Emater-MG encourages the use of low-cost rural sanitation technologies

Emater-MG / Disclosure

A simple sanitary sewage treatment system in rural areas is already in operation in more than 3,500 properties in Minas Gerais, implemented with guidance from the State Technical Assistance and Rural Extension Company (Emater-MG). These are Evapotranspiration Tanks (Tevap), a type of ecological septic tank.

Each of these tanks prevents 50,000 liters of sewage per year from being dumped into the environment without treatment. In other words, in Minas Gerais, thanks to this low-cost technology, 175 million liters of sewage are no longer polluting the soil and water every year. In addition, there are 3,500 beds of ornamental plants and flowers decorating rural residences in more than 500 municipalities in the state.

“With this technology, sanitary sewage turns into flowers”, summarizes environmental engineer Jane Terezinha Leal, from the Technical Department at Emater-MG.

In addition to the ecological collection and treatment of sanitary sewage, Emater-MG also offers technical assistance for the treatment and adequate disposal of water from sinks, showers, drains and washing machines (so-called “grey water”). These are the Banan Tree Circles, already implemented in around 1,500 rural residences in the state.

Jane Terezinha explains that the two effluent treatment systems are complementary. “These are ecological, simple and low-cost solutions to a major problem, which is basic rural sanitation,” she says.

The environmental engineer also highlights that the number of properties benefiting must be even higher, as the numbers cited are only for systems installed with direct guidance from Emater-MG, the company that invests the most in the dissemination of these technologies in Brazil.

“But there are other institutions that carry out similar work, or even rural producers who carry out the implementation on their own initiative, with the help of neighbors, for example”, ponders Jane.


Rural sanitation is still a serious problem in Brazil, as the environmental engineer points out.

“Unfortunately, even today, less than 30% of rural properties have adequate collection and treatment of sanitary waste. In more than 70% of them, sewage is released into the open air or, at most, dumped into rudimentary septic tanks, which results in major pollution of the soil and water courses”, laments the state technical coordinator of Environmental Sanitation at Emater -MG.

The expert points out that this contaminated water attracts disease vectors such as rats, mosquitoes and other harmful insects, putting people’s health at risk.

“The social and environmental damage caused by a lack of basic sanitation is enormous”, highlights Jane, who also remembers the danger of spreading the diseaseAedes aegypti, responsible for the transmission of dengue and other arboviruses. “This mosquito prefers clean, still water to reproduce, but it also proliferates in dirty water”, he highlights.

Emater-MG / Disclosure
Emater-MG / Disclosure

How it works

To be efficient in dealing with the sewage problem in rural areas, the ‘secret’ of Tevap-type septic tanks is how they work. They are waterproofed excavated tanks (to prevent the infiltration of contaminated water into the soil) in which used tires are lined up at the bottom.

The tire tunnel acts as a fermentation chamber in which the bacteria present in the sewage will digest the organic matter present in the waste. The resulting material, already transformed into smaller molecules, will rise by capillarity through the various layers of stones, sand and earth, until it is absorbed by the roots of ornamental plants grown in the soil above the pit.

Jane Terezinha Leal explains that plants work like a water pump and the leaves are sprinklers that release water in the form of steam into the environment. Meanwhile, the organic matter, already transformed into molecules small enough to be absorbed by the roots, will function as fertilizer for the vegetables.

An important point in the system is that food plants must not be grown on the Tevap pit, to avoid the risk of food contamination by pathological agents. And, to facilitate evapotranspiration (release of water vapor), species with broad leaves are recommended (with many stomata, structures that release water into the environment and cultivation must be in full sun, 12 hours a day, to stimulate evapotranspiration.

Another advantage pointed out by the environmental engineer is that it is not necessary to clean the ecological septic tank, as is done in common septic tanks, which accumulate sludge at the bottom.

“Maintenance is like gardening, with pruning dry leaves and replacing seedlings. The Tevap pit will be working well if the plants are beautiful. And insects such as butterflies and pillbugs in the soil indicate the health of the system. Furthermore, there is no return bad smell for the environment”, he says.


It is necessary to size the Tevap according to the number of toilet users in the home. The recommended option, to avoid excess water in the system, is a flush tank with a capacity of up to six liters, such as those attached behind the toilet, or those that are suspended, very common in rural areas.

“The valves inside the wall use up to 50 liters of water per flush, which would destabilize the system”, informs the Emater-MG coordinator.

Emater-MG / Disclosure
Emater-MG / Disclosure

Other precautions are to avoid excessive use of bleach or flushing antibiotics down the toilet (remnants of medicines, such as syrups). This is to avoid eliminating the bacteria present, responsible for the biological balance of the system.

Among the most suitable plants to be cultivated above the ecological fossa are strelitzia (or bird-of-paradise), cana-indica (also known as garden banana), maria-sem-shame, guaimbé-da-folha- wavy, Colocasia esculenta (or black yam), calla lily and hydrangeas. They all absorb a lot of water from the soil, unlike cacti and succulents, which are not recommended for use in Tevap.

gray water

Another ecological sanitation technology, which avoids stagnant water around rural residences, is the Banan Tree Circle. It is an alternative for the final disposal of gray water from rural residences. These are the waters that were used to wash clothes, in kitchen and bathroom sinks, in drains and in showers.

Emater-MG / Disclosure
Emater-MG / Disclosure

It is a circle excavated in the ground, with a depth of 60 centimeters and a diameter of 1.40 meters. The hole is covered with straw material, such as small twigs, leaves and other plant debris. Around it, banana trees are planted, which have a high water demand, which helps to remove water from the soil, preventing the ditch from accumulating moisture.

It is important to surround the Banana Tree Circle to avoid accidents with people and animals. Opening the Circle can be done manually, with suitable tools. The use of an excavator makes the service easier, but is not essential.

According to Jane Terezinha, this system and Tevap are complementary, as gray water, with its own treatment, will not be released with the sanitary sewage into the ecological septic tank, which would cause overload and biological imbalance.

The Emater-MG coordinator warns that the Evapotranspiration Tanks and Banana Tree Circles are not suitable for collecting and treating effluents from corrals or agro-industries that exist on the property. In these cases, there are other solutions that can be recommended by the company’s technicians.

Emater-MG is a company linked to the State Department of Agriculture, Livestock and Supply (Seapa).

The article is in Portuguese

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