TO THE CHAGRIN of almost nobody expect Montgomery County Executive James P. Gleason, the controversial Dickerson sewage-treatment plant seems to have been laid mercifully to rest. True, Mr. Gleason may appeal a federal court decision upholding the Environmental Protection Agency's 1976 veto of the plant. But outside of Mr. Gleason's office, there's little enthusiasm left for the battle - or the plant. Pumping sewage some 20 miles uphill for treatment, and releasing the effluent upstream from public water intakes, was never an demands, which EPA's veto was not only resonable, as District Judge John Lewis Smith Jr. has held, but right.

Assuming Dickerson is dead, several governments have work to do. In view of Mr. Gleason's stance, the Montgomery County Council will have to take the lead in devising smaller, less expensive alternatives. One tempting course, sending more sewage to the Piscataway treatment plant, can probably be ruled out; economecs and physics may favor that, but Prince George's County emphatically does not. Montgomery may well have to treat its wastes on its own ground - and we mean that literally, in part because land treatment shoould get much more earnest cosideration than it has so far.

Then there's the District government, which had supported Dickerson in order to reduce suburban demands on Blue Plains. City officials predict that, as development brings more residents and workers, the Districts's waste-treatment needs will increase at least 10 percent by 1995. Perhaps a third of that could be provided, though, by finding and fixing the various leaks that now let underground water into the city's pipes. The pressure could also be eased by strong enforcement of water-saving rules for new and rehabilitated buildings.

The final force involved is the Council of Governments, which is now trying to put together a 20-year regional pollution-control plan. At Mr. Gleason's insistence, COG had made Dickerson a key part of that plan - and thus made the whole package rather unreal. Now COG can try again. While Montgomery County and the District revise their plans, officials from other jurisdictions should not just wait and watch. For one thing, they could join in urging the federal government, as the area's largest landlord and tenant, to lauch a strict water-saving program now. Beyond that, other parts of the COG draft need to be tightened up. If everyone cooperates, the death of Dickerson could produce a wiser regional program - at less public cost.