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Two Toilet Tasks
The design of any toilet involves two specific tasks: (1) transporting the waste to the treatment area, and (2) disposing of the waste. Some systems are simple and singular, whereas public facilities often require complex mechanisms. Waste can drop straight down directly into a tank or treatment unit, or it must be moved horizontally or laterally. To facilitate the horizontal transportation of human waste, aids are employed such as water, foam, air vacuum, or physically carrying it. When it comes to the actual disposal of the waste, there are five basic methods: no treatment at all which on any large scale should not be an option, composting for re-use on the land, incinerating to ash for disposal in the ground or the water, biological treatment for disposal into a water body, or dehydration sterilization for disposal in the ground.
There are five main categories of waterless toilets and sanitation systems on the market:
- portable toilets, often found at construction sites
- vault toilets, often found in large parks
- composting toilets
- incinerating toilets
- evaporative sanitation systems
"A composting toilet?
What's that? Isn't it like an outhouse?" "Maybe it will solve
all my drainfield problems and I won't even
need a septic tank." "If I get one, I want the most
energy efficient kind that doesn't need any power." These are some
common reactions to the words "composting
There are many ways to transport and dispose of human waste. Most of them are anaerobic. In China along the farm roadsides are outhouses with signs asking please to be used by passers-by. For centuries human waste has been composted and used as fertilizer in China and the same land is still being farmed, while in America after a few decades of chemical fetrilizers large areas of land have become sterile. When the flush toilet was invented people loved the concept of having it all washed away out of sight to somewhere else; they no longer had to see or deal with their own waste. This "Flush and Forget" attitude has permeated American culture and life styles. Still there are alternative options for the disposal of human waste. One of the oldest is manual removal, where the toilet sits above a container (like a pot -- hence, "potty" or "honey pot") that periodically needs to be hand-carried to a pit or to a holding tank where contents are dumped.
The use of holding tanks is prevalent in a number of situations. RV's, boats, trains, airlines and other forms of transportation which used to dump their toilets directly out wherever they were now use holding tanks that unload into septics or sewers. Portable toilets seen at worksites and large public events have to dump a mixture of toxic chemicals and unhealthy feces: not an environmentally sound practice. Recycling oil toilets use oil rather than water to flush; the light materials float to the top and are removed, while the oil is recirculated until it, too, needs to be disposed of. Incinerating toilets burn up the waste, using electricity, natural gas, or propane, leaving nothing but a fine ash. Another method of transporting waste is a pneumatic system like that in Sweden where all the toilets in the city are connected to a central vacuum. In Arizona and other arid states, lagoon systems are used, where a fenced-in pond collects the sewage; the scum that develops on the surface grows algae and the sun treats it, while the solids settle to the bottom and anaerobically decompose. In some areas of ten acres or more, evapotranspiration is allowed, wherein the land is flooded and allowed to evaporate on its own time. In parts of India, a country where all the available trees have already been cut down and used for fuel, the manure from the pigs and chickens is scooped into digestor tanks which produce just enough methane each day to fuel the family cookstoves. The Circulaire system is an extremely high-tech total recycling system that continuously recirculates all household water from toilets and laundry back to drinking water and showers, etc.; it encorporateschemicals, filters, electricity, and a centralized computer monitoring system located in Colorado. The more complex a system, the more possibilities there are for break-down.
At the other extreme, in Sweden, over forty years ago, the Clivus Multrum was invented, from which hundreds of varieties of offshoot aerobic composting toilet designs have come and gone. The one thing they all have in common is that they are simple to understand, build, operate and maintain, with minimal problems and maximum benefit to the environment. These units range from $3000 to $6000. The Clivus Multrum, the CTS, the Vera, and the Phoenix are the ultimatewaterless toilet systems. They consume all wet organics: toilet wastes, all kitchen scraps and compost, floor sweepings, occassional leaves and garden wastes, cooking grease and oil, and whatever else decomposes. There is no odor; in fact, the system acts as a bathroom ventilator so that the room itself never smells, and what comes out the roof vent is nothing more than carbon dioxide and water. If you were to climb up on the roof of a house with a conventional water-flush anaerobic toilet you would smell sulfur, ammonia, methane, and other unpleasant odors. If you recycle your glass, metal, paper and plastics; put all your wet organics in the compost tank; burn all your dry organics in an efficient airtight woodstove; and avoid plastic, styrofoam and any non-recyclablematerials by leaving all excess packaging at the store where you bought it as a socialstatement, then you have literally no garbage. You can bottle the liquid from the holding tank and sell it as concentrated liquid plant fertilizer, since the nitrites in the urine convert to nitrates which plants need. If you need to retrieve anything valuable that fallsdown the toilet, nothing is lost. The toilet is silent, requires minimal maintenance, has no moving parts (except the Phoenix and the Vera), has no pipes to keep from freezing, and is actually personally satisfying to use. Composting toilets avoid pollution; manage pathological wastes; create a valuable fertilizer; save water, energy and money; anderadicate the flush toilet.
There are times when these large tanks are not applicable. For example, if there is noroom for a tank under the toilet, like in the basement; if the use requirements are small, like one person part-time; or if price is a great concern. In such instances, the smaller "dry" or dehydration toilets are more practical than the true composters, even though theydo use more power and require more frequent maintenance. Because these containers are small -- ranging from two to three feet square -- they have to employ supplementary heat,stirring and aeration to aid and speed up the rate of decomposition, while fans keep the air flowing from the room down into the toilet and up the vent. These toilets are easy to use -- simply plug in the cord and install the vent -- and can be moved readily to otherlocations. They range in price from $800 to $2800, and average around $1200. For people who already are on city sewers but don't like wasting valuable drinking water, there is yet another option: ultra-low water-flush toilets. Most of these operate on the principal of a high blast and use 1.6 gallons instead of five to seven gallons per flush. There are models that use as little as one quart per flush and a Japanese toilet that uses a one-cup foam flush. These range in price from $125 to $800.
So much for the issue of toilet water, called
black water. How about the rest of the water,
the graywater: sink, shower, laundry
and bath water? Somehow all this water must
be disposed of. There are actually only four basic options: (1) allow
the water to percolate into the ground, (2)
evaporate the water into the air, (3) purify the water to such a
degree that it can be safely added to existing bodies of water, or so that
it can be reused over and over again in a
closed system, or (4) don't use water.
Treating water in the ground is the most common method because it has been tested and is the least expensive option. Soil works because viruses cannot survive very long in the cold, the distance between grains of sand are great, and there are predators that eat viruses; yet, viruses can travel up to three feet from the source in dry soil, and when transported in water, viruses have been detected thirty feet and farther from the source.
In 1990 the State of Washington put out its second set of guidelines pertaining to composting toilets and graywater disposal. Although the final say is up to eachindividual county, the state allows a 40% reduction in drainfield size and a 50%
reduction in septic tank size with the use of a waterless toilet. Drainfields or mounds must be located at least 100' from the source or any body of water. Evaporating the water takes either time, space, or fuel. There is a book on cogenerationthat proposes a plan for owner-building a wood-fired brick heater used in conjunctionwith graywater to produce steam-powered electricity and steam heat for a household thathas access to burnable fuels. If the design encorporated the efficient preheating
principals of the Dobson "Grendel" burner, air pollution could be reduced to well below the strictest emmision standards.
Filtration systems work well but are very expensive. The ultimate would be to catch and contain all rainwater in the vicinity, treat it without chemicals, pump it with the wind, and heat it with the sun. By not using water at all for toilets, the rest of the household water can so much moreeasily be treated and disposed of that there are hundreds of viable and sensible options in
existence. The problem is that most of them are either illegal or pricy. With enough interest, both of these inhibiting factors can be dispelled.
Look at CalTech's design for Bill Gates' contest:
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