Atotonilco WWTP (Mexico D.F.)

Latin America’s Largest Wastewater Treatment Plant.


The Atotonilco WWTP is the world’s largest facility built in a single phase and the third largest in terms of treatment capacity. It is located in the municipality of Atotonilco de Tula, between the districts of San José Acoculco and Melchor Ocampo (El Salto), a municipality of Tepeji del Río, in the State of Hidalgo.

The Atotonilco WWTP has a nominal treatment capacity of 35 m3/s and a maximum capacity of 50 m3/s, including final evacuation of the solid waste and sludge generated. The plant is equipped with a cogeneration system to avail of the biogas produced in digestion, thereby enabling maximum energy savings.

The contract for the construction and operation of the facility was awarded to a consortium made up of Acciona Agua, Promotora del Desarrollo de América Latina, S.A. de C.V., Controladora de Operaciones de Infraestructura, S.A. de C.V. (ICA); Atlatec, S.A. de C.V ; Desarrollo y Construcciones Urbanas, S.A. de C.V. and Green Gas Pioneer Crossing Energy, LLC. The contract entered into encompasses the provision of services for the preliminary design, detailed design and construction of the plant, as well as the treatment of wastewater from the Valley of Mexico for a period of 25 years.

The contract includes the construction and subsequent operation of the World’s largest wastewater treatment plant built in a single phase, which is located in Atotonilco, in the Mexican State of Hidalgo. The facility will treat the wastewater of 10.5 million people and the treated water will be reused for the irrigation of 80,000 hectares of land. Total investment in the plant amounted to almost €660 million.

The location of the plant was chosen because the black waters of the Valley of Mexico are discharged in the municipality of Atotonilco de Tula, where the irrigation districts of the region begin. Therefore, it will be possible to use the treated water for irrigation. For over 100 years, the wastewater from the metropolitan area of the Valley of Mexico has been used directly for the irrigation of the cultivated land of the Mezquital Valley of the State of Hidalgo, without undergoing any prior treatment. Flood irrigation is used for the cultivation of crops, primarily corn and fodder.

The Atotonilco WWTP is the largest sewage and wastewater treatment project undertaken in Mexico to date and it affords significant social, environmental and sustainability benefits. The design contract was awarded in October 2009 and construction began in 2010. The plant is currently at the commissioning stage and will go into operation at the beginning of 2016.

Outstanding amongst the social benefits is the fact that the water produced will be mainly reused to improve cultivation practices and extend current agricultural areas. This represents a significant improvement in terms of health and the environment within the area of influence of the WWTP and that of the Endhó dam.

By purifying 60% of the wastewater in the Valley of Mexico, this plant will mainly
benefit 700,000 people in the Mezquital Valley (300,000 people live in the irrigation areas). The infrastructure will provide great benefits for the population of the State of Hidalgo. It will improve the health conditions of the people and will enable the use of treated water in agriculture (preserving the nutrients in the wastewater but removing the contaminants), as well as facilitating technical improvements in irrigation systems and the production of crops with a higher added value.

This report provides an outline of the sewage system in the Valley of Mexico, of which the Atotonilco WWTP forms part, as well as a detailed description of the objectives, raw water inflows, effluent and water treatment lines of the plant.

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