IA Sewage Plant Focuses on Phosphorus

Tuesday, May 10, 2016 @ 05:05 PM gHale


Iowa’s largest sewage treatment plant is investing $19 million in new equipment that will reduce the amount of phosphorus, a harmful contaminant commonly found in the state’s waterways.

Phosphorus does not pose the same danger to drinking water as nitrates, but it can lead to algae blooms that steal oxygen from local lakes and choke out aquatic life. It’s also a major contributor to the dead zone in the Gulf of Mexico.

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“Nitrogen is like beer, but phosphorus is like vodka,” University of Iowa research engineer Chris Jones said. “You just need a tiny bit (of phosphorus) to have an effect on aquatic life in lakes and streams.”

Blue-green toxic algae has become a perennial plague in late summer for Iowa waterways and in states downstream. The rapid growth of algal blooms closed a record number of Iowa beaches in 2015.

Within two years, the Des Moines Metropolitan Wastewater Reclamation Authority will be able to remove more than 2,000 pounds of phosphorus a day from the wastewater flowing through its facility on the city’s southeast side. That’s nearly 80 percent of the phosphorus that comes down the pipes from 17 communities in three central Iowa counties, and a 30 percent increase in the amount of phosphorus it removes today.

The new equipment will convert the chemical into fertilizer pellets that will end up packaged and sold to farmers.

“It’s a big step toward meeting our goals in the nutrient-reduction strategy,” said Adam Schneider, water quality coordinator with the Iowa Department of Natural Resources. “A (phosphorus) load reduction will likely help locally, in the vicinity of the facility, and ultimately with the downstream load into the Mississippi and into the Gulf of Mexico.”

It’s a sizable investment for the Des Moines WRA, but utility officials said the equipment will pay for itself over the course of 10 years by reducing wear and tear on machinery caused by phosphorus and through the sale of fertilizer pellets.

The Des Moines WRA consists of 17 communities that stretch from Polk City to Norwalk and Bondurant to Waukee. It has an approximately $34 million annual budget generated through sewer fees.

The utility’s board of directors approved a request for proposals for contractors last month. It expects to build the facility in 2017 and open in 2018.

“It will actually pay for itself,” said Larry Hare, treatment manager at Des Moines WRA.

The utility spends about $100,000 a year to remove and clean struvite, a crystal caused by the phosphorus that forms on equipment and clogs up pipes like cholesterol in arteries.

Des Moines’ plan for phosphorus removal is similar to facilities built during the past decade in Madison, WI, Portland, OR, and Chicago.