A study of Prince George's County trash disposal, as expected, concluded that a massive incinerator should be built, and recommended a popular mandatory recycling program that makes the plan politically more acceptable.

The recommendation, made last week after a five-month study by a consulting firm, comes on the heels of a controversial attempt to purchase a 307-acre site in the fast-growing Bowie area last spring for new landfill space or an incinerator. County Executive Parris Glendening proposed buying the land in addition to expanding the existing Sandy Hill landfill, but after an emotionally charged debate, the County Council voted down the proposal.

"We've got to find new technology and that was part of the whole Sandy Hill question," said Council Chairwoman Hilda R. Pemberton. "We will just have to find a system that will have the least impact on the people and be the most efficient for the county."

So far, the proposal has been met with guarded acceptance. Both the chairman of the 25-member citizens study group reviewing the recommendations and a Prince George's County Civic Federation leader are backing a mandatory recycling program. The advisory board will consider the proposals at a meeting Tuesday and could make a recommendation for action to Glendening by the end of the month.

"It sounds like a good idea," said Carmen Anderson, past president of the civic federation. "It beats the heck out of landfills."

"Everybody on the committee favors recycling," said Robert A. Manzi, chairman of the advisory board.

The most difficult decisions, Manzi and county officials said, will be choosing a site for the incinerator and coming up with the estimated $333 million to build it. Barbara G. Yuhas, an evironmental planner for the county's Department of Environment, said a recommendation of a site and a mechanism for financing could come as early as June.

To get public reaction early and to head off the type of public outcry that characterized the site selection of the Montgomery County trash incinerator this summer, the county has surveyed 10,000 county residents. The results of the survey, which asked residents to list factors that should go into the selection of a home for the incinerator, should be completed by the first week of October.

While county officials will not rule out putting the incinerator in the heavily populated and fast-growing northern section of the county, the more likely site is the rural southern part of Prince George's, with at least one transfer point in the urbanized areas.

Financing could come from county bonds with annual operating costs, estimated to be $58 million, offset by dumping fees and money earned by selling steam or electricity generated from burning garbage to a utility company. Or, as in the case of Baltimore, a private corporation could build and operate the facility with a guarantee from the county that it would provide garbage to burn.