Some Maryland homeowners with septic systems would be required to pay thousands of dollars for equipment to help keep nitrogen pollution out of ground water and ultimately the Chesapeake Bay, under a proposal detailed yesterday by Gov. Parris N. Glendening.

The proposal, which some local government officials call premature, would require counties to designate areas in which new homes with septic systems and any systems needing repair or replacement would require the nitrogen-reducing upgrade. Officials say the enhancement would add up to $7,000 to the typical price tag--$3,000 to $5,000--for a basic septic system, with about $200 in annual maintenance costs.

"What we're trying to deal with here is the environmental effects of the nitrogen that goes into the Chesapeake Bay," said John Frece, the governor's special assistant on Smart Growth.

Septic systems are used mostly by rural homeowners to dispose of their wastewater because their homes are not connected to public sewers. A report by a task force appointed by Glendening (D) to study the issue said septics account for about 6 percent of the nitrogen that reaches the bay. By far the bulk of such pollution comes from municipal sewage systems and industrial and agricultural sources, the task force found.

But officials say as efforts to reduce nitrogen pollution are being stepped up in other areas, septic systems need further regulation, too.

"Pollution always migrates to the areas of least regulation," said Dane Bauer, deputy director of the Water Management Administration for the Department of Environment. "If you're making everybody do something, you need to make people on septic systems do something."

The proposal would affect some of the 400,000 Maryland homes on septic systems, but officials don't know exactly how many. State officials estimate that 30,000 homes have septic systems that are failing, with their waste contaminating ground water. Counties would use a set of state criteria to designate special areas of concern within which the improved systems would be required. Residents living in areas with failing septic systems, in drinking water supply areas or in areas where soil is already contaminated with nitrogen are among those who could expect to be affected.

The Maryland Association of Counties, among others, has expressed concern over the proposal.

"Whatever the merits of requiring nitrogen-reducing systems . . . the burden of inspecting them, and dealing with the public outrage . . . that heat's going to be taken by local environmental health directors and local elected officials," said John Woolums, associate director of the Association of Counties. "We're all in this together toward reducing nutrient levels, but the merits of certain strategies and the costs just have to be fully explored before we jump into anything this radically new."

Woolums suggested that a pilot program for the enhanced systems might be a better approach.

The task force report recommended giving existing property owners tax credits of up to $1,100 a year for three years for installing the new systems.