In an action expected to save hundreds of companies as estimated $200 million in future clean-up costs, the Environmental Protection Agency yesterday relaxed water pollution standards for 64 industry groups.

The action stemmed from a 1977 congressional mandate to the agency to weed out regulations that were found to be "unreasonably stringent" and costly.

In announcing yesterday's decision, EPA Deputy Administrator Barbara Blum said the regulations in question were found to be "tougher and more expensive than needed."

The regulations being withdrawn would have forced companies in such industries as food processing, glass manufacturing and ferroalloys to spend millions by 1984 to reach what the EPA called slightly tougher water pollution rules for nontoxic "conventional pollutants," including suspended solids, oil and grease.

"Most of the effective industries are already removing up to 98 percent of the conventional pollutants in their discharges," Blum said. "Additional requirements to clean up that last few percent could cost them as much -- or more -- than they have spent so far.

"These [new] regulations will result in substantial savings to affected industries. They will ensure that further spending to control conventional pollutants will be cost-effective and reasonable in terms of the result achieved."

The relaxed regulations call for companies to substitute the best conventional pollutant control technology (BCT) for the more advanced, more expensive, best available technology (BAT), formerly required in the regulations.

The EPA said the new regulations meant that pollution controls on industry will cost no more than controls on a municipal sewage treatment plant.

All of the plants covered by the new regulations are known as "secondary" plants and generally do not discharge toxic wastes in significant amounts.

EPA said it later would look at "primary" industries to see if any changes could be made in regulations governing that sector. The EPA said the tougher BAT controls will continue to be required for toxic pollutant discharges.

EPA reviewed 93 industry subcategories in the latest evaluation and relaxed regulations for 64 of them.

Among the industries for which the standards were not relaxed were asbestos plants and some food processing plants.

EPA'S new regulations will go into effect in 30 days.