Protecting Puget Sound through source control

Industrial users learn about the primary sedimentation tank during their tour of South Treatment Plant in Renton.

As a conveyor belt crawls along carrying soggy garbage and wipes in the screening room, and the sound of trickling water echoes through the clarifier tanks, it’s clear that touring South Treatment Plant in Renton is a full-on sensory experience.

“It was amazing to see that the treatment process relies mostly on natural, simple science,” says Melanie Gourley, senior manager of strategic sourcing and sustainability at Seattle-based whiskey maker Westland Distillery.

These tours have given industrial users — commercial customers regulated by the King County Industrial Waste Program (KCIW) — a chance to see firsthand how wastewater is treated and cleaned. They also illustrate how businesses can help protect the regional wastewater system they use and ultimately the water quality in Puget Sound.

Local manufacturers, such as Skills Inc. in Auburn, are required by KCIW permit to pretreat its wastewater before it’s discharged to King County’s regional system.

This fall, KCIW is reaching out to 11,000 businesses across our wastewater service area with a comprehensive Industrial User Survey. The survey comes out every five years and is designed to gauge what kinds of chemicals, fats, and other types of waste materials are being sent into the wastewater system. For the first time, the survey will also include questions about PFAS, also known as “forever chemicals,” and 6PPD-Q, the toxic tire dust chemical known to kill coho salmon.

“We hope the plant tours give our industrial users a deeper understanding of our work, while the survey helps us connect with new businesses and build partnerships,” says KCIW Project Manager Kristin Painter, who’s leading the survey program.

While most wastewater in King County comes from homes, about 3 to 5% of total flows entering the system come from all types of businesses — including hospitals, dentist offices, auto shops, manufacturers, and bakeries. Industrial wastewater can be more acidic, contain chemicals that our treatment process can’t break down, or carry fats and food waste that clog sewer pipes.

Because protecting water quality in Puget Sound begins with homes and businesses, KCIW inspectors work directly with industrial users to ensure harmful chemicals, heavy metals, and other pollutants don’t enter our system. About 650 of these businesses are large enough to require a KCIW permit to remove these substances through a pretreatment process before it reaches the local sewer agency pipes and the regional county-owned pipes.

Keeping harmful chemicals out of our wastewater system helps ensure our Loop biosolids is safe for farmers to use on their fields to improve soil conditions and boost crop yields.

If industrial chemicals make their way into our system, they can disrupt the treatment process, even wiping out the beneficial bacteria that treat solids (yes, poop!). The presence of chemicals in certain concentrations can also impact our ability to land apply Loop biosolids and puts our facilities at risk of violating federal and state clean water permit requirements, which set strict limits on what treatment plants can safely discharge treated water into Puget Sound.

“Our treatment plants — some built nearly 60 years ago — are designed as physical and biological processes to remove solids and treat for pathogens and bacteria,” says Mark Henley, KCIW manager. “They aren’t designed to remove inorganic pollutants, such as heavy metals and petroleum products, and that’s why source control and pretreatment at the business level are critical before wastewater ever reaches us.”

To stay in compliance with the federal and state standards, KCIW’s survey helps determine how to effectively manage industrial waste streams with businesses to protect public health and the environment.

“Whether your business has a KCIW permit or you run a mom-and-pop shop, we want to connect with everyone,” says Painter. “By identifying and closing information gaps, we can help keep harmful chemicals out of the system and potentially avoid costly problems or penalties down the road.”

The new survey questions about PFAS and 6PPD-Q will help us better understand how these chemicals are getting into our waste systems so that we can take action to curb their use. It also builds off the ongoing efforts to directly sample wastewater, biosolids, and landfill leachate that is reaching the treatment plants. The results of a 12-month study of PFAS in King County waste systems were released earlier this year.

“Through source control, pretreatment and collaboration, our goal is to protect Puget Sound and make sure future generations can enjoy the clean water and natural environment in our backyard,” says Painter.

During a tour of South Treatment Plant in Renton, industrial users hold a rope to visualize a 10-foot-diameter pipe that carries water into the facility.