Montgomery County's long-running battle to install a new trash landfill has moved to the jurisdiction of the Maryland State Department of Health and Mental Hygiene.

After narrowing the choice down from 24 sites proposed more than a year ago, the county has applied to the state health department for two permits to install solid waste sanitary landfills. One proposed site is in Potomac at Persimmon Tree Road and Bradley Bouleyard and the other is in Laytonsville at Rte. 108, Zion Road and Riggs Road.

The state health department launched public hearings on the proposed Potomac site last week at Churchill High School On Monday night at Magruder High School, anotherpublic hearing began on the proposed Laytonsville site.

The first session at each hearing featured a brief statement by county planners, followed by about three hours of testimony from area residents.

"The application for permits before the state is the last opportunity to avoid a state of public health emergency in the county," said landfill project manager Andrea Weirich, pointing to a December 1977 state health department order directing the county to "immediately identify a site or sites for a sanitary landfill and to obtain permits."

By 1981, when the current Gude-Southlawn landfill reaches its maximum capacity, there must be a place to dispose of the 473,000 tons of refuse produced in the county each year, Weirich told the approximately 300 persons at the first Laytonsville hearing.

Although the county is "fully committed and is proceeding toward a resource recovery system, which will recycle most of the solide wastes," Werlich said, a landfill must still be used for the nonrecyclables and as a backup.

At the first session of the Laytonsville public hearing, citizens presented a range of objections to the planned sites.

"First and foremost, is the life and death issue of the pollution of potable water in an area where everyone depends on wells," said John Wehrle, of the Greater Laytonsville Civic Association.

A touching plea by Mount Zion resident Thelma Carter to save the oldest black community in Montgomery County drew sustained applause from the emotional crowd, as did farmer Gordon Key's testimony that the landfill would ruin farmland.

Other citisens' objections included the safety hazard and noise pollution created by trash trucks, destruction of wildlife and the change in the community from the rural-residential to industrial-commercial.

Residents suggested expansion of the current Gude landfill or accelerating the construction of a resource-recovery system as alternatives to installing a new landfill.

While Potomac residents expressed many of these same concerns, their strongest argument centered on hazards to aircrafts posed by landfills located near airline flight corridors.

Representatives of about two dozen citizens' groups called the Committee to Save Our Land produced a Federal Aviation Administration report that says trash landfills attract high-flying birds which could interfere with aircraft approaching or leaving an airport. Birds striking an aircraft in midflight could cause a crash, the report says.

The proposed Potomac site lies beneath a flight path for planes entering and leaving Washington National Airport, noted the group's attorney, Alfred L. Scanlan.

However, the county's detailed $22,000 report on the "bird issue," prepared by consultants Dames and Moore, said the landfills would pose "no increased risk" to airplanes.

The Potomac site hearings were continued in Baltimore last week, and the hearing examiner is expected to rule on the case on Oct. 2 on the strength of "bird issue" testimony. If further testimony is required, the hearings will resume on Oct. 3 in Baltimore.

The Laytonsville hearings resumed at the Board of Education auditorium in Rockville on Tuesday and are scheduled to run through next week, if necessary.

The hearing examiners will then make recommendations for permit approval or disapproval to State Secretary of Health and Mental Hygiene Neil Solomon.

After the state has made a decision on the permit application, County Executive James Gleason will hold a public hearing on the site selection and acquisition.