HERE'S AN IDEA from Herbert Tucker, head of the city's sanitation services: let's give Anacostia the best trash-collection system in the city. By using 82-gallon containers -- distributed free of charge by the city government -- a week's worth of trash can be stored safe from rats and accidental spills. No more cans that get turned over, no smelly, messy spills, less garbage-can noise and no plastic bags that burst open. Not only would the new plan improve trash collection in the area; it would also save $696,000 in city money every year. The plan Mr. Tucker has in mind is already in effect in Atlanta, and people there generally think it's a fine idea. It would be good if the plan could be put into effect throughout the city, but Anacostia -- with its wide alleys and detached houses -- is ideally suited to it.

Sounds great. But when Mr. Tucker and Mayor Barry introduced the plan as part of the 1981 city budget, many people said it was -- garbage. Opposition was based on its main feature: trash would be picked up once a week instead of on the twice-weekly schedule now in use.

Some Anacostians grumbled that what the new plan essentially means is fewer city services for the poorest part of the city. Anacostia already has less than the rest of the city west of the river. Fewer supermarkets, for instance -- only five for about 210,000 people, a third of the city's population. Fewer banks and department stores. And dramatically fewer movie theaters: there are none.The idea of less trash removal invited visions of dank and fetid garbage strewn along Martin Luther King Avenue as hordes of rats sat at curbside feasting on it.

The opposition also took on a racial tone. Ward 3 has a large number of detached houses and wide alleys, like Anacostia. Why didn't the city try out its plan there? Because it is a largely white, upper-income area? Mr. Tucker said the Ward 3 area was too strangely shaped to allow his santiation service to judge if the plan works. Anacostia is by itself, on the other side of the river, making it obvious whether or not a special trash-removal plan is working.

But none of Mr. Tucker's explanations of why the new money-saving and potentially better system should be put in Anacostia speaks to the main problem. The proposal has to gain acceptance. As things now stand, it would be a political liability for the mayor. Like every other politician who has ever campaigned in Anacostia, Mr. Barry promised not to forget what was on the other side of the river when he got into office. If he approves the plan, it could be said that he went back on that promise and is sticking Anacostia with an experimental trash-collection system. If he disapproves of the plan just because of Anacostians' feeling that they have been the city's stepchild, the Mayor could be seen as shying away from the truly tough decisions that would benefit both the city and Anacostia in the long run.

Mayor Barry has yet to make a final decision.It might be best for him -- and for Anacostians -- if Southeast neighborhood groups and Advisory Neighborhood Commissions were to hold a forum on the pros and cons of the new plan. The mayor could attend -- and listen carefully. It is important that the city save money. But it is also in the best interest of the city that Anacostians not feel they've, once again, been trashed.