Both arguments have the hard-sell sound of a TV commercial for the newest wash-day wonder.

Ban phosphate detergents, says the environmental staff at the Metropolitan Washington Council of Governments, and you will save millions of dollars in sewage treatment costs.

Keep the detergents on the shelves, say soap makers, or you'll have the wash-day blues all over Washington.

The audience for the claims and counter-claims is the local governments who are membersof COG, the regional planning agency.

A good indication of what the region thinks of the arguments will come today, when the COG Water Resources Board votes on a proposed ban of phosphate detergents in the area. The water board includes representatives from the District, suburban Maryland and Northern Virginia.

Phosphate detergents are great cleaners, everyone agrees. Nothing beats them for digging out tough dirt. But many scientists say phosphates also are a major cause of water pollution. Phosphates contain the chemical phosphorus, which can trigger the growth of algae in water, the scientists say. The algae consume oxygen, leaving fish gasping, and can produce thick nets of vegatation that ruin boating andswimming.

Local officials say that all this happened in the Potomac in the late '60s and early '70s, and that is when the drive to ban phosphate detergents began. But the drive soon ran out of gas, because of expected consumer reaction and counter arguments that nitrogen, not phosphorus, triggered algae growth. In the end, only one area jurisdiction approved a phosphate ordinance, Prince George's County, and the ceiling it set is not exceeded by any of the detergents on the market. When the region decided to tackle phosphates by building sewage treatment plants that would take phosphorus out ofwaste water, the question seemed settled.

In last few years, however, the ban-the-phosphates drive has gotten new life.

To begin with, says COG's environmental staff, removing the phosphates from waste waterhas become tremendously expensive. It takes about 10 pounds of chemicals to remove one pound of phosphorus from waste water. The cost of the chemicals has escalated. Some of them more than $9 for 100 pounds, andlocal officials say hundreds of tons are needed each day.

The treatment also has produced an unpleasant by-product -- sludge. Every pound of chemicals used to removephosphorus from waste water produces a pound of sludge. In the metropolitan area, that has added up to an almost overwhelming problem of what to do with the sludge.

The COG environmental staff estimates that a phorphate ban would save up to $6.3 million in the costs of treating sewage and disposing of the sludge.

The COG staff cites the results of a program in the Great Lakes region, where all the states except Ohio have approved a ban on phosphate detergents in an effort to clean up the heavily polluted lakes.

Austan S. Librach, director of the COG Department of Environmental Programs, says that since the ban startd three years ago the Great Lakes have been cleaned up considerably, and that annual savings in sewage treatment costs have totaled $14 million.

It's time, say Librach and his staff, to do the same in the Wasington area.

Detergent makers don't agree.

"They're trying to do that again?" asked an incredulous Theodore E. Brenner, president of the Soap and Detergent Association, which represents major detergent makers such as Procter & Gamble and Colgate.

"It (the ban) would have zero positive impact on water quality in the Washington area," Brenner said, "and a negative impact on consumers."

Brenner said the phosphate content of detergents (about 6 percent, down from 12 percent a decade ago) is too low to be a major factor in phosphorus pollution.

If a ban were approved, popular detergents would still be on grocery shelves but they would have phosphate substitutes. Brenner says some home economists have found that the substitutes don't clean nearly as well as phosphates and can leave harmful, lime-like deposits in washing machines and on fabrics.

"In general," says Joy A. Schrage, manager of customer assurance for the Whirlpool Corp., "non-phosphates have poor washability. With a phosphate ban, wash-dry habits would have to be altered significantly.

Despite such arguments, the Great Lakes ban seems to have produced few complaints from the public.

"I have seen no complaints in the last two years," said Michael E. Stifler, who has monitored public reaction in Michigan since the state banned phosphate detergents three years ago. "There were two complaints the first year."

The Great Lakes Basin Commission, a regional planning agency made up of state and federal groups, has twice reaffirmed its support for the ban, according to staff scientist William C. Sonzogni.

Stifler acknowledged that some consumers encountered problems with nonphosphate detergents, primarily because they don't work as effectively in the hard water generally found in the Great Lakes region. Washington water is softer.

The answer in such cases, he said, is to use a presoak or liquid detergent. Sometimes, said Whirlpool's Schrage, hotter water will be needed to get out tough stains.

But overall, Stifler said, Great Lakes residents have learned to live with phosphate-free detergents -- and they aren't singing the wash-day blues.