Phosphates from sewage sludge entering Lake Washington

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Phosphates from the human “biosolids” used to fertilize farms are fueling potentially toxic algae blooms in Lake Washington, a main source of drinking water in Brevard County, new sampling shows. 

So, on Tuesday, Brevard County commissioners will consider whether to extend a six-month moratorium on any new permits to apply more municipal sewage sludge to lands within the county. 

“We want to extend the moratorium quick before the current moratorium expires,” said Virginia Barker, director of the county’s Natural Resources Management Department. “It prevents South Florida from convincing ag(ricultural) interests in Brevard from taking more biosolids from what’s already been permitted by the state.”

Commissioners enacted the moratorium on Oct. 8. The temporary biosolids ban did not apply to locations where sewage sludge already is applied, including the Deer Park Ranch, off U.S. 192.

But commissioners wanted to prevent any new biosolids coming from outside the county, until state environmental regulators develop stricter setbacks and other rules for applying the material on land.

The so-called “Class B biosolids” are solids, semi-solids or liquids from sewage treatment plants that contain nutrients such as phosphorus and nitrogen.

Elevated phosphorus and nitrogen in surface water are suspected to have spurred the algae blooms that in recent years plagued Lake Washington, an outcropping of the St. Johns River. Several miles west and upstream from the lake — Melbourne’s main drinking water source — trucks spread the sludge to fertilize pastures. 

Research by regional water managers suggests that disposing these biosolids on rural lands could be poisoning Lake Washington and the other Central Florida lakes where cities draw their tap water. Other suspected sources are St. Johns River Water Management District projects upstream of the lake, nearby development and septic systems east of the lake. 

Brevard County commissioned a $31,000 study after a blue-green algaebloomed in Lake Washington during the summer of 2019.

The study collected 50 soil samples from Deer Park Ranch. The firm Applied Ecology Inc., with supervision from county and University of Florida staff, also gathered 11 water samples and three grass tissue samples. Samples were tested for nitrogen and phosphorus; seven metals; 24 polyfluoroalkyl substances (PFAS); and 58 pharmaceuticals, personal care products and other contaminants of emerging concern at Deer Park Ranch, upstream of and within Lake Washington, and in residential drainage canals entering Lake Washington. 

Sampling during the bloom found low levels of algae toxins, but none that would cause human health concerns, city and county officials said.

“No manmade chemicals suggestive of human health concerns were found leaving Deer Park Ranch,” county officials wrote in a write-up of the study’s results. “While a few pharmaceuticals were found in plant tissue samples on the ranch, these were not found in water leaving the site. Metals leaving the site were low concentrations, below drinking water threshold values, assuming typical hardness values for local surface waters.  

“The only contaminants of emerging concern found leaving the site were PFAS compounds.”

PFAS are a group of persistent chemicals used in fire suppression and many industrial and commercial products for decades and recently identified as posing cancer and other health and environmental risks. Most of the PFAS levels were below laboratory detection limits. 

None of the samples of the two compounds of most concern — PFOA and PFOS — exceeded the lifetime drinking water health advisory of 70 parts per trillion. Nor did they exceed the state’s ecological screening levels for surface waters. 

Canals that drain developed areas east of Lake Washington had higher PFAS levels than waters leaving Deer Park Ranch. One roadside canal sample taken east of the lake had PFOS levels higher than a recently proposed, but provisional, state human health surface water screening level.

The more significant finding was phosphorus, county officials said.

“The soil and water samples both indicate that phosphorus from state-permitted land application of biosolids to cattle pastures is leaving Deer Park Ranch and entering the St. Johns River during periods of heavy rain,” the county’s write-up states.

Soil data shows a long history of land applying biosolids on the ranch beyond the capacity of most pasture soils to hold phosphorus, county officials said. “That release of excess phosphorus contributes to alteration of the natural nitrogen to phosphorus ratios in local surface waters and an associated increased risk of harmful algal blooms in Lake Washington.”

Local county moratoriums are “a temporary stopgap,” county officials said, until new state rules take effect.

Florida Sen. Debbie Mayfield’s Clean Waterways Act (Senate Bill 712), which passed the House and Senate, would take effect July 1, creating stricter setbacks and other rules for land application of sewage sludge.

For at least five years, South Florida sewer plants have been exporting their sewage remnants north to Brevard and other Central Florida counties after stricter local rules on the practice in South Florida were enacted.

Much of Deer Park Ranch, operated by the Kempfer family, crosses over into Osceola County. In 2018, about 3,270 acres of the ranch took 7,484.5 dry tons of biosolids, adding 807,610 pounds of nitrogen and 294,228 pounds of phosphorus to his soils, according to the ranch’s annual report to the Florida Department of Environmental Protection.

Most of the biosolids on his ranch last year came form three places: 2,632 tons from a Miami-Dade sewer plant, and more than 1,000 tons each from sewer plants in Holly Hill in Volusia County and in Orange County, the DEP report says.

Jim Waymer is environment reporter at FLORIDA TODAY.

Contact Waymer at 321-242-3663                                         

or [email protected].

Twitter: @JWayEnviro

Facebook: www.facebook.com/jim.waymer

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