But during a professional conference, Gross’s research caught the eye of Kuldip Kumar, principal environmental scientist at the Metropolitan Water Reclamation District of Chicago, one of the largest wastewater treatment systems in the U.S. Kumar asked Gross if he had ever considered using his system to treat wastewater. The water utility was looking for algae-based solutions for reducing nutrients in wastewater. Gross told Kumar he had not tested that application, but the utility still invited him to work on a pilot study to demonstrate that the system worked.

The system grows algae on vertical conveyer belts. The algae digest nutrients such as nitrogen and phosphorus during treatment, reducing the amounts that remain in effluent and that normally have the potential to contribute to large algal blooms in bodies of water.

“They kind of found us,” Gross says, adding that working with the water utility was a game changer, shifting his focus from biofuels to wastewater treatment.

“We learned a lot,” Gross says. “It was very early-on research.”

One key finding was that changing the orientation of their system to be more vertical reduced the amount of space required to produce algae. Although algae has been an option for nutrient removal in wastewater treatment for decades, its use has been limited because it typically needs large ponds, which require a larger footprint than what most municipal wastewater treatment systems have, Gross says.

From the Lab to the Field

Gross and Wen founded Gross-Wen Technologies in 2014, and used their treatment system to help the city of Slater, Iowa, meet new wastewater nutrient limit requirements on a small, .92-million-gallon-per-day treatment plant. It is currently working with the City of Pasco, Wash., on a project for a new resource recovery facility being built to treat 1.5 billion gallons of wastewater per year and produce renewable natural gas.

Joe Zuback, a former Siemens chief technology officer and a water sector veteran who has followed the evolution of algae in wastewater treatment, says, “When I first saw the technology, I thought this had lots of promise.”

Zuback was also impressed with Gross, who he says has a depth and understanding of the technology he is working with that few startup firm founders have. “Martin has spent years studying algae,” he adds, which helps him think of possibilities other might not.

Zuback is a current board member of Gross-Wen, although he does not have a stake in the company. “I have great hopes for its success,” he says.

The company is currently working with a non-disclosed major oil and gas corporation to study using the company’s algae-based solution to produce aviation fuel, bringing Gross back to his initial interests.

“This is kind of a cool full circle for me professionally, since I got into the space to make biofuels from algae” he says—now using what he has learned to “create a lot of value from the algae that’s produced during the wastewater treatment process to make biofuels.”