The Supreme Court, acknowledging that its decision could force some factories to close, ruled unanimously yesterday that polluting industries must meet federal water cleanup requirements regardless of their costs.

The court, recognizing in a footnote that the ruling would "determine for some plants whether they will continue to exist or not," rejected coal and quarry inudustry arguments that current pollution requirements should be relaxed for companies that cannot afford the often expensive technology to clean waste-water pumped into lakes, streams and rivers.

It was a major victory for environmentalists. The Environmental Protection Agency feared that an opposite ruling would have allowed polluting firms in every industry to delay cleanup measures indefinitely through court suits and administrative proceedings, regardless of whether they could show an inability to pay costs.

Reversing a lower court ruling, the justices said yesterday that Congress, when enacting the Clean Water Act, expressly avoided financial exemptions, though it "anticipated that the 1977 regulations would cause economic hardship and plant closings." Congress, now expected to take a more probusiness stance on such issues, can still amend the law.

The case, Environmental Protection Agency vs. National Crushed Stone Association, was one in a line of challenges by almost every regulated industry to the environmental, health and safety restrictions imposed early in the 1970s that at least 50 firms have blamed for shutting them down. In each court case, the trade associations have maintained that regulators should be forced to moderate rules if they are too costly.

Yesterday's opinion does not settle, all these regulatory controversies -- for example, those involving the cotton dust and benzene exposure standards promulgated by the Occupational Safety and Health Administration. These concern whether OSHA must weigh the costs of regulations against the benefits to those protected. Each regulatory agency has its own enabling laws to be interpreted, a job made more difficult because Congress often has said nothing or been unclear about costs and costs versus benefits.

Yesterday's ruling stemmed from cleanup requirements for thousands of coal, quarry and crushed stone operations around the country. Those industries discharge sand, silt, clay, grease, oil and tar as they pump accumulated water from their mines and quarries. Some also pollute and discharge water as part of their mining process.

The industries were to meet new pollutant levels in two stages. The first stage, for 1977, did not allow for relaxations for companies solely because they were unable to afford the cleanup. In the second stage, set for 1987, Congress specifically allowed variations based on excessive costs, largely because the 1987 standards are to be more stringent than the earlier ones. Industry argued that affordability should be a factor for the 1977 standards as well.

Environmentalists such as the Natural Resources Defense Council said that industry's scheme would "undermine" the Clean Water Act. But the 4th U.S. Circuit Court of Appeals agreed with the companies. The Supreme Court, with Justice Lewis Powell not participating, unanimously reversed the lower court with a ruling that applies to all industrial pollution.

To grant exceptions "because a particular owner or operator cannot meet the normal costs of the technological requirements imposed on him . . . would be inconsistent with this legislative scheme and would allow a level of pollution inconsistent" with the judgement of the EPA, Justice Byron White wrote for the court.

Richard G. Stoll Jr., EPA assistant general counsel, said that the decision, in addition to preventing delays in water cleanup, sent a message to lower courts not to tamper with administrative agency interpretations of laws except in extreme circumstances.

The courts and the agencies have been in continuous struggle over what the regulators regard as undue intervention in their work.