The linen-covered tables, laid by Ridgewell's caterers, were crammed with finger sandwiches, tiny meat-filled pastries, stuffed mushrooms and petits fours.

But the piece de resistance wasn't the food, served on china under a yellow and white striped tent: It was a nest of pipes, pumps and tanks in a dank basement.

"Without this," said the owner, developer Douglas Cobb, "I'd be in a real pickle."

Cobb was showing off an unusual treatment system that will purify the sewage at his nearly finished Village Centre shopping complex in Great Falls and then recycle it for non-drinking uses.

Bellying up both to the tables and the sewage treatment system was a platoon of developers, brokers and other real estate people looking for ways to put offices, shops and other commercial and industrial projects on idle land.

One of their main problems, though, is that sometimes their land isn't near public sewers and may not be suited for septic systems. That can mean that heavy investment costs may yield nothing more than a field of alfalfa.

"I've got several million dollars worth of real estate I can't do anything with," said Robert Rust, vice president of development for Weissburg Development Corp.

The land, located in Montgomery County, is under a sewer moratorium, and can't be developed. But Rust said that if the treatment system used at Village Centre could be used on the Weissberg land, "it might make sense to go ahead with development."

The Great Falls center, which will have 40 tenants, including two restaurants and an assortment of shops and professional offices, is modeled after the historic Sturbridge Village in Massachusetts. Many of Cobb's buildings are sheathed with clapboard, and some even have wooden porches.

Cobb's design, which orginally included underground parking until the cost proved prohibitive, won over much of the local neighborhood opposition to commercial uses in Great Falls. The first tenants will be opening for business in early December.

Another interested visitor at the recent open house was Robert MacPherson, manager of the regional real estate investment office of Prudential Life Insurance Co., which is heavily involved in local ventures.

"We're always looking to keep our options open," MacPherson said. "You might run into a moratorium. This system could open up some outlying areas, such as this one, for development."

Thetford Corp. was not unmindful of its treatment system's potential in the metropolitan area. It was Thetford which sponsored the catered affair at Village Centre and invited 75 developers and realtors -- all of them potential customers for Cycle-Let, as the disposal system is called.

To give the occasion some extra gloss, Thetford, whose over-the-counter-traded stock has taken a beating in recent months but perked up Tuesday afternoon, invited Virginia Lt. Gov. Charles S. Robb to head the list of speakers. Also on hand were Fairfax board chairman John F. Herrity and State Sen. Charles L. Waddell (D-Loudoun).

Cycle-Let's treatment system features a high-technology process that filters partially purified wastewater through a membrane whose holes are as small as the skin's pores. The final effluent, disinfected with ozone gas, is then used again and again as toilet flushwater, sharply reducing total water usage.

Al Coviello, general manager of Thetford's waste products treatment division, said that about 90 percent of the wastewater is recycled. He said Cobb, who paid about $120,000 for his system, won't have any operating costs because they will be more than offset by a $3,600 annual savings in water bills.

During the reception, Thetford officials painted pretty word pictures for developers ("It permits development now!"), and said their system had significant public benefits too, such as conserving water and reducing pollution.

But the system could remove one of the last controls Virginia localities have on development -- the unavailability of sewer. This is especially true in outlaying counties like Loudoun and Fauquier.

"The system's an intriguing, interesting idea," said Waddell, who represents Loudoun, "but I'm concerned. If this allows farmland to develop, then you could see the paving over of Northern Virginia."