Novel Microbubble Reactor for Microplastic Removal
Project Overview
In Harvard’s Engineering Problem Solving and Design Process class, students work with a company to develop an engineering solution to a real-world problem. For this project I was part of a team of engineering students from varied backgrounds (mechanical, electrical, biomedical and environmental disciplines) that worked for BASF, the largest chemical production company in the world. This project was part of the company’s mission to shift towards being a sustainable chemistry company. BASF tasked our group with the challenge of improving nano-and micro-plastic abatement in a plastic production plant.
Microplastics and smaller nanoplastics are very small plastic fragments that can accumulate in ocean biota, killing wildlife, finding their way into people’s drinking water, and absorbing harmful pollutants which increase their toxicity. Removal is necessary to decrease these harmful effects. The team first researched existing solutions and explored the strengths as well as the issues with existing monitoring and abatement systems, before coming up with a unique solution of their own.
Microbubbles were decided on as the abatement mechanism of choice. To make this solution work, the team worked on both the design of a larger reactor system and the specifics of the microbubbles themselves. I was primarily part of designing the reactor system. For this system we had to consider the given effluent wastewater flow rate from BASF, maintaining consistency with the experimental set up and predict reaction rate and efficacy of microplastic and microbubble cohesion. The team projects usages of the reactor system outside of abatement in plastic production and envisions this design applied to 'on site' microplastic collection and analysis in the future.
Why microbubbles? What other approaches were considered for this project?
Microbubbles are an emerging technology for molecular imaging and wastewater treatment. They have been used to remove PFAS plastics from water by “foaming” the plastics at the surface of the water using ozofractionation. The idea was that by using coatings on the outside of the bubbles, we would be able to attract plastics to the outside of the bubbles. Ultimately, by removing the bubbles from the wastewater we would also remove the conglomerated particles.
The other primary abatement mechanism that was considered for this project was magnetic extraction. Magnetite is a naturally occuring iron-oxide mineral that will bond with negatively charged functional groups such as polyurethane and nylon-6 (the assigned plastics from the client). Once the magnetite and microplastics bond, a strong magnet would be used to extract the groups from the wastewater effluent. The primary problem with this solution is that it is unlikely to be fully effective on its own due to the bonding time between magnetite and plastic.
If you are interested in learning more about this project, please see the full report or final presentation to BASF below.
What role did you play in this project?
The project was broken up into a couple of main stages: research, brainstorming, and systems design. During the research and brainstorming stages, all project team members researched the problem space and worked together to create a coherent understanding of the task that lay before us. During the brainstorming stage, each project team member came up with an idea that they thought would work for abatement; my idea was magnetic extraction. We then came together to complete the project with the idea that we thought was most novel and feasible. After this point, I worked primarily with the reactor design team to engineer the tank dimensions and design. I was also in charge of all CAD modeling for this project.