Filtering gardens clean water from the creek that flows into Capibaribe

The waters of the Cavouco creek, which originate inside the Federal University of Pernambuco and flow into the Capibaribe river, in Recife (PE), are being depolluted by filtering gardens. The sustainable technology uses native aquatic plants and stone tanks to filter approximately 360,000 liters of water per day.

In all, the work occupies 7 thousand square meters (m²), in a stretch of this tributary of the Capibaribe, which cuts through Parque do Caiara, in Iputinga, West Zone of the capital of Pernambuco.

The filtering gardens project was implemented by the Recife Agency for Innovation and Strategy (Aries), a non-profit social innovation organization. The execution was possible due to international cooperation with CITInova, coordinated by the Ministry of Science, Technology and Innovation (MCTI). The department works so that the model of filtering gardens is reproduced in other Brazilian cities.

The cost of the action was U$$ 1.4 million, approximately R$ 7 million, financed by the Global Fund for the Environment for (GEF) maintained with donations from industrialized countries and supported by the United Nations (UN).

The director of Agência Aries and coordinator of CITInova projects in Recife, architect and urban planner Mariana Pontes, spoke about this partnership in an interview with Brazil Agency.

“It was very important to have the Ministry of Science, Technology and Innovation with us to test new technologies and keep the focus on innovation, knowing that cities need innovation. It’s very dynamic. The exchange between CITInova’s partners was also very positive, as with the Federal District, which had experience in environmental management”.

On the next 31st, the City Hall of Recife – which worked in partnership with Aries on this pilot project – will assume full operation of the filtering gardens at Parque do Caiara.

The Urban Maintenance and Cleaning Company (Emlurb) will maintain the filtering and landscaping of the gardens.

“We are teaching the operation of the system so that the city hall can continue and so that the park can survive after the end of our participation in the pilot project”, predicts Mariana Pontes.

Recife’s Municipal Secretary of Infrastructure, Marília Dantas, cites the gains from the initiative that cleans up the creek. “There is no generation of sludge or the use of chemical products, and energy consumption is low. [elétrica] and carbon positive. The City Hall will study the case to evaluate the expansion of the project in the city.

For the time being, Emlurb has already invested BRL 500,000 in installing public lighting at the site to attract visitors to the public park. Marília Dantas praises the filtering gardens which, according to her, also have a pedagogical effect for the population.

“The city hall understands that the implementation of this system brings a message of environmental awareness because, if well maintained, it causes a greater relationship between people and nature. It is understood that this message of care for the environment is carried”.

The technology

Work on the filtering gardens began in 2022, and the system actually started operating in February of this year. The total implementation of the project is scheduled for April, with the filtering capacity maintained at around 360,000 liters of water/day.

The technology used in the project is based on natural resources, basically using stones, sand and aquatic plants, through which the water flows. The absorption of nutrients by plant roots, associated with the passage of dirty water through five stone tanks with different substrates, results in the removal and retention of solid waste, such as metals.

The water is then treated without chemicals. This filtering process, mainly of sewage, is continuous. At the same time that the water from the Cavouco stream enters the system, there is purified water leaving and being returned to Capibaribe.

For this project in the Cavouco creek, 7,500 seedlings of 36 types of aquatic macrophytes native to the region were used – such as Heliconia psittacorum, Pontederia cordata, canna generalis, Thalia geniculata, Echinodorus grandiflorus It is Nymphea sp –planted on the stones of the tanks.

The species were selected considering their resistance to the local climate and the landscaping designed for Parque do Caiara. This type of macrophyte vegetation contributes to the maintenance of biodiversity and can serve as an indicator of water quality.

The technology is similar to that used in the depollution of the Seine river, in the city of Paris, France, which was visited by Aries representatives. Mariana points out that in Brazil the experience has already aroused interest, for example, from the Federal University of Pernambuco (UFP) and the city of Florianópolis (SC) for future implementation. “There has been a lot of curiosity.”

The civil engineer responsible for the work in Recife on the filtering gardens by Aries, Renato Martiniano, records that there is a similar technique in Niterói (RJ) and in some national industries. In an interview with Brazil AgencyMartiniano guarantees that the Pernambuco project is a pioneer in public management in the Brazilian Northeast.

He considers that the maintenance of filtering gardens is simple and cheaper than conventional treatment, in addition to respecting the nature of the creek.

“The mouth of Cavouco is a strategic point, where the garden was installed inside the park. I’m happy because it’s a solution design sensitive to water, which interacts with the natural hydrological cycle, that is, captures and returns better quality water to the Capibaribe River.”

Martiniano, who is a specialist in water resources at UFP, defends the activation of more filtering garden systems across the country and innovative ways to promote basic sanitation in smaller areas.

For him, the solution would be an alternative to complement conventional sewage treatment, carried out in large cities with elements considered toxic to human life and fish.

“It is possible for us to take actions, there is no need to centralize this in the traditional sewage treatment system. We can, yes, bring decentralized solutions, without detracting from the other system, which add up to increase water security, treat and protect these bodies and improve the classification of water. Thus, it improves the well-being of people as a whole and the future of generations to come”.

Results

The expectation of Agência Aries is that the sustainable project can reduce between 90% and 95% the pollution of the waters of the Cavouco creek.

Director Mariana says that chemical monitoring tests are already being carried out to assess the quality of water samples from the creek, but that visually, the gray water is giving way to a much less cloudy liquid.

“In the first result, at the entrance to the filtering system, we can see, with the naked eye, the difference in water quality. And especially at the exit, when this water returns to the creek and flows into the [rio] Capibaribe”.

According to Mariana, the oxygenation of the Cavouco waters has increased with the innovative system and is also changing the local microclimate. “It’s full of frogs there, hummingbirds, capybaras and fish. Life is coming”.

“The project is a drop in the ocean. But it is a drop of important contribution because it improves the quality of life of the fish that are there, there are capybaras, alligators and various animals that live in the place. It is an urban river that suffers from the consequences of pollution. But the [Capibaribe] which is so important for Recife is still very polluted”, observes Mariana.

Monitoring the quality of this water from the creek will be frequent, as new systems will be installed in the coming months, at the entrance and exit of the filtering gardens.

New step

MCTI’s CITInova project will be finalized in the coming months, with the intention of replicating the experiences for several years to come.

The general coordinator of Ecosystems and Biodiversity of the ministry Luiz Henrique Mourão do Canto Pereira, announced to the Brazil Agencythat a second edition – CITInova 2, was approved by the Global Environmental Fund with a new profile that will cover three metropolitan regions: Florianópolis, Belém and Teresina.

“It is an even greater challenge because it involves the power of another sphere of government, the state level. This new project will start now, in May or June”, says Pereira.