Each day, 100 to 120 trucks haul more than 700 tons of sludge 65 miles, from the southern tip of the District to an abandoned farm near Poolesville in western Montgomery County.

There the sludge, from the giant Blue Plains regional sewage treatment plant, is buried in trenches three and a half feet deep.

The cost of disposing of the sludge is about $45 a ton, or $31,500 a day.

But if officials of Montgomery and Prince George's Counties and the District weren't fighting among themselves about what to do with their sludge, they could dispose of the stuff for about half that cost.

Because of the rivalries, residents of the three jurisdictions will pay $4.5 million extra for sludge disposal this year. The extra costs next year could reach $10 million.

Although they are not using it, the suburbs and the city have the technology to turn sludge into a usable fertilizer and soil conditioner (compost).

Composting, as the process is called, is not only cheaper than trenching -- $25 to $30 a ton, compared with $45 a ton -- but tends to become more economical as the operation increases in size. Trenching, on the other hand, is sensitive to the costs of gasoline and land, both of which have been rising steeply.

When new land can be found, it tends to be expensive. The Washington Suburban Sanitary Commission (WSSC) has paid from $3,500 to $10,000 an acre for trenching land, according to Montgomery officials. Trenching, they said, consumes almost an acre a day.

Besides costing more than composting, trenching involves other problems.

"The social and environmental impacts are almost overwhelming," Robert S. McGarry, general manager of the WSSC told a recent seminar.

Narrow country roads in western Montgomery have been pulverized by the trucks, county officials said. The Maryland Health Department, worried that buried sludge may make its way into water supplies, has warned that it may quit approving permits for trenching.

Composting is a long-established method of sludge disposal in Europe, but the Washington area has only a small experimental facility at Beltsville, which can handle less than 8 percent of the Blue Plains output, and a slightly larger facility at Blue Plains, which the District built under court order.

Montgomery wants to build a much larger composting plant -- one capable of processing up to 600 tons daily -- near the Montgomery Industrial Park in the Rte. 29 corridor, near the Prince George's line. But Prince George's and neighborhood groups are opposing the facility, which has been approved by the Maryland Health Department.

Prince George's has not built a plant for its own needs because County Executive Lawrence J. Hogan and the County Council have been quarreling over where it should be located. Both sides finally have agreed on a site -- near the county's landfill west of Upper Marlboro -- but construction is a year or more away.

The District could have built a facility at Blue Plains to process its share of sludge, but both the former and the present city administrations have steered away from making a decision until the suburbs decided to help the city get more treatment capacity at the plant. Only recently has the Marion Barry administration begun pursuing the idea of expanding and modernizing the plant at Blue Plains. A decision on the size of the plant and who will build it is expected soon.

Neither and Maryland suburbs nor the city will be able to make the conversion from trenching to composting before 1982.Meanwhile, the costs of trenching continue to rise steeply.

Montgomery officials are bitter about the delays they have encountered in trying to get a plant built in the Rte. 29 corridor.

"Prince George's County officials have done everything they can to block a solution to the problem," County Executive Charles W. Gilchrist said. "Their opposition will force residents of both Montgomery and Prince George's counties to pay higher sewer rates and possible higher taxes."

The new WSSC budget calls for a 40 percent increase in sewer rates -- most of it due to the higher costs of sludge disposal.

"Sludge disposal is having a devastating impact on sewer rates," said WSSC assistant manager John M. Brusnighan.

The impact was demonstrated vividly when the Montgomery and Prince George's county councils met recently in Rockville to approve the new WSSC budget. To raise an extra $3 million to cover the escalating costs of trenching, they had to cut hundreds of thousands of dollars from each of several budget items that used to be considered essential: meter maintenance, spare parts for vehicles and street repairs, among them.

"It's terrible, just terrible," a disconsolate Brusnighan said in the hallway during the budget session. "I don't know what we're going to do."

Prince George's officials reject charges they are responsible for holding up construction of a composting plant in Montgomery.

"We cannot be singled out as the culprit," said Samuel E. Wynkoop, the County Council's administrative officer. "Montgomery County needs to be more realistic and consider going to another site . . . talk about mismanagement of money! They're (Montgomery officials) planning condemnation proceedings (at the site in the Rte. 29 corridor) that may result in $30 million to $40 million to buy covenants." The process of buying convenants eases the restrictions on industrial uses of the land in question.

Where should Montgomery go?

"We're not dictating where Montgomery might locate its facility," said Kenneth V. Duncan, Hogan's chief administrative officer. "However, the WSSC did acquire 700 acres in northern Montgomery, and it has already been used for trenching."

But the Montgomery council has already pledged not to use that site, at Ednor Road and New Hampshire Avenue in eastern Montgomery, for further sludge disposal -- and Montgomery officials say they would be accused of betrayal if they went back on their promise.

Citizen opposition has been a main factor in the region's inability to develop a cheaper and environmentally safer solution to the sludge problem. Although millions of dollars are at stake, local officials concede their governments have made no major effort to explain the problems to their constituents in the hope of enlisting their support.

"It was a blunder," the WSSC's McGarry acknowledged during a question-answer session at the recent sludge seminar. "We should have gotten the citizens involved."