Washington's public food markets - where everybody shopped in the days before supermarkets - are making a comeback.

Catering to shoppers who are literally fed up with frozen vegetables, factory-fresh meat and other products of agri-business conglomerates, the markets promise the return of fresh-from-the-farm eating and mom-and-pop stands.

Within the next year, private developers are expected to open two Washington markets that have been closed for many years, and public improvements will be made at two other markets that are in serious need of modernization.

First to reopen will be the Georgetown Market on M Street NW, which should be back in business shortly after Christmas, following nearly three decades as an auto parts warehouse.

Work is also supposed to begin before the year's end on the O Street Market, between 7th and 9th Streets NW, boarded up since the 1968 riots. The market itself will be reopened, and a new Giant supermarket and a bank will be built next door as part of the commercial revitalization of the Shaw neighborhood.

District of Columbia officials, who played a key role in resurrecting those two projects, are preparing plans for revitalizing two other markets that are alive, but not well - the Fish Wharf off Maine Avenue SW and the Eastern Market off Pennsylvania Avenue SE.

Federal funds will be used to repair physical facilities at the Fish Wharf and Eastern Market and to improve the surrounding neighborhoods to make them more attractive and convenient to shoppers. Private merchants will continue to operate in all the markets, leasing space directly from the city or subleasing from an intermediary market operator.

"The city is now realizing that the markets are one of Washington's treasures," said John Brophy, whose title in city government is public parking administrator, but whose job involves planning for several of the market projects, especially the Fish Wharf.

John Fondersmith of the municipal planning office said the city's efforts to revitalize the markets have increased because "we've recognized them as valuable not only in the commercial sense but in relation to the character they establish in a neighborhood."

Consumer desire for a different kind of food and "nostalgia for a quieter time" are bringing back markets, theorizes Don Croll, who is in charge of real estate - and markets - for the city's department of general services. Shoppers prefer markets because "at markets you don't buy things that are packed in plastic and you don't get checked out by a computer," Croll adds.

The trend is national. From Seattle to Cincinnatti, old markets are being revived.

None of the District of Columbia market projects is meant to be a major tourist attraction, but both the Georgetown and Fish Wharf projects will contribute to the tourist traffic in their vicinities.

The Georgetown Market is being rehabilitated under a Federal Economic Development Authority grant to look as it did in 1885 when the main portion of the building was built, said Croll.

There has been a market on the Georgetown site since 1750, he explained. The original market is believed to have been in what is now the basement of the building, opening onto the towpath of the C&O Canal; when the canal was built, the land between the Potomac River and M street was regraded, and the M Street building erected atop the old one.

The Georgetown market was abandoned by the city in 1937 but operated privately for a few years after that. It is expected to reopen in early 1979, said John Zimmerman, the developer who is leasing the facility from the District government and who will sublease space to merchants.

Zimmerman said he is in the final stages of negotiations with 10 of the 11 tenants needed to fill the building. On the main level will be about 6,600 square feet of retail space with shops selling fish, meat and poultry, cheese and dairy products, bulk foods - grains, coffees, teas and spices - produce and bakery goods, plus an automated branch bank with a computerised teller machine.

Zimmerman said he is seeking a delicatessen operator to run an eat-in and carry-out food business on the 2,200-foot mezzanine tucked beneath the ceiling of the old building.

The District's lease requires the building to be used for food and food-related items, but that will not prevent Zimmerman from turning the basement into boutiques selling everything from entire custom kitchens to antique kitchenwares and imported wines.

Awnings on either side of the long, narrow structure will shelter additional stalls, Zimmerman said, offering a seasonal merchandise that will range from fruits and vegetables to firewood and Christmas trees.

A much different development is planned for the O Street Market, which is meant to return retail facilities to Shaw, where most stores were burned out or boarded up after the 1968 riots.

That project has slipped back on the calender several times but is now supposed to reopen next year. Black entrepreneur James Adkins has been awarded $1.75 million in federal loans that are supposed to pay half the cost of renovating the historic O Street landmark, which was built in 1868. Adkins, in turn, will lease space.

"The project is definately go," said Giant Food spokesman Barry Scher. Construction of Giant's 35,000-square-foot food and pharmacy store will begin this fall and will take four to six months to complete. The first new supermarket built in the District of Columbia by a major chain since 1968, the Giant store is a joint venture of the Washington retailer, the District of Columbia Development Corp. and the local citizens groups.

City officials hope within the next few weeks to create a community citizens group to advise on improvements to the Eastern Market, said planning official Paul Hart.

The Eastern Market project has been embroiled in controversey over whether the entire building should be used as a market, or whether community groups should be allowed to continue to use the north end of the building as a community center and art gallery, Croll said. A plan to excavate the shallow cellar as a restaurant or shops has been shelved because of the prohibitive cost.

A public meeting is planned for late September to discuss plans for the Fish Wharf, where fishermen have been vending their wares ever since Congress designated the Maine Avenue piers as the "exclusive site for the landing of fish in the District of Columbia."

Nowadays the fish all arrive in trucks and the fishing boats tied up at the pier are little more than floating fish markets.

The dead-end street leading to the wharf will be rebuilt into a paved cul de sac, with a paved parking lot and meters to keep out the L 'Enfant Plaza bureaucrats who've discovered they can park free on the waterfront. A park is planned between the wharf and the nearby yacht club, and the waterfront walkway behind the Maine Avenue seafood restaurants will be extended to the fish wharf. Improvements also are planned for the fish cleaning and oyster shucking house, the market's one deference to contemporary sanitation.

It was sanitation problems that doomed the city's outdoor markets as much as the invention of supermarkets, say planners who've traced the history of the markets. With the invention of refrigeration and the rise of processed foods, the District Commission in the 1930s adopted a policy of eliminating the markets.