VERO BEACH — Indian River County commissioners Tuesday extended a moratorium on spreading partially treated sewage on fields, a practice believed to have polluted Blue Cypress Lake.

The extension will expire in mid-June.

Several speakers at a brief public hearing asked that the moratorium be made a permanent ban on using the sludge, also known as Class B biosolids, as fertilizer.

That would take action by the Legislature, said Commissioner Peter O'Bryan, adding that a permanent ban "is one of our top priorities in the upcoming legislative session."

More:IRC Commission enacts moratorium on sewage sludge as fertilizer

A 2013 state law banned Class B biosolids in South Florida, including the Lake Okeechobee and St. Lucie River watersheds.

That led to an increase in usage to the north, including the St. Johns River watershed, said Commission Chairman Bob Solari.

Blue Cypress Lake is the headwaters of the St. Johns River.

With state action needed to ban biosolids, the moratorium is the best the county can do, without risk of a lawsuit, O'Bryan said.

Ban follows bloom

The board initially enacted a six-month ban on Class B biosolids in mid-July after algae in the western Indian River County lake bloomed with off-the-charts toxic levels.

That moratorium would have run out Monday. The Legislature's session begins in March.

The Fellsmere City Council on Thursday is expected to approve a six-month extension of the biosolid moratorium the panel enacted in August.

Scientific data collected by state agencies and the Ocean Research & Conservation Association indicated the algae bloom was caused by stormwater and groundwater runoff from nearby Pressley Ranch, which was spreading biosolids on its pastures.

The ranch owners have agreed not to use biosolids "at least through 2019," County Attorney Dylan Reingold told commissioners Tuesday.

More: Is sewage sludge from ranch fertilizer polluting Blue Cypress Lake?

Several commissioners lauded the ranch owners for stopping the practice voluntarily.

At the urging of the Florida Department of Environmental Protection, the ranch owners agreed to suspend biosolid use during last year's summer rainy season.

Sewage sludge was last spread on the ranch's pastures in May.

Owners of Corrigan Ranch, another farm in western Indian River County with a permit to spread sewage sludge, told county officials Monday the ranch has not used biosolids in several years and will not use them in the future.

The benefits of biosolids to large-tract owners include free fertilizer and/or getting paid to dispose of municipal waste.

Action follows investigation

Action by the DEP and county came about six weeks after a TCPalm investigation questioned whether the ranch's biosolids were to blame for rising phosphorus levels, which can — and two weeks later did — cause a highly toxic blue-green algae bloom in the lake.

Class B biosolids have been treated, but still contain pathogens and heavy metals.

More: TCPalm's award-winning "Laying Waste" investigation on biosolids

Pressley Ranch, southwest of the lake, began spreading biosolids on 3,059 acres of pasture in 2013 to help grow Bahia grass for cattle grazing.

The ranch spread more than 5,277 dry tons in 2017, according to DEP documents. That's about 1.7 tons per acre — the weight of 10 Boeing 747 jumbo jets.

A water sample from a Blue Cypress Lake algae bloom tested in mid-June contained the toxin microcystin at a level of 4,700 parts per billion, according to the Ocean Research and Conservation Association in Fort Pierce.

The World Health Organization considers microcystin levels higher than 2,000 parts per billion "very highly hazardous" in recreational contact.

Microcystin can cause nausea and vomiting if ingested, and rash or hay fever symptoms if touched or inhaled. Drinking water with the toxins can cause long-term liver disease.

More: Toxin in blue-green algae could trigger neurological diseases, scientists say