The Montgomery County Department of Environmental Protection recommended yesterday that the county expand its controversial landfill, build a mass-burn incinerator at either Shady Grove or Dickerson and implement expanded recycling programs for items such as glass and aluminum to deal with mounting garbage.

County Executive Charles W. Gilchrist is expected to make a final decision on how to dispose of the county's trash after an all-day public hearing on Aug. 9.

Although John L. Menke, director of the environmental department, acknowledged that his recommendations would be opposed by some community groups, he said the three-pronged plan was in the county's best interest. "The probability is very low of finding new options that would have significantly greater community acceptance, coupled with reasonable cost and reliability," he said. "The time for a decision is now."

The debate over Montgomery trash has been raging for years between the county and residents who do not want garbage facilities near their neighborhoods.

County officials have conducted a research program that is expected to cost nearly $7 million by the end of the decade.

The four-year-old Oaks Landfill in Laytonsville will reach capacity by 1990, and county planners have predicted that it would take three to five years to begin operating a new facility.

"Solid waste management issues have been studied by Montgomery County for 15 years, and we have not been able to decide on a long-term solution," Menke said.

He called the landfill expansion moderate and said he was rejecting further expansion options.

Laytonsville residents immediately criticized the announcement.

"The county made a gentleman's agreement with this community that the landfill was a short-term solution," said Wanda Meyers, a community activist who lives in Laytonsville a few miles from the Oaks Landfill. "We object to any expansion."

But Menke said that a 1982 agreement between the county and citizens groups specifically noted that the county might enlarge the dump, which handles all county refuse.

"The citizens groups fear the seepage of waste products into the local ground water and other environmental problems. To support their protests, they have pointed to recent allegations by crane operators at the Shady Grove transfer station that hazardous wastes have been dumped at the landfill.

County and state officials maintain that the charges about hazardous waste dumping are false and come from disgruntled transfer station employes.

"There is no problem," Menke said. "But we're going to review it, and if we can tighten it up even more there we will."

Menke's recommendation of a mass-burn incinerator at the Shady Grove transfer station also faces stiff opposition from Shady Grove activists.

"What concerns us most are the unregulated emissions from a mass-burn facility, particularly dioxin, cadmium and other heavy metals," said Margaret L. Erickson, president of a group of local residents. "These are known carcinogenic materials."

However, the county recommendations, which focused on unregulated emissions, concluded that the incinerator "had minimal health effects."

Dickerson area activists also criticized the plan. "This feels very familiar to us," said Bev Thoms of the Sugarloaf Citizens Association.