The Virginia State Water Control Board, its members peering over quart jars of blue-green algae gathered from the Potomac, today turned aside a request to force Northern Virginia areas to tighten standards for dumping waste water in the river.

The board instead commissioned a study of the issue and asked for voluntary compliance by local jurisdictions on standards the board eased only last spring.

The hearing was the latest step in a summer-long controversy involving local officials and citizen groups who have sparred over the causes of the worst infestation of algae south of the Woodrow Wilson bridge in almost a decade and what should be done about it.

Competing witnesses flashed a variety of pictures and aquatic measuring charts and graphs for the seven-member board, offering conflicting testimony that the algae resulted from treated sewage, unusual weather conditions, high levels of runoffs from streets and other development, or a combination of all those factors.

"Quite simply, the river system went into shock," said Thomas M. Schwarberg, a water control board aide who suggested further study of the complex issue.

The board's ruling was a partial setback for Noman Cole, a resident of Mason Neck along the Potomac and a former member of the water board.

Cole has charged that the often foul-smelling algae, which can clog boat motors and chokes off marine life, results from an oversupply of phosphorus discharged by nine water treatment plants spread along the Potomac from Arlington south to Prince William County.

"It's clear that where there is a sewer plant there is a problem," said Cole, who served on the water board from 1970 to 1974. Cole presented voluminous documents that he said showed algae formations concentrated near Pohick Bay, site of Fairfax County's Lower Potomac plant, and other bay areas of the Potomac adjacent to treatment plants.

Cole had asked the board to require all nine treatment plants to limit phosphorus effluent to .2 miligrams per liter of water year-round.

Earlier this year, the board allowed Fairfax and some other jurisdictions to increase the phosphorus content to 1.0 except during the period from June to September, the hottest months with temperatures ideal for growing algae Today the board asked jurisdictions to comply with the .2 limit year-around if possible.

Last week, Fairfax volunteered to extend the .2 level through December, a three-month extension that will cost about $150,000 in extra treatment, according to J. Hamilton Lambert, the county executive.

Board of Supervisors member Audrey Moore, Democrat of Annandale, who spoke at today's hearing, said the extension, which she supported, was "political" and only meant to help supervisors, who she said were coming under heavy politcial pressure to do something about the river.

H. S. Hulme, Arlington's director of public works, told the board his county's treatment plant could not even meet the higher standard for phosphorus. "There is no known answer" to the algae problem, Hulme said.

The water board said it expects an interim report on the problem in December.