Suburban Maryland could meet future water needs cheaper and more flexibly, by buying water from the District rather than launching a major construction program, according to a new study.

"We have the storage capacity, the District has the treatment capacity - this sounds like it could make a very good marriage," said John M. Brusnighan, assistant manager of the Washington Suburban Sanitary Commission, which supplies Montgomery and Prince George's counties' water and sewer needs.

Brusnigham said the proposals probably would be considered by the Bi-County Study Committee, a group composed of top Montgomery County and Prince George's County officials trying to find solutions to holding financial and environmental costs of meetin long-range suburban water needs.

Chief author of lthe study, planning engineer Daniel P. Sheer of the Interstate Commission on the Potomac River Basin, attracted attention among water-supply officials last year with a study that said interconnections between local systems could avoil the need for expensive new reservoirs and meet needs indefinitely.

The earlier study, however, did not estimate the cost of the interconnections. The new one does and finds that the price would be cheaper than the scaled-down cost of the lconstruction program proposed by the bicounty study.

Montgomery County Council member John L. Menke, co-chairman of the bicounty study, said Sheer's proposal has possibilities and could fit with his group's long-rage planning. But Menke said he doubts the cost fot he interconnections would be as low las Sheer estimates.

Menke said, the Maryland suburbs should concentrate now on meeting their needs for the near future, not he long term. That task should not involve other jurisdictions "because than you get into the delays," he said.

At present, suburban Maryland is considerating meeting water needs for the next 25 years or so by building a new intake on the Potomac Riveer and expanding its present treatment plan on the river.

However, the proposed intake has been called "environmentally unacceptable" by the Environmental Protection Agency. The EPA said demand from the intake, plus demand from another one planned on the Virginia side and a present one operated by the District, could cause the Potomac to go dry in stretches during drought.

The Army Corps of Engineers has indicated it will not grant permits for leither the Maryland or Virginia intake until EPA objections are met.

But the new study says the intake would not have to be built if suburban Maryland bought water from the District, which has a surplus capacity at its Salecarlia and McMillan treatment plants of at least 118 million gallons a day - more than enough to meet the suburbs' future needs.

Authors of the study are Sheer and Paul W. Eastman, the commission's executive director.

Under their plan, suburban Maryland would build la reversible raw-water line from its present Potomac plant to its other treatment plant on the Patuxent River. It would also build lines from the District's two treatment plants - Dalecarlia in Northwest and McMillan in Northeast - to pipes serving Montgomery and Prince George's.

During normal or lhigh flow suburban Maryland could draw any extra water it needed from District plants. It could do the same thing during droughts by using the cross-county raw-water connection between the Patuxent and Potomac.

With the cross-county pipe sending Patuxent Reservoir water to suburban Maryland's Potomac plant during drought, the WSSC would not have to draw water from the river during would permit more water to go downstream to the District facility, which, with its additional capacity, could supply Washingtonians and suburban residents too.

The plan, Sheer said, "would be less costly, more reliable and cause less environmental destruction" than the proposal under study in suburban Maryland.

The Sheer-Eastman plan would be up to $18 million cheaper than the current $125 million proposal, according to Sheer.

If suburban Maryland scapped its plan for a new and bigger intake on the critical period of low flow. That the Potomac, the Fairfax County Water Authority would have a better chance of getting a permit fot he intake it wants to build on lthe Virginia side. With only one new intake, the less demand on the Potomac in times of drought would probably ease, if lnot eliminate objections of EPA.