Gross-Wen Technologies first municipal system shows promise

The water being discharged from the city of Slater’s water treatment plant is “crystal clear, some of the cleanest wastewater I’ve seen in Iowa,” said Max Gangestad, chief operating officer for Gross-Wen Technologies.

The Slater-based company has developed a system that uses algae to treat wastewater.  Its first municipal system went online last year. 

Gangestad said that since the city of Slater installed the system in March 2023, the city has seen decreased nitrogen levels and improved the quality of water the city’s treatment plant discharges into the headwaters of Fourmile Creek.

“It’s a good check mark for our technology and a good marketing tool,” he said.

Gross-Wen, founded in 2014 by Martin Gross and Zhiyou Wen at Iowa State University, also has a commercial scale system at the University of Iowa that is funded through the Iowa Economic Development Authority and the university. It’s designed to push the technology from a research perspective and not intended to meet permit standards, Gangestad said.

“So Slater is the first installation that we have as part of the formal treatment process to meet the permit,” he said.

The technology involves growing algae on a conveyor system that  the wastewater runs through as part of the treatment process. In the treatment of the wastewater, the algae removes nitrogen, which can be sold and used to develop various byproducts.

Despite early signs of success, there is a lot of work to be done before more communities or organizations adopt the technology, Gangestad said.

“The water industry is a slow adopter; there’s no FOMO [fear of missing out] in the water industry,” he said. “When you’re installing technology, that’s a huge capital expense that you want to be darn sure that it works.”

But Gross-Wen’s algae system, developed to help industry and municipalities sustainably treat their wastewater more effectively and economically, is getting noticed.

In addition to launching the Slater project, Gross-Wen signed a contract last year with a developer called Burnham for a project in Pasco, Wash. There, it will help treat wastewater from six industries. After cleaning the water, it will be applied to farm ground through irrigation.

“So they’re taking water from six different [agricultural] processors and cleaning it well enough that it can be used as irrigation for them, so really making a circular economy,” Gangestad said.

The project is estimated at $170 million and includes the installation of a digester to recover gas and sell it as renewable natural gas. The digester is separate from what Gross-Wen will bring to the project.

“Treating industrial wastewater rich in [bacteria that can only live in an oxygen-rich environment] and nitrogen is normally seen as a challenge,” said Michael Henao, the city of Pasco’s environmental compliance coordinator, in a release. “This is an opportunity to complete the industrial symbiotic loop by providing treatment to local industries, producing renewable natural gas and algae-based fertilizer, removing CO2 [carbon dioxide] from the atmosphere, and closing the loop by providing water for agriculture use.”

The project will include 130 belts that will grow and move the algae through the water treatment process. The equipment will be manufactured by Doerfer Cos. in Waverly before it is shipped to Pasco, where it will be assembled on-site.

Construction is scheduled to be completed in early 2025.

Gross-Wen also received a nod in a March 2024 article in the London-based Financial Times about the growth in water technology to address climate change. 

Gangestad said Gross-Wen also has “a number of good-sized projects in the works throughout the Midwest.”

Success in Slater

Mark Estrem, Slater’s public works director, said primary factors influencing the city’s decision to partner with Gross-Wen included the fewer labor hours required to run the Gross-Wen system and the ability to reduce the city’s carbon footprint.

“If you can go a little bit green, why not?” he said.

There is also a revenue stream created for the city through the sale of the algae to companies using it for various byproducts.

“Not very often can you say that you get any return on your wastewater plant, so we are getting a small return,” Estrem said.

Estrem said the city had to do something to address ammonia limits in the water discharged from its plant because it was exceeding allowable limits a few months a year. Since the Gross-Wen system was installed, the city has been under those wastewater permit limits, he said.

Estrem acknowledged some “growing pains” but said those are all on the city’s end of the process and that the Gross-Wen technology is working as expected.

He said the city continues to work with Gross-Wen to address the issues and that the local presence of Gross-Wen gives the city confidence it will continue to receive the company’s support as it overcomes those challenges.

What’s next?

As it looks to expand the use of its wastewater treatment system, Gross-Wen is also increasing its focus on maximizing the value of byproducts from the algae that is grown to treat wastewater.

Gangestad said research is underway on possibly turning the algae into bioplastics for shoe inserts or potentially making it into sustainable aviation fuel.

Currently, the algae is used as turf fertilizer on high-end golf courses, he said.

“We see a huge potential to really maximize the value of the algae,” Gangestad said.