A new filtration system is separating water from cow manure as part of a Dane County effort to clean up lakes and streams.
AQUA Innovations began operation earlier this summer of a $1.65 million system outside Middleton that takes liquid manure from three local dairy farms and extracts nutrients, such as nitrogen and phosphorus, and solids that can be spread onto fields as fertilizer.
Manure from the farms first goes to the neighboring GL Dairy Biogas project, which extracts methane from the manure and food waste to generate electricity. Dirty water is then piped into the AQUA system and in about two hours, treated water, considered clean enough to drink, trickles out of a 4-inch pipe into the Pheasant Branch Creek, which feeds into Lake Mendota.
The concentrated nutrients are returned to the farmers, who end up with less manure to haul and spread and can apply it more selectively, which reduces the risk of rain washing it off the land.
Too much phosphorus in the water causes plants and bacteria to flourish, which can lead to fish kills, smelly rafts of rotting weeds and blooms of toxic algae that force beaches to close.
County Executive Joe Parisi said the project is essential to the county’s ongoing efforts to clean up the Yahara watershed.
The system currently processes about 25 million gallons per year but can handle up to 40 million gallons. AQUA Innovations CEO John Sorenson said it costs about 0.4 to 0.5 cents per gallon to operate — a cost covered by the participating farms.
Sara Walling, agricultural resource management administrator for the state Department of Agriculture, Trade and Consumer Protection, called the project “a fabulous example of innovation” to help farmers.
While the Sharon-based company has built similar systems before, this is the first to serve multiple farms. Sorenson said he hopes to replicate the model elsewhere.