Clays to improve industrial waters treatment
FGUSAL/DICYT Although industries must treat contaminated water before releasing this pollutants to the environment, the current technology does not completely eliminate some substances coming from the pharmaceutical and food industries. Researchers of the University of Salamanca have tested a new system that can be implemented into current WWTP, using clay columns as an adsorption system.
"Clays are innocuous, cheap and versatile materials that can be recycled to eliminate polluting substances" declared to DiCYT Carmen del Hoyo, researcher at the Department of Inorganic Chemistry.
Although the urban sewage treatment plants are responsible for cleaning the wastewater before returning it to the environment, they normally does not eliminate some contaminants coming from pharmaceutical and food industries. It is what is known as emerging pollutants and "has not yet been determined what would be the limits of their concentration so that they do not affect public health."
The University of Salamanca proposal is to incorporate adsorption columns in the WWTP. Adsorption consists of attracting dissolved substances and retaining them on a surface. In this case, researchers have proved that the clays provide appropriate qualities, so they performed experiments with columns filled with these materials to be used as filters in purification stations of industries.
Recently, they have carried out a proof of concept in collaboration with the food company Gullón, known above all for the production of cookies, to verify the effectiveness of this system in the plant that the company has in Aguilar de Campoo (Palencia).
Marina Solange Lozano's Phd., which was directed by Carmen del Hoyo and Professor Ebner Azuara Nieto, from the Universidad Veracruzana (Mexico), analyzed clay adsorbents to eliminate additives from the food industry sitting down the foundations for this work. The study took into account polluting substances such as tartrazine, amaranth and safranin against fibrous clay adsorbents, such as sepiolite, and lamellar adsorbents, such as montmorillonite. These clays can be used either in their natural state or with modifications to improve their adsorption capacity, for example, by means of calcination or a treatment with ultrasound and acid.
In addition, researchers also analyzed the opposite process, desorption. " It is important not only to know if clays are able to retain pollutants but also, for how long they manage to maintained an adequate retention capacity that assured that contaminants aren´t released again into the environment", says Carmen del Hoyo.
Tests in a real environment
The experiments were initially carried out with small amounts of clay, so it was necessary to design a more ambitious project to demonstrate that clay adsorption columns fulfill their purpose in a real situation such as an actual WWTP from a working company. For this reason, the scientists applied to the Proof of Concept contest of the General Foundation from the University of Salamanca, within the TCUE program of the Regional Government of Castilla y León, co-financed with FEDER funds. They also contacted Gullón to carry out the tests in their facilities.
"The columns are installed at the end of the treatment of the WWTP to eliminate emerging pollutants before being release to the environment, in this case, Pisuerga river waters," says the expert. The tests were used to determine the rate of adsorption of the contaminants, marked by a peristaltic pump that incorporates the solution.
The good results has encouraged the research team to apply for a patent. Although for the tests that have been carried out in the Palencia it only have been used small colums, researchers think that, "this methodology can be extrapolated to the real size of a WWTP based on the materials studied in this project".
The next step would be to design adsorption columns that mix, for example, two types of materials. One possibility is that the adsorbents are not only inorganic, as is the case of clay, but also organic, as it is described in other scientific works. For this reason, the research group of Carmen del Hoyo, which is led by Jorge Cuéllar Antequera, also works with other types of materials in search of the same objective: to improve the decontamination of wastewaters.