Embrapa Vegetables and IICA invest in study and research on the treatment of effluents for use in agriculture

Brasilia, 28 May 2021 (IICA). In the face of climate change and water scarcity and contamination, the use of treated domestic wastewater is an increasingly attractive option for meeting the demand for water. With agriculture one of the potential beneficiaries, the Inter-American Institute for Cooperation on Agriculture (IICA) is participating in projects aimed at the development of suitable technologies in Brazil.

A case in point is an inexpensive model of a wastewater treatment station (WWTS) that was developed in collaboration with the Brazilian Agricultural Research Company (Embrapa). Safety and efficiency tests are now being carried out involving the use of treated effluents to irrigate vegetables.

An area of 200 m2 was planted with lettuce in Brazil’s capital, Brasilia.

The tests carried out to determine the quality of the water and the soil yielded excellent results.

“The result was the same on all the plots planted with lettuce, regardless of the source of the irrigation water or the production system employed: there was no contamination or difference in productivity rates,” said environmental engineer Carlos Eduardo Pacheco, an Embrapa researcher.

The official went on to explain that drip irrigation was used on the plots of lettuce so that the effluent came into contact with the soil rather than the leaves, thereby minimizing the risk of contamination.

“When treated effluent is used to irrigate vegetables, for additional safety it is best not to utilize sprinklers, which would spray water directly on the leaves, although the treated wastewater is of very high quality,” the professional remarked.

Tested on a real scale on the experimental fields of Embrapa Vegetables, the prototype was developed not only to permit the use of treated effluent to irrigate vegetable crops, but also to deliver an efficient, inexpensive treatment system that can be constructed with easily available materials and adopted by rural communities and native populations, such as indigenous peoples and quilombolas (descendants of slaves), who, in most cases, do not have basic sanitation services.

The treatment station has a compact design and was built to scale to process a flow of wastewater generated by up to 500 people, equivalent to a daily volume of 50 m3 (50,000 liters). The estimated cost of implementation is R$ 80,000 (USD 15,100).

The system in question is significantly cheaper than individual effluent treatment models, which usually serve a single family. It is possible to deliver these same results to all the families in a given community, with the WWTS adapted to the number of beneficiaries.

“More people’s needs can be met with a comparatively smaller investment than in the case of individual systems,” observed Heithel Silva, IICA technical coordinator in Brazil.

Following the positive first results of the recycling of wastewater to grow lettuce, the validation tests will be expanded throughout 2021 with the installation of treatment stations in rural communities in the semiarid region in the northeast of the country.

The first municipal district to receive a WWTS validation unit will be Petrolin, in the state of Pernambuco, under a joint effort involving the Ministry of Regional Development, the Companhia de Desenvolvimento dos Vales do São Francisco e do Parnaíba (Codevasf), Embrapa, IICA and municipal public agencies.

“A project of this kind not only addresses questions of sanitation and the treatment and use of effluents, but also opens up new horizons for the productive inclusion of the communities involved, incorporating, as it does, precepts that guarantee food and nutrition security. This is a direct consequence of crop diversification, which is often hindered by lack of water and the risk of contamination of nearby water sources,” Silva added.

In a related development, IICA and the Empresa Baiana de Águas e Saneamento SA (Embasa) contracted a study that established the potential for using effluent treated by the company in the state of Bahía. The work considered the flow of wastewater treated by Embasa (approximately 5,478 liters per second).

The company currently operates 134 sewerage systems in 103 of Bahía’s 417 municipal districts. The network has 1.4 million connections and 363 wastewater treatment plants. The objective of the study was to analyze the potential of the state’s municipal districts and regions to recycle water, with a view to increasing it to permit the intensive use of effluents in agriculture. The study focused on the development of the practice in semiarid areas and for industrial purposes, and was also used to gain a better grasp of the State’s potential for integrated water resource planning.

“Given current water scarcity, it is essential that we organize spaces for reflection and exchange to discuss alternative ways of managing and expanding the water supply, since much of Bahia forms part of the Semi-arid Region,” remarked Júlio Mota, Embasa’s Manager of Operational Technology.

The use of effluents from wastewater treatment plants (WWTS) for non-potable purposes, such as agricultural, industrial and urban activities and groundwater recharge, is only just getting off the ground in Brazil. Nonetheless, the practice is seen as an option for a sustainable future, with social and economic advantages.

Gabriel Delgado, IICA Representative in Brazil, reports that the Institute set up a group to study the possibilities of disseminating the technology across Latin America and the Caribbean, given its promising results and positive impact on the development of rural areas and the environment.

“It is important to work on the diversity of the water matrix. The initiative will serve as a model for a national platform and as a learning experience, so that other countries begin prioritizing strategic work on recycling policies and programs in the Latin American and Caribbean countries,” Delgado suggested.

The projections of the Intergovernmental Panel on Climate Change (IPCC) estimate that rainfall could decrease by 30% by the end of this century.

All regions of Brazil except for the south of the country are expected to see a fall in average annual precipitation by 2100. The Northeast will be the Brazilian region most affected, with the risk that semi-arid areas will become arid. Climate change threatens rainfall patterns not only in Brazil, but across the entire planet (e.g., in the Central American Dry Corridor, among other vulnerable areas of the region).

The Embasa study included the production of a Handbook of Operations and Recycling Practices, which offers guidelines on how to set about reusing water. The handbook includes regulatory aspects, control and monitoring methods, and information about how to raise public awareness and increase acceptance of the project, as well as a list of the entities and stakeholders involved.

Fifteen projects involving the use of treated effluents are currently underway in Brazil.

For Cristina Costa, coordinator of the project with Embasa at IICA/Brazil, no universal solution exists for providing sewerage services or to guarantee water security.

The expert pointed out that the local context has to be analyzed and a set of viable solutions to guarantee water security taken into account, with diversification of the water supply matrix. The viability of other initiatives also has to be verified, in addition to recycling, desalination, groundwater, loss reduction, and decontamination of bodies of water. “The reuse of water is increasingly becoming part of the national water supply portfolio, especially in regions where water is scarce,” she said.

“While the United States is the country that recycles most water, Mexico and China are investing more and more, along with Australia, which is suffering the severe effects of climate change”, she added, noting that the practice gives value to effluents.

In Brazil, the company that recycles most water for industrial use is located in Sao Paulo. The use of treated wastewater is one of the strategies that sanitation companies will use to provide safe, sustainable solutions to the problem of growing water scarcity across the globe, and the high cost of finding new water sources.

More information:
IICA Institutional Communication Division
comunicacion.institucional@iica.int