Scientists develop a water arsenic removal system for rural schools in Chaco | Uses agricultural waste and nanomaterials

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Researchers from the National University of the Northeast (UNNE) and the National University of the South (UNS) are working on the development of a remediation system for water contaminated with arsenic to be installed in rural schools in Chaco. It is a low cost equipment, simple to operate and easy to scale, designed so that it can be easily replicated in other institutions with the same problem.

Our system is based on the adsorption method and is eco-friendly since, instead of using chemical agents to remove arsenic, it uses agricultural biomass residues.”, explains the engineer Sergio Roshdestwensky, researcher at the Faculty of Engineering of the UNNE and director of the project. In addition, this method is cheaper than others that are usually implemented, such as reverse osmosis, which uses resins that are expensive to replace and generate a greater amount of waste.

Arsenic is a natural contaminant present in a large part of the Argentine territory, especially in the Chaco-Pampean plain. Prolonged intake of water or food with a high arsenic content can cause different pathologiessuch as chronic regional endemic hydroarsenicism (HACRE), a disease that can cause cancer and skin conditions.

The drinking water odyssey

UNNE researchers have been studying the arsenic problem since 2014. The first thing they did was map the entire province to analyze the arsenic content in groundwater. Once the map was finished, they decided to promote different actions. Thus they began to work with two rural schools in the Almirante Brown and General Güemes departments, which they arrived at for another project. “We were making a repellent for dengue but the covid came and it turned into gel alcohol. Working with them, we saw that they had a water problem”, says the engineer.

Meanwhile, in the Buenos Aires city of Bahía Blanca, a group from the Southern Institute of Chemistry (Inquisur–Conicet/UNS), led by doctors Veronica Lasalle and Fernanda Horst, had been working for some time on the design of adsorbent nanomaterials to be applied in water remediation. Within the framework of Natalia Scheverin’s doctoral scholarship, they were able to test the efficiency of these materials in a rural school in the municipality of Villarino. “The teachers brought water cans from their homes to distribute to the students”recalls Lasalle. Years later, the Chaco Institute of Science, Technology and Innovation (ICCTI) acted as a link between both research groups and they began to work together.

The system developed by the scientists is based on the adsorption filtering method. It consists of a filtration column made up of agricultural biomass and inorganic nanoparticles. “Through adsorption, multiple chemical interactions are generated that cause the arsenic to stick to the adsorbent material,” says Lasalle. It can also remove other elements, such as salts and heavy metals.

The treatment circuit that will be placed in schools works like this. First, water is extracted from a well with a pump and stored in a reservoir tank about one meter in diameter by one and a half meters high. Another pump then passes the water through the filter system designed by the researchers. Finally, the already treated water goes to a second tank, ready for consumption. “The idea is to use pumps that work with solar energy because rural schools often have problems with the electricity supply, especially in times of high temperatures.”, precisa Roshdestwensky.

Towards the final prototype

Currently, the team is working on designing the appropriate filter for the water quality of the Chaco schools. The UNNE researchers are in charge of everything related to the sampling and microbiological analysis of the water to determine the arsenic content of each well. These samples then go to INQUISUR, where the system is being tested on a small scale.

We already checked the efficiency of the material. We are now working on moving from the laboratory to a pilot-scale prototype, which is the step prior to real-scale”, Lasalle points out. Researchers from other groups and institutes also participate in this stage, such as engineering specialists who will be in charge of building the prototype. They estimate that the pilot tests will end this year and that, by the middle of next year, they will install the full-scale system in schools. They suggest that the final version can treat between one thousand and two thousand liters of water.

Other aspects to be evaluated will be the useful life of the adsorbent and possible final disposal alternatives for these materials. They will also discuss using two columns instead of one to speed up treatment time. “Our objective is to have the system installed in both schools, but we hope that, later on, other institutions that need it can replicate it. That is why we designed equipment that is easy to operate and build”, remarks Roshdestwensky.

real challenges for science

The lack of access to drinking water is a problem that affects a large part of the Argentine territory. For this reason, the project of the researchers from Chaco and Buenos Aires was one of those selected by the “ImpaCT.AR” Program, a call from the Ministry of Science, Technology and Innovation of the Nation (MINCyT) that seeks to promote inter-institutional research projects that contribute solutions to specific demands of public bodies.

In this case, the ICCTI presented the problem of access to drinking water in the rural schools of the Chaco and the project of the UNNE and UNS scientists obtained funding for two years to respond to this challenge. For Lasalle, this interdisciplinary and interprovincial way of working is very beneficial. And he adds: “Being able to solve such a problem serious such as access to water is a great satisfaction for us. It represents a way of looking at science that luckily I share with many colleagues and that has to do with what we do in the laboratory that helps solve specific problems in society”.

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