In the context of a family home we can save considerable amounts of water and at the same time avoid the production of sewage, using toilets that run without water.
There is a wide variety of designs and proposals on "dry" or "composting" bathrooms, all have in common, that a conventional toilet bowl is not used, that depending on the type, consume between 3 and 20 liters of water in each use.
American Standard 3705.216.021 H2Option Dual Flush Right Height Toilet Bowl, Bone (Bowl Only)
The different proposals for toilets that work without water, we can divide them into two groups: Those that act by dehydration and those that compost the excrements.
Sanitary systems based on dehydration (dry baths)
Something becomes dehydrated if all the water it contains is removed. In a dry bath the content that falls in the treatment chamber is dehydrated; This is achieved with heat, ventilation and the addition of drying material.
You have to reduce the humidity of the content to less than 25% as soon as possible, since at this level the elimination of pathogens is accelerated, there are no bad odors or flies production. The use of a specially designed toilet bowl, which bypasses urine and stores it in a separate container, facilitates dehydration of the stool.
Urine contains most nutrients and is generally free of pathogens, so it can be used directly as a fertilizer, that is, without further processing. In general, it is more difficult to dehydrate excrement mixed with urine, although in extremely dry climates dehydration is facilitated
features
- A special urine separator cup is used - there are both home and industrial models. They have a urine deposit in the front of the cup. From this collector, the urine flows through a hose to an absorption well below or next to the toilet, it can be used as fertilizer in the vegetables (mix 1 part of urine for 5 to 8 parts of water)
- Ashes and lime are used to help dehydrate and neutralize odors.
- Due to the strictly dry handling, little organic matter is produced, therefore, the chambers can be of a smaller size than in the composting toilet.
- The toilet paper is stored in a separate container and subsequently burned.
- Sufficient ventilation must be provided to the solid deposit boxes, for example with a 4-inch chimney, which rises directly without elbows or deviations up to 1m above the roof of the house. The odors of the urine separating cup can be controlled by adding a little water inside the collector after each use.
- The organic matter obtained is harvested annually, does not present any kind of smell, the presence of lime and ash dried and compacted a bit the earth, so it is recommended to mix it with topsoil and sand, before using it as fertilizer For fruit trees do not use this type of fertilizer in vegetables.
- It is usually built with double chamber, which alternates in its use, each one of them has an approximate volume of 60 cubic centimeters and they go roundabout so when one is filled it is left closed to finish the process, while it is filling the other .
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The dry toilet with solar dryer.
It is a variation of this first model. Humidity is the most important risk factor in a sanitary system based on dehydration; but adding a solar heater to the process chamber reduces that risk. This concept was developed in Mexico and systems have been installed, for example, in the Sierra Gorda de Queretaro.
Dry solar wc is used in the same way as dry baths. (There are drawers with prefabricated fiberglass solar dryers) The material in the treatment chamber is human excreta and ashes, and / or a mixture of earth and lime in a ratio of 5: 1. Urine is channeled to an absorption well located near the toilet (or processed as fertilizer). The used toilet paper is placed in a box or bag that is placed near the cup to burn it periodically. It is also built as a double chamber system.
Sanitary systems based on decomposition (composting baths).
Compost is an aerobic biological process subject to controlled conditions in which bacteria, earthworms, fungi and other organisms decompose organic substances to produce humus.
In a composting toilet human excreta and other organic materials are deposited, for example pieces of vegetables, straw, peat, sawdust and coconut shells. It is a treatment chamber where soil microorganisms are responsible for decomposing solids, as happens in a natural environment with all organic materials.
To achieve optimal conditions for compost, you must control the temperature, air circulation, provide some moisture, and ensure a good combination of materials.
The humus produced in the process is an excellent soil conditioner, free of human pathogens, but this depends on achieving the right conditions and that the material is stored for the necessary time in the chamber. To maintain aerobic conditions, sufficient oxygen must circulate in the accumulated material; the compost chamber must have 50 to 60% humidity, a carbon / nitrogen ratio (C: N) of 15: 1 to 30: 1 must be reached, and the temperature must be above 15ºC.
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A great diversity of organisms contribute to the decomposition of faeces and other materials in the sanitary composter. They vary in size, ranging from viruses, bacteria, fungi and algae to worms and insects. All of them play an important role in mixing, aerating and decomposing the content of the material stacked in the treatment chamber: its activity is positive and must be maintained. You can even place earthworms in the sanitary: if the environment favors it, multiply, make holes in the compost material and consume odors and organic matter, transforming them into enriched organic soil.
In general, there is no separation of urine, and a possible excess of nitrogen is balanced by the use of high carbon materials (sawdust, ground straw). Nor does it have to separate the toilet paper, since it is organic material and can be added without problems.
The toilet "clivus" or "clivus multrum".
More than fifty years ago, composting toilets were introduced in weekend homes in Sweden. To date, a wide variety of models have appeared, which are used in different parts of the world.
This type of sanitary has become quite popular in several parts of the world as Mexico for the inclusion of the design in the book "The Barefoot Architect" something like a guide in what refers to Bioconstrucción, it is available to download in our Library as well as more materials on the subject.
It is a compost toilet with a chamber where urine, feces and part of the household's organic waste are processed.
It consists of a compost chamber with an inclined floor, air ducts and, at the lower end, a storage area. A tube connects the pedestal sanitary cup to the receptacle and generally has a special conduit for kitchen waste. There is permanent air circulation thanks to the natural current that originates in the air passages of the compost chamber. The air exits through a vent, sometimes implemented as a fairly complex system of interconnected PVC pipes. Clivus multum not only stool, but also paper
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Commercial dry toilets
There are many models of dry toilets on the market. There are those who compost in the same sanitary and others who compost in different receiving cavities that change shape and volume according to our needs and whose mission is to receive or accumulate, ferment and allow a comfortable and harmless withdrawal of the result.
There is no design limit in the supply of industrial dry toilets either. There are those that consist of a simple composting drum with the cup or seat, and when the bag is filled simply pulls, to the complex systems with rotary reception containers, temperature detectors, aeration systems and electronic control.
These models usually carry aeration systems and even solar collectors, which facilitate the fermentation and drying of organic matter.
In addition, practically all models use the use of microorganisms that collaborate and accelerate the decomposition process of organic matter, also reducing its volume considerably and making an important step of composting within the toilets themselves. Remember that almost 90% of our excrement is water, so the remaining 10% becomes clean and dry organic fertilizer.
Almost all manufacturers are from the United States, Australia, Canada and northern Europe. But the good thing is that they are already distributed all over the world, even here in Spain.
It is very important, also, the work performed by these toilets to reduce the risk of disease transmission that does occur with its discharge to natural channels, as microorganisms also break down bacteria, fungi, pathogenic organisms, etc ...
In summary, the advantages of dry toilets over conventional sanitation can be specified in:
- They do not use water. It is only necessary for occasional cleaning.
- They do not pollute the soil or groundwater.
- They can be integrated into any existing home, including a block of flats.
- They are cheap, because they can self-build.
- They are hygienic and innocuous.
- They do not produce bad odors if they are well designed.
- They do not depend on centralized services.
- They suppose a great saving in canalizations and purification stations.
- They provide resources: fertilizers and fertilizers.
- They allow populations with few resources to access safe sanitation that keeps their waterways clean.