Could Hyattsville solve a 10-year-old conflict with the Washington Suburban Sanitary Commission by selling City Hall to the commission?

For 10 years the WSSC, which provides water and sewage disposal to residents of Montgomery and Prince George's counties, has sought to expand its Hyattsville headquarters and close the offices in Laurel it rents for $600,000 a year.

But proposals to add stories to the four-story building in a residential Hyattsville neighborhood, or to build an annex nearby, have met with strong opposition from area residents. Efforts to expand have been thwarted by petitions and County Council votes since 1971.

So when the Prince George's County Council was greeted by a stream of Hyattsville residents protesting a planned annex at a hearing last week on the WSSC budget, council member Parris Glendenning suggested that the commission buy Hyattsville City Hall, which is five blocks away. Most of the six-story Municipal Building is leased to C&P Telephone, which wants to move out in three years.

The proposal was greeted with enthusiasm by some of the annex's staunchest critics.

Tony Pauletti, who lives opposite WSSC offices and is worried about the effect of the proposed addition on adjoining McGruder Park, said purchase of City Hall by the WSSC "definitely is the most viable way of solving the problem."

Hyattsville Mayor Thomas L. Bass, who with the City Council supports an engineering study by the WSSC on the proposed annex, was equally enthusiastic, but noted the council has yet to decide what it wants to do with the building.

He said the building probably would sell for about $2.5 million, and easily could be expanded. According to WSSC General Manager Robert S. McGarry, the proposed annex would cost $5.4 million. McGarry said the current plan for an annex was chosen after looking at "four or five alternatives," but he said the municipal building was a new idea that had not been considered.

Meanwhile, WSSC officials said the commission still wants permission to go ahead with the engineering study. Last year, the county councils refused to grant the necessary money for the study.

Nobody at last week's commission hearing complained of proposed water and sewer rate increases. The $439.8 million proposed budget calls for an average rate increase of 15 percent. According to WSSC estimates, the average household bill would increase by $33.77 a year, bringing the total to about $265. The annual bill for the most conservative user would increase by $9.89, to $74.47.

The WSSC is barred by law from operating at a deficit. WSSC officials say the higher rates are needed to pay operating costs. The largest single budget increase is to pay bonds for new water and sewer lines. The commission increased water and sewer rates by 22 percent in 1980 and 5 percent in 1981.

The Mongtomery County Council held its last hearing on the proposed WSSC budget two weeks ago. Both counties must agree on a budget by June 1.