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A Firsthand View

2011 October 13

By Trey Cody

Wastewater Treatment 101 

As an intern in EPA Region III’s Water Protection Division, my day typically involved working in the office on projects related to the region’s Healthy Waters Initiative.      

But near the end of my internship this summer, I was able to get a firsthand look at what is being done to treat water in the Philadelphia area. I participated in a tour of the Southwest Water Pollution Control Plant, managed by the Philadelphia Water Department (PWD), viewing the processes that allow the plant to clean around 194 million gallons of wastewater per day.

There are the preliminary treatment processes, which remove the large debris like trash and rocks from the wastewater coming into the plant.  Then there is the removal of smaller particles like dirt and grit in a settling tank. And then, biological processes take over, as various kinds of bacteria and microorganisms go to work to consume the organic matter in the wastewater.  Finally, the water is disinfected (usually with chlorine or UV light) before it is discharged to a neighboring stream. The solids that were taken out of the water during the process are referred to as biosolids, which are usually disposed of in landfills, but can be land-applied as fertilizer.  Who knew all this happened to the water once it went down the drain in my house!  I was surprised by how large the plant was; there are so many processes to keep moving and monitor along the way.  And it wasn’t even that smelly most of the time!

The Southwest Water Pollution Control Plant was built in the early 1950’s, then expanded and renovated from 1975 to 1983 to ensure PWD met the requirements of the Clean Water Act.  This treatment plant is one of three of the PWD’s facilities that treat wastewater before it is discharged back into rivers and streams. 

Do you know where your water goes after you use it, and what happens to it along the way before it goes back into our rivers and streams?  Have you ever visited a wastewater treatment plant?  You can take a virtual tour of one of the largest plants by clicking here.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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