How a Water Treatment Plant Works

Clear Water from Clairifier

I recently took a trip to a sewage treatment plant. It smelled like a century egg but was worth it. Following sewage, as it turns from muddy brown to crystal clear, gave me a refreshing feeling.

There are many ways society treats water. In earlier days, people use to filter water by sand. But later on, we discovered diseases like Cholera, which demanded us to create much better ways of filtering water. Today, our government has passed the Clean Water Act, which prompted the construction of much more sophisticated water treatment plants. 

The Elements of Water Treatment

Water treatment plants are fantastic! They input raw sewage and output clean water and fertilizer. How sustainable! While there are many differences between plants, there are also common similarities. 

Pumps, Pipes, and Storage  

These are the elements responsible for logistics. There is an entire sewage system beneath you, and it’s not only designed to transport your poop, but also to deal with stormwater. 


In earlier days, people pooped in rivers. The natural tributary was the sewers. Today is not too different. Our wastewater eventually makes it’s way to the river or lake or ocean. 

Clive Dobson Illustration of Watersheds
Illustration by Clive Dobson from the book “Watersheds” 1949.

Chemical Treatment,

Chlorine, Lime, Flouride, and Phosphate is commonly added onto the water as “remediation.” Do your research on these chemicals; there is still debate about whether these chemicals are necessary, but for the most part, tap water is safe to drink.


If water is not turbid and is left still, more massive particles will float to the bottom, while lighter particles will rise to the top. We take advantage of this phenomena when treating water. For example, the process of Flocculation involves adding chemicals to water so that small particles clump together, making them heavy enough to sink to the bottom. 

Let us Take a Close Look at Sedimentation 

You may have been driving down the highway and have passed on of these cylindrical structures: 

This is a Clarifier. Clarifiers work with sedimentation to remove impurities in the water. The Clarifier will pump water radially. The water flow is like a donut but more turbulent. Sludge settles to the bottom while clarified water overflows into the next stage. Notice how clear the water is at this state. 


All-in-all, if you live in the United States or a developed country, you will find water treatment plants. They are all around us! I hope this article paints the right image of a water treatment plant.