A Carroll County investor says he has found an answer to the problem of failing septic tanks in areas outside the reach of centralized sewer systems. His invention combines an indoor vacuum toilet with an outside composting container.

Jeremy F. Criss, president of the Bio-Recycler Co. in Sykesville, Md., recently gave a briefing on his new device to Carroll County sanitation officials on his property west of Baltimore.

Criss is a true believer in the need to conserve our dwindling water supplies and recycle body wastes for agricultural use, and consequently is a vigorous opponent of the traditional water-flushed toilet draining into a central sewerage system. He has written:

"It is crucial to the survival of our species that we must process and recycle organic and human waste to restore the fertility of our soil and fertilize our food crops. We must do it in a safe manner that captures all the nutrients, pollutes nothing and is not energy intensive. This cannot be done in a waterbone system."

He is also dubious about the new Swedish compost toilets now being sold in this country. Among their defects, he maintains:

Liquid builds up in the composting container, turning the process anaerobic instead of aerobic, with resulting odors.

There is incomplete composting, resulting in survival of harmful microorganisms in the product.

There is the danger of insect infestation in the house.

In winter, household heat escapes up the vent pipe.

Criss showed the officials the prototype of the mode he is now marketing in many states.

A neat white commode sits in the bathroom; the user activates the system by pressing a pedal. This opens a valve at the bottom of the bowl and at the same time starts an electric motor that creates a strong vacuum in the drain pipes. To illustrate the vacuum's force Criss dropped in a piece of tissue which was quickly whisked away down the drain. No flushing water is needed to move the wastes but the user sprays one or two ounces of water into the bowl as a cleanser. Then the user closes the valve and the motor stops.

Outside the house there is a shed where a small plastic pipe delivers the wastes into the top of a round plastic container, 6 1/2 feet high and 3 feet in diameter. The wastes enter the container with considerable velocity and are sprayed against a Teflon deflector, which breaks up the solids and scatters them within the container. About once a week the owner opens a hatch on top and adds carbonaceous material such as shredded leaves, kitchen scraps and sawdust. Thus the composting materials consist of alternate layers of dispersed body wastes and carbonaceous particles.

Earthworms in the container then digest the materials, speed up the process and produce castings of great fertilizing value. The liquids drain down through the layers of composting materials and run out the bottom into a five-gallon bucket. Thus the composting materials, while consistently moist, are never submerged in liquids and the entire process remains aerobic, with air circulating throughout the materials.

When the bucket under the container is full, the owner empties this valuable "manure tea" into separate outdoor worm-compost beds. Or alternatively, he could use it to irrigate trees, shrubs or flower beds.

In about a year, the finished compost is removed from a hatch at the bottom of the container. The material Criss showed officials was black, moist and odorless. Several earthworms could be seen, as well as their castings and egg capsules.

Criss urges his customers to place the compost in outdoor beds mixed with dead leaves, sawdust or similar materials, and to pour the manure tea over these beds. In this way the amount of finished compost can be greatly multiplied for use in the family vegetable garden. The Criss garden, in a time of devastating heat and drought, is the kind pictured on the covers of seed catalogues.

But for a small yard like the ones in Georgetown, the owner need not go through these additional steps; the compost right out of the container may be placed around trees and shrubs or on flower beds or lawns. The manure tea likewise can be used in this way. But Criss warns that these products should not be used for grwoing vegetables unless they have gone through several months of additional composting in outdoor beds to eliminate harmful organisms.

The large plastic container can be located in a garage, shed or workshop outside the house. In this way there is no chance of losing household heat up the vent pipe or of creating odors. In fact, Criss maintains that the vacuum toilet results in less odor in the bathroom that with a water-flushed toilet, since the air surrounding the commode is sucked down the drain.

One problem with any new sanitation device is the need to obtain permission of local authorities for installation. Several localities have agreed to installation of the Bio-Recycler on an experimental basis, subject to testing the resulting compost in a year.

The new system does not dispose of "gray water" from the house (effluent from laundry, kitchen and bath.) A septic system is still needed for such wastewater, but many sanitation authorities allow use of a smaller septic tank and drain field, since such effluent does not carry a heavy load of harmful organisms. Or in some cases a dry well can be used, or various filtration devices that cleanse the effluent so it can be safely used for watering lawns and gardens.