There was initially some moaning and groaning, but according to city officials, District residents have now begun a love affair with the enormous, green plastic garbage containers called Supercan.

Designed to reduce the need for twice-weekly trash collections in selected neighborhoods, Supercans were dumped on some 2,673 unsuspecting households in July as part of a test to see how well city residents and the can would get along.

Now, D.C. Environmental Services Director William B. Johnson is touting the results of that experiment as an "overwhelming success," with more than 93 percent of those residents responding to a survey, saying they favor continuing the use of the Supercan and the once-a-week trash collection.

In a press release hearlding the positive survey returns, Johnson also includes some of the more adulatory remarks city residents had about their Supercans.

"Supercan has transformed my entire domestic life," one elated Ward 3 resident wrote. "I think it is one of the nicest things to ever happen in the District of Columbia," wrote another happy user from Ward 5. From a Ward 7 enthusiast, "Supercan is 'Super' with me in every way."

An those were some of the milder comments, according to Anne Witt, a deputy administrator at the environmental services office. Witt called the responses "amazing," such as the one from the person who described Supercan as "the trash can I've always dreamed of having," and the several satisfied customers who mailed in Hallmark thank-you cards.

The comments, after eight weeks of experimental use, were in sharp contrast to some of the less positive remarks that first greeted the can's arrival on the lawns and alleys of Wards 3, 4, 5, and 7. City residents complained then that Supercan was too big, too bulky, too hard to move, and too unsightly.

There were complaints from Southeast Washington that the Supercan meant that trash there would be collected less frequently than in other parts of the city. There were protests from Ward 3 in Northwest that the can was made from petroleum-based chemicals in an age of energy shortages. And there was some fear from residents all across the city that the 82-gallon Supercan might prove an enticing but dangerous toy for small children who would be tempted to climb inside.

But all of the initial fears apparently were laid to rest, and, if the city government survey is correct, residents are settling in for a happy and long-lasting partnership with the trash can.

In fact, however, it is a marriage born of necessity. Supercan has been factored into the budget for fiscal year 1982, which the mayor unveiled on Wednsday. When that budget takes effect in October of next year, the Supercan program will be expanded to include about 57,000 District households.

When the program is completely phased in, all the households in Ward 3 except for Georgetown and Glover Park will have a Supercan, as well as all of Ward 4, the top third of Ward 5, all of Wards 7 and 8, and the areas of Ward 6 east of the Anacostia River. Most "inner-city" areas, where there is a higher density population with town houses and apartments, will continue to have the current twice-weekly trash collections.

The city expects to save $2 million a year, once the program is fully in place. The savings result from reduced equipment use and fuel costs, and fewer injuries to employes since the can can be emptied mechanically.