Where others see waste, Gross-Wen Technologies sees opportunity. The Slater-based startup company is working to revolutionize the municipal and industrial wastewater treatment industry, growing algae on wastewater and profiting from both the treatment systems and potential algae bioproducts.
Founded in 2014 by a pair of Iowa State University professors, Dr. Martin Gross and Dr. Zhiyou Wen, Gross-Wen's innovative rotating algal biofilm or RAB system utilizes algae instead of bacteria or chemicals to recover nitrogen and phosphorus from wastewater. The result is clean water that’s ready for final disinfection via chlorination or UV light treatment before being released back into local waterways or returned to area aquifers.
Gross-Wen's RAB system uses large, continuously rotating belts partially submerged in wastewater to grow a thin algal film. As the belts rotate, the algae grows much as it would atop a stagnant body of water. When enough algae has accumulated, it’s harvested and collected for potential use in commercial products, including fertilizer and biofuels.
“Essentially, algae is Mother Nature's way of treating wastewater,” said Phil Gates, Gross-Wen’s director of business development. “Historically speaking, wastewater has been treated using bacterial or chemical-based alternatives. Those are typically more complex and energy consuming.”
In fact, according to Gates, up to 40 percent of municipal energy use can be directly attributed to wastewater treatment. Depending on the region and its climate, the RAB system can cut that number by more than half while also dramatically reducing the amount of chemical treatment agents needed.
Thanks to its modular design, the system is fully scalable and can be modified to fit a variety of treatment facilities.
Slater among company successes
For the City of Slater, their decision to adopt the RAB systems at its new 1 million gallon-a-day wastewater treatment plant was motivated by the need to meet stricter ammonia discharge limits while also saving on labor costs.
“A traditional mechanical wastewater facility really requires a full-time technician,” said Mark Estrem, public works director for the city. “The RAB system cuts that time down to just 15 minutes a day. That’s a significant savings for us.”
The city had traditionally relied on an aerated lagoon system as its primary wastewater treatment method. However, recent changes to federal wastewater discharge standards meant the city’s lagoon system could no longer meet the new, stricter discharge targets.
In December 2018, the Slater City Council approved moving forward with a new $4 million treatment plant that incorporated three 10-belt RAB modules. Additionally, the city designed the system to accommodate an additional three modules, allowing them to easily add treatment capacity as the community grows.
RAB systems are typically less expensive to build than a traditional sequencing-batch reactor, the industry standard in municipal wastewater treatment.
Construction of the new 17,500 square foot greenhouse treatment facility began in 2021. The structure was designed to maximize algae growth with a glass panel roof and temperature-controlled water.
To accommodate the new structure, one of the city’s existing aeration lagoons was drained, desludged, and partially filled. The remaining lagoon footprint was repurposed into a retention pond. The system was completed and brought online in March 2023.
Estrem also points to the improved treated water quality, which is returned to an adjacent series of retention ponds before being discharged into the headwaters of Fourmile Creek.
“The technology works extremely well. Our water quality has never been better. It’s really amazing,” Estem said.
Finding their flow
While Slater was the first municipality to install a full-scale RAB system, there are a growing number of cities and towns across the nation considering the technology. According to Gates, the company now routinely fields calls from across the county and around the world.
In addition to treating municipal wastewater, Gross-Wen is also expanding into industrial wastewater treatment. The company is in the final stages of overseeing a system installation at an industrial facility in Pasco, Wash., where it will clean 4 million gallons of wastewater per day being produced by seven food processors.
“Our system can be applied in a variety of industrial settings, most notably, food and beverage manufacturers,” Gates said. “Its high nutrient content is a really good source for algae to grow on, and therefore, that's a really important industry where we can apply the technology.”
RAB systems can also be utilized to provide industrial pretreatment, secondary municipal treatment, or in agricultural settings, such as in anaerobic digestors where they can help decrease traditionally high greenhouse gas emissions.
Cashing in on algae
In addition to selling and overseeing the installation of their treatment systems, Gross-Wen is also working to create value-added products from the harvested algae.
Currently, the company collects and dries the algae, which is rich in nitrogen and phosphorus, converting it into a commercially available granular turf fertilizer. However, they're studying other potential uses at their research and development facility near Boone.
Inside the greenhouse just off Highway 17 and 195th Street, the company has been working to grow various strains of algae in a variety of wastewater samples, utilizing small-scale versions of their RAB system. The algae is then collected and analyzed to determine which strains could be most commercially viable for applications ranging from soil amendments and fertilizers to bioplastics and biofuels.
With potential applications in various billion-dollar market segments, a growing number of investors are banking on the company’s future success.
To date, Gross-Wen has attracted roughly $15 million from venture capitalists and private investors, including raising $6.5 million in Series A funding. The company is currently undertaking Series B funding to expand its market reach and facilitate product development.
“We have a variety of potential products we're working on that I’m really excited about,” said Gates. “We’re a young company, and this is really just the beginning.”
For more information on Gross-Wen, visit them online at Algae.com.