A new residential microwave television service creeping into the Washington area could present tough competition to the District's long-awaited cable television system, according to industry and government sources.

The microwave services can share up to four channels set aside for each educational institution licensed for educational broadcasting and transmit entertainment, news, sports and public affairs via receiving dishes to homes or apartment houses.

The Federal Communications Commission has authorized schools and nonprofit institutions with educational broadcasting licenses to lease their unused microwave capacity to commercial operators as a way to encourage new service while giving schools a new source of revenue.

By mid-1985, for example, Microband Corp. of America plans to begin broadcasting over four channels assigned to the D. C. public school system. Microband operates Marquee Television Network, a one-channel television service that supplies about 40,000 D.C. customers with Home Box Office programming. The University of the District of Columbia also is considering obtaining a license and leasing out channels to commercial firms.

But the competition such services could provide to the District's cable system -- which is not expected to begin operations for several years -- is raising fears among some city officials.

"I'm furious" about the agreement between the school system and Microwave Corp., said Betty Ann Kane, head of the D. C. City Council committee on public services and cable television. Kane said the school system had asked for space on the coming cable system while negotiating the separate agreement.

"It's a very difficult situation when you have the city and you have public agencies competing," she said. "If it's going to be a commercial use that competes with the cable system, there is a reason for concern."

The city has completed negotiations with District Cablevision Inc., a cable television operator, for a cable television system and expects to grant a franchise by for the project by mid-December, an aide to Kane said. That would allow the city to receive cable service within five years.

The FCC ruling allowing commercial use of educational channels set off a rush of license requests from microwave television operators and educational groups.

More than 16,000 applications for microwave television licenses have been filed by commercial firms, along with 600 to 700 new requests by educational institutions for licensing, according to an FCC official. The microwave service "could very well be competitive with cable," he said.

"MDS may destroy the future of cable, which is ultimately a much better, complete, and democratic service," said Andrew Jay Schwartzman, director of the Media Access Project, a consumer interest group. "This new service can provide pay television channels more quickly and more cheaply than cable can."

Schwartzman also said he was concerned that standards for obtaining educational broadcasting licenses are too loose. An FCC official said the agency is considering new criteria for granting the licenses.

Network for Instructional Television, a nationwide nonprofit organization, will supply programming to the D.C. school system, said Arthur Stambler, a lawyer who represents NITV.

Microband Corp. will pay the school system to use the same channels to broadcast pay television into the District.

Microband Chairman Mark Foster said his company has agreements with about 18 educational institutions and approached about 50.

"We are just trying to satisfy a definite demand among the public," Foster said. "We have just as much right to be providing a service as cable does."

Meanwhile, George Mason University, which now broadcasts C-Span and Cable News Network programming to some D.C. schools and businesses, is planning to make a microwave television service available to Washington-area residents within the next year, said Michael Kelly, director of telecommunications for the university.

Kelly, who did not want to relinquish control of programming to a commercial operator, said the university will provide the service in a joint venture with another broadcaster. Kelly said commercial operators who approached the school "did not have an understanding of educational needs."

"We will definitely cut into the cable market to a certain extent in Washington and will be competing with cable directly," he said.

The University of Maryland and George Washington University want to reserve their channels for future educational use, spokesmen said. Georgetown and American University do not have educational broadcasting licenses. The University of the District of Columbia does not yet have a license but may apply for one, a spokesman said.