Madison Metropolitan Sewerage District ships record volume of phosphorus out of watershed

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MADISON, WIS. – As part of ongoing efforts to improve regional water quality, Madison Metropolitan Sewerage District shipped a record volume of phosphorus out of the watershed in 2017.

The phosphorus was shipped out as tiny pellets of struvite fertilizer under the brand name Crystal Green. Michael Mucha, the District’s chief engineer and director, said removing the phosphate-based mineral advances goals for resource recovery even as the utility achieves a 96 percent phosphorus reduction in the wastewater stream.

“We’re turning a problem nutrient into a renewable resource that’s needed to grow crops,” Mucha said. “In the meantime, we’re increasing the efficiency of our own operations. It’s a win for the environment, the economy and the communities we serve.”

During 2017, the District produced 585.1 tons of struvite fertilizer, up from 497.7 tons in in 2016. The struvite total is equivalent to 146,000 pounds of pure phosphorus and as a controlling nutrient, a single pound of phosphorus can lead to 500 pounds of algae.

The District also set a record for biogas production in 2017 as it churned out 305.1 million cubic feet, up from 269.9 million cubic feet in 2016. The District used this biogas supply to generate more than 7.4 million kilowatt-hours of electric power to offset its own energy use.

During the year, the District cleaned and reclaimed 16.03 billion gallons of water, up from 14.87 billion in 2016 and the highest total since 2010. The District’s outfalls account for more than 90 percent of the flow at the discharge points that feed Badfish Creek State Wildlife Area and Badger Mill Creek, a class II trout stream. The District returned approximately 14.8 billion gallons of water to Badfish Creek and 1.2 billion gallons to Badger Mill Creek while reusing 184 million gallons for purposes within the plant.

Although the Madison Water Utility recently reported a 50-year low in water pumping during 2017, inflows to Madison Metropolitan Sewerage District’s Nine Springs Wastewater Treatment Plant increased in 2017 due to wet weather and continued growth among the 26 area customer communities the District serves. The sewerage District operates sanitary-only sewers; however, rain and snowmelt may enter the system and affect flow volume.

Other resources reclaimed by the District in 2017 included processing of 2.1 million gallons of class A liquid biosolids into class A cake biosolids, which hold potential in diverse markets including residential application. The District also produced 35.8 million gallons of Metrogro biosolids for use as a sustainable, local fertilizer by farmers in the region.