Lucian Pintilie, the Romanian director whose production of "Tartuffe" literally shook the foundations of Arena Stage last spring, will return for the 1985-86 season. He has been signed to direct "The Wild Duck," and his notions about Henrik Ibsen's drama are, apparently, every bit as unconventional as they were for the Molie re comedy. The show is tentatively set for the Kreeger Theater in late January.

The upcoming season -- the theater's 35th -- will open officially on Oct. 4 with Bertolt Brecht's parable "The Good Person of Szechuan." The "good person" ("good woman" in most translations) is a kind-hearted prostitute who discovers that goodness cannot survive, unaided, in the cruel world. Garland Wright will direct the epic-sized show in the Arena. Also scheduled for the Arena are:

* "Women and Water" (opening late November) -- the newest addition to playwright John Guare's projected four-play cycle about post-Civil War America. This is the play, in fact, that gets the whole cycle going; it takes place on the bloody battlefields of the Civil War, where Lydie Breeze, a nurse, hatches the notion of founding a utopian commune on the island of Nantucket and inspires several soldiers to follow her. (Two of the plays in the cycle -- "Gardenia," which shows the commune coming apart, and "Lydie Breeze," which picks up some of the characters and their offspring 20 years later -- were performed in 1984 by the New Playwrights' Theatre.) Arena's associate producing director, Douglas C. Wager, will stage the drama with Cary Ann Spear, one of the new members of the recently expanded company, taking the role of Lydie.

* Restoration" (January) -- From controversial English author Edward Bond, a new play that mixes the typical chicanery of 17th-century Restoration comedy with political observations and topical songs very much of today.

* The Philadelphia Story" (March) -- Philip Barry's classy 1939 comedy about a young, headstrong socialite, Tracy Lord, and why her wedding to a priggish snob never comes off. Elinor Renfield, who staged last season's torrid "Passion Play," will direct.

* The Taming of the Shrew" (May) -- Shakespeare's robust chronicle of the courtship of Kate and Petruchio, the former as rebellious as the latter is resolved to break her willful spirit. Wager, who believes the play is not necessarily the antifeminist piece it's come to appear, also directs this one.

Besides "The Wild Duck," the Kreeger shows will be:"

* 'night Mother" (October) -- Marsha Norman's Pulitzer Prize-winning drama. James C. Nicola will stage the taut, two-character work, which begins when a daughter calmly informs her mother that she is going to commit suicide and ends, 90 minutes later, when she pulls the trigger.

* "The Regard of Flight" (December) -- A one-man show starring Bill Irwin -- clown, pantomimist, dancer, vaudevillian, merry prankster and, incidentally, a recipient of one of this year's MacArthur grants.

* "Old Times" (May) -- Harold Pinter's tantalizingly opaque drama about a husband, a wife and the other woman, to be staged by Wright.

Arena also has booked "Avner the Eccentric" into the Kreeger as a preseason attraction beginning Sept. 10. Avner Eisenberg is the man's real name, and apparently he doesn't utter a word in his one-man clown show, although he has been known to balance a ladder on his chin, perform a miniature high-wire act and devour a stack of paper napkins with a relish that has you believing they are pancakes hot off the griddle. After several months of talks, the Studio Theatre has negotiated a contract with Actors' Equity Association, which officially sets the theater at 1401 Church St. NW on the road to becoming a fully professional operation. Under the terms of what is called a "small professional theater contract," the theater will employ a minimum of 15 Equity members in the coming season. What that will probably boil down to is an Equity stage manager and two Equity actors for each of the Studio's five shows.

Up to now, the usual salary for a Studio performer has been $50 a week, but under the new contract the Equity actors will receive $100 a week, plus a minimum of $80 a week for rehearsals. Although many of the small theater groups in Washington have been talking about similarly upgrading their operations, the Studio is the first to make the move.

"It's an extremely significant step for us," said Joy Zinoman, the Studio's artistic director. "Obviously, this contract opens us up to a whole new range of actors. That doesn't have to be stated. But it also has everything to do with getting the kind of material I want for this theater." Playwrights and their agents, she pointed out, are reluctant to entrust works to an amateur theater. The Studio's new professional status will give it greater leverage in securing the rights to new, unproduced plays or to recent off-Broadway hits.

The first show to be produced under the contract will be a stage version of Arthur Miller's television drama about the Holocaust, "Playing for Time," which opens the Studio's eighth season in mid-September. The budget for the coming season, Zinoman said, will be approximately $330,000 -- up from $270,000 this past season. Gala Hispanic Theater will perform "The House of Bernarda Alba" at the Public Theatre in New York on Aug. 10, as part of the fifth annual Festival Latino en Neuvo York . . . Lisa Waltz, who plays Nora, the older cousin in Neil Simon's "Brighton Beach Memoirs" at the National, will re-create the part in the movie version, scheduled to start filming Sept. 9. The plum role of Eugene, the playwright's 15-year-old alter ego, has been landed by Jonathan Silverman, who's now in the Broadway edition. Meanwhile, "Brighton Beach" will extend its run at the National by three weeks. It'll stay here until Aug. 25 . . . "A Weekend at the Broadwater Gulf," a new play by Harry Bagdasian, who left his post as artistic director of the New Playwrights' Theatre a year ago to concentrate on his own writing career, will get a staged reading in Arena's Old Vat Room on Monday, Aug. 5, at 7:30 p.m. Admission is free.