The sale of commonly used phosphate detergents would be banned in the region under a proposal endorsed by the Metropolitan Council of Governments's water board.

Though the board -- which includes representatives from all local governments -- approved a similar proposal three years ago, local jurisdictions declined to act on it at that time. Before a ban can go into effect, local jurisdictions have to approve it. Currently, there is no such ban imposed in the area.

This time, however, local officials and utilities are supporting the ban, at the same time that the Virginia State Water Control Board has dropped its long-standing opposition.

COG staff have estimated that a ban on phosphate-based detergents, which contribute as pollutants to the volume of sewage sludge, would bring a $2.8 million annual savings in the cost of sludge disposal. The savings would rise to $3.3 million annually when area treatment plants are operating at full capacity in the future.

Disposal of sewage sludge has become a major environmental and fiscal problem in the area.As the big Blue Plains regional treatment plant and other facilities have improved their ability to clean up waste water, they have generated thousands of tons of sludge, a byproduct of the process, every day. All this sludge has to be disposed of, and the costs have increased steeply.

As they have in the past, the nation's soap makers, through their New York-based Soap and Detergent Association, fought the proposed ban, saying it would not result in the savings predicted by the COG staff. Association spokesman also claimed that if area residents were forced to use nonphosphate-based detergents, they would pay about $4.30 more a year in hot water and bleach costs.

But the COG staff, noting that 59 million Americans live with phosphate bans, mostly in the Great Lakes region, said that phosphorus concentrations in waste water have fallen from 35 to 40 percent where bans are in effect. Phosphorus is an essential nutrient in plant growth, but in heavy concentrations in waste water it can be serious pollutant, especially in a slow-moving estuary such as the Potomac River.

One of the major arguments against the ban has been the claim that detergents without phosphates don't clean as well. The COG staff said surveys have turned up little evidence of widespread consumer resistance, and major soap makers have introduced a variety of nonphosphate detergents to give consumers a choice.

The vote last week by COG's water resources planning board was 8-1 with one abstention. The opposing vote was cast by Prince William County. Fairfax County's alternate abstained because the county's regular representative, Supervisor James M. Scott (D-Providence), was absent, and the alternate was uncertain of the county's position.