Montogmery County will begin trucking sludge to the rural town of Dickerson next weeek after satisfying a citizens group that the composting facility where the sludge will be taken will be closed by 1982.

County executive Charles W. Gilchrist announced yesterday what he called an "unprecedented" agreement with the Sugarloaf Citizens Association and the state Department of Health and Mental Hygiene that sets out all the conditions for composting 400 tos of sludge daily at a $7-million plant recently completed on 40 acres of farmland in Dickerson.

Under the composting method, sludge is mixed with wood chips, set out to dry and sold as fertilizer. An alternative method, trenching -- where the sludge is buried -- is opposed by citizen groups throughout the county as a waste of land and a health hazard.

Montgomery County is due to take its turn Feb. 1 in disposing of Montgomery and Prince George's portion of the sludge from the Blue Plains treatment plant, but citizen opposition to both trenchng and the Dickerson composting plant left the county with a tangle of legal battles and no health permit to open the plant in time.

The county recieved a health permit yesterday that is the state's go-ahead for the plant. Starting Monday, Dickerson wll recieve 100 tons of sludge daily, building up to its 400-ton capacity by the end of the month.

The citizens group agreed this week to withdraw from adjudicatory hearings against the health permit and to drop a suit pending in circuit court against the plant in return for guarantees that the plant will colse when a permanent composting plant in Calverton opens and that every effort will be made to open that plant by Sept. 1, 1982.

"Preparation of the Calverton site, a mile from the Montgomery-Prince George's counties' border, has begun over the objections of Prince George's County residents who allege it will pollute groundwater in their communities.

"We started out trying to kill the facility and we failed, said Stephen P. Quarles, president of the Sugarloaf Citizens Association. "On the other hand, the agreement is almost historical in the kinds of promises the county had made. It is a sophisticated planning for sludge that the county has never done before. Our feeling is that they've admitted they short-changed the citizen's in the past."

The county agreed to set up a planning process to find alternatives to the Dickerson facility of Calverton is not ready in time or if other plants are need in the future.

Gilchrist hailed the agreement as singnaling the end of the sludge trenching "forever."

"Am I satisfied? No. I feel we've been taken advantage of because there's not many people out here," said Beverly Thoms of Dickerson. "The big drawing card for this contract is that it provides for planning a permanent solution.

"But the war is not over. They still have to apply for more permits and we will oppose them."

The coounty does not yet have permission to spray storm water runoff onto the property or screen the compost to retrieve wood chips, two operations that would make the procedure more economical. The citizens say those operations pose water and air pollution dangers.