WT: Congratulations on making the Forbes 30 Under 30 List for 2023! This recognition is perhaps the crowning jewel of your list of awards -- which includes the US Department of Energy naming your Company as Leader in Advanced Filtration and Water Recovery Technologies.
Please tell us what drives your entrepreneurial spirit.

Rappaport: My inspiration for solving environmental challenges began in my early summers as an outdoor adventure camp counsellor – teaching whitewater stand-up paddleboarding, kayaking, and rafting on the Potomac River before college. I went to Tufts University to study environmental engineering because it seemed like the most direct route to build problem-solving skills and get exposure to cutting-edge ideas being applied to environmental conservation and resource management

At Tufts, I also fell in love with entrepreneurship. I never used to think of myself as a creative individual. I had no talent or expertise in the arts, music, or more classically creative disciplines – but I came to view innovation as a medium for driven, impact-motivated people to apply creativity and technical skills to solve major world problems.

Along the way, I found that the people who gravitate toward innovation, both the young, emerging leaders and the veterans who generously share their wisdom and expertise, challenged me in the best way possible and yielded a community of lifelong friendships and partners.

As ZwitterCo grows, watching the impact of our team’s efforts in creating real value for customers and partners is incredibly motivating and widens my perspective on all that could be possible to scale. It is humbling and rewarding to see how our message of water reuse and environmental stewardship resonates with so many potential users in so many applications and geographies. It’s also a rare experience to be part of a team that is so unified toward this shared purpose.

WT: When did you co-found your start-up, ZwitterCo? Where did your research begin?  How did you assemble your team?

Rappaport: After undergrad, I stayed at Tufts to pursue a Master of Science in Innovation and Management, which was a three-semester start-up boot camp. The premise of the program was to work on any topic that you were passionate about, work as hard as you could toward venture development, and figure out where you were by the time the program finished.

I was incredibly lucky to connect with the office of Technology Transfer at Tufts, where I learned about the early research on these revolutionary membranes – what we now refer to as ‘zwitterionic membrane technology’ that was invented by Dr. Ayse Asatekin

 in the chemical engineering department. The business plan for ZwitterCo was the final output of my master’s program and led us to win first place in the tufts $100k New Ventures competition.

I was connected to our current Chief Technology Officer and Co-Founder, Chris Drover, through Dr. Asatekin. 

At the time Chris was finishing his Master's Degree in Chemical Engineering at Tufts after having spent the early part of his career at Doble Engineering and Oasys Water. I met Chris Roy, another co-founder, and the current Head of Technical Services when we both attended MIT’s Water Innovation Prize Event. Chris Roy had previously been in field engineering and R&D roles in Veolia’s ceramic membrane division. The three of us launched ZwitterCo in May 2018.

WT: As an “aquapreneur”, you clearly identified problems that require solutions. What are those problems and why is there an urgency for solutions?

Rappaport: For so long, water has been a vast resource that society did not expect could run out. Clean water is something we do not think about until it is gone, and it cannot be easily replaced. Water is becoming less predictable, and droughts are becoming more severe. Half the world is predicted to live under water stress by 2025

Eventually, sustainable water reuse will not just be an ESG metric, but a license to operate.

If commercial plants had the ability to reuse their wastewater, more water would remain available for public use – up to 500 billion gallons (about 1892705000000 L) a day. Reusing wastewater with superfiltration membrane technology increases sustainability within agricultural and industrial practices, leading to water security for public health and other critical industries

WT: What are zwitterions?

Rappaport: A Zwitterion (also known as an “inner salt”) is a special class of molecule that is highly hydrophilic. Zwitterions have both positively and negatively charged groups in proximity, and these charges pull water to the zwitterion while repelling organic components (like proteins, fats, and oils) that stick to traditional membranes and impede their filtration capacity.

WT: Please describe to our viewers how your proprietary membrane chemistry works and what it achieves.

Rappaport: ZwitterCo’s zwitterionic membrane technology delivers what the water industry has been seeking for decades; a rugged polymeric membrane that is immune to irreversible fouling and solves the toughest wastewater separation challenges.

Traditional membranes “foul” or clog up with particulates and organic debris rapidly. This means for tough-to-treat wastewaters, membrane replacement occurs frequently, increasing the operational complexity and cost of running wastewater plants, and making them impractical as a high-volume solution.

ZwitterCo membranes, by contrast, perform as new after every cleaning cycle. ZwitterCo’s patented zwitterionic copolymers self-assemble into hydrophilic channels, acting like flumes at a water park, ushering through H2O molecules, and repelling everything unable to flow through its narrow pores.

Our membranes can be used in a wide variety of new applications and operating environments, given their ability to handle streams containing fats and oils that standard membranes cannot. They also last longer than membranes made from traditional chemistry, allowing organizations to reclaim the full value of their resources while reducing maintenance and overhead costs.

The company is building a suite of membrane products with these and other capabilities, bringing the precision and reliability of filtration to historically underserved markets.

WT: How do the super filtration (SF) membranes work?

Rappaport:  Superfiltration membranes fall between the ultrafiltration and nanofiltration classifications. They demonstrate high nanofiltration-like organic rejection and low ultrafiltration-like inorganic/salt rejection.

ZwitterCo pioneered the term superfiltration in reference to its membrane, an extremely low-fouling membrane offering unprecedented filtration for the most challenging separations. ZwitterCo SF membranes can be cleaned with chlorine and are extremely low fouling on streams that have been considered unsustainable in the past. With these characteristics, SF membranes can be a great option for applications requiring a separation of components.

WT: Your website states that you work with industrial operators and integration companies looking for alternatives to distressed filtration systems, chemically intensive processes, or processes that cannot achieve desired discharge or reuse quality. Describe the work you are doing in each of these categories referring to the problems and your solution benefits.

Rappaport: ZwitterCo has provided membranes for more than 20 commercial installations that will treat ≥ million gallons of wastewater per day. Solugen, a Houston-based company that manufactures chemicals and materials using enzymes, uses ZwitterCo’s membranes and has recycled 10 million gallons (about 37854100 L) of water so far.