The Environmental Protection Agency yesterday bluntly warned the elected leaders of the District of Columbia, suburban Maryland and Fairfax County that they risk a federally imposed sewer moratorium that could halt the growing construction boom in the area.

Jack J. Schramm, administrator for EPA's regional office, laid down the threat after the region's leaders failed, as they have many times in the past, to reach agreement on disposal of the mounting output of sludge at the Blue Plains regional sewage treatment plant.

The meeting had been called by Schramm to break the deadlock before the sludge controversy goes back to U.S. court on Wednesday,but the meeting went nowhere.

When the outcome became apparent, Schramm said EPA would consider asking the court to impose a moratorium or that the agency might impose one without going to court.

Listening at the other side of the table were D. C. Mayor Walter E. Washington, Montgomery County Executive James P. Gleason, Prince George's Board Chairman Francis W. White and Fairfax Board Chairman John F. Herrity.

"Perhaps the elected officials of the region should be locked up in a room with some sludge until they reach a solution," said R. Robert Linores, president of the Metropolitan Board of Trade, which represents business and commerce. "All the jurisdictions are trying to attract business. If there is a threat like this (moratorium), and organization coming to the area will have second thoughts."

Schramm acknowledged that a moratorium would be an "extreme action," but said "it might force resolution of the sludge problem."

Sludge is the semisolid residue of sewage treatment. At present, the 900 tons produced daily at Blue Plains are buried in trenches in Prince George's. When Blue Plains goes to advanced treatment in 1980, about 1,800 tons will be produced daily.

A moratorium, even if it lasted only at short time, would have an immediate, crippling effect on new development in the area. The District of Columbia, which is experiencing a building boom, would have to stop all new growth, and Montgomery and Prince George's countries would have to stop most of theirs.

Fairfax County is less dependent on Blue Plains, but even so, a moratorium would halt will development in the fast-growing northwestern part of th country, including the new town of Reston.

EPA could impose a moratorium because Blue Plains is violating its federal discharge permit. Starting last January, D.C.'s Department of Environmental Services, which operates the plant, cut back on the level of treatment because it could not process all the sludge being produced.

Jean Levesque, the District of Columbia's lumbia's director of water resources administration, said the city could resume better treatment - and thus end permit violations - probably by Aug. 1, when he said four new sludge dewatering filters should be in operation.

But Levesque said that if there is not a quick solution to the regional dispute on getting rid of sludge, Blue Plains would have to revert to a lower treatment level - and more permit violations.

Schramm emphasized that a moratorium would be a "last resort," but he said: "We (the regional EPA office) are going to be playing a more active role than in the past. I think EPA is going to have to take a look at the Washington metropolitan area as a whole and make some decisions that will help the region move to a solution . . ."

What to do with the 900 tons of sludge produced daily at Blue Plains is one of the area's most troublesome environmental problems. U.S. District Court Judge John Lewis Smith Jr. has ordered each jurisdiction using the plant to take care of its own share after Sept. 21 when a trenching operation in Prince George's in scheduled to end.

Suburban Maryland and Fairfax said they would handle their share, but Washington said it has not been able to find any suitable sites in the city for composting sludge, and wants to use a location outside the city.

The suburbs said they would oppose any plan by the District of Columbia to set up a composting facility on their land, even at a federal installation.

Yesterday's meeting broke upwith the city and the suburbs still sharply divided on a solution.