Cleaning a Lake with Sludge

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How UW Tacoma students are using waste product to clean storm water

The inside of the shipping container at Wapato Lake, the hidden site of a water quality research project. | Photos by Cody Char.A shipping container sits near Wapato Lake, far from the Port of Tacoma. It is filled not with cargo, but with plastic jugs with cities written on them: Richland, Aberdeen, Everett.

The container houses a research project of UW Tacoma’s Center for Urban Waters. This project brings together several community institutions, as UW Tacoma partners with Metro Parks Tacoma and the City of Tacoma on a Department of Ecology grant.

The research team hopes to find out whether they can use a waste product to remove phosphorus contamination from storm water runoff. If they succeed, they could help solve longstanding water quality problems not just for Wapato Lake, but for freshwater lakes around the state.

A Struggling Lake

Toxic algae blooms closed Wapato Lake in south Tacoma for much of the past summer; in 2007, it was declared the “most toxic lake” in Washington state.[1]

Most of the water flowing into the lake is urban storm water runoff, filled with phosphorus from farms and residential areas. Phosphorus itself isn’t harmful (“You can drink water with phosphorus in it,” says Center for Urban Waters Research Scientist Andy James) but high levels of it cause toxic algae to flourish in the water.

UW Tacoma and other community organizations have long been interested in the water quality of Wapato Lake. Professor Jim Gawel has brought his students there for research projects. “There’s been a little bit of history of study at the lake,” says James. “It’s been a concern for a long time. And it’s set up that we might be able to do something about it.”

Water treatment residuals, or WTR, mixed with gravel and sand. The experiment tests these mixtures to see which is most effective at removing phosphorus from storm water. The Shipping Container in the Park

The current project partners UW Tacoma with the City of Tacoma and Metro Parks Tacoma to clean the water coming into the lake with a surprising tool: another waste product.

Water treatment plants all around the state filter their drinking water with aluminum or iron compounds. “It’s like sludge when it comes out,” says Center for Urban Waters Research Assistant Alex Gipe, environmental studies and sciences ’13. Facilities often have to pay to have the resulting muck, called water treatment residual (WTR), removed. But it also turns out to be a great way to absorb phosphorus.

“The idea is to take their waste product and use it in little treatment systems to clean storm water,” says James.

The research team took that sludge from treatment plants, dried it and crushed it into hard pellets that look like the gravel at the bottom of fish tanks. In the shipping container, the team filters storm water coming into the park through a mix of these pellets, gravel and sand, then tests the incoming water to see how well each WTR removed phosphorus and suspended solids.

Carrie Shannon, environmental sciences ‘15, stands next to the water filtration system inside the shipping container.The city names written on the plastic jugs represent the treatment plant the WTR came from. WTR from Chehalis has a more solid texture than WTR from Everett. “It definitely differs, the amount of phosphorus they remove, depending on what they’re made of,” Gipe explains. 

As the City of Tacoma opens its new drinking water filtration facility, it will use data from this experiment to influence what chemicals it uses to treat drinking water, helping produce a WTR that effectively removes phosphorus and can be used to treat storm water throughout the area.[2]

Partnering for Tacoma

This project is part of a partnership between UW Tacoma, the City of Tacoma and Metro Parks Tacoma on a Department of Ecology grant that began mid-2014 and will finish this June. “Part of the reason (the Center for Urban Waters) was set up was to encourage … this kind of partnership,” says James. “The city has regulatory responsibility, and we can do research that helps them do their jobs better.”

“The City of Tacoma and Metro Parks have been great to us. They’ve been very big supporters,” says Gipe. “(Thanks to them for) being so accommodating, to let us leave this big ugly box here for a while,” he adds, gesturing to the shipping container.

Student Powered

The research team. From left to right, Brian Hite, Carrie Shannon, Alex Gipe and Andy James.

This experiment is powered by UW Tacoma students and alumni. “Students have largely been doing most all the work,” says James. “It’s useful work and it’s good that they get involved in it.” The project gives the students and alumni for real-world lab experience.

Undergraduate Research Assistant Carrie Shannon, environmental sciences ‘15, got involved at the end of her first quarter at UW Tacoma, when her chemistry instructor, Meg Henderson, announced that the Center for Urban Waters was looking for interns. “I really didn’t think anyone was going to respond back to me, because I don’t have a science background. I was in the Navy (before coming to UW Tacoma),” Shannon recalls. “But I definitely went to the UW to major in environmental sciences.”  That enthusiasm and motivation must have come through in her application, because she got the gig.

Shannon plans to go on to graduate school, and is currently considering the UW environmental forestry program. “The plan is to save the world! As much as I can,” she laughs.

Gipe started as an intern on a different Center for Urban Waters project, but came on board the phosphorus research project as it was losing an intern. A UW Tacoma alumnus, Gipe works on several projects at the Center for Urban Waters, helps manage the building’s labs, and plans to go to graduate school.

The team pumps storm water up into the storage container via a tube that reaches down into the sewer.

Research Assistant Brian Hite, environmental science ‘12, started researching phosphorus in storm water four years ago while at UW Tacoma after taking a class with Professor Joel Baker.

“I was really interested in hydrology and asked him if I could come on, because I thought the Center for Urban Waters was really interesting facility with lots of research opportunities,” says Hite. He earned his master’s in engineering from UW’s Seattle campus at the end of autumn quarter, and splits his time between the center and Cardno, an international environmental services company.

Looking Ahead

As a next step, the team hopes to engineer a full-scale device to process incoming storm water – something that might take the form of a weir wall, filter socks or vault filters, rather than in a shipping container near the parking lot. Each design would need to cater to the environment type; water coming from a storm drain might be best-treated with a filter sock, while a smaller lake might be better-treated with a weir wall.

From the experiment, the City of Tacoma and Department of Ecology hope to learn whether WTRs can treat phosphorus in storm water around the city and the state. “Is this a local thing that only works for the City of Tacoma or is it something that we can use and scale up?” asks Hite. “It’s showing so far that it does have the promise of scaling up.”

If successful, this research could help clean up lakes around the region and the state, including the long-damaged Wapato Lake.New urban studies faculty member Britta Ricker is also looking into getting involved at Wapato Lake. She is looking into a project that would use drones to measure the algae blooms in the lake. “I’m always looking for projects. One of my students actually connected me with Andy,” she says.

Waste No More

The unassuming shipping container conceals innovation at work: collaboration between organizations to clean a historically damaged lake, and possibly lakes around the state, while effectively using a waste product.

Hite sums up the key to the project: “We’re removing a waste product from the garbage stream and reducing costs for cities by taking one of their waste products and turning it into a product that’s actually good for the environment.”

[1] Source: "Conventional Analysis Lab," Center for Urban Waters.

[2] For information on the new facility, visit:


Written by: 
Abby Rhinehart / February 20, 2015
Media contact: 

John Burkhardt, UW Tacoma Communications, 253-692-4536 or