Being a good neighbor & controlling odors

It’s important for King County facilities to be a good neighbor to the people who live, work and play near us. At the County’s South Treatment Plant in Renton, we work 24-7 to treat the water that people use in homes and businesses before releasing the treated water back to Puget Sound to become part of the water cycle again.

Part of being a good neighbor means that we work hard to control odors that come from the wastewater treatment process—which can get gassy! Treating dirty water at a wastewater treatment plant produces hydrogen sulfide, which not only can smell like rotten eggs but also corrodes pipes. In order to improve odor control, we recently completed a project at South Treatment Plant to repair the odor control equipment.

odor control equipment

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

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.”

South Plant is part of a big, regional sewer system in King County. We have five treatment plants, 72 pump and regulator stations, seven combined overflow treatment and storage facilities, and 391 miles of large pipes that take wastewater flows from local sewer districts.

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. Carbon attracts and traps odorous compounds. Scrubbing carbon looks like black pellets, and when they’re all used up they turn into small sandy particles that can’t absorb any more odors.

A recently completed project at South Plant placed fresh odor-absorbing carbon into large towers to improve air quality. Other odor control projects include maintenance crews patching leaky panels and installing a new chemical pump that helps neutralize pungent gas. A few years earlier, the septage haul dump site had its odor control tower upgraded and refreshed with new carbon.

Yee notes that managing odors is key for our big system and doesn’t just happen once the sewage reaches the treatment plant. “Odor control starts in the pipes,” he said.

South Treatment Plant serves people who live and work in cities located east and south of Lake Washington (see our system map here). Inside those miles of pipe, sewage gets treated with a nitrate chemical each spring and summer to help lessen the amount of corrosive gas eating away at pipes that also produces smells.

Hydrogen sulfide corrosion in a sewer pipe

Hydrogen sulfide occurs naturally in sewage. It causes odors and corrodes pipes.

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 jump the fence line, 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 wet scrubbers at King County’s South Treatment Plant in Renton.