When a plastic bag gets carelessly thrown onto the street, a snack wrapper is left behind on a nature trail or a soda bottle just misses the corner garbage can, it can eventually end up in Philadelphia’s waterways.
Using Innovation to Clean Up Plastic Pollution
Engineering students design solution to remove trash from the Schuylkill River.
(l-r) Recent mechanical engineering grads Brian Dobson, Jerry Sanders and Kyle Diaz developed a solution to address the trash problem on the Schuylkill River.
Literal tons of debris float down the Delaware and Schuylkill Rivers annually, which harm wildlife, interfere with recreational activities and transport plastics and pollutants. For their senior capstone project, three mechanical engineering students developed an innovative solution to address this environmental menace.
Peg Shaw, a consultant with the East Falls Development Corp. (EFDC), worked with the students over the past year. She points to the “over-loved” Wissahickon Valley Park and Creek as a prime example of the area’s ubiquitous trash issue; approximately 16,000 pounds of litter and recycling were removed from the park and creek in 2018.
“Trash in our waterways is a worldwide problem, and Philly is no exception,” she says.
Their proposed two-stage strategy would use an underwater "bubble barrier" to help divert debris to be collected inside a "watergoat," a U-shaped rope with buoys attached.
Just downstream from where the Wissahickon Creek empties into the Schuylkill River, the EFDC will build the East Falls River Landing later this summer. The space in East Fairmount Park on the Schuylkill banks will serve as a new public launching spot for non-motorized boats, making it ideal for fishing, kayaking, canoeing and other recreational paddling activities.
Here’s where 2021 Jefferson grads Kyle Diaz, Brian Dobson and Jerry Sanders, aided by adviser and engineering professor Dr. Radika Bhaskar, enter the scene. In anticipation of the landing’s construction, they spent their senior year developing a unique two-stage system—“a bubble barrier” and “watergoat”—to collect and remove plastic waste in the Schuylkill.
When the East Falls River Landing is built later this summer on the Schuylkill banks, it will serve as a new public launching spot for non-motorized boats.
To construct the barrier portion, they drilled holes into a PVC pipe and then fed pressurized air through the underwater tube, Diaz explains. It took numerous trials (some with slow-motion video; see below) to discover the perfect bubble size and velocity to create the necessary rift at the top of the water.
They envision the barrier to be placed at an angle to work with the river’s natural flow and help push the trash down and off to the side, says Diaz, an avid fisherman.
Next, the watergoat—a U-shaped rope with buoys attached—collects this floating waste, yet importantly, doesn’t disturb nearby wildlife, he says. Here, too, they ran through several trials to analyze the river’s ebb and flow and realize they needed longer rope and thicker buoys, as well as an anchor.
The engineering students used an air compressor and waterproof camera for the bubble barrier experimental setup. The checkerboard background aided with measurements.
The engineering team also originally proposed the trash be pulled in automatically when full. However, Shaw suggested an alternative approach that could be more educational for the public, thereby raising awareness of the issue.
“I thought the system could be visually captivating and engaging to the community if the trash collected could be easily accessed and removed by volunteers,” says Shaw, project director of the East Falls River Landing for the EFDC. “For example, the newly established Friends of the East Falls River Landing can organize stewardship and programming activities. And, of course, trash cleanup is always on the list.”
The students tested their watergoat on the Schuylkill River as part of their capstone project.
Along with working with local groups in the creation process, the team kept in contact with the Philadelphia Water Department, which takes care of the city’s rivers and streams.
“Trash has been a challenge for us for many years,” acknowledges Matt Fritch, an environmental engineer with the Water Department’s Watershed Protection Program.
They operate a trash-skimming vessel that regularly collects waste from the area rivers for the landfill or recycling, he says. It’s an expensive and time- and labor-intensive operation. These realities made the students’ prototypes so exciting.
“They stuck with a passive solution and something that wouldn’t take a ton of energy and manpower,” he says. “They’re letting the river do the work of carrying the trash. I give them a lot of credit for getting into the details and considering the wildlife too. Aside from the physics of it, you’re talking about the biology and ecology.”
With imaging software, the students tested the bubble diameter and velocity. Bubbles need sufficient velocity to provide enough force to adequately move debris in the water.
With the three students now graduated, they will pass along their research to another Jefferson engineering team to continue the project in the fall, Diaz says. The system could be implemented in the near future if all goes well.
Hoping to work as a design technician or with home automation, Diaz says the project provided valuable real-world experience as he built relationships with various stakeholders and the community. (The team made a formal presentation to the EFDC board in May.)
“It’s a big talking point on interviews and shows how I’ve put together everything I’ve learned throughout my four years here,” he says.
Through time-lapse video of the site, the students could see how their watergoat prototype handled the river’s ebb and flow over a week.
Sanders, too, enjoyed his time working on the project and playing a role in helping the environment. He says he also benefited from learning new skills on budgeting and logistics, as well as the connections gained over the year. Sanders interned with the Philadelphia Water Department where he learned first-hand how the water from the Delaware and Schuylkill Rivers makes its way to the city’s faucets.
Dr. Bhaskar says she’s proud of the students for working on a critical real-world problem all while grappling with pandemic-related challenges, such as supply-chain delays.
“The scale of our plastic pollution is staggering,” says Dr. Bhaskar, noting the group’s attention to the entire system impressed her the most. “It was exciting to watch their enthusiasm for a project that has a demonstrable impact on their local environment and community. They considered how volunteer groups might engage, how their proposed solution might operate over time and how to prevent harm to wildlife relying on the river. All these dimensions added complexity to their capstone project.”
