Four years ago, Maryland environmentalists, officials of counties bordering the Patuxent River and scientists studying the Chesapeake Bay agreed to support a massive cleanup of the polluted Patuxent, which stretches from St. Mary's County northwest to the Frederick County border.

Today, some officials are encouraged, saying they have seen more fish and oysters along the lower river. Both had been declining because of the water quality.

But other officials say that the only real progress in returning the 110-mile river to its water-quality level of 30 years ago has been made on paper. They say that actual improvement in the treatment of 40 million gallons of sewage dumped into the Patuxent daily is still at least two or three years away.

"If you ever had a place where there has been a consensus on the need for a cleanup, it's been the Patuxent," said Constance Lieder, the chairperson of the Patuxent River Commission and secretary of Maryland's Department of State Planning. "But the bottom line is that almost nothing has been implemented."

The 11 members of the Patuxent River Commission recently took an all-day boat trip along the river "to see how things have changed," Lieder said.

Last year, as part of the clean-up-the-bay initiative, the state also adopted strict controls over land use along the Patuxent and its tributaries to direct development away from the riverside and help preserve adjoining farm and forest land.

Rich Dolesh, who is in charge of the Patuxent River Park for the Maryland-National Capital Park and Planning Commission, says the state is beginning to concentrate on the river on the theory that, "If you can't save the Patuxent, you'll never save the Chesapeake."

Control of phosphorus and nitrogen entering the river in sewage discharges is of particular concern to environmentalists. In large amounts, the two elements, while supporting the growth of algae, rob other river life of sufficient oxygen .

The treated sewage dumped into the Patuxent each day finds its way into the Chesapeake Bay, which has also been targeted for a full-scalestate cleanup. The Patuxent drainage basin touches on seven counties and covers about one-tenth of Maryland's land surface.

Last year, Ann Arundel County was found to be dumping potentially harmful sludge into the river from its Crofton area treatment plant, one of seven plants along the river. The state later fined the county.

Also last year, a privately owned sewage plant in Prince George's County was also fined for inadequately treating sewage it dumped into the fine was part of a neew get-tough policy against sewage plant pollution throughout the state.

Ken Shanks, a state Health Department planner, said the control of phosphorus and nitrogen has not improved greatly since 1981. But Peter Tinsley, who heads the state Office of Environmental Programs said such improvements take time.

Howard County Council and Patuxent River Commission member Ruth Keeton takes a more optimistic view of the cleanup efforts.

In 1982, Howard County completed a $43-million imprpovement of its sewage treatment plant. Since then, Keeton said, phosphorus levels there have been greatly reduced.

"Since our plant opened, we have received for treatment 85 tons of phosphorus, and we've removed 80 tons," Keeton said this week. "That's 95 percent no longer going into the river, and that's encouraging.

"We now have the most sophisticated sewage treatment system in the state," she said. "Right behind us, Anne Arundel is upgrading their plant and Prince George's will be shortly behind them. Calvert County also has a project.

"In the next few years, we're going to continue to show improvement," she said. "This is one of those situations where you can either look at how far we have to go or look at it this way -- we're on the move."