Phosphorus is found in unspoiled parts of the Everglades at levels below or around 10 parts per billion, say scientists from the South Florida Water Management District.

At a public meeting Thursday before state regulators, the sugar industry and other farmers are expected to argue that they should be allowed to pour 15 to 20 parts per billion, or more. Their numbers are based on findings from their own studies.

"It may sound like a very mundane and boring technical dialogue but a lot is at stake here," said Ernie Barnett, director of ecosystem projects for the Florida Department of Environmental Protection. "Both sides are pretty polarized."

According to an Audubon of Florida official, if the limit goes higher than 10 parts per billion, "the Everglades dies."

The scientific analysis out there "all seems to irrevocably point to 10 parts per billion as the appropriate criterion," Charles Lee, the group's senior vice president, said.

Farmers -- whose sugar and vegetable fields south of Lake Okeechobee are producing most of the phosphorus pollution entering the Everglades -- could face higher cleanup bills for the ecosystem if their suggested standard doesn't prevail. Growers are paying a portion of a $800 million Everglades cleanup bill also shouldered by taxpayers.

When phosphorus pours into the Everglades at levels higher than 10 parts per billion, it alters the marsh landscape, replacing signature knife-edged sawgrass with dense stands of cattails. The fertilizer is washed into the marsh along with agricultural storm water.

By holding phosphorus to 10 parts per billion, "you are really getting down to [the amount found in] rainwater," Barnett said. "You're really getting pretty pure."

Debate on the matter should grow hotter starting on Thursday at a public meeting in West Palm Beach before Florida's Environmental Regulation Commission and the DEP.

Water managers have been building more than 47,000 acres of filter marshes on the northern lip of the Everglades to sift phosphorus from the dirty farm water. But their stormwater treatment areas only reduce the wetland pollutant to about 22 parts per billion.

The pollution standard at issue will determine how much more the water must be cleaned.

Barbara Miedema, spokeswoman for the Sugar Cane Growers Cooperative, said the marsh may be better off with a range of allowable amounts of phosphorus, since it is home to sawgrass plains and other types of wilderness-like tree islands.

The Environmental Regulation Commission -- a seven-member environmental rule-making body -- will take up the subject at 9 a.m. at the DEP's Southeast District Office, 400 N. Congress Ave. Other public meetings will follow.

Under a 1994 state law called the Everglades Forever act, the regulation commission has a deadline of December 2003 to adopt an official standard, which won't be enforced for three years after that.

The DEP, which has been studying the issue, will make a recommendation to the regulation commission, which can then reject, accept or modify it.

In a strange twist for environmental advocacy, Audubon of Florida and environmental groups say they would prefer that the regulation commission set no pollution limit at all.

Their reason: If the regulators fail to propose a standard, 10 or otherwise, state law provides a default. That figure is 10.

But if the regulation commission adopts a number, that standard can be challenged before a state administrative law judge, who does not have to give a greater weight to the findings of environmental regulators than to special interests. Environmentals fear that situation.

"We think that would be a travesty for government agencies ... to fail to act," said Miedema, with the sugar cane cooperative. "It's not using taxpayer dollars wisely."

Florida already has a phosphorus limit for the Everglades but it takes the form of a "narrative," not numeric, standard. It says basically that phosphorus entering the marsh cannot cause "an imbalance of natural populations of aquatic flora and fauna."

The phrasing is harder to enforce than a numeral.

The DEP has not yet chosen a standard to push, but it likely will be in the low end of the 10 to 20 range, Barnett said.

Neil Santaniello can be reached at nsantaniello@sun-sentinel.com or 561-243-6625.