Blue-green algae have returned to the Lower Potomac River for the first time in years, and Noman Cole, a Potomac watcher for 22 years and one-time czar of Virginia's waterways, is convinced he knows why.

Five weeks ago, shortly before clumps of algae started floating in Pohick Bay and into the river, the Virginia State Water Control Board, at the behest of Fairfax County, relaxed the discharge standards for a sewage treatment plant upstream from the bay.

Cole, who was the water board's chairman from 1970 to 1974 and used the position as a pulpit to wage a concerted battle against polluters, says the algal growth is the product of the high levels of ammonia that Virginia is allowing from the county-run Lower Potomac plant. Cole says the ammonia is combining with the phosphorous discharges to produce the blue-green algae.

Virginia "went too far" in relaxing the standards, Cole says, to the point that Fairfax's effluent is laced with ammonia that is five to seven times or more than the level being dumped into the Potomac upstream from the District's Blue Plains treatment plant or Maryland's Piscataway plant.

"Virginia to me is the bad actor because of these relaxed standards," says Cole, now 50 and a bit grayer and paunchier than when he first waged war on Fairfax's dump-the-sewage-in-the-river policies of the early 1970s. Time has not softened his tart tongue.

Told that some area officials reject his charges, Cole, who has meticulously collected samples of algea-laden water, snaps: "I'd like for him to drink one of my bottles and he'd go the same way as the fish."

Few county officials greeted such verbal onslaughts a decade ago with anything but disdain. Now the cast of Fairfax officialdom has changed, but its view of Cole, a nuclear engineer, and his contentions has not.

Richard J. Gozikowski, director of the county's waste mangement office, and Allen Hogge, Lower Potomac's plant manager, both said that the recent weather--daily temperatures in the 90s with little rain--has caused water stagnation and given the algae a chance to flourish.

"We're having a problem currently, but there's no way it can be blamed on the waste water treatment plant," Gozikowski said. "Noman Cole may think he knows it all, but I don't think anyone in the world does."

Austan Librach, director of environmental programs for the Metropolitan Washington Council of Governments, said that the algae are most prominent in the Potomac below the Woodrow Wilson Bridge, but algae seem to be spreading elsewhere.

Librach said he is uncertain why the growth is occurring but said "the primary culprit looks like the spring runoff particularly the pollutants carried into the river in combination with the heat and the lack of rain." He said that for at least part of the river, higher ammonia levels, as Cole contends, "may contribute to a part of the problem."

There also are algal growths on the Occoquan Reservoir, downstream from the Upper Occoquan Sewage Authority's treatment plant, which removes virtually all ammonia from its effluent. Millard Robbins, the authority's executive director, says he is not sure why the growths--the worst since the plant near Manassas opened five years ago--are occurring.

It may even be because of the gaggle of Canada geese that has claimed the reservoir as its home, Robbins said. "They're rather prolific dischargers."

Because of its toxicity, the algae can be harmful to marine life, but so far they have mostly just given the Lower Potomac and some other parts of the river a murky, greenish hue.

By all accounts, the river is vastly cleaner than it was a decade ago when Washington-area governments routinely dumped raw sewage into the river and did not treat human wastes nearly as effectively as today.

Cole says he is worried that the advances he helped promote in the 1970s might be forfeited. "We made major gains and now we're backsliding," he says.

Under the new standards, Fairfax does not have to meet any requirement for treatment of ammonia in the effluent it can discharge from the Lower Potomac plant, located along Rte. 1 in southern Fairfax. The county is easily meeting both the old and new standards for removal of other pollutants from the plant.

The state approved the change in standards after Fairfax officials, including county board Chairman John F. Herrity and County Executive J. Hamilton Lambert, complained last year about what Herrity called "excessively stringent embayment standards that are not necessary for maintenance of acceptable water quality."

Lambert said in a letter that the state's delay in "setting realistic discharge standards" at the Lower Potomac plant had added $20 million to the cost of Fairfax's planned expansion of the facility. Lower Potomac can treat up to 36 million gallons of sewage a day and Fairfax hopes to expand it to 54 million gallons.

Two weeks ago, Cole's 22-year-old son Nelson, a senior at the University of Mississippi, spotted the algae in the Pohick and the river while boating in the vicinity of the Coles' waterfront home near the tip of Mason Neck. The elder Cole took water samples from various spots and took the specimens to the Occoquan Watershed Monitoring Laboratory for analysis.

As it turned out, the ammonia and phosphorous levels in Cole's samples were highest in Pohick Bay, downstream from the Lower Potomac plant, and much lower in Potomac estuaries where there are no sewage treatment plants.

"You can talk all you want about the weather , but the only difference among the water samples is the sewer plant spewing out copious quantities of ammonia," Cole said.

"There's no way that statement can be proven," retorts Fairfax's Gozikowski. "Obviously algae is not uniform in its growth."