#WishIknew – What is turbidity?

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When you have a question about process automation that needs a short answer, let us know with #WishIknew and @Visaya! We’ll reply with a #WishIknew post. It’ll give a quick explanation, then some related articles, videos, or reviews if you want to know more.

I wish I knew what turbidity is!

You probably heard at some point someone saying the water of a river looks turbid. So what does that mean? Some people would say that means the water looks cloudy. That gives you the general idea but doesn’t tell you much else.

Turbidity is an optical characteristic. It refers to the degree of clarity a liquid has. Water, for example, can have colloidal matter or suspended particles that make it cloudy. The more particles or colloidal matter you have in the water, the higher its turbidity.

Courtesy of Water USGS

You’ll almost always find suspended solids in water. Some of them are big and heavy enough to settle to the bottom of a container if you leave it standing for a while. We call these settleable solids, naturally. Smaller particles will take a longer time to settle, if they settle at all (colloidal solids don’t). All these particles contribute to making the water turbid.

Okay, we used water to explain the concept of turbidity. However, we have liquids in our daily lives that are turbid by nature. Milk contains suspended emulsified proteins. Wastewater has suspended particles we don’t want to think about. And wheat beer contains yeast cells. Mmmm, beer.

As for units to measure turbidity, you have a choice. The most common are Nephelometric Turbidity Units (NTUs), often used for water and wastewater, and Formazin Nephelometric Units (FTUs), the reference unit in the ISO 7027 (European) turbidity method.

Hope you learned something today!

To learn more check out this video:

Related tags: #WishIknew Analytics Basic Devies English Principle turbidity
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