What's a Septic System

If you have always been hooked up to a municipal water supply and "flushing" for all these years without a single thought about what happened after that, the topic of this article may be completely new to you.

But it's really important. If you live in a rural area, or want to go completely "off the grid," one of the first subjects you will need to address is that of sewage handling. The laws are different in almost every state, and some are very strict.

In Vermont, for example, if your land fails the "perc" test (short for percolate; simply, if your land will not accommodate the installation of a septic tank), the only alternative you may be allowed will be what's known as a "mound system." The Vermont law's wording says that other kinds of septic systems may be allowable on an individual basis — in practice, however, here as elsewhere, the approval system can be difficult (see Summary of VT rules).

Mound systems involve hauling in a tremendous amount of gravel, and last time we looked they ran anywhere from $15,000 on up, depending upon your location. In other words, they are really expensive.

Besides "perc" and "mound system," the other words you need to know are "graywater" and "blackwater." Graywater is the stuff that goes down the drain — dishes, laundry, bathing, and showering are the biggest creators of graywater. In a well designed, ecologically self-contained home like an Earthship (see our EarthShip article), graywater can be recycled to the tank of your toilet. If you use pure, biodegradable soaps, graywater also can serve to water your garden.

When you flush, "blackwater" is the result. This is what's involved in your septic, or sewage management, system.

If you have a septic tank or a mound system, the water portion of your blackwater "percolates" down through the ground or mound, which filters it. If the filtration is inadequate, your blackwater may contaminate the local groundwater — hence the "perc" test and the need, if you fail it, to install a mound of gravel.

The solid portion of blackwater, which goes into a tank, naturally decomposes. Various products are available to hasten this decomposition process and improve septic system performance. Periodically, also, septic tanks need to be "pumped." This service runs anywhere from $150 on up.

"Biological" Treatment Systems

Here, we will discuss sewage handling that fits into a "sustainable" category — systems that recycle, rather than simply dumping blackwater into the ground and "wasting" the solid wastes. Sustainable sewage treatment outputs purified water that, in some cases, can even be recycled back to the toilet tank, and biological wastes that have been sanitized so that they can be used for other things — like fertilizer — or input to methane- or alcohol-production systems.

The short form is this: The output from a biological treatment system could conceivably help to fuel your furnace!

Biological treatment systems work by first filtering out solids. This is called "pre-screening." The solid residue is first treated through the use of anaerobic bacteria and enzymes, which rapidly break down suspended organic acids into soluble organic compounds — basically, they "digest" it. Aerobic treatment then oxidizes the bacteria, outputting carbon dioxide and water. The "effluent" from this system is clarified and disinfected.

There are a number of biological treatment systems on the market. An Ecoflo unit, for example, is one domestic wastewater treatment system that is added to your septic system. It is comprised of a fiberglass tank and utilizes a specially treated peat-based filter bed to purify wastewater coming from a septic tank. It has the same criteria as a the elevated sand mound. This unit costs $5000, and by the time it's completely installed, about $12,000. See EcoFloPa.com.

Bio-Microbics offers what's known as the Fast system of sewage treatment. Prices for this unit start at around $2000, but again installation of a total septic system with this unit would probably run in the neighborhood of $9000. The Fast system can be viewed at BioMicrobics.com.

Composting Toilets

Another choice for sewage treatment is the composting toilet plus graywater recycling. If your state will allow this, composting toilets cost approximately $1300 (see EnviroLet.com, for example), but you also need graywater treatment and recycling systems with these (for more information, try GreyWater.com).

Finally, BioMax offers single-unit composting systems that have passed requirements already in some states. The BioMax of Washington page for residential systems is at BioMaxWa.com. Biomax Quebec, Canada, is at BioMax.qc.ca.

For Larger Applications

In researching this article, I enjoyed reading the material at WaterRecycling.com. This is a research site that talks about how we can use soil, plants, sand filters, and mound marshes instead of machines, tanks and chemicals — just the way Mother Nature does it. The systems under consideration here, however, are for applications involving a lot of acreage. They are not for in-town or small-lot usage.

On a larger scale, also, recent research seems to indicate that channeling effluent into marshlands is a viable method for states and municipalities to handle sewage treatment. See http://www.technews.vt.edu/Archives/1996/Oct/96340.html.