What Happens to Our Water Once It Goes Down the Drain?



Staff had the opportunity to visit the Valencia Water Reclamation Plant when they held an open house to the public.  We have included a narration about the educational experience.

As an education specialist for CLWA, I have a pretty good understanding of drinking water treatment but was interested in what happens to the water once it is used and leaves our homes via the sewer system, and I hoped this open house would answer many of my questions.  I thought it was fascinating and I did learn a great deal about sewage.

As a society, we take for granted the fact that when we turn on the faucet in our homes we have clean, treated tap water ready for our use. Rarely do we ever give any thought to the process it takes to get our tap water cleaned and piped to our houses. That being said, we generally think even less about the water once it goes down the drain or gets flushed away. With that in mind, I thought it would be helpful to share with you a few points of interest about that process from my tour of the Valencia Water Reclamation Plant.

One of two plants in the Santa Clarita Valley, the Valencia Water Reclamation Plant treats over 500 BILLION gallons of sewage per year, and they operate 24/7 in order to get that done.

The process begins as the sewage wastewater enters the plant. It is screened and large metal rakes pull debris from the raw sewage. This is where larger items, such as washcloths or toys or other items that may have been flushed or somehow entered the sewage system, are separated from the waste.  The screened items are removed and taken to a landfill for disposal and the waste begins its treatment process.

The Sanitation Districts of Los Angeles are serious about being good neighbors and strive to keep the odor to a minimum despite the fact that they are dealing with a fairly noxious product. One way they keep the smell minimal is with this odor treatment called a scrubber. This mechanism scrubs the odors from the wastewater so surrounding areas experience virtually no smell while they are cleaning 13-14 million gallons of sewage per day. In fact, on the tour, the odor was barely noticeable. That is pretty amazing!

The solid waste is treated through a fairly lengthy process involving large tanks called digesters, where the biosolids are processed for 20-30 days. The solid waste is then sent to an area where it is pressed to extract all the water. It looked like a giant accordion. The waste is kept at 97 degrees the entire time in order to kill bacteria. It takes several hours to press the water out of the waste and form a product called “cake.”

Cake is a compacted form of the biosolid waste and has very little water left in it by the end of the process. It has also been treated and contains very little bacteria. From this point, the cake is then loaded into trucks, removed to farms in the Bakersfield area, and used as fertilizer on non-edible crops.

While the solids are being treated and removed from the plant the waste water is going through a different treatment process. Special bacteria are grown and infused in the water that aid in cleaning. The bacteria need air to survive and do their job, so air is continuously pumped up from the bottom of the tanks to keep them alive and functioning. This step is called aeration. The water goes through several tanks during this process, becoming clearer with each step.


After its trip through the aeration tanks, the water then makes its way through the filters to clear out any remaining particulates and to clarify the water.

Chlorine is added as a final disinfection and then removed before it is released into the river. This is the reclaimed water at the very end of the reclamation process. At this point, it is actually cleaner than the drinking water in many other countries around the world.

Once it has completed the treatment process, the water goes to one of two places. Some of the reclaimed water is stored by CLWA and only used to irrigate parks and golf courses. The rest is released into the Santa Clara River.

So there you have it. A mere 8-10 hours after entering the plant, most of the reclaimed water is released back into the Santa Clara River to make its way out to Oxnard and Ventura and the Pacific Ocean. The standards for the cleanliness of this reclaimed sewage water are so high technically you could drink it, but we don’t. The high standards are so that we don’t have a negative impact on the environment and so that the water can benefit the ecosystem downstream.


I want to thank the Sanitation Districts of Los Angeles County and in particular the Valencia Water Reclamation Plant for the very informative tour, for doing such a great job cleaning up our mess, and doing it so well that we rarely even notice it.