From Iowa and Ohio, farmers and wastewater treatment plants are all too familiar with the issue of phosphorus runoff into rivers, streams, and other bodies of water.
But there could be help on the way. Since 2003, a Wisconsin researcher has made it his goal to reduce the amount of phosphorus released back into watersheds from wastewater treatment plant biosolids through phosphorus crystallization.
For Phillip Barak, a soil sciences professor at the University of Wisconsin at Madison, the experience of seeing wastewater treatments struggle with the buildup of excess phosphorus and with its disposal suddenly spurred an idea. “It became a eureka moment,” he says. “If we can get the phosphorus out of the biosolids, then you have a win-win.”
Here's how the system currently works:
As wastewater enters a treatment plant, some of the phosphorus crystallizes. This coats the plant's pipes and tanks, creating a nuisance for the operators. The remaining phosphorus exits the plant in the form of biosolids. The treatment plant then sells or gives away the nutrient-rich biosolids to farmers who apply it to their land.
The problem? The phosphorus in the biosolids is too highly concentrated, which reduces the benefit of nitrogen found in the solids. Additionally, this highly concentrated biosolids are often being applied to land in the same watershed as the plant, which also discharges its low-phosphorus content effluent water. The end result is that the same phosphorus essentially runs into the water again, which is not a very efficient system.
But Barak has a different approach. In his solution, the phosphorus is removed from the biosolids in the usable form of brushite, a calcium phosphate mineral. The biosolids then have a more balanced concentration of phosphorus and nitrogen. The recovered phosphorus can be used just like traditional phosphorus on farms, but should result in less runoff.
“This is a sustainable source of phosphorus,” says Barak, who says this recovered phosphorus is just as effective as what farmers would buy from their regular supplier. As for the price tag, "it will cost about the same as traditional phosphorus.”
Will it work? Barak and his team just completed their first pilot of their phosphorus recovery process at a wastewater treatment plant in the Chicago area.
According to Barak, there will be two sides to the business as it develops. One group will work with the wastewater treatment plants, selling Barak's process for removing phosphorus with the guarantee that his company will then buy the nutrient. The other side of the business will be farm-focused and sell the recovered phosphorus to growers.
He says they have been talking to cooperatives and other fertilizer sellers to get the brushite phosphorus on the market. From the fall pilot operations, the group currently has a stock of brushite for field testing in several locations in the US for the 2016 season. “Right now, we’re staying close to home in Wisconsin and Illinois, while looking into opportunities in Indiana, Ohio and other states,” Barak says.
“We have an obligation to do the best we can to efficiently use this natural resource,” Barak says. “Recycling is one way to stretch those resources for the future.”