many pathogens, causing the potential for intestinal sickness and waterborne disease outbreaks.

Water Turbidity Standards

Due to the environmental and health concerns of turbidity, standards exist to limit and reduce it, determine the efficiency of the treatment method and ensure compliance with governmental regulations.

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Turbidity is measured in nephelometric turbidity units (NTU). The Environmental Protection Agency (EPA) requires that 95% of drinking water in one month have a 0.5 NTU or less turbidity reading. Samples may not be higher than 5 NTU at any time.

How to Measure Turbidity by Spectrophotometer

HunterLab’s turbidity test procedure uses a spectrophotometer. These machines offer color measurement solutions to ensure the water’s visual appeal and standard of quality. The turbidity measurement method it uses is light penetration. A light is shined through the sample and the amount of light that is scattered and reflected back to the sensor measures the turbidity. A liquid with high turbidity has intensely scattered light and vice versa. The spectrophotometer assesses color values such as APHA, Gardener and Platinum Cobalt, and turbidity values such as Haze% adhering to the American Society for Testing Materials (ASTM) D1003 Procedure B.

Contact HunterLab

Water’s color — or its clearness — is what makes it look clean and drinkable. Bottled water manufacturers and similar businesses in the food and beverage industry need their water to be consistently clear to ensure that their product is safe and appealing to consumers. HunterLab offers color measurement solutions for water that provide data for judging water quality.

For more information about our turbidity measurement methods, contact us online.