ST. PETERSBURG – Sometime between Christmas and New Year’s, the flow of waste from an abandoned Manatee County phosphate plant into a shallow harbor off Tampa Bay will resume.

Ten million gallons of partially treated waste water were discharged last month before alarmed Bay watchers persuaded the state to suspend the operation.

This time, the nutrient-laden waste water will undergo advanced treatment to remove much of the nitrogen posing a threat to the fragile estuary.

Even so, tons of nitrogen, which can spawn Bay killing algae blooms, will pour into Bishop’s Harbor from the defunct Piney Point plant – with no end in sight.

“Even with [advanced treatment], it still ends up to be a substantial amount of nitrogen,” said Janet Llewellyn, deputy director for water facilities at the Florida Department of Environmental Protection.

Llewellyn journeyed from Tallahassee on Thursday to attend a special meeting of the Agency on Bay Management, a contingent of biologists, local officials and others concerned with maintaining the health of Tampa Bay.

“This is a time bomb,” said Rich Paul, who manages the bird sanctuaries of Tampa Bay for Audubon of Florida.

More than a billion gallons of acid waste water is stored at the idle Manatee County facility.

All of it must be disposed of before the two mountains of slightly radioactive phosphogypsum can be capped and officially closed.

Of more immediate concern to state regulators is some 45 million gallons that must be dumped as soon as possible to prevent a catastrophic spill of untreated acid water into the Bay.

“We have not yet fully recovered from the effects of [Tropical Storm] Gabrielle,” said Nadim Fuleihan, an engineer who has assessed the plant’s holding capacity.

Gabrielle’s torrential rains in September precipitated a crisis that prompted the DEP to issue an emergency order to discharge up to 68 million gallons of treated waste into the harbor before the plant’s dikes burst.

Another 150 million gallons must be siphoned before the summer rainy season, Fuleihan said Thursday.

Piney Point is one of two fertilizer plants abandoned earlier this year when the New York-based Mulberry Co. declared bankruptcy.

Faced with an unmanned chemical plant with dire environmental potential, the DEP secured the site until a Polk County judge appointed Tampa lawyer Louis Timchak Jr. receiver for both plants.

“My No. 1 concern is to preserve and protect the environment,” Timchak said.

The Bay and harbor are beginning to be effected by the Piney Point discharge, said Rob Brown, Manatee County’s water quality administrator.

Water analysis has shown the previous discharge produced an increase in chlorophyll and a reduction of water clarity, which can lead to the destruction of vital sea grass beds.

Additional treatment to reduce nitrogen might avert the immediate crisis of an overburdened storage system, but it doesn’t necessarily offer a long-term solution, Brown said, noting the nitrogen removed from the water ends up in the atmosphere.

And what goes up, eventually comes down, some of it into the Bay.

“We’re investigating a number of alternatives long- range,” said Gary Uebelhoer, an environmental consultant hired by Timchak to assess the site.

Among the options: applying the waste water to land, injecting it into deep wells beneath the aquifer or finding an industrial water consumer willing to use it.

Cost is a significant consideration because the state is footing the bill.

“There is no culpable party here,” Llewellyn said. “There are no deep pockets to take care of this.”

The Legislature allocated $16 million from a state trust fund to maintain both plants this year.

More will be needed until the matter is settled once and for all.

The ideal solution would be to find a buyer for the facilities who would take responsibility for the environmental legacy of the previous owner, Timchak said.

“As you can imagine, the market is not very strong for used phosphogypsum plants with lots of process water sitting around,” he said.