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New test program in Muscatine uses green, slimy plant to clean wastewater

The Muscatine Water and Resource Recovery Facility is using algae to remove nitrogen and phosphorus from its wastewater.

MUSCATINE, Iowa — Muscatine is testing a natural solution to treat some of its wastewater.

The Muscatine Water and Resource Recovery Facility installed a new Rotating Algal Biofilm System this month. It uses algae to remove nitrogen and phosphorus from wastewater.

"We send that water clean back into the Mississippi River, but it does still contain nutrients like nitrogen and phosphorus," said WRRF Director Jon Koch. "So the new regulations that are coming down the pike from the EPA to the DNR here in Iowa saya that we have to remove those nutrients from the water so that it doesn't go down into the Gulf of Mexico, where it creates what's called the Gulf Hypoxic Zone, which actually takes the oxygen out of the water and kills fish."

There are other ways to remove the nutrients from the water, such as using chemicals, but Koch said that can be more expensive and would require changes to be made to the treatment plant.

With this system, the wastewater gets run into a greenhouse and the algae grows on vertical conveyor belts that dip in and out of the water. 

"It's kind of a nice, neat way to (clean the water) using something natural," Koch said. "Algae has been doing this for millions of years, and we're just going to utilize it for our benefit now."

The algae get scrapped off the belts every so often and can be dried and turned into fertilizer. 

The RAB System was a project that a professor and graduate student started at Iowa State University, Koch said.

"(They) were trying to come up with ways to use algae to clean water, either out of ponds or industrially or out at the farms," he said. "I was there as a wastewater professional and they said this is probably an application we could find to use in wastewater as well. That was almost 10 years ago."

Since then, the researchers started the company, Gross-Wen Technologies, based in Slater, Iowa.

The company visited the WRRF in 2019 and proposed the pilot program, but it got put on hold because of the pandemic.

The new system does more than just protect the waterways, Koch explained. 

Nitrogen and phosphorus can lead to struvite, which is a rock-hard formation that forms inside of the WRRF's pipes and pumps.

"We have to clean that all out. It's incredibly expensive and difficult for our staff and treatment plants all over the world are dealing with struvite, so if we can grab that phosphorus before it even gets into there, we can solve two problems," Koch said. "Plus, we're going to be saving electricity, so we save money. And then we get to sell the algae at the end, which is a revenue source."

Since this is just a pilot system, only around 10,000 gallons of wastewater a day are filtered through the algae. Muscatine's WRRF treats around 3 million gallons daily.

The pilot program will run for six months.

"We don't expect to really see a whole lot of difference in our discharge at the moment," Koch said. "Basically what we want to do is prove that the algae runs and we'll sample the water going in and the water coming out. And if we see that big difference that we can say okay, now how many belts do you need? How big of a project do we need to build here in order to really affect what we want?"

The original cost for the six-month project was $100,000, but it ended up being $30,000.

After the six months end, Koch said WRRF has a report due to the DNR outlining what it plans on doing in the future. He said installing a larger, permanent system to remove the nutrients could be done by 2025. That project would cost around $2 million.

Muscatine also wants to use it with its watershed projects, so strips would be placed in the watershed amongst the farm ground to absorb the nitrogen and phosphorus.

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