What’s that smell? Controlling & reporting odors

It’s important to us that our wastewater facilities to be a good neighbor to the people who live, work and play near them. Part of being a good neighbor means that we work hard to control odors / smells that come from the wastewater treatment process—which can get gassy!

odor control equipment
This Willy-Wonka-looking equipment reduces odors that are produced during the sewer treatment process at South Treatment Plant.

Why does sewage smell?

Treating dirty water at a treatment plant produces hydrogen sulfide, which not only can smell like rotten eggs but also corrodes pipes. We invest in odor control equipment at all of our treatment plants and in many of our smaller facilities.

Wastewater process analyst Steve Yee has worked at South Plant for 35 years and says that odors from the treatment plant tend to be more of an issue when the weather warms up.

“The hotter the sewage gets, the greater the bacteria that produces hydrogen sulfide can grow,” he said. “It’s the summer we’re most concerned about.”

Is it us? It may be algae rotting on the beach

Every summer we receive calls from community members who say our sewers stink. While we investigate all odor complaints, our crews commonly have to break the news that the summer odor you reported isn’t coming from our sewer system. Our sharp-nosed investigators have found a variety of culprits, but the most common cause of odor complaints in the summer is on our beaches – a seaweed called macro algae, commonly known as sea lettuce, is thriving in our waters, washing up on our shores, and as the temperature rises, rotting.

Rotting sea lettuce produces hydrogen sulfide which smells like rotten eggs or sewage
Rotting sea lettuce and other algae on beaches and in lakes can produce hydrogen sulfide which smells like rotten eggs or sewage.

Rotting sea lettuce produces hydrogen sulfide which smells like rotten eggs or sewage, and dimethyl sulfide (DMS) which smells like rotting shellfish. According to the Washington State Department of Ecology, the smell of seaweed and other marine life is a natural part of beach ecology.

How do we control sewer odors?

So, what helps to make the process of treating raw sewage smell better? One way to control odors is to use carbon to “scrub” the hydrogen sulfide before it is released into the air. Scrubbing carbon looks like black pellets that attract and trap odorous compounds. At our treatment plants, this can look like odor-absorbing carbon in large, “Willy Wonka” towers to improve air quality.

Other odor control methods we use include covering treatment processes so no air leaks out or chemical pumps that help neutralize pungent gas. Some of our odor control starts in the pipes before they reach our treatment plants. Treating the sewage with chemicals not only helps lessen odors, it also reduces the amount of corrosive gas eating away at our pipes and therefore helps protect ratepayer’s investments.

Hydrogen sulfide corrosion in a sewer pipe
Hydrogen sulfide occurs naturally in sewage. It causes odors and corrodes pipes.

Smell something you think is us? Give us a call!

We put lot of investment into good operations and maintenance practices to keep nuisance odors from leaving the site and bothering our neighbors. Still, we plan for any fugitive odors that may escape, and that’s when we need the public’s help to identify and catch them. The best thing neighbors can do? Call our 24/7 odor control hotline right away if you smell something so our operators can track down the source. Every odor complaint is logged and tracked, and plant operations makes it their goal to respond and identify the issue within two hours.

Odor control equipment
Odor control equipment at the South Treatment Plant