Its operating expenses are up to 80 percent lower than those of other conventional plants, and due to its simple operation, it does not require qualified technical personnel.
Claudia Villalobos
After conducting a diagnostic study throughout the national territory, Marco Antonio Garzón Zúñiga, a scientist from the Instituto Politécnico Nacional (IPN), concluded that, despite the importance of wastewater treatment plants, there is a deficit of them in Mexico. Even though governmental organizations make efforts for their installation, many end up abandoned because operating and maintenance costs are burdensome.
The expert in wastewater treatment, affiliated with the Centro Interdisciplinario de Investigación para el Desarrollo Integral Regional(CIIDIR), Durango Unit, pointed out that part of the problem lies in the fact that many plants operate using mechanically forced aeration generated by compressors or fans that consume a lot of electrical energy, thereby increasing costs.
"As part of the study, we observed that most of these installations operate with complicated processes that require qualified technical personnel; when operated by individuals without specific knowledge, they malfunction or provide inadequate treatment to wastewater, resulting in poor-quality final products," he said.
To address these issues, Dr. Garzón Zúñiga developed a system whose construction cost is equivalent to that of other infrastructures of this type but with simple operation and low electricity consumption. "The installation cost is comparable to that of other plants; however, the one developed at the Politécnico does not require specialized technical personnel, as no specific knowledge is needed to operate it. Operators are trained for one or two weeks and are usually people living in the installation areas," he explained.
To ensure that the treated water meets the standards outlined in the corresponding regulations, the technology at CIIDIR Durango was designed based on three types of filtration: physical, physicochemical, and biological, each to remove different types of contaminants.
The polytechnic expert mentioned that before biofiltration, pretreatment is carried out using screens to remove debris and sand with a sand remover.
He emphasized that human activities vary throughout the day, so the composition of wastewater changes continuously, as it does during rainy or dry seasons. Therefore, the plant designed at the Polytechnic Institute is equipped with a reactor whose function is to homogenize the fluid's quality.
After pretreatment, the water undergoing treatment is passed through another reactor that uses natural organic materials capable of performing physical, physicochemical, or adsorption and biofiltration tasks.
Physical filtration is carried out to remove suspended particles from wastewater (fats and materials trapped in the filter material).
The water enters the filter from the top, gravity passes through the bed of natural materials, and through physicochemical filtration, synthetic chemical compounds present in daily use products such as shampoo, cream, cosmetics, as well as medication residues, among others, are separated from the water. This removal is carried out using a chemical adsorption method, useful for retaining or degrading some dissolved contaminants that are difficult to remove with other processes.
We aim to ensure that the final product is water suitable for the irrigation of crops, thereby contributing to food production for household consumption.
The final purification step is biological. As the water descends, it passes through organic filters on which different groups of bacteria grow, forming a microbial community whose function is to degrade dissolved contaminants that were not retained through physical and physicochemical filtration. "The biological process renews the entire filtration, which is the innovation of our system because as the water descends, its composition changes, and it is gradually purified until it exits at the bottom with the characteristics of regenerated wastewater, suitable for reuse in other activities," explained the specialist affiliated with Level I of the National System of Researchers (SNI).
Marco Antonio Garzón Zúñiga mentioned that since the filters are built with natural materials, a part of them degrades slowly over time, and after 4 or 5 years, they need to be replaced.
"The maintenance service is provided by the company Ingeniería Hidráulica e Hidrológica de Durango S.A. de C.V., which was granted the concession of the technology through a non-exclusive exploitation license," said the IPN specialist with over 20 years of experience in wastewater treatment research.
In addition to maintenance, the company is authorized to carry out the design and installation of the system tailored to the specific needs of the client since the basic principle is the same, but it adapts according to the volume of water to be processed and the concentration and type of contaminants, among other aspects considered in a preliminary study to ensure the technology efficiently fulfills its purpose.
Unlike other treatment plants, the operating expenses of the technology developed at IPN are lower because it does not require chemicals such as coagulants and flocculants, which, combined with low energy consumption and no need for skilled labor, reduces operation and maintenance costs by up to 80 percent compared to conventional treatment plants like activated sludge plants.
"This represents an opportunity to promote the installation of our system and thus reduce the use of potable water in activities that can be carried out with regenerated water," warned the IPN specialist.
Two plants The wastewater treatment system is already operating on a real scale in two plants. One is located in a small hotel in a tourist center in Puerto Escondido, Oaxaca, while the second treats municipal wastewater in a particular area of residential subdivisions in the city of Durango, and the regenerated water from both plants is used for irrigation of green areas.
"Since it is a suitable technology for treating domestic or municipal wastewater, it is recommended to install it in schools, institutions, research centers, residential areas, condominiums, hotels, eco-tourism centers (cabins) located in mountains or rural areas," the expert mentioned.
The civil engineering doctor from Laval University in Quebec, Canada, added that the system is also very useful for renewing wastewater from pig or cattle farms, as well as in textile industries using dyes and even in oil companies.
An option to address drought
The polytechnic researcher explained that droughts caused by climate change and untimely rains, which are underutilized due to lack of time to infiltrate, adequately moisturize the soil, and recharge aquifers, are factors influencing a lower availability of vital liquid.
"Therefore, it is increasingly important to have wastewater treatment systems that are suitable and economical for regenerating this fluid," said Dr. Marco Antonio Garzón, who showed an interest in science, nature, and water conservation from an early age.
It is increasingly important to have wastewater treatment systems that are suitable and economical for regenerating this fluid.
The development of this applied technology of biofiltration on organic beds is a clear example of the inventiveness of polytechnic scientists. The next stage of this line of research, which has been carried out at CIIDIR Durango since 2014, will focus on combining this technique with another developed at the center to offer an alternative in arid and semi-arid areas for using regenerated water in food production for domestic animals and humans.
"This way, we can have an impact on communities where water scarcity prevails and, as a result, they face economic problems because the limited or nonexistent availability of vital liquid prevents them from cultivating their lands. We aim to ensure that the final product is water suitable for crop irrigation, thereby contributing to food production for household consumption," explained the IPN expert.
Scientific and technological development requires the contribution of various disciplines. Behind this system is nearly a decade of research, during which different projects were designed, converging into this innovative technology. Dr. Garzón Zúñiga has worked with a team for 10 years, including Dr. Juan Manuel Vigueras Cortés, affiliated with CIIDIR Durango.
Additionally, Dr. Garzón Zúñiga has benefited from the contributions of Dr. Blanca Estela Barragán Huerta from the Escuela Nacional de Ciencias Biológicas (ENCB); Dr. Iván Moreno Andrade from the National Autonomous University of Mexico (UNAM), Juriquilla Campus; Dr. Liliana García Sánchez and Dr. Edson Estrada Arriaga, both from the Mexican Institute of Water Technology (IMTA), as well as Dr. Patrick Drogui from the National Institute of Scientific Research in Quebec, Canada, and Dr. Gerardo Bahena from Laval University and the Industrial Research Center of Quebec, Canada.
CIIDIR Durango does not offer undergraduate studies; however, around 30 students from the Technological Institute of Durango (ITD), the Polytechnic University of Durango (Unipoli Dgo), the Juárez University of the State of Durango (UJED), the Technological University of Rodeo, Durango (UTRodeo), and the Superior Technological Institute of Santiago Papasquiaro, Durango (ITSSP), have participated in the project by developing their thesis works.
Dr. Garzón Zúñiga informed that individuals interested in installing this system in residential areas, schools, institutions, companies, or industries can request information from Engineer Sergio Salazar López, a specialist at Ingeniería Hidráulica e Hidrológica de Durango, which holds the commercial exploitation license for the patent.
Selección Gaceta Politécnica #173. (April 30th, 2024). IPN Imagen Institucional: Read the full magazine in Spanish here.
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